arcmsr: clear outbound doorbell buffer

diff -uprN a/drivers/scsi/arcmsr/arcmsr_hba.c b/drivers/scsi/arcmsr/arcmsr_hba.c
@@ -2934,11 +2934,23 @@ static void arcmsr_clear_doorbell_queue_
 		break;
 	case ACB_ADAPTER_TYPE_C: {
 		struct MessageUnit_C *reg = (struct MessageUnit_C *)acb->pmuC;
-		uint32_t outbound_doorbell;
+		uint32_t outbound_doorbell, i;
 		/* empty doorbell Qbuffer if door bell ringed */
 		outbound_doorbell = readl(&reg->outbound_doorbell);
 		writel(outbound_doorbell, &reg->outbound_doorbell_clear);
 		writel(ARCMSR_HBCMU_DRV2IOP_DATA_READ_OK, &reg->inbound_doorbell);
+		for (i = 0; i < 200; i++) {
+			msleep(20);
+			outbound_doorbell = readl(&reg->outbound_doorbell);
+			if (outbound_doorbell &
+				ARCMSR_HBCMU_IOP2DRV_DATA_WRITE_OK) {
+				writel(outbound_doorbell,
+					&reg->outbound_doorbell_clear);
+				writel(ARCMSR_HBCMU_DRV2IOP_DATA_READ_OK,
+					&reg->inbound_doorbell);
+			} else
+				break;
+		}
 		}
 	}
 }

@@ -3166,9 +3178,7 @@ sleep:
 				arcmsr_get_firmware_spec(acb);
 				arcmsr_start_adapter_bgrb(acb);
 				/* clear Qbuffer if door bell ringed */
-				outbound_doorbell = readl(&reg->outbound_doorbell);
-				writel(outbound_doorbell, &reg->outbound_doorbell_clear); /*clear interrupt */
-				writel(ARCMSR_HBCMU_DRV2IOP_DATA_READ_OK, &reg->inbound_doorbell);
+				arcmsr_clear_doorbell_queue_buffer(acb);
 				/* enable outbound Post Queue,outbound doorbell Interrupt */
 				arcmsr_enable_outbound_ints(acb, intmask_org);
 				atomic_set(&acb->rq_map_token, 16);