[PATCH v4] platform/chrome: mfd/cros_ec_debugfs: Add debugfs entry to retrieve EC uptime.

[Tim Wawrzynczak]

The new debugfs entry 'uptime' is being made available to userspace so that
a userspace daemon can synchronize EC logs with host time.

Signed-off-by: Tim Wawrzynczak <twawrzynczak@xxxxxxxxxxxx>
---
Enric, AFAIK only the cros_ec supports the 'uptime' command for now.
And yes, the file does need to be seekable; the userspace daemon that
consumes the file keeps the file open and seeks back to the beginning
to get the latest uptime value.
Based on your second response to v3, I kept the separate 'create_uptime'
function b/c of the logic for checking support for the uptime command.
Let me know if you'd like me to move all of that logic into _probe.

Changelist from v3:
 1) Don't check return values of debugfs_* functions.
 2) Only expose 'uptime' file if EC supports it.
---
 Documentation/ABI/testing/debugfs-cros-ec | 10 +++
 drivers/platform/chrome/cros_ec_debugfs.c | 78 +++++++++++++++++++++++
 2 files changed, 88 insertions(+)
 create mode 100644 Documentation/ABI/testing/debugfs-cros-ec

diff --git a/Documentation/ABI/testing/debugfs-cros-ec b/Documentation/ABI/testing/debugfs-cros-ec
new file mode 100644
index 000000000000..24b781c67a4c
--- /dev/null
+++ b/Documentation/ABI/testing/debugfs-cros-ec
@@ -0,0 +1,10 @@
+What:		/sys/kernel/debug/cros_ec/uptime
+Date:		March 2019
+KernelVersion:	5.1
+Description:
+		Read-only.
+		Reads the EC's current uptime information
+		(using EC_CMD_GET_UPTIME_INFO) and prints
+		time_since_ec_boot_ms into the file.
+		This is used for synchronizing AP host time
+		with the cros_ec log.
diff --git a/drivers/platform/chrome/cros_ec_debugfs.c b/drivers/platform/chrome/cros_ec_debugfs.c
index 71308766e891..226545a2150b 100644
--- a/drivers/platform/chrome/cros_ec_debugfs.c
+++ b/drivers/platform/chrome/cros_ec_debugfs.c
@@ -201,6 +201,50 @@ static int cros_ec_console_log_release(struct inode *inode, struct file *file)
 	return 0;
 }
 
+static int cros_ec_get_uptime(struct cros_ec_device *ec_dev, u32 *uptime)
+{
+	struct {
+		struct cros_ec_command msg;
+		struct ec_response_uptime_info resp;
+	} __packed ec_buf;
+	struct ec_response_uptime_info *resp;
+	struct cros_ec_command *msg;
+
+	msg = &ec_buf.msg;
+	resp = (struct ec_response_uptime_info *)msg->data;
+
+	msg->command = EC_CMD_GET_UPTIME_INFO;
+	msg->version = 0;
+	msg->insize = sizeof(*resp);
+	msg->outsize = 0;
+
+	ret = cros_ec_cmd_xfer_status(ec_dev, msg);
+	if (ret < 0)
+		return ret;
+
+	*uptime = resp->time_since_ec_boot_ms;
+	return 0;
+}
+
+static ssize_t cros_ec_uptime_read(struct file *file,
+				   char __user *user_buf,
+				   size_t count,
+				   loff_t *ppos)
+{
+	struct cros_ec_debugfs *debug_info = file->private_data;
+	struct cros_ec_device *ec_dev = debug_info->ec->ec_dev;
+	char read_buf[32];
+	int ret;
+	u32 uptime;
+
+	ret = cros_ec_get_uptime(ec_dev, &uptime);
+	if (ret < 0)
+		return ret;
+
+	ret = scnprintf(read_buf, sizeof(read_buf), "%u\n", uptime);
+	return simple_read_from_buffer(user_buf, count, ppos, read_buf, ret);
+}
+
 static ssize_t cros_ec_pdinfo_read(struct file *file,
 				   char __user *user_buf,
 				   size_t count,
@@ -269,6 +313,13 @@ const struct file_operations cros_ec_pdinfo_fops = {
 	.llseek = default_llseek,
 };
 
+const struct file_operations cros_ec_uptime_fops = {
+	.owner = THIS_MODULE,
+	.open = simple_open,
+	.read = cros_ec_uptime_read,
+	.llseek = default_llseek,
+};
+
 static int ec_read_version_supported(struct cros_ec_dev *ec)
 {
 	struct ec_params_get_cmd_versions_v1 *params;
@@ -413,6 +464,29 @@ static int cros_ec_create_pdinfo(struct cros_ec_debugfs *debug_info)
 	return 0;
 }
 
+static int cros_ec_create_uptime(struct cros_ec_debugfs *debug_info)
+{
+	struct cros_ec_debugfs *debug_info = file->private_data;
+	struct cros_ec_device *ec_dev = debug_info->ec->ec_dev;
+	u32 uptime;
+	int ret;
+
+	/*
+	 * If the EC does not support the uptime command, which is
+	 * indicated by xfer_status() returning -EINVAL, then no
+	 * debugfs entry will be created.
+	 */
+	ret = cros_ec_get_uptime(ec_dev, &uptime);
+
+	if (ret == -EINVAL)
+		return supported;
+
+	debugfs_create_file("uptime", 0444, debug_info->dir, debug_info,
+			&cros_ec_uptime_fops);
+
+	return 0;
+}
+
 static int cros_ec_debugfs_probe(struct platform_device *pd)
 {
 	struct cros_ec_dev *ec = dev_get_drvdata(pd->dev.parent);
@@ -442,6 +516,10 @@ static int cros_ec_debugfs_probe(struct platform_device *pd)
 	if (ret)
 		goto remove_log;
 
+	ret = cros_ec_create_uptime(debug_info);
+	if (ret)
+		goto remove_log;
+
 	ec->debug_info = debug_info;
 
 	dev_set_drvdata(&pd->dev, ec);
-- 
2.20.1