scsi: ufs: use async operation for hibern8 operation

When enabling/disabling hibern8, we will call flush_work
to wait for the task finished. Using async operation
to avoid long waiting time.

Bug: 138085490
Test: Boot, cat /sys/kernel/debug/ufshcd0/show_hba and
check hibern8_exit_cnt
Signed-off-by: Martin Liu <liumartin@google.com>
Signed-off-by: Alexander Winkowski <dereference23@outlook.com>
Change-Id: I427cd8e40cbc6674a145142babbd92a1062dc511

drivers/scsi/ufs/ufshcd.c

@@ -3350,19 +3350,15 @@ static ssize_t ufshcd_hibern8_on_idle_enable_show(struct device *dev,
 			hba->hibern8_on_idle.is_enabled);
 }
 
-static ssize_t ufshcd_hibern8_on_idle_enable_store(struct device *dev,
-		struct device_attribute *attr, const char *buf, size_t count)
+
+static void ufshcd_hibern8_on_idle_switch_work(struct work_struct *work)
 {
-	struct ufs_hba *hba = dev_get_drvdata(dev);
+	struct ufs_hba *hba;
 	unsigned long flags;
 	u32 value;
 
-	if (kstrtou32(buf, 0, &value))
-		return -EINVAL;
-
-	value = !!value;
-	if (value == hba->hibern8_on_idle.is_enabled)
-		goto out;
+	hba = container_of(work, struct ufs_hba, hibern8_on_idle_enable_work);
+	value = !hba->hibern8_on_idle.is_enabled;
 
 	/* Update auto hibern8 timer value if supported */
 	if (ufshcd_is_auto_hibern8_supported(hba)) {
@@ -3386,6 +3382,28 @@ static ssize_t ufshcd_hibern8_on_idle_enable_store(struct device *dev,
 
 	hba->hibern8_on_idle.is_enabled = value;
 out:
+	return;
+}
+
+static ssize_t ufshcd_hibern8_on_idle_enable_store(struct device *dev,
+		struct device_attribute *attr, const char *buf, size_t count)
+{
+	struct ufs_hba *hba = dev_get_drvdata(dev);
+	u32 value;
+
+	if (kstrtou32(buf, 0, &value))
+		return -EINVAL;
+
+	mutex_lock(&hba->hibern8_on_idle.enable_mutex);
+	/*
+	 * make sure that former operation has been done before we exectue
+	 * next action. This could gareatee the order and synconization.
+	 */
+	flush_work(&hba->hibern8_on_idle_enable_work);
+	if (hba->hibern8_on_idle.is_enabled != !!value)
+		schedule_work(&hba->hibern8_on_idle_enable_work);
+	mutex_unlock(&hba->hibern8_on_idle.enable_mutex);
+
 	return count;
 }
 
@@ -12954,12 +12972,15 @@ int ufshcd_init(struct ufs_hba *hba, void __iomem *mmio_base, unsigned int irq)
 	INIT_WORK(&hba->card_detect_work, ufshcd_card_detect_handler);
 	INIT_WORK(&hba->rls_work, ufshcd_rls_handler);
 	INIT_WORK(&hba->fatal_mode_work, ufshcd_fatal_mode_handler);
+	INIT_WORK(&hba->hibern8_on_idle_enable_work,
+			ufshcd_hibern8_on_idle_switch_work);
 
 	/* Initialize UIC command mutex */
 	mutex_init(&hba->uic_cmd_mutex);
 
 	/* Initialize mutex for device management commands */
 	mutex_init(&hba->dev_cmd.lock);
+	mutex_init(&hba->hibern8_on_idle.enable_mutex);
 
 #if IS_ENABLED(CONFIG_BLK_TURBO_WRITE)
 	/* Initialize TW ctrl mutex */

drivers/scsi/ufs/ufshcd.h

@@ -520,6 +520,7 @@ enum ufshcd_hibern8_on_idle_state {
  * @delay_attr: sysfs attribute to control delay_attr
  * @enable_attr: sysfs attribute to enable/disable hibern8 on idle
  * @is_enabled: Indicates the current status of hibern8
+ * @enable_mutex: protect sys node race from multithread access
  */
 struct ufs_hibern8_on_idle {
 	struct delayed_work enter_work;
@@ -531,6 +532,7 @@ struct ufs_hibern8_on_idle {
 	struct device_attribute delay_attr;
 	struct device_attribute enable_attr;
 	bool is_enabled;
+	struct mutex enable_mutex;
 };
 
 /**
@@ -1079,6 +1081,7 @@ struct ufs_hba {
 	struct work_struct eh_work;
 	struct work_struct eeh_work;
 	struct work_struct rls_work;
+	struct work_struct hibern8_on_idle_enable_work;
 
 	/* HBA Errors */
 	u32 errors;