Merge tag 'for-linus-5.14-1' of git://github.com/cminyard/linux-ipmi

Pull IPMI driver updates from Corey Minyard:
 "Mostly a restructure of the kcs_bmc driver to make it easier to use
  with different types of devices, and just to clean things up and
  improve things.

  Also some bug fixes for the kcs_bmc driver.

  One fix to the IPMI watchdog to stop the timer when the action is
  none. Not a big deal, but it's the right thing to do"

* tag 'for-linus-5.14-1' of git://github.com/cminyard/linux-ipmi:
  ipmi: kcs_bmc_aspeed: Fix less than zero comparison of a unsigned int
  ipmi: kcs_bmc_aspeed: Optionally apply status address
  ipmi: kcs_bmc_aspeed: Fix IBFIE typo from datasheet
  ipmi: kcs_bmc_aspeed: Implement KCS SerIRQ configuration
  dt-bindings: ipmi: Add optional SerIRQ property to ASPEED KCS devices
  dt-bindings: ipmi: Convert ASPEED KCS binding to schema
  ipmi: kcs_bmc: Add serio adaptor
  ipmi: kcs_bmc: Enable IBF on open
  ipmi: kcs_bmc: Allow clients to control KCS IRQ state
  ipmi: kcs_bmc: Decouple the IPMI chardev from the core
  ipmi: kcs_bmc: Strip private client data from struct kcs_bmc
  ipmi: kcs_bmc: Split headers into device and client
  ipmi: kcs_bmc: Turn the driver data-structures inside-out
  ipmi: kcs_bmc: Split out kcs_bmc_cdev_ipmi
  ipmi: kcs_bmc: Rename {read,write}_{status,data}() functions
  ipmi: kcs_bmc: Make status update atomic
  ipmi: kcs_bmc_aspeed: Use of match data to extract KCS properties
  ipmi/watchdog: Stop watchdog timer when the current action is 'none'

11 files changed, 1492 insertions, 673 deletions

diff --git a/drivers/char/ipmi/Kconfig b/drivers/char/ipmi/Kconfig
index 07847d9a459a..249b31197eea 100644
--- a/drivers/char/ipmi/Kconfig
+++ b/drivers/char/ipmi/Kconfig
@@ -124,6 +124,33 @@ config NPCM7XX_KCS_IPMI_BMC
 	  This support is also available as a module.  If so, the module
 	  will be called kcs_bmc_npcm7xx.
 
+config IPMI_KCS_BMC_CDEV_IPMI
+	depends on IPMI_KCS_BMC
+	tristate "IPMI character device interface for BMC KCS devices"
+	help
+	  Provides a BMC-side character device implementing IPMI
+	  semantics for KCS IPMI devices.
+
+	  Say YES if you wish to expose KCS devices on the BMC for IPMI
+	  purposes.
+
+	  This support is also available as a module. The module will be
+	  called kcs_bmc_cdev_ipmi.
+
+config IPMI_KCS_BMC_SERIO
+	depends on IPMI_KCS_BMC && SERIO
+	tristate "SerIO adaptor for BMC KCS devices"
+	help
+	  Adapts the BMC KCS device for the SerIO subsystem. This allows users
+	  to take advantage of userspace interfaces provided by SerIO where
+	  appropriate.
+
+	  Say YES if you wish to expose KCS devices on the BMC via SerIO
+	  interfaces.
+
+	  This support is also available as a module. The module will be
+	  called kcs_bmc_serio.
+
 config ASPEED_BT_IPMI_BMC
 	depends on ARCH_ASPEED || COMPILE_TEST
 	depends on REGMAP && REGMAP_MMIO && MFD_SYSCON
diff --git a/drivers/char/ipmi/Makefile b/drivers/char/ipmi/Makefile
index 0822adc2ec41..84f47d18007f 100644
--- a/drivers/char/ipmi/Makefile
+++ b/drivers/char/ipmi/Makefile
@@ -23,6 +23,8 @@ obj-$(CONFIG_IPMI_POWERNV) += ipmi_powernv.o
 obj-$(CONFIG_IPMI_WATCHDOG) += ipmi_watchdog.o
 obj-$(CONFIG_IPMI_POWEROFF) += ipmi_poweroff.o
 obj-$(CONFIG_IPMI_KCS_BMC) += kcs_bmc.o
+obj-$(CONFIG_IPMI_KCS_BMC_SERIO) += kcs_bmc_serio.o
+obj-$(CONFIG_IPMI_KCS_BMC_CDEV_IPMI) += kcs_bmc_cdev_ipmi.o
 obj-$(CONFIG_ASPEED_BT_IPMI_BMC) += bt-bmc.o
 obj-$(CONFIG_ASPEED_KCS_IPMI_BMC) += kcs_bmc_aspeed.o
 obj-$(CONFIG_NPCM7XX_KCS_IPMI_BMC) += kcs_bmc_npcm7xx.o
diff --git a/drivers/char/ipmi/ipmi_watchdog.c b/drivers/char/ipmi/ipmi_watchdog.c
index 32c334e34d55..e4ff3b50de7f 100644
--- a/drivers/char/ipmi/ipmi_watchdog.c
+++ b/drivers/char/ipmi/ipmi_watchdog.c
@@ -371,16 +371,18 @@ static int __ipmi_set_timeout(struct ipmi_smi_msg  *smi_msg,
 	data[0] = 0;
 	WDOG_SET_TIMER_USE(data[0], WDOG_TIMER_USE_SMS_OS);
 
-	if ((ipmi_version_major > 1)
-	    || ((ipmi_version_major == 1) && (ipmi_version_minor >= 5))) {
-		/* This is an IPMI 1.5-only feature. */
-		data[0] |= WDOG_DONT_STOP_ON_SET;
-	} else if (ipmi_watchdog_state != WDOG_TIMEOUT_NONE) {
-		/*
-		 * In ipmi 1.0, setting the timer stops the watchdog, we
-		 * need to start it back up again.
-		 */
-		hbnow = 1;
+	if (ipmi_watchdog_state != WDOG_TIMEOUT_NONE) {
+		if ((ipmi_version_major > 1) ||
+		    ((ipmi_version_major == 1) && (ipmi_version_minor >= 5))) {
+			/* This is an IPMI 1.5-only feature. */
+			data[0] |= WDOG_DONT_STOP_ON_SET;
+		} else {
+			/*
+			 * In ipmi 1.0, setting the timer stops the watchdog, we
+			 * need to start it back up again.
+			 */
+			hbnow = 1;
+		}
 	}
 
 	data[1] = 0;
diff --git a/drivers/char/ipmi/kcs_bmc.c b/drivers/char/ipmi/kcs_bmc.c
index f292e74bd4a5..03d02a848f3a 100644
--- a/drivers/char/ipmi/kcs_bmc.c
+++ b/drivers/char/ipmi/kcs_bmc.c
@@ -1,458 +1,189 @@
 // SPDX-License-Identifier: GPL-2.0
 /*
  * Copyright (c) 2015-2018, Intel Corporation.
+ * Copyright (c) 2021, IBM Corp.
  */
 
-#define pr_fmt(fmt) "kcs-bmc: " fmt
-
-#include <linux/errno.h>
-#include <linux/io.h>
-#include <linux/ipmi_bmc.h>
+#include <linux/device.h>
+#include <linux/list.h>
 #include <linux/module.h>
-#include <linux/platform_device.h>
-#include <linux/poll.h>
-#include <linux/sched.h>
-#include <linux/slab.h>
+#include <linux/mutex.h>
 
 #include "kcs_bmc.h"
 
-#define DEVICE_NAME "ipmi-kcs"
-
-#define KCS_MSG_BUFSIZ    1000
-
-#define KCS_ZERO_DATA     0
+/* Implement both the device and client interfaces here */
+#include "kcs_bmc_device.h"
+#include "kcs_bmc_client.h"
 
+/* Record registered devices and drivers */
+static DEFINE_MUTEX(kcs_bmc_lock);
+static LIST_HEAD(kcs_bmc_devices);
+static LIST_HEAD(kcs_bmc_drivers);
 
-/* IPMI 2.0 - Table 9-1, KCS Interface Status Register Bits */
-#define KCS_STATUS_STATE(state) (state << 6)
-#define KCS_STATUS_STATE_MASK   GENMASK(7, 6)
-#define KCS_STATUS_CMD_DAT      BIT(3)
-#define KCS_STATUS_SMS_ATN      BIT(2)
-#define KCS_STATUS_IBF          BIT(1)
-#define KCS_STATUS_OBF          BIT(0)
+/* Consumer data access */
 
-/* IPMI 2.0 - Table 9-2, KCS Interface State Bits */
-enum kcs_states {
-	IDLE_STATE  = 0,
-	READ_STATE  = 1,
-	WRITE_STATE = 2,
-	ERROR_STATE = 3,
-};
-
-/* IPMI 2.0 - Table 9-3, KCS Interface Control Codes */
-#define KCS_CMD_GET_STATUS_ABORT  0x60
-#define KCS_CMD_WRITE_START       0x61
-#define KCS_CMD_WRITE_END         0x62
-#define KCS_CMD_READ_BYTE         0x68
-
-static inline u8 read_data(struct kcs_bmc *kcs_bmc)
+u8 kcs_bmc_read_data(struct kcs_bmc_device *kcs_bmc)
 {
-	return kcs_bmc->io_inputb(kcs_bmc, kcs_bmc->ioreg.idr);
+	return kcs_bmc->ops->io_inputb(kcs_bmc, kcs_bmc->ioreg.idr);
 }
+EXPORT_SYMBOL(kcs_bmc_read_data);
 
-static inline void write_data(struct kcs_bmc *kcs_bmc, u8 data)
+void kcs_bmc_write_data(struct kcs_bmc_device *kcs_bmc, u8 data)
 {
-	kcs_bmc->io_outputb(kcs_bmc, kcs_bmc->ioreg.odr, data);
+	kcs_bmc->ops->io_outputb(kcs_bmc, kcs_bmc->ioreg.odr, data);
 }
+EXPORT_SYMBOL(kcs_bmc_write_data);
 
-static inline u8 read_status(struct kcs_bmc *kcs_bmc)
+u8 kcs_bmc_read_status(struct kcs_bmc_device *kcs_bmc)
 {
-	return kcs_bmc->io_inputb(kcs_bmc, kcs_bmc->ioreg.str);
+	return kcs_bmc->ops->io_inputb(kcs_bmc, kcs_bmc->ioreg.str);
 }
+EXPORT_SYMBOL(kcs_bmc_read_status);
 
-static inline void write_status(struct kcs_bmc *kcs_bmc, u8 data)
+void kcs_bmc_write_status(struct kcs_bmc_device *kcs_bmc, u8 data)
 {
-	kcs_bmc->io_outputb(kcs_bmc, kcs_bmc->ioreg.str, data);
+	kcs_bmc->ops->io_outputb(kcs_bmc, kcs_bmc->ioreg.str, data);
 }
+EXPORT_SYMBOL(kcs_bmc_write_status);
 
-static void update_status_bits(struct kcs_bmc *kcs_bmc, u8 mask, u8 val)
+void kcs_bmc_update_status(struct kcs_bmc_device *kcs_bmc, u8 mask, u8 val)
 {
-	u8 tmp = read_status(kcs_bmc);
-
-	tmp &= ~mask;
-	tmp |= val & mask;
-
-	write_status(kcs_bmc, tmp);
+	kcs_bmc->ops->io_updateb(kcs_bmc, kcs_bmc->ioreg.str, mask, val);
 }
+EXPORT_SYMBOL(kcs_bmc_update_status);
 
-static inline void set_state(struct kcs_bmc *kcs_bmc, u8 state)
+irqreturn_t kcs_bmc_handle_event(struct kcs_bmc_device *kcs_bmc)
 {
-	update_status_bits(kcs_bmc, KCS_STATUS_STATE_MASK,
-					KCS_STATUS_STATE(state));
-}
+	struct kcs_bmc_client *client;
+	irqreturn_t rc = IRQ_NONE;
 
-static void kcs_force_abort(struct kcs_bmc *kcs_bmc)
-{
-	set_state(kcs_bmc, ERROR_STATE);
-	read_data(kcs_bmc);
-	write_data(kcs_bmc, KCS_ZERO_DATA);
+	spin_lock(&kcs_bmc->lock);
+	client = kcs_bmc->client;
+	if (client)
+		rc = client->ops->event(client);
+	spin_unlock(&kcs_bmc->lock);
 
