[PATCH 2/3] mfd: cros_ec: add debugfs, console log file

[Nicolas Boichat <drinkcat@chromium.org>]

From: Eric Caruso <ejcaruso@chromium.org>

If the EC supports the new CONSOLE_READ command type, then we
place a console_log file in debugfs for that EC device which allows
us to grab EC logs. The kernel will poll every 10 seconds for the
log and keep its own buffer, but userspace should grab this and
write it out to some logs which actually get rotated.

Signed-off-by: Eric Caruso <ejcaruso@chromium.org>
Signed-off-by: Nicolas Boichat <drinkcat@chromium.org>
---
 drivers/platform/chrome/Makefile          |   3 +-
 drivers/platform/chrome/cros_ec_debugfs.c | 347 ++++++++++++++++++++++++++++++
 drivers/platform/chrome/cros_ec_debugfs.h |  27 +++
 drivers/platform/chrome/cros_ec_dev.c     |   7 +
 include/linux/mfd/cros_ec.h               |   4 +
 5 files changed, 387 insertions(+), 1 deletion(-)
 create mode 100644 drivers/platform/chrome/cros_ec_debugfs.c
 create mode 100644 drivers/platform/chrome/cros_ec_debugfs.h

diff --git a/drivers/platform/chrome/Makefile b/drivers/platform/chrome/Makefile
index 4f34627..3870afe 100644
--- a/drivers/platform/chrome/Makefile
+++ b/drivers/platform/chrome/Makefile
@@ -2,7 +2,8 @@
 obj-$(CONFIG_CHROMEOS_LAPTOP)		+= chromeos_laptop.o
 obj-$(CONFIG_CHROMEOS_PSTORE)		+= chromeos_pstore.o
 cros_ec_devs-objs			:= cros_ec_dev.o cros_ec_sysfs.o \
-					   cros_ec_lightbar.o cros_ec_vbc.o
+					   cros_ec_lightbar.o cros_ec_vbc.o \
+					   cros_ec_debugfs.o
 obj-$(CONFIG_CROS_EC_CHARDEV)		+= cros_ec_devs.o
 obj-$(CONFIG_CROS_EC_LPC)		+= cros_ec_lpc.o
 obj-$(CONFIG_CROS_EC_PROTO)		+= cros_ec_proto.o
diff --git a/drivers/platform/chrome/cros_ec_debugfs.c b/drivers/platform/chrome/cros_ec_debugfs.c
new file mode 100644
index 0000000..225f936
--- /dev/null
+++ b/drivers/platform/chrome/cros_ec_debugfs.c
@@ -0,0 +1,347 @@
+/*
+ * cros_ec_debugfs - debug logs for Chrome OS EC
+ *
+ * Copyright 2015 Google, Inc.
+ *
+ * This program is free software; you can redistribute it and/or modify
+ * it under the terms of the GNU General Public License as published by
+ * the Free Software Foundation; either version 2 of the License, or
+ * (at your option) any later version.
+ *
+ * This program is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
+ * GNU General Public License for more details.
+ *
+ * You should have received a copy of the GNU General Public License
+ * along with this program. If not, see <http://www.gnu.org/licenses/>.
+ */
+
+#include <linux/circ_buf.h>
+#include <linux/debugfs.h>
+#include <linux/delay.h>
+#include <linux/fs.h>
+#include <linux/mfd/cros_ec.h>
+#include <linux/mfd/cros_ec_commands.h>
+#include <linux/mutex.h>
+#include <linux/poll.h>
+#include <linux/sched.h>
+#include <linux/slab.h>
+#include <linux/wait.h>
+
+#include "cros_ec_dev.h"
+#include "cros_ec_debugfs.h"
+
+#define LOG_SHIFT		14
+#define LOG_SIZE		(1 << LOG_SHIFT)
+#define LOG_POLL_SEC		10
+
+#define CIRC_ADD(idx, size, value)	(((idx) + (value)) & ((size) - 1))
+
+/* struct cros_ec_debugfs - ChromeOS EC debugging information
+ *
+ * @ec: EC device this debugfs information belongs to
+ * @dir: dentry for debugfs files
+ * @log_buffer: circular buffer for console log information
+ * @read_msg: preallocated EC command and buffer to read console log
+ * @log_mutex: mutex to protect circular buffer
+ * @log_wq: waitqueue for log readers
+ * @log_poll_work: recurring task to poll EC for new console log data
+ */
+struct cros_ec_debugfs {
+	struct cros_ec_dev *ec;
+	struct dentry *dir;
+	struct circ_buf log_buffer;
+	struct cros_ec_command *read_msg;
+	struct mutex log_mutex;
+	wait_queue_head_t log_wq;
+	struct delayed_work log_poll_work;
+};
+
+/*
+ * We need to make sure that the EC log buffer on the UART is large enough,
+ * so that it is unlikely enough to overlow within LOG_POLL_SEC.
+ */
+static void cros_ec_console_log_work(struct work_struct *__work)
+{
+	struct cros_ec_debugfs *debug_info =
+		container_of(to_delayed_work(__work),
+			     struct cros_ec_debugfs,
+			     log_poll_work);
+	struct cros_ec_dev *ec = debug_info->ec;
+	struct circ_buf *cb = &debug_info->log_buffer;
+	struct cros_ec_command snapshot_msg = {
