net: wwan: iosm: device trace collection using relayfs

This patch brings in support for device trace collection.
It implements relayfs interface for pushing device trace
from kernel space to user space.

Driver gets the debugfs base directory associated to WWAN
Device and creates trace_control and trace debugfs for
device tracing. Both trace_control & trace debugfs are
created under /sys/kernel/debug/wwan/wwan0/.

In order to collect device trace on trace0 interface, user
need to write 1 to trace_ctl interface.

Signed-off-by: M Chetan Kumar <m.chetan.kumar@linux.intel.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

1 files changed, 173 insertions, 0 deletions

diff --git a/drivers/net/wwan/iosm/iosm_ipc_trace.c b/drivers/net/wwan/iosm/iosm_ipc_trace.c
new file mode 100644
index 000000000000..c5fa12599c2b
--- /dev/null
+++ b/drivers/net/wwan/iosm/iosm_ipc_trace.c
@@ -0,0 +1,173 @@
+// SPDX-License-Identifier: GPL-2.0-only
+/*
+ * Copyright (C) 2020-2021 Intel Corporation.
+ */
+
+#include <linux/wwan.h>
+#include "iosm_ipc_trace.h"
+
+/* sub buffer size and number of sub buffer */
+#define IOSM_TRC_SUB_BUFF_SIZE 131072
+#define IOSM_TRC_N_SUB_BUFF 32
+
+#define IOSM_TRC_FILE_PERM 0600
+
+#define IOSM_TRC_DEBUGFS_TRACE "trace"
+#define IOSM_TRC_DEBUGFS_TRACE_CTRL "trace_ctrl"
+
+/**
+ * ipc_trace_port_rx - Receive trace packet from cp and write to relay buffer
+ * @ipc_trace:  Pointer to the ipc trace data-struct
+ * @skb:        Pointer to struct sk_buff
+ */
+void ipc_trace_port_rx(struct iosm_trace *ipc_trace, struct sk_buff *skb)
+{
+	if (ipc_trace->ipc_rchan)
+		relay_write(ipc_trace->ipc_rchan, skb->data, skb->len);
+
+	dev_kfree_skb(skb);
+}
+
+/* Creates relay file in debugfs. */
+static struct dentry *
+ipc_trace_create_buf_file_handler(const char *filename,
+				  struct dentry *parent,
+				  umode_t mode,
+				  struct rchan_buf *buf,
+				  int *is_global)
+{
+	*is_global = 1;
+	return debugfs_create_file(filename, mode, parent, buf,
+				   &relay_file_operations);
+}
+
+/* Removes relay file from debugfs. */
+static int ipc_trace_remove_buf_file_handler(struct dentry *dentry)
+{
+	debugfs_remove(dentry);
+	return 0;
+}
+
+static int ipc_trace_subbuf_start_handler(struct rchan_buf *buf, void *subbuf,
+					  void *prev_subbuf,
+					  size_t prev_padding)
+{
+	if (relay_buf_full(buf)) {
+		pr_err_ratelimited("Relay_buf full dropping traces");
+		return 0;
+	}
+
+	return 1;
+}
+
+/* Relay interface callbacks */
+static struct rchan_callbacks relay_callbacks = {
+	.subbuf_start = ipc_trace_subbuf_start_handler,
+	.create_buf_file = ipc_trace_create_buf_file_handler,
+	.remove_buf_file = ipc_trace_remove_buf_file_handler,
+};
+
+/* Copy the trace control mode to user buffer */
+static ssize_t ipc_trace_ctrl_file_read(struct file *filp, char __user *buffer,
