scsi: ufs: Improve interrupt handling for shared interrupts

For shared interrupts, the interrupt status might be zero, so check that
first.

Link: https://lore.kernel.org/r/20200811133936.19171-2-adrian.hunter@intel.comReviewed-by: Avri Altman <avri.altman@wdc.com>
Signed-off-by: Adrian Hunter <adrian.hunter@intel.com>
Signed-off-by: Martin K. Petersen <martin.petersen@oracle.com>

drivers/scsi/ufs/ufshcd.c

@@ -5944,7 +5944,7 @@ static irqreturn_t ufshcd_sl_intr(struct ufs_hba *hba, u32 intr_status)
  */
 static irqreturn_t ufshcd_intr(int irq, void *__hba)
 {
-	u32 intr_status, enabled_intr_status;
+	u32 intr_status, enabled_intr_status = 0;
 	irqreturn_t retval = IRQ_NONE;
 	struct ufs_hba *hba = __hba;
 	int retries = hba->nutrs;
@@ -5958,7 +5958,7 @@ static irqreturn_t ufshcd_intr(int irq, void *__hba)
 	 * read, make sure we handle them by checking the interrupt status
 	 * again in a loop until we process all of the reqs before returning.
 	 */
-	do {
+	while (intr_status && retries--) {
 		enabled_intr_status =
 			intr_status & ufshcd_readl(hba, REG_INTERRUPT_ENABLE);
 		if (intr_status)
@@ -5967,7 +5967,7 @@ static irqreturn_t ufshcd_intr(int irq, void *__hba)
 			retval |= ufshcd_sl_intr(hba, enabled_intr_status);
 
 		intr_status = ufshcd_readl(hba, REG_INTERRUPT_STATUS);
-	} while (intr_status && --retries);
+	}
 
 	if (enabled_intr_status && retval == IRQ_NONE) {
 		dev_err(hba->dev, "%s: Unhandled interrupt 0x%08x\n",