+		.command = EC_CMD_CONSOLE_SNAPSHOT + ec->cmd_offset,
+	};
+
+	struct ec_params_console_read_v1 *read_params =
+		(struct ec_params_console_read_v1 *)debug_info->read_msg->data;
+	uint8_t *ec_buffer = (uint8_t *)debug_info->read_msg->data;
+	int idx;
+	int buf_space;
+	int ret;
+
+	ret = cros_ec_cmd_xfer(ec->ec_dev, &snapshot_msg);
+	if (ret < 0) {
+		dev_err(ec->dev, "EC communication failed\n");
+		goto resched;
+	}
+	if (snapshot_msg.result != EC_RES_SUCCESS) {
+		dev_err(ec->dev, "EC failed to snapshot the console log\n");
+		goto resched;
+	}
+
+	/* Loop until we have read everything, or there's an error. */
+	mutex_lock(&debug_info->log_mutex);
+	buf_space = CIRC_SPACE(cb->head, cb->tail, LOG_SIZE);
+
+	while (1) {
+		if (!buf_space) {
+			dev_info_once(ec->dev,
+				      "Some logs may have been dropped...\n");
+			break;
+		}
+
+		memset(read_params, '\0', sizeof(*read_params));
+		read_params->subcmd = CONSOLE_READ_RECENT;
+		ret = cros_ec_cmd_xfer(ec->ec_dev, debug_info->read_msg);
+		if (ret < 0) {
+			dev_err(ec->dev, "EC communication failed\n");
+			break;
+		}
+		if (debug_info->read_msg->result != EC_RES_SUCCESS) {
+			dev_err(ec->dev,
+				"EC failed to read the console log\n");
+			break;
+		}
+
+		/* If the buffer is empty, we're done here. */
+		if (ret == 0 || ec_buffer[0] == '\0')
+			break;
+
+		idx = 0;
+		while (idx < ret && ec_buffer[idx] != '\0' && buf_space > 0) {
+			cb->buf[cb->head] = ec_buffer[idx];
+			cb->head = CIRC_ADD(cb->head, LOG_SIZE, 1);
+			idx++;
+			buf_space--;
+		}
+
+		wake_up(&debug_info->log_wq);
+	}
+
+	mutex_unlock(&debug_info->log_mutex);
+
+resched:
+	schedule_delayed_work(&debug_info->log_poll_work,
+			      msecs_to_jiffies(LOG_POLL_SEC * 1000));
+}
+
+static int cros_ec_console_log_open(struct inode *inode, struct file *file)
+{
+	file->private_data = inode->i_private;
+
+	return nonseekable_open(inode, file);
+}
+
+static ssize_t cros_ec_console_log_read(struct file *file, char __user *buf,
+					size_t count, loff_t *ppos)
+{
+	struct cros_ec_debugfs *debug_info = file->private_data;
+	struct circ_buf *cb = &debug_info->log_buffer;
+	ssize_t ret;
+
+	mutex_lock(&debug_info->log_mutex);
+
+	while (!CIRC_CNT(cb->head, cb->tail, LOG_SIZE)) {
+		if (file->f_flags & O_NONBLOCK) {
+			ret = -EAGAIN;
+			goto error;
+		}
+
+		mutex_unlock(&debug_info->log_mutex);
+
+		ret = wait_event_interruptible(debug_info->log_wq,
+					CIRC_CNT(cb->head, cb->tail, LOG_SIZE));
+		if (ret < 0)
+			return ret;
+
+		mutex_lock(&debug_info->log_mutex);
+	}
+
+	/* Only copy until the end of the circular buffer, and let userspace
+	 * retry to get the rest of the data.
+	 */
+	ret = min_t(size_t, CIRC_CNT_TO_END(cb->head, cb->tail, LOG_SIZE),
+		    count);
+
+	if (copy_to_user(buf, cb->buf + cb->tail, ret)) {
+		ret = -EFAULT;
+		goto error;
+	}
+
+	cb->tail = CIRC_ADD(cb->tail, LOG_SIZE, ret);
+
+error:
+	mutex_unlock(&debug_info->log_mutex);
+	return ret;
+}
+
+static unsigned int cros_ec_console_log_poll(struct file *file,
+					     poll_table *wait)
+{
+	struct cros_ec_debugfs *debug_info = file->private_data;
+	unsigned int mask = 0;
+
+	poll_wait(file, &debug_info->log_wq, wait);
+
+	mutex_lock(&debug_info->log_mutex);
+	if (CIRC_CNT(debug_info->log_buffer.head,
+		     debug_info->log_buffer.tail,
+		     LOG_SIZE))
+		mask |= POLLIN | POLLRDNORM;
+	mutex_unlock(&debug_info->log_mutex);
+
+	return mask;
+}
+
+static int cros_ec_console_log_release(struct inode *inode, struct file *file)
+{
+	return 0;
+}
+
+const struct file_operations cros_ec_console_log_fops = {
+	.owner = THIS_MODULE,
+	.open = cros_ec_console_log_open,
+	.read = cros_ec_console_log_read,
+	.llseek = no_llseek,
+	.poll = cros_ec_console_log_poll,
+	.release = cros_ec_console_log_release,
+};
+
+static int ec_read_version_supported(struct cros_ec_dev *ec)
+{
+	struct ec_params_get_cmd_versions_v1 *params;
+	struct ec_response_get_cmd_versions *response;
+	int ret;
+
+	struct cros_ec_command *msg;
+
+	msg = kzalloc(sizeof(*msg) + max(sizeof(params), sizeof(response)),
+		GFP_KERNEL);
+	if (!msg)
+		return 0;
+
+	msg->command = EC_CMD_GET_CMD_VERSIONS + ec->cmd_offset;
+	msg->outsize = sizeof(params);
