1 files changed, 290 insertions, 0 deletions
diff --git a/drivers/i2c/i2c-slave-testunit.c b/drivers/i2c/i2c-slave-testunit.c
new file mode 100644
index 000000000000..6de4307050dd
--- /dev/null
+++ b/drivers/i2c/i2c-slave-testunit.c
@@ -0,0 +1,290 @@
+// SPDX-License-Identifier: GPL-2.0-only
+/*
+ * I2C slave mode testunit
+ *
+ * Copyright (C) 2020 by Wolfram Sang, Sang Engineering <wsa@sang-engineering.com>
+ * Copyright (C) 2020 by Renesas Electronics Corporation
+ */
+
+#include <generated/utsrelease.h>
+#include <linux/bitops.h>
+#include <linux/completion.h>
+#include <linux/gpio/consumer.h>
+#include <linux/i2c.h>
+#include <linux/init.h>
+#include <linux/module.h>
+#include <linux/of.h>
+#include <linux/slab.h>
+#include <linux/workqueue.h> /* FIXME: is system_long_wq the best choice? */
+
+#define TU_VERSION_MAX_LENGTH 128
+
+enum testunit_cmds {
+	TU_CMD_READ_BYTES = 1,	/* save 0 for ABORT, RESET or similar */
+	TU_CMD_SMBUS_HOST_NOTIFY,
+	TU_CMD_SMBUS_BLOCK_PROC_CALL,
+	TU_CMD_GET_VERSION_WITH_REP_START,
+	TU_CMD_SMBUS_ALERT_REQUEST,
+	TU_NUM_CMDS
+};
+
+enum testunit_regs {
+	TU_REG_CMD,
+	TU_REG_DATAL,
+	TU_REG_DATAH,
+	TU_REG_DELAY,
+	TU_NUM_REGS
+};
+
+enum testunit_flags {
+	TU_FLAG_IN_PROCESS,
+	TU_FLAG_NACK,
+};
+
+struct testunit_data {
+	unsigned long flags;
+	u8 regs[TU_NUM_REGS];
+	u8 reg_idx;
+	u8 read_idx;
+	struct i2c_client *client;
+	struct delayed_work worker;
+	struct gpio_desc *gpio;
+	struct completion alert_done;
+};
+
+static char tu_version_info[] = "v" UTS_RELEASE "\n\0";
+
+static int i2c_slave_testunit_smbalert_cb(struct i2c_client *client,
+					  enum i2c_slave_event event, u8 *val)
+{
+	struct testunit_data *tu = i2c_get_clientdata(client);
+
+	switch (event) {
+	case I2C_SLAVE_READ_PROCESSED:
+		gpiod_set_value(tu->gpio, 0);
+		fallthrough;
+	case I2C_SLAVE_READ_REQUESTED:
+		*val = tu->regs[TU_REG_DATAL];
+		break;
+
+	case I2C_SLAVE_STOP:
+		complete(&tu->alert_done);
+		break;
+
+	case I2C_SLAVE_WRITE_REQUESTED:
+	case I2C_SLAVE_WRITE_RECEIVED:
+		return -EOPNOTSUPP;
+	}
+
+	return 0;
+}
+
+static int i2c_slave_testunit_slave_cb(struct i2c_client *client,
+				     enum i2c_slave_event event, u8 *val)
+{
+	struct testunit_data *tu = i2c_get_clientdata(client);
+	bool is_proc_call = tu->reg_idx == 3 && tu->regs[TU_REG_DATAL] == 1 &&
+			    tu->regs[TU_REG_CMD] == TU_CMD_SMBUS_BLOCK_PROC_CALL;
+	bool is_get_version = tu->reg_idx == 3 &&
+			      tu->regs[TU_REG_CMD] == TU_CMD_GET_VERSION_WITH_REP_START;
+	int ret = 0;
+
+	switch (event) {
+	case I2C_SLAVE_WRITE_REQUESTED:
+		if (test_bit(TU_FLAG_IN_PROCESS | TU_FLAG_NACK, &tu->flags)) {
+			ret = -EBUSY;
+			break;
+		}
+
+		memset(tu->regs, 0, TU_NUM_REGS);
+		tu->reg_idx = 0;
+		tu->read_idx = 0;
+		break;
+
+	case I2C_SLAVE_WRITE_RECEIVED:
+		if (test_bit(TU_FLAG_IN_PROCESS | TU_FLAG_NACK, &tu->flags)) {
+			ret = -EBUSY;
+			break;
+		}
+
+		if (tu->reg_idx < TU_NUM_REGS)
+			tu->regs[tu->reg_idx] = *val;
+		else
+			ret = -EMSGSIZE;
+
+		if (tu->reg_idx <= TU_NUM_REGS)
+			tu->reg_idx++;
+
+		/* TU_REG_CMD always written at this point */
+		if (tu->regs[TU_REG_CMD] >= TU_NUM_CMDS)
+			ret = -EINVAL;
+
+		break;
+
+	case I2C_SLAVE_STOP:
+		if (tu->reg_idx == TU_NUM_REGS) {
+			set_bit(TU_FLAG_IN_PROCESS, &tu->flags);
+			queue_delayed_work(system_long_wq, &tu->worker,
+					   msecs_to_jiffies(10 * tu->regs[TU_REG_DELAY]));
+		}
+
+		/*
+		 * Reset reg_idx to avoid that work gets queued again in case of
+		 * STOP after a following read message. But do not clear TU regs
+		 * here because we still need them in the workqueue!