-	kcs_bmc->phase = KCS_PHASE_ERROR;
-	kcs_bmc->data_in_avail = false;
-	kcs_bmc->data_in_idx = 0;
-}
-
-static void kcs_bmc_handle_data(struct kcs_bmc *kcs_bmc)
-{
-	u8 data;
-
-	switch (kcs_bmc->phase) {
-	case KCS_PHASE_WRITE_START:
-		kcs_bmc->phase = KCS_PHASE_WRITE_DATA;
-		fallthrough;
-
-	case KCS_PHASE_WRITE_DATA:
-		if (kcs_bmc->data_in_idx < KCS_MSG_BUFSIZ) {
-			set_state(kcs_bmc, WRITE_STATE);
-			write_data(kcs_bmc, KCS_ZERO_DATA);
-			kcs_bmc->data_in[kcs_bmc->data_in_idx++] =
-						read_data(kcs_bmc);
-		} else {
-			kcs_force_abort(kcs_bmc);
-			kcs_bmc->error = KCS_LENGTH_ERROR;
-		}
-		break;
-
-	case KCS_PHASE_WRITE_END_CMD:
-		if (kcs_bmc->data_in_idx < KCS_MSG_BUFSIZ) {
-			set_state(kcs_bmc, READ_STATE);
-			kcs_bmc->data_in[kcs_bmc->data_in_idx++] =
-						read_data(kcs_bmc);
-			kcs_bmc->phase = KCS_PHASE_WRITE_DONE;
-			kcs_bmc->data_in_avail = true;
-			wake_up_interruptible(&kcs_bmc->queue);
-		} else {
-			kcs_force_abort(kcs_bmc);
-			kcs_bmc->error = KCS_LENGTH_ERROR;
-		}
-		break;
-
-	case KCS_PHASE_READ:
-		if (kcs_bmc->data_out_idx == kcs_bmc->data_out_len)
-			set_state(kcs_bmc, IDLE_STATE);
-
-		data = read_data(kcs_bmc);
-		if (data != KCS_CMD_READ_BYTE) {
-			set_state(kcs_bmc, ERROR_STATE);
-			write_data(kcs_bmc, KCS_ZERO_DATA);
-			break;
-		}
-
-		if (kcs_bmc->data_out_idx == kcs_bmc->data_out_len) {
-			write_data(kcs_bmc, KCS_ZERO_DATA);
-			kcs_bmc->phase = KCS_PHASE_IDLE;
-			break;
-		}
-
-		write_data(kcs_bmc,
-			kcs_bmc->data_out[kcs_bmc->data_out_idx++]);
-		break;
-
-	case KCS_PHASE_ABORT_ERROR1:
-		set_state(kcs_bmc, READ_STATE);
-		read_data(kcs_bmc);
-		write_data(kcs_bmc, kcs_bmc->error);
-		kcs_bmc->phase = KCS_PHASE_ABORT_ERROR2;
-		break;
-
-	case KCS_PHASE_ABORT_ERROR2:
-		set_state(kcs_bmc, IDLE_STATE);
-		read_data(kcs_bmc);
-		write_data(kcs_bmc, KCS_ZERO_DATA);
-		kcs_bmc->phase = KCS_PHASE_IDLE;
-		break;
-
-	default:
-		kcs_force_abort(kcs_bmc);
-		break;
-	}
-}
-
-static void kcs_bmc_handle_cmd(struct kcs_bmc *kcs_bmc)
-{
-	u8 cmd;
-
-	set_state(kcs_bmc, WRITE_STATE);
-	write_data(kcs_bmc, KCS_ZERO_DATA);
-
-	cmd = read_data(kcs_bmc);
-	switch (cmd) {
-	case KCS_CMD_WRITE_START:
-		kcs_bmc->phase = KCS_PHASE_WRITE_START;
-		kcs_bmc->error = KCS_NO_ERROR;
-		kcs_bmc->data_in_avail = false;
-		kcs_bmc->data_in_idx = 0;
-		break;
-
-	case KCS_CMD_WRITE_END:
-		if (kcs_bmc->phase != KCS_PHASE_WRITE_DATA) {
-			kcs_force_abort(kcs_bmc);
-			break;
-		}
-
-		kcs_bmc->phase = KCS_PHASE_WRITE_END_CMD;
-		break;
-
-	case KCS_CMD_GET_STATUS_ABORT:
-		if (kcs_bmc->error == KCS_NO_ERROR)
-			kcs_bmc->error = KCS_ABORTED_BY_COMMAND;
-
-		kcs_bmc->phase = KCS_PHASE_ABORT_ERROR1;
-		kcs_bmc->data_in_avail = false;
-		kcs_bmc->data_in_idx = 0;
-		break;
-
-	default:
-		kcs_force_abort(kcs_bmc);
-		kcs_bmc->error = KCS_ILLEGAL_CONTROL_CODE;
-		break;
-	}
-}
-
-int kcs_bmc_handle_event(struct kcs_bmc *kcs_bmc)
-{
-	unsigned long flags;
-	int ret = -ENODATA;
-	u8 status;
-
-	spin_lock_irqsave(&kcs_bmc->lock, flags);
-
-	status = read_status(kcs_bmc);
-	if (status & KCS_STATUS_IBF) {
-		if (!kcs_bmc->running)
-			kcs_force_abort(kcs_bmc);
-		else if (status & KCS_STATUS_CMD_DAT)
-			kcs_bmc_handle_cmd(kcs_bmc);
-		else
-			kcs_bmc_handle_data(kcs_bmc);
-
-		ret = 0;
-	}
-
-	spin_unlock_irqrestore(&kcs_bmc->lock, flags);
-
-	return ret;
+	return rc;
 }
 EXPORT_SYMBOL(kcs_bmc_handle_event);
 
-static inline struct kcs_bmc *to_kcs_bmc(struct file *filp)
-{
-	return container_of(filp->private_data, struct kcs_bmc, miscdev);
-}
-
-static int kcs_bmc_open(struct inode *inode, struct file *filp)
+int kcs_bmc_enable_device(struct kcs_bmc_device *kcs_bmc, struct kcs_bmc_client *client)
 {
-	struct kcs_bmc *kcs_bmc = to_kcs_bmc(filp);
-	int ret = 0;
+	int rc;
 
 	spin_lock_irq(&kcs_bmc->lock);
-	if (!kcs_bmc->running)
-		kcs_bmc->running = 1;
-	else
-		ret = -EBUSY;
-	spin_unlock_irq(&kcs_bmc->lock);
-
-	return ret;
-}
-
-static __poll_t kcs_bmc_poll(struct file *filp, poll_table *wait)
-{
-	struct kcs_bmc *kcs_bmc = to_kcs_bmc(filp);
-	__poll_t mask = 0;
-
-	poll_wait(filp, &kcs_bmc->queue, wait);
+	if (kcs_bmc->client) {
+		rc = -EBUSY;
+	} else {
+		u8 mask = KCS_BMC_EVENT_TYPE_IBF;
 
-	spin_lock_irq(&kcs_bmc->lock);
-	if (kcs_bmc->data_in_avail)
-		mask |= EPOLLIN;
+		kcs_bmc->client = client;
+		kcs_bmc_update_event_mask(kcs_bmc, mask, mask);
+		rc = 0;
+	}
 	spin_unlock_irq(&kcs_bmc->lock);
 
-	return mask;
+	return rc;
 }
+EXPORT_SYMBOL(kcs_bmc_enable_device);
 
-static ssize_t kcs_bmc_read(struct file *filp, char __user *buf,
-			    size_t count, loff_t *ppos)
+void kcs_bmc_disable_device(struct kcs_bmc_device *kcs_bmc, struct kcs_bmc_client *client)
 {
-	struct kcs_bmc *kcs_bmc = to_kcs_bmc(filp);
-	bool data_avail;
-	size_t data_len;
-	ssize_t ret;
-
-	if (!(filp->f_flags & O_NONBLOCK))
-		wait_event_interruptible(kcs_bmc->queue,
-					 kcs_bmc->data_in_avail);
-
-	mutex_lock(&kcs_bmc->mutex);
-
 	spin_lock_irq(&kcs_bmc->lock);
-	data_avail = kcs_bmc->data_in_avail;
-	if (data_avail) {
-		data_len = kcs_bmc->data_in_idx;
-		memcpy(kcs_bmc->kbuffer, kcs_bmc->data_in, data_len);
-	}
-	spin_unlock_irq(&kcs_bmc->lock);
-
-	if (!data_avail) {
-		ret = -EAGAIN;
-		goto out_unlock;
-	}
-
-	if (count < data_len) {
-		pr_err("channel=%u with too large data : %zu\n",
-			kcs_bmc->channel, data_len);
-
-		spin_lock_irq(&kcs_bmc->lock);
-		kcs_force_abort(kcs_bmc);
-		spin_unlock_irq(&kcs_bmc->lock);
+	if (client == kcs_bmc->client) {
+		u8 mask = KCS_BMC_EVENT_TYPE_IBF | KCS_BMC_EVENT_TYPE_OBE;
 
-		ret = -EOVERFLOW;
-		goto out_unlock;
-	}
-
-	if (copy_to_user(buf, kcs_bmc->kbuffer, data_len)) {
-		ret = -EFAULT;
-		goto out_unlock;
-	}
-
-	ret = data_len;
-
-	spin_lock_irq(&kcs_bmc->lock);
-	if (kcs_bmc->phase == KCS_PHASE_WRITE_DONE) {
-		kcs_bmc->phase = KCS_PHASE_WAIT_READ;
-		kcs_bmc->data_in_avail = false;
-		kcs_bmc->data_in_idx = 0;
-	} else {
-		ret = -EAGAIN;
+		kcs_bmc_update_event_mask(kcs_bmc, mask, 0);
+		kcs_bmc->client = NULL;
 	}
 	spin_unlock_irq(&kcs_bmc->lock);
-
-out_unlock:
-	mutex_unlock(&kcs_bmc->mutex);
-
-	return ret;
 }
+EXPORT_SYMBOL(kcs_bmc_disable_device);
 
-static ssize_t kcs_bmc_write(struct file *filp, const char __user *buf,
-			     size_t count, loff_t *ppos)
+int kcs_bmc_add_device(struct kcs_bmc_device *kcs_bmc)
 {
-	struct kcs_bmc *kcs_bmc = to_kcs_bmc(filp);
-	ssize_t ret;
-
-	/* a minimum response size '3' : netfn + cmd + ccode */
-	if (count < 3 || count > KCS_MSG_BUFSIZ)
-		return -EINVAL;
-
-	mutex_lock(&kcs_bmc->mutex);
-
-	if (copy_from_user(kcs_bmc->kbuffer, buf, count)) {
-		ret = -EFAULT;
-		goto out_unlock;
-	}
+	struct kcs_bmc_driver *drv;
+	int error = 0;
+	int rc;
 
-	spin_lock_irq(&kcs_bmc->lock);
-	if (kcs_bmc->phase == KCS_PHASE_WAIT_READ) {
-		kcs_bmc->phase = KCS_PHASE_READ;
-		kcs_bmc->data_out_idx = 1;
-		kcs_bmc->data_out_len = count;
-		memcpy(kcs_bmc->data_out, kcs_bmc->kbuffer, count);
-		write_data(kcs_bmc, kcs_bmc->data_out[0]);
-		ret = count;
-	} else {
-		ret = -EINVAL;
+	spin_lock_init(&kcs_bmc->lock);
+	kcs_bmc->client = NULL;
+
+	mutex_lock(&kcs_bmc_lock);
+	list_add(&kcs_bmc->entry, &kcs_bmc_devices);
+	list_for_each_entry(drv, &kcs_bmc_drivers, entry) {
+		rc = drv->ops->add_device(kcs_bmc);
+		if (!rc)
+			continue;
+
+		dev_err(kcs_bmc->dev, "Failed to add chardev for KCS channel %d: %d",
+			kcs_bmc->channel, rc);
+		error = rc;
 	}
-	spin_unlock_irq(&kcs_bmc->lock);
-
-out_unlock:
-	mutex_unlock(&kcs_bmc->mutex);
+	mutex_unlock(&kcs_bmc_lock);
 
-	return ret;
+	return error;
 }
+EXPORT_SYMBOL(kcs_bmc_add_device);
 
-static long kcs_bmc_ioctl(struct file *filp, unsigned int cmd,
-			  unsigned long arg)
+void kcs_bmc_remove_device(struct kcs_bmc_device *kcs_bmc)
 {
-	struct kcs_bmc *kcs_bmc = to_kcs_bmc(filp);
-	long ret = 0;
+	struct kcs_bmc_driver *drv;
+	int rc;
 
-	spin_lock_irq(&kcs_bmc->lock);
-
-	switch (cmd) {
-	case IPMI_BMC_IOCTL_SET_SMS_ATN:
-		update_status_bits(kcs_bmc, KCS_STATUS_SMS_ATN,
-				   KCS_STATUS_SMS_ATN);
-		break;
-
-	case IPMI_BMC_IOCTL_CLEAR_SMS_ATN:
-		update_status_bits(kcs_bmc, KCS_STATUS_SMS_ATN,
-				   0);
-		break;
-
-	case IPMI_BMC_IOCTL_FORCE_ABORT:
-		kcs_force_abort(kcs_bmc);
-		break;
-
-	default:
-		ret = -EINVAL;
-		break;
+	mutex_lock(&kcs_bmc_lock);
+	list_del(&kcs_bmc->entry);
+	list_for_each_entry(drv, &kcs_bmc_drivers, entry) {
+		rc = drv->ops->remove_device(kcs_bmc);
+		if (rc)
+			dev_err(kcs_bmc->dev, "Failed to remove chardev for KCS channel %d: %d",
+				kcs_bmc->channel, rc);
 	}
-
-	spin_unlock_irq(&kcs_bmc->lock);
-
-	return ret;
+	mutex_unlock(&kcs_bmc_lock);
 }
+EXPORT_SYMBOL(kcs_bmc_remove_device);
 
-static int kcs_bmc_release(struct inode *inode, struct file *filp)
+void kcs_bmc_register_driver(struct kcs_bmc_driver *drv)
 {
-	struct kcs_bmc *kcs_bmc = to_kcs_bmc(filp);
-
-	spin_lock_irq(&kcs_bmc->lock);
-	kcs_bmc->running = 0;
-	kcs_force_abort(kcs_bmc);
-	spin_unlock_irq(&kcs_bmc->lock);
+	struct kcs_bmc_device *kcs_bmc;
+	int rc;
 
-	return 0;
+	mutex_lock(&kcs_bmc_lock);
+	list_add(&drv->entry, &kcs_bmc_drivers);
+	list_for_each_entry(kcs_bmc, &kcs_bmc_devices, entry) {
+		rc = drv->ops->add_device(kcs_bmc);
+		if (rc)
+			dev_err(kcs_bmc->dev, "Failed to add driver for KCS channel %d: %d",
+				kcs_bmc->channel, rc);
+	}
+	mutex_unlock(&kcs_bmc_lock);
 }
+EXPORT_SYMBOL(kcs_bmc_register_driver);
 
-static const struct file_operations kcs_bmc_fops = {
-	.owner          = THIS_MODULE,
-	.open           = kcs_bmc_open,
-	.read           = kcs_bmc_read,
-	.write          = kcs_bmc_write,
-	.release        = kcs_bmc_release,
-	.poll           = kcs_bmc_poll,
-	.unlocked_ioctl = kcs_bmc_ioctl,
-};
-
-struct kcs_bmc *kcs_bmc_alloc(struct device *dev, int sizeof_priv, u32 channel)
+void kcs_bmc_unregister_driver(struct kcs_bmc_driver *drv)
 {
-	struct kcs_bmc *kcs_bmc;
-
-	kcs_bmc = devm_kzalloc(dev, sizeof(*kcs_bmc) + sizeof_priv, GFP_KERNEL);
-	if (!kcs_bmc)
-		return NULL;
-
-	spin_lock_init(&kcs_bmc->lock);
-	kcs_bmc->channel = channel;
+	struct kcs_bmc_device *kcs_bmc;
+	int rc;
 