+	msg->insize = sizeof(response);
+
+	params = (struct ec_params_get_cmd_versions_v1 *)msg->data;
+	params->cmd = EC_CMD_CONSOLE_READ;
+	response = (struct ec_response_get_cmd_versions *)msg->data;
+
+	ret = cros_ec_cmd_xfer(ec->ec_dev, msg) >= 0 &&
+		msg->result == EC_RES_SUCCESS &&
+		(response->version_mask & EC_VER_MASK(1));
+
+	kfree(msg);
+
+	return ret;
+}
+
+static int cros_ec_create_console_log(struct cros_ec_debugfs *debug_info)
+{
+	struct cros_ec_dev *ec = debug_info->ec;
+	char *buf;
+	int read_params_size;
+	int read_response_size;
+
+	if (!ec_read_version_supported(ec)) {
+		dev_warn(ec->dev,
+			"device does not support reading the console log\n");
+		return 0;
+	}
+
+	buf = devm_kzalloc(ec->dev, LOG_SIZE, GFP_KERNEL);
+	if (!buf)
+		return -ENOMEM;
+
+	read_params_size = sizeof(struct ec_params_console_read_v1);
+	read_response_size = ec->ec_dev->max_response;
+	debug_info->read_msg = devm_kzalloc(ec->dev,
+		sizeof(*debug_info->read_msg) +
+			max(read_params_size, read_response_size), GFP_KERNEL);
+	if (!debug_info->read_msg)
+		return -ENOMEM;
+
+	debug_info->read_msg->version = 1;
+	debug_info->read_msg->command = EC_CMD_CONSOLE_READ + ec->cmd_offset;
+	debug_info->read_msg->outsize = read_params_size;
+	debug_info->read_msg->insize = read_response_size;
+
+	debug_info->log_buffer.buf = buf;
+	debug_info->log_buffer.head = 0;
+	debug_info->log_buffer.tail = 0;
+
+	mutex_init(&debug_info->log_mutex);
+	init_waitqueue_head(&debug_info->log_wq);
+
+	if (!debugfs_create_file("console_log",
+				 S_IFREG | S_IRUGO,
+				 debug_info->dir,
+				 debug_info,
+				 &cros_ec_console_log_fops))
+		return -ENOMEM;
+
+	INIT_DELAYED_WORK(&debug_info->log_poll_work,
+			  cros_ec_console_log_work);
+	schedule_delayed_work(&debug_info->log_poll_work, 0);
+
+	return 0;
+}
+
+static void cros_ec_cleanup_console_log(struct cros_ec_debugfs *debug_info)
+{
+	if (debug_info->log_buffer.buf) {
+		cancel_delayed_work_sync(&debug_info->log_poll_work);
+		mutex_destroy(&debug_info->log_mutex);
+	}
+}
+
+int cros_ec_debugfs_init(struct cros_ec_dev *ec)
+{
+	struct cros_ec_platform *ec_platform = dev_get_platdata(ec->dev);
+	const char *name = ec_platform->ec_name;
+	struct cros_ec_debugfs *debug_info;
+	int ret;
+
+	debug_info = devm_kzalloc(ec->dev, sizeof(*debug_info), GFP_KERNEL);
+	if (!debug_info)
+		return -ENOMEM;
+
+	debug_info->ec = ec;
+	debug_info->dir = debugfs_create_dir(name, NULL);
+	if (!debug_info->dir)
+		return -ENOMEM;
+
+	ret = cros_ec_create_console_log(debug_info);
+	if (ret)
+		goto remove_debugfs;
+
+	ec->debug_info = debug_info;
+
+	return 0;
+
+remove_debugfs:
+	debugfs_remove_recursive(debug_info->dir);
+	return ret;
+}
+
+void cros_ec_debugfs_remove(struct cros_ec_dev *ec)
+{
+	if (!ec->debug_info)
+		return;
+
+	debugfs_remove_recursive(ec->debug_info->dir);
+	cros_ec_cleanup_console_log(ec->debug_info);
+}
diff --git a/drivers/platform/chrome/cros_ec_debugfs.h b/drivers/platform/chrome/cros_ec_debugfs.h
new file mode 100644
index 0000000..1ff3a50
--- /dev/null
+++ b/drivers/platform/chrome/cros_ec_debugfs.h
@@ -0,0 +1,27 @@
+/*
+ * Copyright 2015 Google, Inc.
+ *
+ * This program is free software; you can redistribute it and/or modify
+ * it under the terms of the GNU General Public License as published by
+ * the Free Software Foundation; either version 2 of the License, or
+ * (at your option) any later version.
+ *
+ * This program is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
+ * GNU General Public License for more details.
+ *
+ * You should have received a copy of the GNU General Public License
+ * along with this program. If not, see <http://www.gnu.org/licenses/>.
+ */
+
+#ifndef _DRV_CROS_EC_DEBUGFS_H_
+#define _DRV_CROS_EC_DEBUGFS_H_
+
+#include "cros_ec_dev.h"
+
+/* debugfs stuff */
+int cros_ec_debugfs_init(struct cros_ec_dev *ec);
+void cros_ec_debugfs_remove(struct cros_ec_dev *ec);
+
+#endif  /* _DRV_CROS_EC_DEBUGFS_H_ */
diff --git a/drivers/platform/chrome/cros_ec_dev.c b/drivers/platform/chrome/cros_ec_dev.c
index 8abd80d..7d51f69 100644
--- a/drivers/platform/chrome/cros_ec_dev.c
+++ b/drivers/platform/chrome/cros_ec_dev.c
@@ -23,6 +23,7 @@
 #include <linux/slab.h>
 #include <linux/uaccess.h>
 
