scsi: ufs: Remove locking from around single register writes

Single register writes are atomic and hence do not need to be surrounded by
locking. Additionally, MMIO writes are typically posted asynchronously.
Hence, there is no guarantee that these have finished by the time the
spin_unlock*() call has finished. See also the nonposted-mmio property of
the Open Firmware tree. See also pci_iomap().

Link: https://lore.kernel.org/r/20220419225811.4127248-21-bvanassche@acm.orgTested-by: Bean Huo <beanhuo@micron.com>
Reviewed-by: Avri Altman <avri.altman@wdc.com>
Reviewed-by: Bean Huo <beanhuo@micron.com>
Signed-off-by: Bart Van Assche <bvanassche@acm.org>
Signed-off-by: Martin K. Petersen <martin.petersen@oracle.com>

drivers/scsi/ufs/ufs-mediatek.c

@@ -171,7 +171,6 @@ static int ufs_mtk_hce_enable_notify(struct ufs_hba *hba,
 				     enum ufs_notify_change_status status)
 {
 	struct ufs_mtk_host *host = ufshcd_get_variant(hba);
-	unsigned long flags;
 
 	if (status == PRE_CHANGE) {
 		if (host->unipro_lpm) {
@@ -185,12 +184,8 @@ static int ufs_mtk_hce_enable_notify(struct ufs_hba *hba,
 			ufs_mtk_crypto_enable(hba);
 
 		if (host->caps & UFS_MTK_CAP_DISABLE_AH8) {
-			spin_lock_irqsave(hba->host->host_lock, flags);
 			ufshcd_writel(hba, 0,
 				      REG_AUTO_HIBERNATE_IDLE_TIMER);
-			spin_unlock_irqrestore(hba->host->host_lock,
-					       flags);
-
 			hba->capabilities &= ~MASK_AUTO_HIBERN8_SUPPORT;
 			hba->ahit = 0;
 		}
@@ -994,13 +989,10 @@ static void ufs_mtk_vreg_set_lpm(struct ufs_hba *hba, bool lpm)
 
 static void ufs_mtk_auto_hibern8_disable(struct ufs_hba *hba)
 {
-	unsigned long flags;
 	int ret;
 
 	/* disable auto-hibern8 */
-	spin_lock_irqsave(hba->host->host_lock, flags);
 	ufshcd_writel(hba, 0, REG_AUTO_HIBERNATE_IDLE_TIMER);
-	spin_unlock_irqrestore(hba->host->host_lock, flags);
 
 	/* wait host return to idle state when auto-hibern8 off */
 	ufs_mtk_wait_idle_state(hba, 5);

drivers/scsi/ufs/ufshcd.c

@@ -4207,14 +4207,10 @@ EXPORT_SYMBOL_GPL(ufshcd_auto_hibern8_update);
 
 void ufshcd_auto_hibern8_enable(struct ufs_hba *hba)
 {
-	unsigned long flags;
-
 	if (!ufshcd_is_auto_hibern8_supported(hba))
 		return;
 
-	spin_lock_irqsave(hba->host->host_lock, flags);
 	ufshcd_writel(hba, hba->ahit, REG_AUTO_HIBERNATE_IDLE_TIMER);
-	spin_unlock_irqrestore(hba->host->host_lock, flags);
 }
 
  /**