-	mutex_init(&kcs_bmc->mutex);
-	init_waitqueue_head(&kcs_bmc->queue);
-
-	kcs_bmc->data_in = devm_kmalloc(dev, KCS_MSG_BUFSIZ, GFP_KERNEL);
-	kcs_bmc->data_out = devm_kmalloc(dev, KCS_MSG_BUFSIZ, GFP_KERNEL);
-	kcs_bmc->kbuffer = devm_kmalloc(dev, KCS_MSG_BUFSIZ, GFP_KERNEL);
-
-	kcs_bmc->miscdev.minor = MISC_DYNAMIC_MINOR;
-	kcs_bmc->miscdev.name = devm_kasprintf(dev, GFP_KERNEL, "%s%u",
-					       DEVICE_NAME, channel);
-	if (!kcs_bmc->data_in || !kcs_bmc->data_out || !kcs_bmc->kbuffer ||
-	    !kcs_bmc->miscdev.name)
-		return NULL;
-	kcs_bmc->miscdev.fops = &kcs_bmc_fops;
+	mutex_lock(&kcs_bmc_lock);
+	list_del(&drv->entry);
+	list_for_each_entry(kcs_bmc, &kcs_bmc_devices, entry) {
+		rc = drv->ops->remove_device(kcs_bmc);
+		if (rc)
+			dev_err(kcs_bmc->dev, "Failed to remove driver for KCS channel %d: %d",
+				kcs_bmc->channel, rc);
+	}
+	mutex_unlock(&kcs_bmc_lock);
+}
+EXPORT_SYMBOL(kcs_bmc_unregister_driver);
 
-	return kcs_bmc;
+void kcs_bmc_update_event_mask(struct kcs_bmc_device *kcs_bmc, u8 mask, u8 events)
+{
+	kcs_bmc->ops->irq_mask_update(kcs_bmc, mask, events);
 }
-EXPORT_SYMBOL(kcs_bmc_alloc);
+EXPORT_SYMBOL(kcs_bmc_update_event_mask);
 
 MODULE_LICENSE("GPL v2");
 MODULE_AUTHOR("Haiyue Wang <haiyue.wang@linux.intel.com>");
+MODULE_AUTHOR("Andrew Jeffery <andrew@aj.id.au>");
 MODULE_DESCRIPTION("KCS BMC to handle the IPMI request from system software");
diff --git a/drivers/char/ipmi/kcs_bmc.h b/drivers/char/ipmi/kcs_bmc.h
index eb9ea4ce78b8..fa408b802c79 100644
--- a/drivers/char/ipmi/kcs_bmc.h
+++ b/drivers/char/ipmi/kcs_bmc.h
@@ -6,54 +6,14 @@
 #ifndef __KCS_BMC_H__
 #define __KCS_BMC_H__
 
-#include <linux/miscdevice.h>
+#include <linux/list.h>
 
-/* Different phases of the KCS BMC module.
- *  KCS_PHASE_IDLE:
- *            BMC should not be expecting nor sending any data.
- *  KCS_PHASE_WRITE_START:
- *            BMC is receiving a WRITE_START command from system software.
- *  KCS_PHASE_WRITE_DATA:
- *            BMC is receiving a data byte from system software.
- *  KCS_PHASE_WRITE_END_CMD:
- *            BMC is waiting a last data byte from system software.
- *  KCS_PHASE_WRITE_DONE:
- *            BMC has received the whole request from system software.
- *  KCS_PHASE_WAIT_READ:
- *            BMC is waiting the response from the upper IPMI service.
- *  KCS_PHASE_READ:
- *            BMC is transferring the response to system software.
- *  KCS_PHASE_ABORT_ERROR1:
- *            BMC is waiting error status request from system software.
- *  KCS_PHASE_ABORT_ERROR2:
- *            BMC is waiting for idle status afer error from system software.
- *  KCS_PHASE_ERROR:
- *            BMC has detected a protocol violation at the interface level.
- */
-enum kcs_phases {
-	KCS_PHASE_IDLE,
-
-	KCS_PHASE_WRITE_START,
-	KCS_PHASE_WRITE_DATA,
-	KCS_PHASE_WRITE_END_CMD,
-	KCS_PHASE_WRITE_DONE,
+#define KCS_BMC_EVENT_TYPE_OBE	BIT(0)
+#define KCS_BMC_EVENT_TYPE_IBF	BIT(1)
 
-	KCS_PHASE_WAIT_READ,
-	KCS_PHASE_READ,
-
-	KCS_PHASE_ABORT_ERROR1,
-	KCS_PHASE_ABORT_ERROR2,
-	KCS_PHASE_ERROR
-};
-
-/* IPMI 2.0 - Table 9-4, KCS Interface Status Codes */
-enum kcs_errors {
-	KCS_NO_ERROR                = 0x00,
-	KCS_ABORTED_BY_COMMAND      = 0x01,
-	KCS_ILLEGAL_CONTROL_CODE    = 0x02,
-	KCS_LENGTH_ERROR            = 0x06,
-	KCS_UNSPECIFIED_ERROR       = 0xFF
-};
+#define KCS_BMC_STR_OBF		BIT(0)
+#define KCS_BMC_STR_IBF		BIT(1)
+#define KCS_BMC_STR_CMD_DAT	BIT(3)
 
 /* IPMI 2.0 - 9.5, KCS Interface Registers
  * @idr: Input Data Register
@@ -66,43 +26,21 @@ struct kcs_ioreg {
 	u32 str;
 };
 
-struct kcs_bmc {
-	spinlock_t lock;
+struct kcs_bmc_device_ops;
+struct kcs_bmc_client;
 
+struct kcs_bmc_device {
+	struct list_head entry;
+
+	struct device *dev;
 	u32 channel;
-	int running;
 
-	/* Setup by BMC KCS controller driver */
 	struct kcs_ioreg ioreg;
-	u8 (*io_inputb)(struct kcs_bmc *kcs_bmc, u32 reg);
-	void (*io_outputb)(struct kcs_bmc *kcs_bmc, u32 reg, u8 b);
-
-	enum kcs_phases phase;
-	enum kcs_errors error;
-
-	wait_queue_head_t queue;
-	bool data_in_avail;
-	int  data_in_idx;
-	u8  *data_in;
-
-	int  data_out_idx;
-	int  data_out_len;
-	u8  *data_out;
 
-	struct mutex mutex;
-	u8 *kbuffer;
+	const struct kcs_bmc_device_ops *ops;
 
-	struct miscdevice miscdev;
-
-	unsigned long priv[];
+	spinlock_t lock;
+	struct kcs_bmc_client *client;
 };
 
-static inline void *kcs_bmc_priv(struct kcs_bmc *kcs_bmc)
-{
-	return kcs_bmc->priv;
-}
-
-int kcs_bmc_handle_event(struct kcs_bmc *kcs_bmc);
-struct kcs_bmc *kcs_bmc_alloc(struct device *dev, int sizeof_priv,
-					u32 channel);
 #endif /* __KCS_BMC_H__ */
diff --git a/drivers/char/ipmi/kcs_bmc_aspeed.c b/drivers/char/ipmi/kcs_bmc_aspeed.c
index eefe362f65f0..92a37b33494c 100644
--- a/drivers/char/ipmi/kcs_bmc_aspeed.c
+++ b/drivers/char/ipmi/kcs_bmc_aspeed.c
@@ -9,10 +9,12 @@
 #include <linux/errno.h>
 #include <linux/interrupt.h>
 #include <linux/io.h>
+#include <linux/irq.h>
 #include <linux/mfd/syscon.h>
 #include <linux/module.h>
 #include <linux/of.h>
 #include <linux/of_address.h>
+#include <linux/of_device.h>
 #include <linux/platform_device.h>
 #include <linux/poll.h>
 #include <linux/regmap.h>
@@ -20,24 +22,53 @@
 #include <linux/slab.h>
 #include <linux/timer.h>
 
-#include "kcs_bmc.h"
+#include "kcs_bmc_device.h"
 
 
 #define DEVICE_NAME     "ast-kcs-bmc"
 
 #define KCS_CHANNEL_MAX     4
 
+/*
+ * Field class descriptions
+ *
+ * LPCyE	Enable LPC channel y
+ * IBFIEy	Input Buffer Full IRQ Enable for LPC channel y
+ * IRQxEy	Assert SerIRQ x for LPC channel y (Deprecated, use IDyIRQX, IRQXEy)
+ * IDyIRQX	Use the specified 4-bit SerIRQ for LPC channel y
+ * SELyIRQX	SerIRQ polarity for LPC channel y (low: 0, high: 1)
+ * IRQXEy	Assert the SerIRQ specified in IDyIRQX for LPC channel y
+ */
+
+#define LPC_TYIRQX_LOW       0b00
+#define LPC_TYIRQX_HIGH      0b01
+#define LPC_TYIRQX_RSVD      0b10
+#define LPC_TYIRQX_RISING    0b11
+
 #define LPC_HICR0            0x000
 #define     LPC_HICR0_LPC3E          BIT(7)
 #define     LPC_HICR0_LPC2E          BIT(6)
 #define     LPC_HICR0_LPC1E          BIT(5)
 #define LPC_HICR2            0x008
-#define     LPC_HICR2_IBFIF3         BIT(3)
-#define     LPC_HICR2_IBFIF2         BIT(2)
-#define     LPC_HICR2_IBFIF1         BIT(1)
+#define     LPC_HICR2_IBFIE3         BIT(3)
+#define     LPC_HICR2_IBFIE2         BIT(2)
+#define     LPC_HICR2_IBFIE1         BIT(1)
 #define LPC_HICR4            0x010
 #define     LPC_HICR4_LADR12AS       BIT(7)
 #define     LPC_HICR4_KCSENBL        BIT(2)
+#define LPC_SIRQCR0	     0x070
+/* IRQ{12,1}E1 are deprecated as of AST2600 A3 but necessary for prior chips */
+#define     LPC_SIRQCR0_IRQ12E1	     BIT(1)
+#define     LPC_SIRQCR0_IRQ1E1	     BIT(0)
+#define LPC_HICR5	     0x080
+#define     LPC_HICR5_ID3IRQX_MASK   GENMASK(23, 20)
+#define     LPC_HICR5_ID3IRQX_SHIFT  20
+#define     LPC_HICR5_ID2IRQX_MASK   GENMASK(19, 16)
+#define     LPC_HICR5_ID2IRQX_SHIFT  16
+#define     LPC_HICR5_SEL3IRQX       BIT(15)
+#define     LPC_HICR5_IRQXE3         BIT(14)
+#define     LPC_HICR5_SEL2IRQX       BIT(13)
+#define     LPC_HICR5_IRQXE2         BIT(12)
 #define LPC_LADR3H           0x014
 #define LPC_LADR3L           0x018
 #define LPC_LADR12H          0x01C
@@ -52,21 +83,64 @@
 #define LPC_STR2             0x040
 #define LPC_STR3             0x044
 #define LPC_HICRB            0x100
-#define     LPC_HICRB_IBFIF4         BIT(1)
+#define     LPC_HICRB_EN16LADR2      BIT(5)
+#define     LPC_HICRB_EN16LADR1      BIT(4)
+#define     LPC_HICRB_IBFIE4         BIT(1)
 #define     LPC_HICRB_LPC4E          BIT(0)
+#define LPC_HICRC            0x104
+#define     LPC_HICRC_ID4IRQX_MASK   GENMASK(7, 4)
+#define     LPC_HICRC_ID4IRQX_SHIFT  4
+#define     LPC_HICRC_TY4IRQX_MASK   GENMASK(3, 2)
+#define     LPC_HICRC_TY4IRQX_SHIFT  2
+#define     LPC_HICRC_OBF4_AUTO_CLR  BIT(1)
+#define     LPC_HICRC_IRQXE4         BIT(0)
 #define LPC_LADR4            0x110
 #define LPC_IDR4             0x114
 #define LPC_ODR4             0x118
 #define LPC_STR4             0x11C
+#define LPC_LSADR12	     0x120
+#define     LPC_LSADR12_LSADR2_MASK  GENMASK(31, 16)
+#define     LPC_LSADR12_LSADR2_SHIFT 16
+#define     LPC_LSADR12_LSADR1_MASK  GENMASK(15, 0)
+#define     LPC_LSADR12_LSADR1_SHIFT 0
+
+#define OBE_POLL_PERIOD	     (HZ / 2)
+
+enum aspeed_kcs_irq_mode {
+	aspeed_kcs_irq_none,
+	aspeed_kcs_irq_serirq,
+};
 
 struct aspeed_kcs_bmc {
+	struct kcs_bmc_device kcs_bmc;
+
 	struct regmap *map;
+
+	struct {
+		enum aspeed_kcs_irq_mode mode;
+		int id;
+	} upstream_irq;
+
+	struct {
+		spinlock_t lock;
+		bool remove;
+		struct timer_list timer;
+	} obe;
 };
 
+struct aspeed_kcs_of_ops {
+	int (*get_channel)(struct platform_device *pdev);
+	int (*get_io_address)(struct platform_device *pdev, u32 addrs[2]);
+};
 
-static u8 aspeed_kcs_inb(struct kcs_bmc *kcs_bmc, u32 reg)
+static inline struct aspeed_kcs_bmc *to_aspeed_kcs_bmc(struct kcs_bmc_device *kcs_bmc)
 {
-	struct aspeed_kcs_bmc *priv = kcs_bmc_priv(kcs_bmc);
+	return container_of(kcs_bmc, struct aspeed_kcs_bmc, kcs_bmc);
+}
+
+static u8 aspeed_kcs_inb(struct kcs_bmc_device *kcs_bmc, u32 reg)
+{
+	struct aspeed_kcs_bmc *priv = to_aspeed_kcs_bmc(kcs_bmc);
 	u32 val = 0;
 	int rc;
 
@@ -76,15 +150,66 @@ static u8 aspeed_kcs_inb(struct kcs_bmc *kcs_bmc, u32 reg)
 	return rc == 0 ? (u8) val : 0;
 }
 