+					size_t count, loff_t *ppos)
+{
+	struct iosm_trace *ipc_trace = filp->private_data;
+	char buf[16];
+	int len;
+
+	mutex_lock(&ipc_trace->trc_mutex);
+	len = snprintf(buf, sizeof(buf), "%d\n", ipc_trace->mode);
+	mutex_unlock(&ipc_trace->trc_mutex);
+
+	return simple_read_from_buffer(buffer, count, ppos, buf, len);
+}
+
+/* Open and close the trace channel depending on user input */
+static ssize_t ipc_trace_ctrl_file_write(struct file *filp,
+					 const char __user *buffer,
+					 size_t count, loff_t *ppos)
+{
+	struct iosm_trace *ipc_trace = filp->private_data;
+	unsigned long val;
+	int ret;
+
+	ret = kstrtoul_from_user(buffer, count, 10, &val);
+	if (ret)
+		return ret;
+
+	mutex_lock(&ipc_trace->trc_mutex);
+	if (val == TRACE_ENABLE && ipc_trace->mode != TRACE_ENABLE) {
+		ipc_trace->channel = ipc_imem_sys_port_open(ipc_trace->ipc_imem,
+							    ipc_trace->chl_id,
+							    IPC_HP_CDEV_OPEN);
+		if (!ipc_trace->channel) {
+			ret = -EIO;
+			goto unlock;
+		}
+		ipc_trace->mode = TRACE_ENABLE;
+	} else if (val == TRACE_DISABLE && ipc_trace->mode != TRACE_DISABLE) {
+		ipc_trace->mode = TRACE_DISABLE;
+		/* close trace channel */
+		ipc_imem_sys_port_close(ipc_trace->ipc_imem,
+					ipc_trace->channel);
+		relay_flush(ipc_trace->ipc_rchan);
+	}
+	ret = count;
+unlock:
+	mutex_unlock(&ipc_trace->trc_mutex);
+	return ret;
+}
+
+static const struct file_operations ipc_trace_fops = {
+	.open = simple_open,
+	.write = ipc_trace_ctrl_file_write,
+	.read  = ipc_trace_ctrl_file_read,
+};
+
+/**
+ * ipc_trace_init - Create trace interface & debugfs entries
+ * @ipc_imem:   Pointer to iosm_imem structure
+ *
+ * Returns: Pointer to trace instance on success else NULL
+ */
+struct iosm_trace *ipc_trace_init(struct iosm_imem *ipc_imem)
+{
+	struct iosm_trace *ipc_trace = kzalloc(sizeof(*ipc_trace), GFP_KERNEL);
+	struct dentry *debugfs_pdev;
+
+	if (!ipc_trace)
+		return NULL;
+
+	ipc_trace->mode = TRACE_DISABLE;
+	ipc_trace->dev = ipc_imem->dev;
+	ipc_trace->ipc_imem = ipc_imem;
+	ipc_trace->chl_id = IPC_MEM_CTRL_CHL_ID_3;
+
+	mutex_init(&ipc_trace->trc_mutex);
+	debugfs_pdev = wwan_get_debugfs_dir(ipc_imem->dev);
+
+	ipc_trace->ctrl_file = debugfs_create_file(IOSM_TRC_DEBUGFS_TRACE_CTRL,
+						   IOSM_TRC_FILE_PERM,
+						   debugfs_pdev,
+						   ipc_trace, &ipc_trace_fops);
+
+	ipc_trace->ipc_rchan = relay_open(IOSM_TRC_DEBUGFS_TRACE,
+					  debugfs_pdev,
+					  IOSM_TRC_SUB_BUFF_SIZE,
+					  IOSM_TRC_N_SUB_BUFF,
+					  &relay_callbacks, NULL);
+
+	return ipc_trace;
+}
+
+/**
+ * ipc_trace_deinit - Closing relayfs, removing debugfs entries
+ * @ipc_trace: Pointer to the iosm_trace data struct
+ */
+void ipc_trace_deinit(struct iosm_trace *ipc_trace)
+{
+	debugfs_remove(ipc_trace->ctrl_file);
+	relay_close(ipc_trace->ipc_rchan);
+	mutex_destroy(&ipc_trace->trc_mutex);
+	kfree(ipc_trace);
+}