+		 */
+		tu->reg_idx = 0;
+
+		clear_bit(TU_FLAG_NACK, &tu->flags);
+		break;
+
+	case I2C_SLAVE_READ_PROCESSED:
+		/* Advance until we reach the NUL character */
+		if (is_get_version && tu_version_info[tu->read_idx] != 0)
+			tu->read_idx++;
+		else if (is_proc_call && tu->regs[TU_REG_DATAH])
+			tu->regs[TU_REG_DATAH]--;
+
+		fallthrough;
+
+	case I2C_SLAVE_READ_REQUESTED:
+		if (is_get_version)
+			*val = tu_version_info[tu->read_idx];
+		else if (is_proc_call)
+			*val = tu->regs[TU_REG_DATAH];
+		else
+			*val = test_bit(TU_FLAG_IN_PROCESS, &tu->flags) ?
+					tu->regs[TU_REG_CMD] : 0;
+		break;
+	}
+
+	/* If an error occurred somewhen, we NACK everything until next STOP */
+	if (ret)
+		set_bit(TU_FLAG_NACK, &tu->flags);
+
+	return ret;
+}
+
+static void i2c_slave_testunit_work(struct work_struct *work)
+{
+	struct testunit_data *tu = container_of(work, struct testunit_data, worker.work);
+	unsigned long time_left;
+	struct i2c_msg msg;
+	u8 msgbuf[256];
+	u16 orig_addr;
+	int ret = 0;
+
+	msg.addr = I2C_CLIENT_END;
+	msg.buf = msgbuf;
+
+	switch (tu->regs[TU_REG_CMD]) {
+	case TU_CMD_READ_BYTES:
+		msg.addr = tu->regs[TU_REG_DATAL];
+		msg.flags = I2C_M_RD;
+		msg.len = tu->regs[TU_REG_DATAH];
+		break;
+
+	case TU_CMD_SMBUS_HOST_NOTIFY:
+		msg.addr = 0x08;
+		msg.flags = 0;
+		msg.len = 3;
+		msgbuf[0] = tu->client->addr;
+		msgbuf[1] = tu->regs[TU_REG_DATAL];
+		msgbuf[2] = tu->regs[TU_REG_DATAH];
+		break;
+
+	case TU_CMD_SMBUS_ALERT_REQUEST:
+		if (!tu->gpio) {
+			ret = -ENOENT;
+			break;
+		}
+		i2c_slave_unregister(tu->client);
+		orig_addr = tu->client->addr;
+		tu->client->addr = 0x0c;
+		ret = i2c_slave_register(tu->client, i2c_slave_testunit_smbalert_cb);
+		if (ret)
+			goto out_smbalert;
+
+		reinit_completion(&tu->alert_done);
+		gpiod_set_value(tu->gpio, 1);
+		time_left = wait_for_completion_timeout(&tu->alert_done, HZ);
+		if (!time_left)
+			ret = -ETIMEDOUT;
+
+		i2c_slave_unregister(tu->client);
+out_smbalert:
+		tu->client->addr = orig_addr;
+		i2c_slave_register(tu->client, i2c_slave_testunit_slave_cb);
+		break;
+
+	default:
+		break;
+	}
+
+	if (msg.addr != I2C_CLIENT_END) {
+		ret = i2c_transfer(tu->client->adapter, &msg, 1);
+		/* convert '0 msgs transferred' to errno */
+		ret = (ret == 0) ? -EIO : ret;
+	}
+
+	if (ret < 0)
+		dev_err(&tu->client->dev, "CMD%02X failed (%d)\n", tu->regs[TU_REG_CMD], ret);
+
+	clear_bit(TU_FLAG_IN_PROCESS, &tu->flags);
+}
+
+static int i2c_slave_testunit_probe(struct i2c_client *client)
+{
+	struct testunit_data *tu;
+
+	tu = devm_kzalloc(&client->dev, sizeof(struct testunit_data), GFP_KERNEL);
+	if (!tu)
+		return -ENOMEM;
+
+	tu->client = client;
+	i2c_set_clientdata(client, tu);
+	init_completion(&tu->alert_done);
+	INIT_DELAYED_WORK(&tu->worker, i2c_slave_testunit_work);
+
+	tu->gpio = devm_gpiod_get_index_optional(&client->dev, NULL, 0, GPIOD_OUT_LOW);
+	if (IS_ERR(tu->gpio))
+		return PTR_ERR(tu->gpio);
+
+	if (gpiod_cansleep(tu->gpio)) {
+		dev_err(&client->dev, "GPIO access which may sleep is not allowed\n");
+		return -EDEADLK;
+	}
+
+	if (sizeof(tu_version_info) > TU_VERSION_MAX_LENGTH)
+		tu_version_info[TU_VERSION_MAX_LENGTH - 1] = 0;
+
+	return i2c_slave_register(client, i2c_slave_testunit_slave_cb);
+};
+
+static void i2c_slave_testunit_remove(struct i2c_client *client)
+{
+	struct testunit_data *tu = i2c_get_clientdata(client);
+
+	cancel_delayed_work_sync(&tu->worker);
+	i2c_slave_unregister(client);
+}
+
+static const struct i2c_device_id i2c_slave_testunit_id[] = {
+	{ "slave-testunit" },
+	{ }
+};
+MODULE_DEVICE_TABLE(i2c, i2c_slave_testunit_id);
+
+static struct i2c_driver i2c_slave_testunit_driver = {
+	.driver = {
+		.name = "i2c-slave-testunit",
+	},
+	.probe = i2c_slave_testunit_probe,
+	.remove = i2c_slave_testunit_remove,
+	.id_table = i2c_slave_testunit_id,
+};
+module_i2c_driver(i2c_slave_testunit_driver);
+
+MODULE_AUTHOR("Wolfram Sang <wsa@sang-engineering.com>");
+MODULE_DESCRIPTION("I2C slave mode test unit");
+MODULE_LICENSE("GPL v2");