-static void aspeed_kcs_outb(struct kcs_bmc *kcs_bmc, u32 reg, u8 data)
+static void aspeed_kcs_outb(struct kcs_bmc_device *kcs_bmc, u32 reg, u8 data)
 {
-	struct aspeed_kcs_bmc *priv = kcs_bmc_priv(kcs_bmc);
+	struct aspeed_kcs_bmc *priv = to_aspeed_kcs_bmc(kcs_bmc);
 	int rc;
 
 	rc = regmap_write(priv->map, reg, data);
 	WARN(rc != 0, "regmap_write() failed: %d\n", rc);
+
+	/* Trigger the upstream IRQ on ODR writes, if enabled */
+
+	switch (reg) {
+	case LPC_ODR1:
+	case LPC_ODR2:
+	case LPC_ODR3:
+	case LPC_ODR4:
+		break;
+	default:
+		return;
+	}
+
+	if (priv->upstream_irq.mode != aspeed_kcs_irq_serirq)
+		return;
+
+	switch (kcs_bmc->channel) {
+	case 1:
+		switch (priv->upstream_irq.id) {
+		case 12:
+			regmap_update_bits(priv->map, LPC_SIRQCR0, LPC_SIRQCR0_IRQ12E1,
+					   LPC_SIRQCR0_IRQ12E1);
+			break;
+		case 1:
+			regmap_update_bits(priv->map, LPC_SIRQCR0, LPC_SIRQCR0_IRQ1E1,
+					   LPC_SIRQCR0_IRQ1E1);
+			break;
+		default:
+			break;
+		}
+		break;
+	case 2:
+		regmap_update_bits(priv->map, LPC_HICR5, LPC_HICR5_IRQXE2, LPC_HICR5_IRQXE2);
+		break;
+	case 3:
+		regmap_update_bits(priv->map, LPC_HICR5, LPC_HICR5_IRQXE3, LPC_HICR5_IRQXE3);
+		break;
+	case 4:
+		regmap_update_bits(priv->map, LPC_HICRC, LPC_HICRC_IRQXE4, LPC_HICRC_IRQXE4);
+		break;
+	default:
+		break;
+	}
 }
 
+static void aspeed_kcs_updateb(struct kcs_bmc_device *kcs_bmc, u32 reg, u8 mask, u8 val)
+{
+	struct aspeed_kcs_bmc *priv = to_aspeed_kcs_bmc(kcs_bmc);
+	int rc;
+
+	rc = regmap_update_bits(priv->map, reg, mask, val);
+	WARN(rc != 0, "regmap_update_bits() failed: %d\n", rc);
+}
 
 /*
  * AST_usrGuide_KCS.pdf
@@ -99,118 +224,237 @@ static void aspeed_kcs_outb(struct kcs_bmc *kcs_bmc, u32 reg, u8 data)
  *     C. KCS4
  *        D / C : CA4h / CA5h
  */
-static void aspeed_kcs_set_address(struct kcs_bmc *kcs_bmc, u16 addr)
+static int aspeed_kcs_set_address(struct kcs_bmc_device *kcs_bmc, u32 addrs[2], int nr_addrs)
 {
-	struct aspeed_kcs_bmc *priv = kcs_bmc_priv(kcs_bmc);
+	struct aspeed_kcs_bmc *priv = to_aspeed_kcs_bmc(kcs_bmc);
 
-	switch (kcs_bmc->channel) {
+	if (WARN_ON(nr_addrs < 1 || nr_addrs > 2))
+		return -EINVAL;
+
+	switch (priv->kcs_bmc.channel) {
 	case 1:
-		regmap_update_bits(priv->map, LPC_HICR4,
-				LPC_HICR4_LADR12AS, 0);
-		regmap_write(priv->map, LPC_LADR12H, addr >> 8);
-		regmap_write(priv->map, LPC_LADR12L, addr & 0xFF);
+		regmap_update_bits(priv->map, LPC_HICR4, LPC_HICR4_LADR12AS, 0);
+		regmap_write(priv->map, LPC_LADR12H, addrs[0] >> 8);
+		regmap_write(priv->map, LPC_LADR12L, addrs[0] & 0xFF);
+		if (nr_addrs == 2) {
+			regmap_update_bits(priv->map, LPC_LSADR12, LPC_LSADR12_LSADR1_MASK,
+					   addrs[1] << LPC_LSADR12_LSADR1_SHIFT);
+
+			regmap_update_bits(priv->map, LPC_HICRB, LPC_HICRB_EN16LADR1,
+					   LPC_HICRB_EN16LADR1);
+		}
 		break;
 
 	case 2:
-		regmap_update_bits(priv->map, LPC_HICR4,
-				LPC_HICR4_LADR12AS, LPC_HICR4_LADR12AS);
-		regmap_write(priv->map, LPC_LADR12H, addr >> 8);
-		regmap_write(priv->map, LPC_LADR12L, addr & 0xFF);
+		regmap_update_bits(priv->map, LPC_HICR4, LPC_HICR4_LADR12AS, LPC_HICR4_LADR12AS);
+		regmap_write(priv->map, LPC_LADR12H, addrs[0] >> 8);
+		regmap_write(priv->map, LPC_LADR12L, addrs[0] & 0xFF);
+		if (nr_addrs == 2) {
+			regmap_update_bits(priv->map, LPC_LSADR12, LPC_LSADR12_LSADR2_MASK,
+					   addrs[1] << LPC_LSADR12_LSADR2_SHIFT);
+
+			regmap_update_bits(priv->map, LPC_HICRB, LPC_HICRB_EN16LADR2,
+					   LPC_HICRB_EN16LADR2);
+		}
 		break;
 
 	case 3:
-		regmap_write(priv->map, LPC_LADR3H, addr >> 8);
-		regmap_write(priv->map, LPC_LADR3L, addr & 0xFF);
+		if (nr_addrs == 2) {
+			dev_err(priv->kcs_bmc.dev,
+				"Channel 3 only supports inferred status IO address\n");
+			return -EINVAL;
+		}
+
+		regmap_write(priv->map, LPC_LADR3H, addrs[0] >> 8);
+		regmap_write(priv->map, LPC_LADR3L, addrs[0] & 0xFF);
 		break;
 
 	case 4:
-		regmap_write(priv->map, LPC_LADR4, ((addr + 1) << 16) |
-			addr);
+		if (nr_addrs == 1)
+			regmap_write(priv->map, LPC_LADR4, ((addrs[0] + 1) << 16) | addrs[0]);
+		else
+			regmap_write(priv->map, LPC_LADR4, (addrs[1] << 16) | addrs[0]);
+
 		break;
 
 	default:
-		break;
+		return -EINVAL;
 	}
+
+	return 0;
 }
 
-static void aspeed_kcs_enable_channel(struct kcs_bmc *kcs_bmc, bool enable)
+static inline int aspeed_kcs_map_serirq_type(u32 dt_type)
 {
-	struct aspeed_kcs_bmc *priv = kcs_bmc_priv(kcs_bmc);
+	switch (dt_type) {
+	case IRQ_TYPE_EDGE_RISING:
+		return LPC_TYIRQX_RISING;
+	case IRQ_TYPE_LEVEL_HIGH:
+		return LPC_TYIRQX_HIGH;
+	case IRQ_TYPE_LEVEL_LOW:
+		return LPC_TYIRQX_LOW;
+	default:
+		return -EINVAL;
+	}
+}
 
-	switch (kcs_bmc->channel) {
+static int aspeed_kcs_config_upstream_irq(struct aspeed_kcs_bmc *priv, u32 id, u32 dt_type)
+{
+	unsigned int mask, val, hw_type;
+	int ret;
+
+	if (id > 15)
+		return -EINVAL;
+
+	ret = aspeed_kcs_map_serirq_type(dt_type);
+	if (ret < 0)
+		return ret;
+	hw_type = ret;
+
+	priv->upstream_irq.mode = aspeed_kcs_irq_serirq;
+	priv->upstream_irq.id = id;
+
+	switch (priv->kcs_bmc.channel) {
 	case 1:
-		if (enable) {
-			regmap_update_bits(priv->map, LPC_HICR2,
-					LPC_HICR2_IBFIF1, LPC_HICR2_IBFIF1);
-			regmap_update_bits(priv->map, LPC_HICR0,
-					LPC_HICR0_LPC1E, LPC_HICR0_LPC1E);
-		} else {
-			regmap_update_bits(priv->map, LPC_HICR0,
-					LPC_HICR0_LPC1E, 0);
-			regmap_update_bits(priv->map, LPC_HICR2,
-					LPC_HICR2_IBFIF1, 0);
-		}
+		/* Needs IRQxE1 rather than (ID1IRQX, SEL1IRQX, IRQXE1) before AST2600 A3 */
 		break;
-
 	case 2:
-		if (enable) {
-			regmap_update_bits(priv->map, LPC_HICR2,
-					LPC_HICR2_IBFIF2, LPC_HICR2_IBFIF2);
-			regmap_update_bits(priv->map, LPC_HICR0,
-					LPC_HICR0_LPC2E, LPC_HICR0_LPC2E);
-		} else {
-			regmap_update_bits(priv->map, LPC_HICR0,
-					LPC_HICR0_LPC2E, 0);
-			regmap_update_bits(priv->map, LPC_HICR2,
-					LPC_HICR2_IBFIF2, 0);
-		}
-		break;
+		if (!(hw_type == LPC_TYIRQX_LOW || hw_type == LPC_TYIRQX_HIGH))
+			return -EINVAL;
+
+		mask = LPC_HICR5_SEL2IRQX | LPC_HICR5_ID2IRQX_MASK;
+		val = (id << LPC_HICR5_ID2IRQX_SHIFT);
+		val |= (hw_type == LPC_TYIRQX_HIGH) ? LPC_HICR5_SEL2IRQX : 0;
+		regmap_update_bits(priv->map, LPC_HICR5, mask, val);
 
-	case 3:
-		if (enable) {
-			regmap_update_bits(priv->map, LPC_HICR2,
-					LPC_HICR2_IBFIF3, LPC_HICR2_IBFIF3);
-			regmap_update_bits(priv->map, LPC_HICR0,
-					LPC_HICR0_LPC3E, LPC_HICR0_LPC3E);
-			regmap_update_bits(priv->map, LPC_HICR4,
-					LPC_HICR4_KCSENBL, LPC_HICR4_KCSENBL);
-		} else {
-			regmap_update_bits(priv->map, LPC_HICR0,
-					LPC_HICR0_LPC3E, 0);
-			regmap_update_bits(priv->map, LPC_HICR4,
-					LPC_HICR4_KCSENBL, 0);
-			regmap_update_bits(priv->map, LPC_HICR2,
-					LPC_HICR2_IBFIF3, 0);
-		}
 		break;
+	case 3:
+		if (!(hw_type == LPC_TYIRQX_LOW || hw_type == LPC_TYIRQX_HIGH))
+			return -EINVAL;
+
+		mask = LPC_HICR5_SEL3IRQX | LPC_HICR5_ID3IRQX_MASK;
+		val = (id << LPC_HICR5_ID3IRQX_SHIFT);
+		val |= (hw_type == LPC_TYIRQX_HIGH) ? LPC_HICR5_SEL3IRQX : 0;
+		regmap_update_bits(priv->map, LPC_HICR5, mask, val);
 
+		break;
 	case 4:
-		if (enable)
-			regmap_update_bits(priv->map, LPC_HICRB,
-					LPC_HICRB_IBFIF4 | LPC_HICRB_LPC4E,
-					LPC_HICRB_IBFIF4 | LPC_HICRB_LPC4E);
-		else
-			regmap_update_bits(priv->map, LPC_HICRB,
-					LPC_HICRB_IBFIF4 | LPC_HICRB_LPC4E,
-					0);
+		mask = LPC_HICRC_ID4IRQX_MASK | LPC_HICRC_TY4IRQX_MASK | LPC_HICRC_OBF4_AUTO_CLR;
+		val = (id << LPC_HICRC_ID4IRQX_SHIFT) | (hw_type << LPC_HICRC_TY4IRQX_SHIFT);
+		regmap_update_bits(priv->map, LPC_HICRC, mask, val);
 		break;
+	default:
+		dev_warn(priv->kcs_bmc.dev,
+			 "SerIRQ configuration not supported on KCS channel %d\n",
+			 priv->kcs_bmc.channel);
+		return -EINVAL;
+	}
+
+	return 0;
+}
+
+static void aspeed_kcs_enable_channel(struct kcs_bmc_device *kcs_bmc, bool enable)
+{
+	struct aspeed_kcs_bmc *priv = to_aspeed_kcs_bmc(kcs_bmc);
 
+	switch (kcs_bmc->channel) {
+	case 1:
+		regmap_update_bits(priv->map, LPC_HICR0, LPC_HICR0_LPC1E, enable * LPC_HICR0_LPC1E);
+		return;
+	case 2:
+		regmap_update_bits(priv->map, LPC_HICR0, LPC_HICR0_LPC2E, enable * LPC_HICR0_LPC2E);
+		return;
+	case 3:
+		regmap_update_bits(priv->map, LPC_HICR0, LPC_HICR0_LPC3E, enable * LPC_HICR0_LPC3E);
+		regmap_update_bits(priv->map, LPC_HICR4,
+				   LPC_HICR4_KCSENBL, enable * LPC_HICR4_KCSENBL);
+		return;
+	case 4:
+		regmap_update_bits(priv->map, LPC_HICRB, LPC_HICRB_LPC4E, enable * LPC_HICRB_LPC4E);
+		return;
 	default:
-		break;
+		pr_warn("%s: Unsupported channel: %d", __func__, kcs_bmc->channel);
+		return;
 	}
 }
 
-static irqreturn_t aspeed_kcs_irq(int irq, void *arg)
+static void aspeed_kcs_check_obe(struct timer_list *timer)
+{
+	struct aspeed_kcs_bmc *priv = container_of(timer, struct aspeed_kcs_bmc, obe.timer);
+	unsigned long flags;
+	u8 str;
+
+	spin_lock_irqsave(&priv->obe.lock, flags);
+	if (priv->obe.remove) {
+		spin_unlock_irqrestore(&priv->obe.lock, flags);
+		return;
+	}
+
+	str = aspeed_kcs_inb(&priv->kcs_bmc, priv->kcs_bmc.ioreg.str);
+	if (str & KCS_BMC_STR_OBF) {
+		mod_timer(timer, jiffies + OBE_POLL_PERIOD);
+		spin_unlock_irqrestore(&priv->obe.lock, flags);
+		return;
+	}
+	spin_unlock_irqrestore(&priv->obe.lock, flags);
+
+	kcs_bmc_handle_event(&priv->kcs_bmc);
+}
+
+static void aspeed_kcs_irq_mask_update(struct kcs_bmc_device *kcs_bmc, u8 mask, u8 state)
 {
-	struct kcs_bmc *kcs_bmc = arg;
+	struct aspeed_kcs_bmc *priv = to_aspeed_kcs_bmc(kcs_bmc);
 
-	if (!kcs_bmc_handle_event(kcs_bmc))
-		return IRQ_HANDLED;
+	/* We don't have an OBE IRQ, emulate it */
+	if (mask & KCS_BMC_EVENT_TYPE_OBE) {
+		if (KCS_BMC_EVENT_TYPE_OBE & state)
+			mod_timer(&priv->obe.timer, jiffies + OBE_POLL_PERIOD);
+		else
+			del_timer(&priv->obe.timer);
+	}
 
