[PATCH v3 1/1] scsi: ufs: core: Support Updating UIC Command Timeout

[Bao D. Nguyen]

The default UIC command timeout still remains 500ms.
Allow platform drivers to override the UIC command
timeout if desired.

In a real product, the 500ms timeout value is probably good enough.
However, during the product development where there are a lot of
logging and debug messages being printed to the uart console,
interrupt starvations happen occasionally because the uart may
print long debug messages from different modules in the system.
While printing, the uart may have interrupts disabled for more
than 500ms, causing UIC command timeout.
The UIC command timeout would trigger more printing from
the UFS driver, and eventually a watchdog timeout may
occur unnecessarily.

Add support for overriding the UIC command timeout value
with the newly created uic_cmd_timeout kernel module parameter.
Default value is 500ms. Supported values range from 500ms
to 2 seconds.

Signed-off-by: Bao D. Nguyen <quic_nguyenb@xxxxxxxxxxx>
Suggested-by: Bart Van Assche <bvanassche@xxxxxxx>
Reviewed-by: Bart Van Assche <bvanassche@xxxxxxx>
---
 drivers/ufs/core/ufshcd.c | 34 +++++++++++++++++++++++++++++-----
 1 file changed, 29 insertions(+), 5 deletions(-)

diff --git a/drivers/ufs/core/ufshcd.c b/drivers/ufs/core/ufshcd.c
index 21429ee..421e295 100644
--- a/drivers/ufs/core/ufshcd.c
+++ b/drivers/ufs/core/ufshcd.c
@@ -51,8 +51,10 @@
 
 
 /* UIC command timeout, unit: ms */
-#define UIC_CMD_TIMEOUT	500
-
+enum {
+	UIC_CMD_TIMEOUT_DEFAULT	= 500,
+	UIC_CMD_TIMEOUT_MAX	= 2000,
+};
 /* NOP OUT retries waiting for NOP IN response */
 #define NOP_OUT_RETRIES    10
 /* Timeout after 50 msecs if NOP OUT hangs without response */
@@ -113,6 +115,28 @@ static bool is_mcq_supported(struct ufs_hba *hba)
 module_param(use_mcq_mode, bool, 0644);
 MODULE_PARM_DESC(use_mcq_mode, "Control MCQ mode for controllers starting from UFSHCI 4.0. 1 - enable MCQ, 0 - disable MCQ. MCQ is enabled by default");
 
+static int uic_cmd_timeout_set(const char *val, const struct kernel_param *kp)
+{
+	unsigned int n;
+	int ret;
+
+	ret = kstrtou32(val, 0, &n);
+	if (ret != 0 || n < UIC_CMD_TIMEOUT_DEFAULT || n > UIC_CMD_TIMEOUT_MAX)
+		return -EINVAL;
+
+	return param_set_int(val, kp);
+}
+
+static const struct kernel_param_ops uic_cmd_timeout_ops = {
+	.set = uic_cmd_timeout_set,
+	.get = param_get_uint,
+};
+
+static unsigned int uic_cmd_timeout = UIC_CMD_TIMEOUT_DEFAULT;
+module_param_cb(uic_cmd_timeout, &uic_cmd_timeout_ops, &uic_cmd_timeout, 0644);
+MODULE_PARM_DESC(uic_cmd_timeout,
+		"UFS UIC command timeout in milliseconds. Defaults to 500ms. Supported values range from 500ms to 2 seconds inclusively");
+
 #define ufshcd_toggle_vreg(_dev, _vreg, _on)				\
 	({                                                              \
 		int _ret;                                               \
@@ -2460,7 +2484,7 @@ static inline bool ufshcd_ready_for_uic_cmd(struct ufs_hba *hba)
 {
 	u32 val;
 	int ret = read_poll_timeout(ufshcd_readl, val, val & UIC_COMMAND_READY,
-				    500, UIC_CMD_TIMEOUT * 1000, false, hba,
+				    500, uic_cmd_timeout * 1000, false, hba,
 				    REG_CONTROLLER_STATUS);
 	return ret == 0;
 }
@@ -2520,7 +2544,7 @@ ufshcd_wait_for_uic_cmd(struct ufs_hba *hba, struct uic_command *uic_cmd)
 	lockdep_assert_held(&hba->uic_cmd_mutex);
 
 	if (wait_for_completion_timeout(&uic_cmd->done,
-					msecs_to_jiffies(UIC_CMD_TIMEOUT))) {
+					msecs_to_jiffies(uic_cmd_timeout))) {
 		ret = uic_cmd->argument2 & MASK_UIC_COMMAND_RESULT;
 	} else {
 		ret = -ETIMEDOUT;
@@ -4298,7 +4322,7 @@ static int ufshcd_uic_pwr_ctrl(struct ufs_hba *hba, struct uic_command *cmd)
 	}
 
 	if (!wait_for_completion_timeout(hba->uic_async_done,
-					 msecs_to_jiffies(UIC_CMD_TIMEOUT))) {
+					 msecs_to_jiffies(uic_cmd_timeout))) {
 		dev_err(hba->dev,
 			"pwr ctrl cmd 0x%x with mode 0x%x completion timeout\n",
 			cmd->command, cmd->argument3);
-- 
2.7.4