scsi: ufs: core: Simplify ufshcd_auto_hibern8_update()

Calls to ufshcd_auto_hibern8_update() are already serialized: this function
is either called if user space software is not running (preparing to
suspend) or from a single sysfs store callback function.  Kernfs serializes
sysfs .store() callbacks. No functionality is changed.
Reviewed-by: Bao D. Nguyen <quic_nguyenb@quicinc.com>
Reviewed-by: Can Guo <quic_cang@quicinc.com>
Cc: Avri Altman <avri.altman@wdc.com>
Signed-off-by: Bart Van Assche <bvanassche@acm.org>
Link: https://lore.kernel.org/r/20231214192416.3638077-3-bvanassche@acm.orgSigned-off-by: Martin K. Petersen <martin.petersen@oracle.com>

drivers/ufs/core/ufshcd.c

@@ -4423,21 +4423,13 @@ static void ufshcd_configure_auto_hibern8(struct ufs_hba *hba)
 
 void ufshcd_auto_hibern8_update(struct ufs_hba *hba, u32 ahit)
 {
-	unsigned long flags;
-	bool update = false;
+	const u32 cur_ahit = READ_ONCE(hba->ahit);
 
-	if (!ufshcd_is_auto_hibern8_supported(hba))
+	if (!ufshcd_is_auto_hibern8_supported(hba) || cur_ahit == ahit)
 		return;
 
-	spin_lock_irqsave(hba->host->host_lock, flags);
-	if (hba->ahit != ahit) {
-		hba->ahit = ahit;
-		update = true;
-	}
-	spin_unlock_irqrestore(hba->host->host_lock, flags);
-
-	if (update &&
-	    !pm_runtime_suspended(&hba->ufs_device_wlun->sdev_gendev)) {
+	WRITE_ONCE(hba->ahit, ahit);
+	if (!pm_runtime_suspended(&hba->ufs_device_wlun->sdev_gendev)) {
 		ufshcd_rpm_get_sync(hba);
 		ufshcd_hold(hba);
 		ufshcd_configure_auto_hibern8(hba);