-	return IRQ_NONE;
+	if (mask & KCS_BMC_EVENT_TYPE_IBF) {
+		const bool enable = !!(state & KCS_BMC_EVENT_TYPE_IBF);
+
+		switch (kcs_bmc->channel) {
+		case 1:
+			regmap_update_bits(priv->map, LPC_HICR2, LPC_HICR2_IBFIE1,
+					   enable * LPC_HICR2_IBFIE1);
+			return;
+		case 2:
+			regmap_update_bits(priv->map, LPC_HICR2, LPC_HICR2_IBFIE2,
+					   enable * LPC_HICR2_IBFIE2);
+			return;
+		case 3:
+			regmap_update_bits(priv->map, LPC_HICR2, LPC_HICR2_IBFIE3,
+					   enable * LPC_HICR2_IBFIE3);
+			return;
+		case 4:
+			regmap_update_bits(priv->map, LPC_HICRB, LPC_HICRB_IBFIE4,
+					   enable * LPC_HICRB_IBFIE4);
+			return;
+		default:
+			pr_warn("%s: Unsupported channel: %d", __func__, kcs_bmc->channel);
+			return;
+		}
+	}
 }
 
-static int aspeed_kcs_config_irq(struct kcs_bmc *kcs_bmc,
+static const struct kcs_bmc_device_ops aspeed_kcs_ops = {
+	.irq_mask_update = aspeed_kcs_irq_mask_update,
+	.io_inputb = aspeed_kcs_inb,
+	.io_outputb = aspeed_kcs_outb,
+	.io_updateb = aspeed_kcs_updateb,
+};
+
+static irqreturn_t aspeed_kcs_irq(int irq, void *arg)
+{
+	struct kcs_bmc_device *kcs_bmc = arg;
+
+	return kcs_bmc_handle_event(kcs_bmc);
+}
+
+static int aspeed_kcs_config_downstream_irq(struct kcs_bmc_device *kcs_bmc,
 			struct platform_device *pdev)
 {
 	struct device *dev = &pdev->dev;
@@ -231,13 +475,10 @@ static const struct kcs_ioreg ast_kcs_bmc_ioregs[KCS_CHANNEL_MAX] = {
 	{ .idr = LPC_IDR4, .odr = LPC_ODR4, .str = LPC_STR4 },
 };
 
-static struct kcs_bmc *aspeed_kcs_probe_of_v1(struct platform_device *pdev)
+static int aspeed_kcs_of_v1_get_channel(struct platform_device *pdev)
 {
-	struct aspeed_kcs_bmc *priv;
 	struct device_node *np;
-	struct kcs_bmc *kcs;
 	u32 channel;
-	u32 slave;
 	int rc;
 
 	np = pdev->dev.of_node;
@@ -245,166 +486,213 @@ static struct kcs_bmc *aspeed_kcs_probe_of_v1(struct platform_device *pdev)
 	rc = of_property_read_u32(np, "kcs_chan", &channel);
 	if ((rc != 0) || (channel == 0 || channel > KCS_CHANNEL_MAX)) {
 		dev_err(&pdev->dev, "no valid 'kcs_chan' configured\n");
-		return ERR_PTR(-EINVAL);
-	}
-
-	kcs = kcs_bmc_alloc(&pdev->dev, sizeof(struct aspeed_kcs_bmc), channel);
-	if (!kcs)
-		return ERR_PTR(-ENOMEM);
-
-	priv = kcs_bmc_priv(kcs);
-	priv->map = syscon_node_to_regmap(pdev->dev.parent->of_node);
-	if (IS_ERR(priv->map)) {
-		dev_err(&pdev->dev, "Couldn't get regmap\n");
-		return ERR_PTR(-ENODEV);
-	}
-
-	rc = of_property_read_u32(np, "kcs_addr", &slave);
-	if (rc) {
-		dev_err(&pdev->dev, "no valid 'kcs_addr' configured\n");
-		return ERR_PTR(-EINVAL);
+		return -EINVAL;
 	}
 
-	kcs->ioreg = ast_kcs_bmc_ioregs[channel - 1];
-	aspeed_kcs_set_address(kcs, slave);
-
-	return kcs;
+	return channel;
 }
 
-static int aspeed_kcs_calculate_channel(const struct kcs_ioreg *regs)
+static int
+aspeed_kcs_of_v1_get_io_address(struct platform_device *pdev, u32 addrs[2])
 {
-	int i;
+	int rc;
 
-	for (i = 0; i < ARRAY_SIZE(ast_kcs_bmc_ioregs); i++) {
-		if (!memcmp(&ast_kcs_bmc_ioregs[i], regs, sizeof(*regs)))
-			return i + 1;
+	rc = of_property_read_u32(pdev->dev.of_node, "kcs_addr", addrs);
+	if (rc || addrs[0] > 0xffff) {
+		dev_err(&pdev->dev, "no valid 'kcs_addr' configured\n");
+		return -EINVAL;
 	}
 
-	return -EINVAL;
+	return 1;
 }
 
-static struct kcs_bmc *aspeed_kcs_probe_of_v2(struct platform_device *pdev)
+static int aspeed_kcs_of_v2_get_channel(struct platform_device *pdev)
 {
-	struct aspeed_kcs_bmc *priv;
 	struct device_node *np;
 	struct kcs_ioreg ioreg;
-	struct kcs_bmc *kcs;
 	const __be32 *reg;
-	int channel;
-	u32 slave;
-	int rc;
+	int i;
 
 	np = pdev->dev.of_node;
 
 	/* Don't translate addresses, we want offsets for the regmaps */
 	reg = of_get_address(np, 0, NULL, NULL);
 	if (!reg)
-		return ERR_PTR(-EINVAL);
+		return -EINVAL;
 	ioreg.idr = be32_to_cpup(reg);
 
 	reg = of_get_address(np, 1, NULL, NULL);
 	if (!reg)
-		return ERR_PTR(-EINVAL);
+		return -EINVAL;
 	ioreg.odr = be32_to_cpup(reg);
 
 	reg = of_get_address(np, 2, NULL, NULL);
 	if (!reg)
-		return ERR_PTR(-EINVAL);
+		return -EINVAL;
 	ioreg.str = be32_to_cpup(reg);
 
-	channel = aspeed_kcs_calculate_channel(&ioreg);
-	if (channel < 0)
-		return ERR_PTR(channel);
+	for (i = 0; i < ARRAY_SIZE(ast_kcs_bmc_ioregs); i++) {
+		if (!memcmp(&ast_kcs_bmc_ioregs[i], &ioreg, sizeof(ioreg)))
+			return i + 1;
+	}
 
-	kcs = kcs_bmc_alloc(&pdev->dev, sizeof(struct aspeed_kcs_bmc), channel);
-	if (!kcs)
-		return ERR_PTR(-ENOMEM);
+	return -EINVAL;
+}
 
-	kcs->ioreg = ioreg;
+static int
+aspeed_kcs_of_v2_get_io_address(struct platform_device *pdev, u32 addrs[2])
+{
+	int rc;
 
-	priv = kcs_bmc_priv(kcs);
-	priv->map = syscon_node_to_regmap(pdev->dev.parent->of_node);
-	if (IS_ERR(priv->map)) {
-		dev_err(&pdev->dev, "Couldn't get regmap\n");
-		return ERR_PTR(-ENODEV);
+	rc = of_property_read_variable_u32_array(pdev->dev.of_node,
+						 "aspeed,lpc-io-reg",
+						 addrs, 1, 2);
+	if (rc < 0) {
+		dev_err(&pdev->dev, "No valid 'aspeed,lpc-io-reg' configured\n");
+		return rc;
 	}
 
-	rc = of_property_read_u32(np, "aspeed,lpc-io-reg", &slave);
-	if (rc)
-		return ERR_PTR(rc);
+	if (addrs[0] > 0xffff) {
+		dev_err(&pdev->dev, "Invalid data address in 'aspeed,lpc-io-reg'\n");
+		return -EINVAL;
+	}
 
-	aspeed_kcs_set_address(kcs, slave);
+	if (rc == 2 && addrs[1] > 0xffff) {
+		dev_err(&pdev->dev, "Invalid status address in 'aspeed,lpc-io-reg'\n");
+		return -EINVAL;
+	}
 
-	return kcs;
+	return rc;
 }
 
 static int aspeed_kcs_probe(struct platform_device *pdev)
 {
-	struct device *dev = &pdev->dev;
-	struct kcs_bmc *kcs_bmc;
+	const struct aspeed_kcs_of_ops *ops;
+	struct kcs_bmc_device *kcs_bmc;
+	struct aspeed_kcs_bmc *priv;
 	struct device_node *np;
-	int rc;
+	bool have_upstream_irq;
+	u32 upstream_irq[2];
+	int rc, channel;
+	int nr_addrs;
+	u32 addrs[2];
 
-	np = dev->of_node->parent;
+	np = pdev->dev.of_node->parent;
 	if (!of_device_is_compatible(np, "aspeed,ast2400-lpc-v2") &&
 	    !of_device_is_compatible(np, "aspeed,ast2500-lpc-v2") &&
 	    !of_device_is_compatible(np, "aspeed,ast2600-lpc-v2")) {
-		dev_err(dev, "unsupported LPC device binding\n");
+		dev_err(&pdev->dev, "unsupported LPC device binding\n");
 		return -ENODEV;
 	}
 
-	np = dev->of_node;
-	if (of_device_is_compatible(np, "aspeed,ast2400-kcs-bmc") ||
-	    of_device_is_compatible(np, "aspeed,ast2500-kcs-bmc"))
-		kcs_bmc = aspeed_kcs_probe_of_v1(pdev);
-	else if (of_device_is_compatible(np, "aspeed,ast2400-kcs-bmc-v2") ||
-		 of_device_is_compatible(np, "aspeed,ast2500-kcs-bmc-v2"))
-		kcs_bmc = aspeed_kcs_probe_of_v2(pdev);
-	else
+	ops = of_device_get_match_data(&pdev->dev);
+	if (!ops)
 		return -EINVAL;
 
-	if (IS_ERR(kcs_bmc))
-		return PTR_ERR(kcs_bmc);
+	channel = ops->get_channel(pdev);
+	if (channel < 0)
+		return channel;
 
-	kcs_bmc->io_inputb = aspeed_kcs_inb;
-	kcs_bmc->io_outputb = aspeed_kcs_outb;
+	nr_addrs = ops->get_io_address(pdev, addrs);
+	if (nr_addrs < 0)
+		return nr_addrs;
 
-	rc = aspeed_kcs_config_irq(kcs_bmc, pdev);
+	np = pdev->dev.of_node;
+	rc = of_property_read_u32_array(np, "aspeed,lpc-interrupts", upstream_irq, 2);
+	if (rc && rc != -EINVAL)
+		return -EINVAL;
+
+	have_upstream_irq = !rc;
+
+	priv = devm_kzalloc(&pdev->dev, sizeof(*priv), GFP_KERNEL);
+	if (!priv)
+		return -ENOMEM;
+
+	kcs_bmc = &priv->kcs_bmc;
+	kcs_bmc->dev = &pdev->dev;
+	kcs_bmc->channel = channel;
+	kcs_bmc->ioreg = ast_kcs_bmc_ioregs[channel - 1];
+	kcs_bmc->ops = &aspeed_kcs_ops;
+
+	priv->map = syscon_node_to_regmap(pdev->dev.parent->of_node);
+	if (IS_ERR(priv->map)) {
+		dev_err(&pdev->dev, "Couldn't get regmap\n");
+		return -ENODEV;
+	}
+
+	spin_lock_init(&priv->obe.lock);
+	priv->obe.remove = false;
+	timer_setup(&priv->obe.timer, aspeed_kcs_check_obe, 0);
+
+	rc = aspeed_kcs_set_address(kcs_bmc, addrs, nr_addrs);
 	if (rc)
 		return rc;
 
-	dev_set_drvdata(dev, kcs_bmc);
+	/* Host to BMC IRQ */
+	rc = aspeed_kcs_config_downstream_irq(kcs_bmc, pdev);
+	if (rc)
+		return rc;
+
+	/* BMC to Host IRQ */
+	if (have_upstream_irq) {
+		rc = aspeed_kcs_config_upstream_irq(priv, upstream_irq[0], upstream_irq[1]);
+		if (rc < 0)
+			return rc;
+	} else {
+		priv->upstream_irq.mode = aspeed_kcs_irq_none;
+	}
+
+	platform_set_drvdata(pdev, priv);
 
+	aspeed_kcs_irq_mask_update(kcs_bmc, (KCS_BMC_EVENT_TYPE_IBF | KCS_BMC_EVENT_TYPE_OBE), 0);
 	aspeed_kcs_enable_channel(kcs_bmc, true);
 
-	rc = misc_register(&kcs_bmc->miscdev);
+	rc = kcs_bmc_add_device(&priv->kcs_bmc);
 	if (rc) {
-		dev_err(dev, "Unable to register device\n");
+		dev_warn(&pdev->dev, "Failed to register channel %d: %d\n", kcs_bmc->channel, rc);
 		return rc;
 	}
 
-	dev_dbg(&pdev->dev,
-		"Probed KCS device %d (IDR=0x%x, ODR=0x%x, STR=0x%x)\n",
-		kcs_bmc->channel, kcs_bmc->ioreg.idr, kcs_bmc->ioreg.odr,
-		kcs_bmc->ioreg.str);
+	dev_info(&pdev->dev, "Initialised channel %d at 0x%x\n",
+			kcs_bmc->channel, addrs[0]);
 
 	return 0;
 }
 
 static int aspeed_kcs_remove(struct platform_device *pdev)
 {
-	struct kcs_bmc *kcs_bmc = dev_get_drvdata(&pdev->dev);
+	struct aspeed_kcs_bmc *priv = platform_get_drvdata(pdev);
+	struct kcs_bmc_device *kcs_bmc = &priv->kcs_bmc;
+
+	kcs_bmc_remove_device(kcs_bmc);
 
