scsi: ufs: core: Add sysfs node for UFS RTC update

Introduce a sysfs node named 'rtc_update_ms' within the kernel, enabling
user to adjust the RTC periodic update frequency to suit the specific
requirements of the system and UFS. Also, this patch allows the user to
disable/enable periodic update RTC in the UFS idle time.

Signed-off-by: Bean Huo <beanhuo@micron.com>
Link: https://lore.kernel.org/r/20231212220825.85255-4-beanhuo@iokpp.de
Acked-by: Avri Altman <avri.altman@wdc.com>
Reviewed-by: Thomas Weißschuh <linux@weissschuh.net>
Signed-off-by: Martin K. Petersen <martin.petersen@oracle.com>

Documentation/ABI/testing/sysfs-driver-ufs

@@ -1474,3 +1474,10 @@ Description:	Indicates status of Write Booster.
 
 		The file is read only.
 
+What:		/sys/bus/platform/drivers/ufshcd/*/rtc_update_ms
+What:		/sys/bus/platform/devices/*.ufs/rtc_update_ms
+Date:		November 2023
+Contact:	Bean Huo <beanhuo@micron.com>
+Description:
+		rtc_update_ms indicates how often the host should synchronize or update the
+		UFS RTC. If set to 0, this will disable UFS RTC periodic update.

drivers/ufs/core/ufs-sysfs.c

@@ -255,6 +255,35 @@ out:
 	return res < 0 ? res : count;
 }
 
+static ssize_t rtc_update_ms_show(struct device *dev, struct device_attribute *attr,
+				  char *buf)
+{
+	struct ufs_hba *hba = dev_get_drvdata(dev);
+
+	return sysfs_emit(buf, "%d\n", hba->dev_info.rtc_update_period);
+}
+
+static ssize_t rtc_update_ms_store(struct device *dev, struct device_attribute *attr,
+				   const char *buf, size_t count)
+{
+	struct ufs_hba *hba = dev_get_drvdata(dev);
+	unsigned int ms;
+	bool resume_period_update = false;
+
+	if (kstrtouint(buf, 0, &ms))
+		return -EINVAL;
+
+	if (!hba->dev_info.rtc_update_period && ms > 0)
+		resume_period_update =  true;
+	/* Minimum and maximum update frequency should be synchronized with all UFS vendors */
+	hba->dev_info.rtc_update_period = ms;
+
+	if (resume_period_update)
+		schedule_delayed_work(&hba->ufs_rtc_update_work,
+				      msecs_to_jiffies(hba->dev_info.rtc_update_period));
+	return count;
+}
+
 static ssize_t enable_wb_buf_flush_show(struct device *dev,
 				    struct device_attribute *attr,
 				    char *buf)
@@ -339,6 +368,7 @@ static DEVICE_ATTR_RW(auto_hibern8);
 static DEVICE_ATTR_RW(wb_on);
 static DEVICE_ATTR_RW(enable_wb_buf_flush);
 static DEVICE_ATTR_RW(wb_flush_threshold);
+static DEVICE_ATTR_RW(rtc_update_ms);
 
 static struct attribute *ufs_sysfs_ufshcd_attrs[] = {
 	&dev_attr_rpm_lvl.attr,
@@ -351,6 +381,7 @@ static struct attribute *ufs_sysfs_ufshcd_attrs[] = {
 	&dev_attr_wb_on.attr,
 	&dev_attr_enable_wb_buf_flush.attr,
 	&dev_attr_wb_flush_threshold.attr,
+	&dev_attr_rtc_update_ms.attr,
 	NULL
 };
 

drivers/ufs/core/ufshcd.c

@@ -8233,9 +8233,9 @@ static void ufshcd_rtc_work(struct work_struct *work)
 	if (!ufshcd_is_ufs_dev_busy(hba) && hba->ufshcd_state == UFSHCD_STATE_OPERATIONAL)
 		ufshcd_update_rtc(hba);
 
-	if (ufshcd_is_ufs_dev_active(hba))
+	if (ufshcd_is_ufs_dev_active(hba) && hba->dev_info.rtc_update_period)
 		schedule_delayed_work(&hba->ufs_rtc_update_work,
-				      msecs_to_jiffies(UFS_RTC_UPDATE_INTERVAL_MS));
+				      msecs_to_jiffies(hba->dev_info.rtc_update_period));
 }
 
 static void ufs_init_rtc(struct ufs_hba *hba, u8 *desc_buf)
@@ -8257,6 +8257,13 @@ static void ufs_init_rtc(struct ufs_hba *hba, u8 *desc_buf)
 		dev_info->rtc_type = UFS_RTC_RELATIVE;
 		dev_info->rtc_time_baseline = 0;
 	}
+
+	/*
+	 * We ignore TIME_PERIOD defined in wPeriodicRTCUpdate because Spec does not clearly state
+	 * how to calculate the specific update period for each time unit. And we disable periodic
+	 * RTC update work, let user configure by sysfs node according to specific circumstance.
+	 */
+	dev_info->rtc_update_period = 0;
 }
 
 static int ufs_get_device_desc(struct ufs_hba *hba)

include/ufs/ufs.h

@@ -591,6 +591,7 @@ struct ufs_dev_info {
 	/* UFS RTC */
 	enum ufs_rtc_time rtc_type;
 	time64_t rtc_time_baseline;
+	u32 rtc_update_period;
 };
 
 /*