mfd: cros_ec: Add support for dumping panic information

This dumps the EC panic information from the previous reboot.

Similar to the information presented by ectool panicinfo, except
that we do not bother doing any parsing (we should write a small
offline tool for that).

Signed-off-by: Nicolas Boichat <[e-mail]>
Reviewed-by: Guenter Roeck <[e-mail]>
Tested-by: Enric Balletbo i Serra <[e-mail]>
Signed-off-by: Benson Leung <[e-mail]>

drivers/platform/chrome/cros_ec_debugfs.c

···
  * @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
+ * @panicinfo_blob: panicinfo debugfs blob
  */
 struct cros_ec_debugfs {
 	struct cros_ec_dev *ec;
 	struct dentry *dir;
+	/* EC log */
 	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;
+	/* EC panicinfo */
+	struct debugfs_blob_wrapper panicinfo_blob;
 };
 
 /*
···
 	}
 }
 
+static int cros_ec_create_panicinfo(struct cros_ec_debugfs *debug_info)
+{
+	struct cros_ec_device *ec_dev = debug_info->ec->ec_dev;
+	int ret;
+	struct cros_ec_command *msg;
+	int insize;
+
+	insize = ec_dev->max_response;
+
+	msg = devm_kzalloc(debug_info->ec->dev,
+			sizeof(*msg) + insize, GFP_KERNEL);
+	if (!msg)
+		return -ENOMEM;
+
+	msg->command = EC_CMD_GET_PANIC_INFO;
+	msg->insize = insize;
+
+	ret = cros_ec_cmd_xfer(ec_dev, msg);
+	if (ret < 0) {
+		dev_warn(debug_info->ec->dev, "Cannot read panicinfo.\n");
+		ret = 0;
+		goto free;
+	}
+
+	/* No panic data */
+	if (ret == 0)
+		goto free;
+
+	debug_info->panicinfo_blob.data = msg->data;
+	debug_info->panicinfo_blob.size = ret;
+
+	if (!debugfs_create_blob("panicinfo",
+				 S_IFREG | S_IRUGO,
+				 debug_info->dir,
+				 &debug_info->panicinfo_blob)) {
+		ret = -ENOMEM;
+		goto free;
+	}
+
+	return 0;
+
+free:
+	devm_kfree(debug_info->ec->dev, msg);
+	return ret;
+}
+
 int cros_ec_debugfs_init(struct cros_ec_dev *ec)
 {
 	struct cros_ec_platform *ec_platform = dev_get_platdata(ec->dev);
···
 	debug_info->dir = debugfs_create_dir(name, NULL);
 	if (!debug_info->dir)
 		return -ENOMEM;
+
+	ret = cros_ec_create_panicinfo(debug_info);
+	if (ret)
+		goto remove_debugfs;
 
 	ret = cros_ec_create_console_log(debug_info);
 	if (ret)