-	misc_deregister(&kcs_bmc->miscdev);
+	aspeed_kcs_enable_channel(kcs_bmc, false);
+	aspeed_kcs_irq_mask_update(kcs_bmc, (KCS_BMC_EVENT_TYPE_IBF | KCS_BMC_EVENT_TYPE_OBE), 0);
+
+	/* Make sure it's proper dead */
+	spin_lock_irq(&priv->obe.lock);
+	priv->obe.remove = true;
+	spin_unlock_irq(&priv->obe.lock);
+	del_timer_sync(&priv->obe.timer);
 
 	return 0;
 }
 
+static const struct aspeed_kcs_of_ops of_v1_ops = {
+	.get_channel = aspeed_kcs_of_v1_get_channel,
+	.get_io_address = aspeed_kcs_of_v1_get_io_address,
+};
+
+static const struct aspeed_kcs_of_ops of_v2_ops = {
+	.get_channel = aspeed_kcs_of_v2_get_channel,
+	.get_io_address = aspeed_kcs_of_v2_get_io_address,
+};
+
 static const struct of_device_id ast_kcs_bmc_match[] = {
-	{ .compatible = "aspeed,ast2400-kcs-bmc" },
-	{ .compatible = "aspeed,ast2500-kcs-bmc" },
-	{ .compatible = "aspeed,ast2400-kcs-bmc-v2" },
-	{ .compatible = "aspeed,ast2500-kcs-bmc-v2" },
+	{ .compatible = "aspeed,ast2400-kcs-bmc", .data = &of_v1_ops },
+	{ .compatible = "aspeed,ast2500-kcs-bmc", .data = &of_v1_ops },
+	{ .compatible = "aspeed,ast2400-kcs-bmc-v2", .data = &of_v2_ops },
+	{ .compatible = "aspeed,ast2500-kcs-bmc-v2", .data = &of_v2_ops },
 	{ }
 };
 MODULE_DEVICE_TABLE(of, ast_kcs_bmc_match);
@@ -421,4 +709,5 @@ module_platform_driver(ast_kcs_bmc_driver);
 