+#include "cros_ec_debugfs.h"
 #include "cros_ec_dev.h"
 
 /* Device variables */
@@ -282,6 +283,9 @@ static int ec_device_probe(struct platform_device *pdev)
 		goto dev_reg_failed;
 	}
 
+	if (cros_ec_debugfs_init(ec))
+		dev_warn(dev, "failed to create debugfs directory\n");
+
 	return 0;
 
 dev_reg_failed:
@@ -296,6 +300,9 @@ cdev_add_failed:
 static int ec_device_remove(struct platform_device *pdev)
 {
 	struct cros_ec_dev *ec = dev_get_drvdata(&pdev->dev);
+
+	cros_ec_debugfs_remove(ec);
+
 	cdev_del(&ec->cdev);
 	device_unregister(&ec->class_dev);
 	return 0;
diff --git a/include/linux/mfd/cros_ec.h b/include/linux/mfd/cros_ec.h
index d641a18..e7001a7 100644
--- a/include/linux/mfd/cros_ec.h
+++ b/include/linux/mfd/cros_ec.h
@@ -151,6 +151,8 @@ struct cros_ec_platform {
 	u16 cmd_offset;
 };
 
+struct cros_ec_debugfs;
+
 /*
  * struct cros_ec_dev - ChromeOS EC device entry point
  *
@@ -158,6 +160,7 @@ struct cros_ec_platform {
  * @cdev: Character device structure in /dev
  * @ec_dev: cros_ec_device structure to talk to the physical device
  * @dev: pointer to the platform device
+ * @debug_info: cros_ec_debugfs structure for debugging information
  * @cmd_offset: offset to apply for each command.
  */
 struct cros_ec_dev {
@@ -165,6 +168,7 @@ struct cros_ec_dev {
 	struct cdev cdev;
 	struct cros_ec_device *ec_dev;
 	struct device *dev;
+	struct cros_ec_debugfs *debug_info;
 	u16 cmd_offset;
 };
 
-- 
2.8.0.rc3.226.g39d4020