arcmsr: clear outbound doorbell buffer completely

Clear outbound doorbell buffer completely for adapter type C.  This is to
prevent getting bad data input from IOP before ioctl command processing
starts.
Signed-off-by: Ching Huang <ching2048@areca.com.tw>
Reviewed-by: Tomas Henzl <thenzl@redhat.com>
Signed-off-by: Christoph Hellwig <hch@lst.de>

drivers/scsi/arcmsr/arcmsr_hba.c

@@ -2870,11 +2870,23 @@ static void arcmsr_clear_doorbell_queue_buffer(struct AdapterControlBlock *acb)
 		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;
+		}
 		}
 	}
 }
@@ -3102,9 +3114,7 @@ static int arcmsr_bus_reset(struct scsi_cmnd *cmd)
 				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);