 MODULE_LICENSE("GPL v2");
 MODULE_AUTHOR("Haiyue Wang <haiyue.wang@linux.intel.com>");
+MODULE_AUTHOR("Andrew Jeffery <andrew@aj.id.au>");
 MODULE_DESCRIPTION("Aspeed device interface to the KCS BMC device");
diff --git a/drivers/char/ipmi/kcs_bmc_cdev_ipmi.c b/drivers/char/ipmi/kcs_bmc_cdev_ipmi.c
new file mode 100644
index 000000000000..486834a962c3
--- /dev/null
+++ b/drivers/char/ipmi/kcs_bmc_cdev_ipmi.c
@@ -0,0 +1,568 @@
+// SPDX-License-Identifier: GPL-2.0
+/*
+ * Copyright (c) 2015-2018, Intel Corporation.
+ */
+
+#define pr_fmt(fmt) "kcs-bmc: " fmt
+
+#include <linux/errno.h>
+#include <linux/io.h>
+#include <linux/ipmi_bmc.h>
+#include <linux/list.h>
+#include <linux/miscdevice.h>
+#include <linux/module.h>
+#include <linux/mutex.h>
+#include <linux/platform_device.h>
+#include <linux/poll.h>
+#include <linux/sched.h>
+#include <linux/slab.h>
+
+#include "kcs_bmc_client.h"
+
+/* Different phases of the KCS BMC module.
+ *  KCS_PHASE_IDLE:
+ *            BMC should not be expecting nor sending any data.
+ *  KCS_PHASE_WRITE_START:
+ *            BMC is receiving a WRITE_START command from system software.
+ *  KCS_PHASE_WRITE_DATA:
+ *            BMC is receiving a data byte from system software.
+ *  KCS_PHASE_WRITE_END_CMD:
+ *            BMC is waiting a last data byte from system software.
+ *  KCS_PHASE_WRITE_DONE:
+ *            BMC has received the whole request from system software.
+ *  KCS_PHASE_WAIT_READ:
+ *            BMC is waiting the response from the upper IPMI service.
+ *  KCS_PHASE_READ:
+ *            BMC is transferring the response to system software.
+ *  KCS_PHASE_ABORT_ERROR1:
+ *            BMC is waiting error status request from system software.
+ *  KCS_PHASE_ABORT_ERROR2:
+ *            BMC is waiting for idle status afer error from system software.
+ *  KCS_PHASE_ERROR:
+ *            BMC has detected a protocol violation at the interface level.
+ */
+enum kcs_ipmi_phases {
+	KCS_PHASE_IDLE,
+
+	KCS_PHASE_WRITE_START,
+	KCS_PHASE_WRITE_DATA,
+	KCS_PHASE_WRITE_END_CMD,
+	KCS_PHASE_WRITE_DONE,
+
+	KCS_PHASE_WAIT_READ,
+	KCS_PHASE_READ,
+
+	KCS_PHASE_ABORT_ERROR1,
+	KCS_PHASE_ABORT_ERROR2,
+	KCS_PHASE_ERROR
+};
+
+/* IPMI 2.0 - Table 9-4, KCS Interface Status Codes */
+enum kcs_ipmi_errors {
+	KCS_NO_ERROR                = 0x00,
+	KCS_ABORTED_BY_COMMAND      = 0x01,
+	KCS_ILLEGAL_CONTROL_CODE    = 0x02,
+	KCS_LENGTH_ERROR            = 0x06,
+	KCS_UNSPECIFIED_ERROR       = 0xFF
+};
+
+struct kcs_bmc_ipmi {
+	struct list_head entry;
+
+	struct kcs_bmc_client client;
+
+	spinlock_t lock;
+
+	enum kcs_ipmi_phases phase;
+	enum kcs_ipmi_errors error;
+
+	wait_queue_head_t queue;
+	bool data_in_avail;
+	int  data_in_idx;
+	u8  *data_in;
+
+	int  data_out_idx;
+	int  data_out_len;
+	u8  *data_out;
+
+	struct mutex mutex;
+	u8 *kbuffer;
+
+	struct miscdevice miscdev;
+};
+
+#define DEVICE_NAME "ipmi-kcs"
+
+#define KCS_MSG_BUFSIZ    1000
+
+#define KCS_ZERO_DATA     0
+
+/* IPMI 2.0 - Table 9-1, KCS Interface Status Register Bits */
+#define KCS_STATUS_STATE(state) (state << 6)
+#define KCS_STATUS_STATE_MASK   GENMASK(7, 6)
+#define KCS_STATUS_CMD_DAT      BIT(3)
+#define KCS_STATUS_SMS_ATN      BIT(2)
+#define KCS_STATUS_IBF          BIT(1)
+#define KCS_STATUS_OBF          BIT(0)
+
+/* IPMI 2.0 - Table 9-2, KCS Interface State Bits */
+enum kcs_states {
+	IDLE_STATE  = 0,
+	READ_STATE  = 1,
+	WRITE_STATE = 2,
+	ERROR_STATE = 3,
+};
+
+/* IPMI 2.0 - Table 9-3, KCS Interface Control Codes */
+#define KCS_CMD_GET_STATUS_ABORT  0x60
+#define KCS_CMD_WRITE_START       0x61
+#define KCS_CMD_WRITE_END         0x62
+#define KCS_CMD_READ_BYTE         0x68
+
+static inline void set_state(struct kcs_bmc_ipmi *priv, u8 state)
+{
+	kcs_bmc_update_status(priv->client.dev, KCS_STATUS_STATE_MASK, KCS_STATUS_STATE(state));
+}
+
+static void kcs_bmc_ipmi_force_abort(struct kcs_bmc_ipmi *priv)
+{
+	set_state(priv, ERROR_STATE);
+	kcs_bmc_read_data(priv->client.dev);
+	kcs_bmc_write_data(priv->client.dev, KCS_ZERO_DATA);
+
+	priv->phase = KCS_PHASE_ERROR;
+	priv->data_in_avail = false;
+	priv->data_in_idx = 0;
+}
+
+static void kcs_bmc_ipmi_handle_data(struct kcs_bmc_ipmi *priv)
+{
+	struct kcs_bmc_device *dev;
+	u8 data;
+
+	dev = priv->client.dev;
+
+	switch (priv->phase) {
+	case KCS_PHASE_WRITE_START:
+		priv->phase = KCS_PHASE_WRITE_DATA;
+		fallthrough;
+
+	case KCS_PHASE_WRITE_DATA:
+		if (priv->data_in_idx < KCS_MSG_BUFSIZ) {
+			set_state(priv, WRITE_STATE);
+			kcs_bmc_write_data(dev, KCS_ZERO_DATA);
+			priv->data_in[priv->data_in_idx++] = kcs_bmc_read_data(dev);
+		} else {
+			kcs_bmc_ipmi_force_abort(priv);
+			priv->error = KCS_LENGTH_ERROR;
+		}
+		break;
+
+	case KCS_PHASE_WRITE_END_CMD:
+		if (priv->data_in_idx < KCS_MSG_BUFSIZ) {
+			set_state(priv, READ_STATE);
+			priv->data_in[priv->data_in_idx++] = kcs_bmc_read_data(dev);
+			priv->phase = KCS_PHASE_WRITE_DONE;
+			priv->data_in_avail = true;
+			wake_up_interruptible(&priv->queue);
+		} else {
+			kcs_bmc_ipmi_force_abort(priv);
+			priv->error = KCS_LENGTH_ERROR;
+		}
+		break;
+
+	case KCS_PHASE_READ:
+		if (priv->data_out_idx == priv->data_out_len)
+			set_state(priv, IDLE_STATE);
+
+		data = kcs_bmc_read_data(dev);
+		if (data != KCS_CMD_READ_BYTE) {
+			set_state(priv, ERROR_STATE);
+			kcs_bmc_write_data(dev, KCS_ZERO_DATA);
+			break;
+		}
+
+		if (priv->data_out_idx == priv->data_out_len) {
+			kcs_bmc_write_data(dev, KCS_ZERO_DATA);
+			priv->phase = KCS_PHASE_IDLE;
+			break;
+		}
+
+		kcs_bmc_write_data(dev, priv->data_out[priv->data_out_idx++]);
+		break;
+
+	case KCS_PHASE_ABORT_ERROR1:
+		set_state(priv, READ_STATE);
+		kcs_bmc_read_data(dev);
+		kcs_bmc_write_data(dev, priv->error);
+		priv->phase = KCS_PHASE_ABORT_ERROR2;
+		break;
+
+	case KCS_PHASE_ABORT_ERROR2:
+		set_state(priv, IDLE_STATE);
+		kcs_bmc_read_data(dev);
+		kcs_bmc_write_data(dev, KCS_ZERO_DATA);
+		priv->phase = KCS_PHASE_IDLE;
+		break;
+
+	default:
+		kcs_bmc_ipmi_force_abort(priv);
+		break;
+	}
+}
+
+static void kcs_bmc_ipmi_handle_cmd(struct kcs_bmc_ipmi *priv)
+{
+	u8 cmd;
+
+	set_state(priv, WRITE_STATE);
+	kcs_bmc_write_data(priv->client.dev, KCS_ZERO_DATA);
+
+	cmd = kcs_bmc_read_data(priv->client.dev);
+	switch (cmd) {
+	case KCS_CMD_WRITE_START:
+		priv->phase = KCS_PHASE_WRITE_START;
+		priv->error = KCS_NO_ERROR;
+		priv->data_in_avail = false;
+		priv->data_in_idx = 0;
+		break;
+
+	case KCS_CMD_WRITE_END:
+		if (priv->phase != KCS_PHASE_WRITE_DATA) {
+			kcs_bmc_ipmi_force_abort(priv);
+			break;
+		}
+
+		priv->phase = KCS_PHASE_WRITE_END_CMD;
+		break;
+
+	case KCS_CMD_GET_STATUS_ABORT:
+		if (priv->error == KCS_NO_ERROR)
+			priv->error = KCS_ABORTED_BY_COMMAND;
+
+		priv->phase = KCS_PHASE_ABORT_ERROR1;
+		priv->data_in_avail = false;
+		priv->data_in_idx = 0;
+		break;
+
+	default:
+		kcs_bmc_ipmi_force_abort(priv);
+		priv->error = KCS_ILLEGAL_CONTROL_CODE;
+		break;
+	}
+}
+
+static inline struct kcs_bmc_ipmi *client_to_kcs_bmc_ipmi(struct kcs_bmc_client *client)
+{
+	return container_of(client, struct kcs_bmc_ipmi, client);
+}
+
+static irqreturn_t kcs_bmc_ipmi_event(struct kcs_bmc_client *client)
+{
+	struct kcs_bmc_ipmi *priv;
+	u8 status;
+	int ret;
+
+	priv = client_to_kcs_bmc_ipmi(client);
+	if (!priv)
+		return IRQ_NONE;
+
+	spin_lock(&priv->lock);
+
+	status = kcs_bmc_read_status(client->dev);
+	if (status & KCS_STATUS_IBF) {
+		if (status & KCS_STATUS_CMD_DAT)
+			kcs_bmc_ipmi_handle_cmd(priv);
+		else
+			kcs_bmc_ipmi_handle_data(priv);
+
+		ret = IRQ_HANDLED;
+	} else {
+		ret = IRQ_NONE;
+	}
+
+	spin_unlock(&priv->lock);
+
+	return ret;
+}
+
+static const struct kcs_bmc_client_ops kcs_bmc_ipmi_client_ops = {
+	.event = kcs_bmc_ipmi_event,
+};
+
+static inline struct kcs_bmc_ipmi *to_kcs_bmc(struct file *filp)
+{
+	return container_of(filp->private_data, struct kcs_bmc_ipmi, miscdev);
+}
+
+static int kcs_bmc_ipmi_open(struct inode *inode, struct file *filp)
+{
+	struct kcs_bmc_ipmi *priv = to_kcs_bmc(filp);
+
+	return kcs_bmc_enable_device(priv->client.dev, &priv->client);
+}
+
+static __poll_t kcs_bmc_ipmi_poll(struct file *filp, poll_table *wait)
+{
+	struct kcs_bmc_ipmi *priv = to_kcs_bmc(filp);
+	__poll_t mask = 0;
+
+	poll_wait(filp, &priv->queue, wait);
+
+	spin_lock_irq(&priv->lock);
+	if (priv->data_in_avail)
+		mask |= EPOLLIN;
+	spin_unlock_irq(&priv->lock);
+
+	return mask;
+}
+
+static ssize_t kcs_bmc_ipmi_read(struct file *filp, char __user *buf,
+			    size_t count, loff_t *ppos)
+{
+	struct kcs_bmc_ipmi *priv = to_kcs_bmc(filp);
+	bool data_avail;
+	size_t data_len;
+	ssize_t ret;
+
+	if (!(filp->f_flags & O_NONBLOCK))
+		wait_event_interruptible(priv->queue,
+					 priv->data_in_avail);
+
+	mutex_lock(&priv->mutex);
+
+	spin_lock_irq(&priv->lock);
+	data_avail = priv->data_in_avail;
+	if (data_avail) {
+		data_len = priv->data_in_idx;
+		memcpy(priv->kbuffer, priv->data_in, data_len);
+	}
+	spin_unlock_irq(&priv->lock);
+
+	if (!data_avail) {
+		ret = -EAGAIN;
+		goto out_unlock;
+	}
+
+	if (count < data_len) {
+		pr_err("channel=%u with too large data : %zu\n",
+			priv->client.dev->channel, data_len);
+
+		spin_lock_irq(&priv->lock);
+		kcs_bmc_ipmi_force_abort(priv);
+		spin_unlock_irq(&priv->lock);
+
+		ret = -EOVERFLOW;
+		goto out_unlock;
+	}
+
+	if (copy_to_user(buf, priv->kbuffer, data_len)) {
+		ret = -EFAULT;
+		goto out_unlock;
+	}
+
+	ret = data_len;
+
+	spin_lock_irq(&priv->lock);
+	if (priv->phase == KCS_PHASE_WRITE_DONE) {
+		priv->phase = KCS_PHASE_WAIT_READ;
+		priv->data_in_avail = false;
+		priv->data_in_idx = 0;
+	} else {
+		ret = -EAGAIN;
+	}
+	spin_unlock_irq(&priv->lock);
+
+out_unlock:
+	mutex_unlock(&priv->mutex);
+
+	return ret;
+}
+
+static ssize_t kcs_bmc_ipmi_write(struct file *filp, const char __user *buf,
+			     size_t count, loff_t *ppos)
+{
+	struct kcs_bmc_ipmi *priv = to_kcs_bmc(filp);
+	ssize_t ret;
+
+	/* a minimum response size '3' : netfn + cmd + ccode */
+	if (count < 3 || count > KCS_MSG_BUFSIZ)
+		return -EINVAL;
+
+	mutex_lock(&priv->mutex);
+
+	if (copy_from_user(priv->kbuffer, buf, count)) {
+		ret = -EFAULT;
+		goto out_unlock;
+	}
+
+	spin_lock_irq(&priv->lock);
+	if (priv->phase == KCS_PHASE_WAIT_READ) {
+		priv->phase = KCS_PHASE_READ;
+		priv->data_out_idx = 1;
+		priv->data_out_len = count;
+		memcpy(priv->data_out, priv->kbuffer, count);
+		kcs_bmc_write_data(priv->client.dev, priv->data_out[0]);
+		ret = count;
+	} else {
+		ret = -EINVAL;
+	}
+	spin_unlock_irq(&priv->lock);
+
+out_unlock:
+	mutex_unlock(&priv->mutex);
+
+	return ret;
+}
+
+static long kcs_bmc_ipmi_ioctl(struct file *filp, unsigned int cmd,
+			  unsigned long arg)
+{
+	struct kcs_bmc_ipmi *priv = to_kcs_bmc(filp);
+	long ret = 0;
+
+	spin_lock_irq(&priv->lock);
+
+	switch (cmd) {
+	case IPMI_BMC_IOCTL_SET_SMS_ATN:
+		kcs_bmc_update_status(priv->client.dev, KCS_STATUS_SMS_ATN, KCS_STATUS_SMS_ATN);
+		break;
+
+	case IPMI_BMC_IOCTL_CLEAR_SMS_ATN:
+		kcs_bmc_update_status(priv->client.dev, KCS_STATUS_SMS_ATN, 0);
+		break;
+
+	case IPMI_BMC_IOCTL_FORCE_ABORT:
+		kcs_bmc_ipmi_force_abort(priv);
+		break;
+
+	default:
+		ret = -EINVAL;
+		break;
+	}
+
+	spin_unlock_irq(&priv->lock);
+
+	return ret;
+}
+
+static int kcs_bmc_ipmi_release(struct inode *inode, struct file *filp)
+{
+	struct kcs_bmc_ipmi *priv = to_kcs_bmc(filp);
+
+	kcs_bmc_ipmi_force_abort(priv);
+	kcs_bmc_disable_device(priv->client.dev, &priv->client);
+
+	return 0;
+}
+
+static const struct file_operations kcs_bmc_ipmi_fops = {
+	.owner          = THIS_MODULE,
+	.open           = kcs_bmc_ipmi_open,
+	.read           = kcs_bmc_ipmi_read,
+	.write          = kcs_bmc_ipmi_write,
+	.release        = kcs_bmc_ipmi_release,
+	.poll           = kcs_bmc_ipmi_poll,
+	.unlocked_ioctl = kcs_bmc_ipmi_ioctl,
+};
+
+static DEFINE_SPINLOCK(kcs_bmc_ipmi_instances_lock);
+static LIST_HEAD(kcs_bmc_ipmi_instances);
+
+static int kcs_bmc_ipmi_add_device(struct kcs_bmc_device *kcs_bmc)
+{
+	struct kcs_bmc_ipmi *priv;
+	int rc;
+
+	priv = devm_kzalloc(kcs_bmc->dev, sizeof(*priv), GFP_KERNEL);
+	if (!priv)
+		return -ENOMEM;
+
+	spin_lock_init(&priv->lock);
+	mutex_init(&priv->mutex);
+
+	init_waitqueue_head(&priv->queue);
+
+	priv->client.dev = kcs_bmc;
+	priv->client.ops = &kcs_bmc_ipmi_client_ops;
+	priv->data_in = devm_kmalloc(kcs_bmc->dev, KCS_MSG_BUFSIZ, GFP_KERNEL);
+	priv->data_out = devm_kmalloc(kcs_bmc->dev, KCS_MSG_BUFSIZ, GFP_KERNEL);
+	priv->kbuffer = devm_kmalloc(kcs_bmc->dev, KCS_MSG_BUFSIZ, GFP_KERNEL);
+
+	priv->miscdev.minor = MISC_DYNAMIC_MINOR;
+	priv->miscdev.name = devm_kasprintf(kcs_bmc->dev, GFP_KERNEL, "%s%u", DEVICE_NAME,
+					   kcs_bmc->channel);
+	if (!priv->data_in || !priv->data_out || !priv->kbuffer || !priv->miscdev.name)
+		return -EINVAL;
+
+	priv->miscdev.fops = &kcs_bmc_ipmi_fops;
+
+	rc = misc_register(&priv->miscdev);
+	if (rc) {
+		dev_err(kcs_bmc->dev, "Unable to register device: %d\n", rc);
+		return rc;
+	}
+
+	spin_lock_irq(&kcs_bmc_ipmi_instances_lock);
+	list_add(&priv->entry, &kcs_bmc_ipmi_instances);
+	spin_unlock_irq(&kcs_bmc_ipmi_instances_lock);
+
+	dev_info(kcs_bmc->dev, "Initialised IPMI client for channel %d", kcs_bmc->channel);
+
+	return 0;
+}
+
+static int kcs_bmc_ipmi_remove_device(struct kcs_bmc_device *kcs_bmc)
+{
+	struct kcs_bmc_ipmi *priv = NULL, *pos;
+
+	spin_lock_irq(&kcs_bmc_ipmi_instances_lock);
+	list_for_each_entry(pos, &kcs_bmc_ipmi_instances, entry) {
+		if (pos->client.dev == kcs_bmc) {
+			priv = pos;
+			list_del(&pos->entry);
+			break;
+		}
+	}
+	spin_unlock_irq(&kcs_bmc_ipmi_instances_lock);
+
+	if (!priv)
+		return -ENODEV;
+
+	misc_deregister(&priv->miscdev);
+	kcs_bmc_disable_device(priv->client.dev, &priv->client);
+	devm_kfree(kcs_bmc->dev, priv->kbuffer);
+	devm_kfree(kcs_bmc->dev, priv->data_out);
+	devm_kfree(kcs_bmc->dev, priv->data_in);
+	devm_kfree(kcs_bmc->dev, priv);
+
+	return 0;
+}
+
+static const struct kcs_bmc_driver_ops kcs_bmc_ipmi_driver_ops = {
+	.add_device = kcs_bmc_ipmi_add_device,
+	.remove_device = kcs_bmc_ipmi_remove_device,
+};
+
+static struct kcs_bmc_driver kcs_bmc_ipmi_driver = {
+	.ops = &kcs_bmc_ipmi_driver_ops,
+};
+
+static int kcs_bmc_ipmi_init(void)
+{
+	kcs_bmc_register_driver(&kcs_bmc_ipmi_driver);
+
+	return 0;
+}
+module_init(kcs_bmc_ipmi_init);
+
+static void kcs_bmc_ipmi_exit(void)
+{
+	kcs_bmc_unregister_driver(&kcs_bmc_ipmi_driver);
+}
+module_exit(kcs_bmc_ipmi_exit);
+
+MODULE_LICENSE("GPL v2");
+MODULE_AUTHOR("Haiyue Wang <haiyue.wang@linux.intel.com>");
+MODULE_AUTHOR("Andrew Jeffery <andrew@aj.id.au>");
+MODULE_DESCRIPTION("KCS BMC to handle the IPMI request from system software");
diff --git a/drivers/char/ipmi/kcs_bmc_client.h b/drivers/char/ipmi/kcs_bmc_client.h
new file mode 100644
index 000000000000..6fdcde0a7169
--- /dev/null
+++ b/drivers/char/ipmi/kcs_bmc_client.h
@@ -0,0 +1,45 @@
+/* SPDX-License-Identifier: GPL-2.0 */
+/* Copyright (c) 2021, IBM Corp. */
+
+#ifndef __KCS_BMC_CONSUMER_H__
+#define __KCS_BMC_CONSUMER_H__
+
+#include <linux/irqreturn.h>
+
+#include "kcs_bmc.h"
+
+struct kcs_bmc_driver_ops {
+	int (*add_device)(struct kcs_bmc_device *kcs_bmc);
+	int (*remove_device)(struct kcs_bmc_device *kcs_bmc);
+};
+
+struct kcs_bmc_driver {
+	struct list_head entry;
+
+	const struct kcs_bmc_driver_ops *ops;
+};
+
+struct kcs_bmc_client_ops {
+	irqreturn_t (*event)(struct kcs_bmc_client *client);
+};
+
+struct kcs_bmc_client {
+	const struct kcs_bmc_client_ops *ops;
+
+	struct kcs_bmc_device *dev;
+};
+
+void kcs_bmc_register_driver(struct kcs_bmc_driver *drv);
+void kcs_bmc_unregister_driver(struct kcs_bmc_driver *drv);
+
+int kcs_bmc_enable_device(struct kcs_bmc_device *kcs_bmc, struct kcs_bmc_client *client);
+void kcs_bmc_disable_device(struct kcs_bmc_device *kcs_bmc, struct kcs_bmc_client *client);
+
+void kcs_bmc_update_event_mask(struct kcs_bmc_device *kcs_bmc, u8 mask, u8 events);
+
+u8 kcs_bmc_read_data(struct kcs_bmc_device *kcs_bmc);
+void kcs_bmc_write_data(struct kcs_bmc_device *kcs_bmc, u8 data);
+u8 kcs_bmc_read_status(struct kcs_bmc_device *kcs_bmc);
+void kcs_bmc_write_status(struct kcs_bmc_device *kcs_bmc, u8 data);
+void kcs_bmc_update_status(struct kcs_bmc_device *kcs_bmc, u8 mask, u8 val);
+#endif
diff --git a/drivers/char/ipmi/kcs_bmc_device.h b/drivers/char/ipmi/kcs_bmc_device.h
new file mode 100644
index 000000000000..17c572f25c54
--- /dev/null
+++ b/drivers/char/ipmi/kcs_bmc_device.h
@@ -0,0 +1,22 @@
+/* SPDX-License-Identifier: GPL-2.0 */
+/* Copyright (c) 2021, IBM Corp. */
+
+#ifndef __KCS_BMC_DEVICE_H__
+#define __KCS_BMC_DEVICE_H__
+
+#include <linux/irqreturn.h>
+
+#include "kcs_bmc.h"
+
+struct kcs_bmc_device_ops {
+	void (*irq_mask_update)(struct kcs_bmc_device *kcs_bmc, u8 mask, u8 enable);
+	u8 (*io_inputb)(struct kcs_bmc_device *kcs_bmc, u32 reg);
+	void (*io_outputb)(struct kcs_bmc_device *kcs_bmc, u32 reg, u8 b);
+	void (*io_updateb)(struct kcs_bmc_device *kcs_bmc, u32 reg, u8 mask, u8 b);
+};
+
+irqreturn_t kcs_bmc_handle_event(struct kcs_bmc_device *kcs_bmc);
+int kcs_bmc_add_device(struct kcs_bmc_device *kcs_bmc);
+void kcs_bmc_remove_device(struct kcs_bmc_device *kcs_bmc);
+
+#endif
diff --git a/drivers/char/ipmi/kcs_bmc_npcm7xx.c b/drivers/char/ipmi/kcs_bmc_npcm7xx.c
index 722f7391fe1f..7961fec56476 100644
--- a/drivers/char/ipmi/kcs_bmc_npcm7xx.c
+++ b/drivers/char/ipmi/kcs_bmc_npcm7xx.c
@@ -17,7 +17,7 @@
 #include <linux/regmap.h>
 #include <linux/slab.h>
 
-#include "kcs_bmc.h"
+#include "kcs_bmc_device.h"
 
 #define DEVICE_NAME	"npcm-kcs-bmc"
 #define KCS_CHANNEL_MAX	3
@@ -38,6 +38,7 @@
 #define KCS2CTL		0x2A
 #define KCS3CTL		0x3C
 #define    KCS_CTL_IBFIE	BIT(0)
+#define    KCS_CTL_OBEIE	BIT(1)
 
 #define KCS1IE		0x1C
 #define KCS2IE		0x2E
@@ -65,6 +66,8 @@ struct npcm7xx_kcs_reg {
 };
 
 struct npcm7xx_kcs_bmc {
+	struct kcs_bmc_device kcs_bmc;
+
 	struct regmap *map;
 
 	const struct npcm7xx_kcs_reg *reg;
@@ -76,9 +79,14 @@ static const struct npcm7xx_kcs_reg npcm7xx_kcs_reg_tbl[KCS_CHANNEL_MAX] = {
 	{ .sts = KCS3ST, .dob = KCS3DO, .dib = KCS3DI, .ctl = KCS3CTL, .ie = KCS3IE },
 };
 
