scsi: ufs: Fix possible unclocked access to auto hibern8 timer register

Before access auto hibner8 timer register, make sure power and clock are
properly configured to avoid unclocked register access.

Link: https://lore.kernel.org/r/1583398391-14273-1-git-send-email-cang@codeaurora.org
Fixes: ba7af5ec ("scsi: ufs: export ufshcd_auto_hibern8_update for vendor usage")
Reviewed-by: Stanley Chu <stanley.chu@mediatek.com>
Signed-off-by: Can Guo <cang@codeaurora.org>
Signed-off-by: Martin K. Petersen <martin.petersen@oracle.com>

drivers/scsi/ufs/ufshcd.c

@@ -3884,18 +3884,25 @@ EXPORT_SYMBOL_GPL(ufshcd_uic_hibern8_exit);
 void ufshcd_auto_hibern8_update(struct ufs_hba *hba, u32 ahit)
 {
 	unsigned long flags;
+	bool update = false;
 
-	if (!(hba->capabilities & MASK_AUTO_HIBERN8_SUPPORT))
+	if (!ufshcd_is_auto_hibern8_supported(hba))
 		return;
 
 	spin_lock_irqsave(hba->host->host_lock, flags);
-	if (hba->ahit == ahit)
-		goto out_unlock;
+	if (hba->ahit != ahit) {
 		hba->ahit = ahit;
-	if (!pm_runtime_suspended(hba->dev))
-		ufshcd_writel(hba, hba->ahit, REG_AUTO_HIBERNATE_IDLE_TIMER);
-out_unlock:
+		update = true;
+	}
 	spin_unlock_irqrestore(hba->host->host_lock, flags);
+
+	if (update && !pm_runtime_suspended(hba->dev)) {
+		pm_runtime_get_sync(hba->dev);
+		ufshcd_hold(hba, false);
+		ufshcd_auto_hibern8_enable(hba);
+		ufshcd_release(hba);
+		pm_runtime_put(hba->dev);
+	}
 }
 EXPORT_SYMBOL_GPL(ufshcd_auto_hibern8_update);