scsi: pm80xx: Fixed system hang issue during kexec boot

When the firmware is not responding, execution of kexec boot causes a system
hang. When firmware assertion happened, driver get notified with interrupt
vector updated in MPI configuration table. Then, the driver will read
scratchpad register and set controller_fatal_error flag to true.

Signed-off-by: Deepak Ukey <deepak.ukey@microchip.com>
Signed-off-by: Viswas G <Viswas.G@microchip.com>
Acked-by: Jack Wang <jinpu.wang@profitbricks.com>
Signed-off-by: Martin K. Petersen <martin.petersen@oracle.com>
diff --git a/drivers/scsi/pm8001/pm8001_hwi.c b/drivers/scsi/pm8001/pm8001_hwi.c
index a14bf50..e37ab97 100644
--- a/drivers/scsi/pm8001/pm8001_hwi.c
+++ b/drivers/scsi/pm8001/pm8001_hwi.c
@@ -1479,6 +1479,12 @@ u32 pm8001_mpi_msg_consume(struct pm8001_hba_info *pm8001_ha,
 		} else {
 			u32 producer_index;
 			void *pi_virt = circularQ->pi_virt;
+			/* spurious interrupt during setup if
+			 * kexec-ing and driver doing a doorbell access
+			 * with the pre-kexec oq interrupt setup
+			 */
+			if (!pi_virt)
+				break;
 			/* Update the producer index from SPC */
 			producer_index = pm8001_read_32(pi_virt);
 			circularQ->producer_index = cpu_to_le32(producer_index);