-static u8 npcm7xx_kcs_inb(struct kcs_bmc *kcs_bmc, u32 reg)
+static inline struct npcm7xx_kcs_bmc *to_npcm7xx_kcs_bmc(struct kcs_bmc_device *kcs_bmc)
 {
-	struct npcm7xx_kcs_bmc *priv = kcs_bmc_priv(kcs_bmc);
+	return container_of(kcs_bmc, struct npcm7xx_kcs_bmc, kcs_bmc);
+}
+
+static u8 npcm7xx_kcs_inb(struct kcs_bmc_device *kcs_bmc, u32 reg)
+{
+	struct npcm7xx_kcs_bmc *priv = to_npcm7xx_kcs_bmc(kcs_bmc);
 	u32 val = 0;
 	int rc;
 
@@ -88,37 +96,53 @@ static u8 npcm7xx_kcs_inb(struct kcs_bmc *kcs_bmc, u32 reg)
 	return rc == 0 ? (u8)val : 0;
 }
 
-static void npcm7xx_kcs_outb(struct kcs_bmc *kcs_bmc, u32 reg, u8 data)
+static void npcm7xx_kcs_outb(struct kcs_bmc_device *kcs_bmc, u32 reg, u8 data)
 {
-	struct npcm7xx_kcs_bmc *priv = kcs_bmc_priv(kcs_bmc);
+	struct npcm7xx_kcs_bmc *priv = to_npcm7xx_kcs_bmc(kcs_bmc);
 	int rc;
 
 	rc = regmap_write(priv->map, reg, data);
 	WARN(rc != 0, "regmap_write() failed: %d\n", rc);
 }
 
-static void npcm7xx_kcs_enable_channel(struct kcs_bmc *kcs_bmc, bool enable)
+static void npcm7xx_kcs_updateb(struct kcs_bmc_device *kcs_bmc, u32 reg, u8 mask, u8 data)
 {
-	struct npcm7xx_kcs_bmc *priv = kcs_bmc_priv(kcs_bmc);
+	struct npcm7xx_kcs_bmc *priv = to_npcm7xx_kcs_bmc(kcs_bmc);
+	int rc;
 
-	regmap_update_bits(priv->map, priv->reg->ctl, KCS_CTL_IBFIE,
-			   enable ? KCS_CTL_IBFIE : 0);
+	rc = regmap_update_bits(priv->map, reg, mask, data);
+	WARN(rc != 0, "regmap_update_bits() failed: %d\n", rc);
+}
+
+static void npcm7xx_kcs_enable_channel(struct kcs_bmc_device *kcs_bmc, bool enable)
+{
+	struct npcm7xx_kcs_bmc *priv = to_npcm7xx_kcs_bmc(kcs_bmc);
 
 	regmap_update_bits(priv->map, priv->reg->ie, KCS_IE_IRQE | KCS_IE_HIRQE,
 			   enable ? KCS_IE_IRQE | KCS_IE_HIRQE : 0);
 }
 
-static irqreturn_t npcm7xx_kcs_irq(int irq, void *arg)
+static void npcm7xx_kcs_irq_mask_update(struct kcs_bmc_device *kcs_bmc, u8 mask, u8 state)
 {
-	struct kcs_bmc *kcs_bmc = arg;
+	struct npcm7xx_kcs_bmc *priv = to_npcm7xx_kcs_bmc(kcs_bmc);
+
+	if (mask & KCS_BMC_EVENT_TYPE_OBE)
+		regmap_update_bits(priv->map, priv->reg->ctl, KCS_CTL_OBEIE,
+				   !!(state & KCS_BMC_EVENT_TYPE_OBE) * KCS_CTL_OBEIE);
 
-	if (!kcs_bmc_handle_event(kcs_bmc))
-		return IRQ_HANDLED;
+	if (mask & KCS_BMC_EVENT_TYPE_IBF)
+		regmap_update_bits(priv->map, priv->reg->ctl, KCS_CTL_IBFIE,
+				   !!(state & KCS_BMC_EVENT_TYPE_IBF) * KCS_CTL_IBFIE);
+}
 
-	return IRQ_NONE;
+static irqreturn_t npcm7xx_kcs_irq(int irq, void *arg)
+{
+	struct kcs_bmc_device *kcs_bmc = arg;
+
+	return kcs_bmc_handle_event(kcs_bmc);
 }
 
-static int npcm7xx_kcs_config_irq(struct kcs_bmc *kcs_bmc,
+static int npcm7xx_kcs_config_irq(struct kcs_bmc_device *kcs_bmc,
 				  struct platform_device *pdev)
 {
 	struct device *dev = &pdev->dev;
@@ -132,11 +156,18 @@ static int npcm7xx_kcs_config_irq(struct kcs_bmc *kcs_bmc,
 				dev_name(dev), kcs_bmc);
 }
 
+static const struct kcs_bmc_device_ops npcm7xx_kcs_ops = {
+	.irq_mask_update = npcm7xx_kcs_irq_mask_update,
+	.io_inputb = npcm7xx_kcs_inb,
+	.io_outputb = npcm7xx_kcs_outb,
+	.io_updateb = npcm7xx_kcs_updateb,
+};
+
 static int npcm7xx_kcs_probe(struct platform_device *pdev)
 {
 	struct device *dev = &pdev->dev;
 	struct npcm7xx_kcs_bmc *priv;
-	struct kcs_bmc *kcs_bmc;
+	struct kcs_bmc_device *kcs_bmc;
 	u32 chan;
 	int rc;
 
@@ -146,11 +177,10 @@ static int npcm7xx_kcs_probe(struct platform_device *pdev)
 		return -ENODEV;
 	}
 
-	kcs_bmc = kcs_bmc_alloc(dev, sizeof(*priv), chan);
-	if (!kcs_bmc)
+	priv = devm_kzalloc(&pdev->dev, sizeof(*priv), GFP_KERNEL);
+	if (!priv)
 		return -ENOMEM;
 
-	priv = kcs_bmc_priv(kcs_bmc);
 	priv->map = syscon_node_to_regmap(dev->parent->of_node);
 	if (IS_ERR(priv->map)) {
 		dev_err(dev, "Couldn't get regmap\n");
@@ -158,22 +188,26 @@ static int npcm7xx_kcs_probe(struct platform_device *pdev)
 	}
 	priv->reg = &npcm7xx_kcs_reg_tbl[chan - 1];
 
+	kcs_bmc = &priv->kcs_bmc;
+	kcs_bmc->dev = &pdev->dev;
+	kcs_bmc->channel = chan;
 	kcs_bmc->ioreg.idr = priv->reg->dib;
 	kcs_bmc->ioreg.odr = priv->reg->dob;
 	kcs_bmc->ioreg.str = priv->reg->sts;
-	kcs_bmc->io_inputb = npcm7xx_kcs_inb;
-	kcs_bmc->io_outputb = npcm7xx_kcs_outb;
+	kcs_bmc->ops = &npcm7xx_kcs_ops;
 
-	dev_set_drvdata(dev, kcs_bmc);
+	platform_set_drvdata(pdev, priv);
 
-	npcm7xx_kcs_enable_channel(kcs_bmc, true);
 	rc = npcm7xx_kcs_config_irq(kcs_bmc, pdev);
 	if (rc)
 		return rc;
 
-	rc = misc_register(&kcs_bmc->miscdev);
+	npcm7xx_kcs_irq_mask_update(kcs_bmc, (KCS_BMC_EVENT_TYPE_IBF | KCS_BMC_EVENT_TYPE_OBE), 0);
+	npcm7xx_kcs_enable_channel(kcs_bmc, true);
+
+	rc = kcs_bmc_add_device(kcs_bmc);
 	if (rc) {
-		dev_err(dev, "Unable to register device\n");
+		dev_warn(&pdev->dev, "Failed to register channel %d: %d\n", kcs_bmc->channel, rc);
 		return rc;
 	}
 
@@ -186,9 +220,13 @@ static int npcm7xx_kcs_probe(struct platform_device *pdev)
 
 static int npcm7xx_kcs_remove(struct platform_device *pdev)
 {
-	struct kcs_bmc *kcs_bmc = dev_get_drvdata(&pdev->dev);
+	struct npcm7xx_kcs_bmc *priv = platform_get_drvdata(pdev);
+	struct kcs_bmc_device *kcs_bmc = &priv->kcs_bmc;
+
+	kcs_bmc_remove_device(kcs_bmc);
 
-	misc_deregister(&kcs_bmc->miscdev);
+	npcm7xx_kcs_enable_channel(kcs_bmc, false);
+	npcm7xx_kcs_irq_mask_update(kcs_bmc, (KCS_BMC_EVENT_TYPE_IBF | KCS_BMC_EVENT_TYPE_OBE), 0);
 
 	return 0;
 }
diff --git a/drivers/char/ipmi/kcs_bmc_serio.c b/drivers/char/ipmi/kcs_bmc_serio.c
new file mode 100644
index 000000000000..7948cabde50b
--- /dev/null
+++ b/drivers/char/ipmi/kcs_bmc_serio.c
@@ -0,0 +1,157 @@
+// SPDX-License-Identifier: GPL-2.0-or-later
+/* Copyright (c) 2021 IBM Corp. */
+
+#include <linux/delay.h>
+#include <linux/device.h>
+#include <linux/errno.h>
+#include <linux/list.h>
+#include <linux/module.h>
+#include <linux/sched/signal.h>
+#include <linux/serio.h>
+#include <linux/slab.h>
+
+#include "kcs_bmc_client.h"
+
+struct kcs_bmc_serio {
+	struct list_head entry;
+
+	struct kcs_bmc_client client;
+	struct serio *port;
+
+	spinlock_t lock;
+};
+
+static inline struct kcs_bmc_serio *client_to_kcs_bmc_serio(struct kcs_bmc_client *client)
+{
+	return container_of(client, struct kcs_bmc_serio, client);
+}
+
+static irqreturn_t kcs_bmc_serio_event(struct kcs_bmc_client *client)
+{
+	struct kcs_bmc_serio *priv;
+	u8 handled = IRQ_NONE;
+	u8 status;
+
+	priv = client_to_kcs_bmc_serio(client);
+
+	spin_lock(&priv->lock);
+
+	status = kcs_bmc_read_status(client->dev);
+
+	if (status & KCS_BMC_STR_IBF)
+		handled = serio_interrupt(priv->port, kcs_bmc_read_data(client->dev), 0);
+
+	spin_unlock(&priv->lock);
+
+	return handled;
+}
+
+static const struct kcs_bmc_client_ops kcs_bmc_serio_client_ops = {
+	.event = kcs_bmc_serio_event,
+};
+
+static int kcs_bmc_serio_open(struct serio *port)
+{
+	struct kcs_bmc_serio *priv = port->port_data;
+
+	return kcs_bmc_enable_device(priv->client.dev, &priv->client);
+}
+
+static void kcs_bmc_serio_close(struct serio *port)
+{
+	struct kcs_bmc_serio *priv = port->port_data;
+
+	kcs_bmc_disable_device(priv->client.dev, &priv->client);
+}
+
+static DEFINE_SPINLOCK(kcs_bmc_serio_instances_lock);
+static LIST_HEAD(kcs_bmc_serio_instances);
+
+static int kcs_bmc_serio_add_device(struct kcs_bmc_device *kcs_bmc)
+{
+	struct kcs_bmc_serio *priv;
+	struct serio *port;
+
+	priv = devm_kzalloc(kcs_bmc->dev, sizeof(*priv), GFP_KERNEL);
+
+	/* Use kzalloc() as the allocation is cleaned up with kfree() via serio_unregister_port() */
+	port = kzalloc(sizeof(*port), GFP_KERNEL);
+	if (!(priv && port))
+		return -ENOMEM;
+
+	port->id.type = SERIO_8042;
+	port->open = kcs_bmc_serio_open;
+	port->close = kcs_bmc_serio_close;
+	port->port_data = priv;
+	port->dev.parent = kcs_bmc->dev;
+
+	spin_lock_init(&priv->lock);
+	priv->port = port;
+	priv->client.dev = kcs_bmc;
+	priv->client.ops = &kcs_bmc_serio_client_ops;
+
+	spin_lock_irq(&kcs_bmc_serio_instances_lock);
+	list_add(&priv->entry, &kcs_bmc_serio_instances);
+	spin_unlock_irq(&kcs_bmc_serio_instances_lock);
+
+	serio_register_port(port);
+
+	dev_info(kcs_bmc->dev, "Initialised serio client for channel %d", kcs_bmc->channel);
+
+	return 0;
+}
+
+static int kcs_bmc_serio_remove_device(struct kcs_bmc_device *kcs_bmc)
+{
+	struct kcs_bmc_serio *priv = NULL, *pos;
+
+	spin_lock_irq(&kcs_bmc_serio_instances_lock);
+	list_for_each_entry(pos, &kcs_bmc_serio_instances, entry) {
+		if (pos->client.dev == kcs_bmc) {
+			priv = pos;
+			list_del(&pos->entry);
+			break;
+		}
+	}
+	spin_unlock_irq(&kcs_bmc_serio_instances_lock);
+
+	if (!priv)
+		return -ENODEV;
+
+	/* kfree()s priv->port via put_device() */
+	serio_unregister_port(priv->port);
+
+	/* Ensure the IBF IRQ is disabled if we were the active client */
+	kcs_bmc_disable_device(kcs_bmc, &priv->client);
+
+	devm_kfree(priv->client.dev->dev, priv);
+
+	return 0;
+}
+
+static const struct kcs_bmc_driver_ops kcs_bmc_serio_driver_ops = {
+	.add_device = kcs_bmc_serio_add_device,
+	.remove_device = kcs_bmc_serio_remove_device,
+};
+
+static struct kcs_bmc_driver kcs_bmc_serio_driver = {
+	.ops = &kcs_bmc_serio_driver_ops,
+};
+
+static int kcs_bmc_serio_init(void)
+{
+	kcs_bmc_register_driver(&kcs_bmc_serio_driver);
+
+	return 0;
+}
+module_init(kcs_bmc_serio_init);
+
+static void kcs_bmc_serio_exit(void)
+{
+	kcs_bmc_unregister_driver(&kcs_bmc_serio_driver);
+}
+module_exit(kcs_bmc_serio_exit);
+
+MODULE_LICENSE("GPL v2");
+MODULE_AUTHOR("Andrew Jeffery <andrew@aj.id.au>");
+MODULE_DESCRIPTION("Adapter driver for serio access to BMC KCS devices");