RE: [PATCH 5/5] megaraid_sas: add mmio barrier after register writes

[Sumit Saxena <sumit.saxena@broadcom.com>]

>-----Original Message-----
>From: Hannes Reinecke [mailto:hare@suse.de]
>Sent: Friday, November 11, 2016 3:15 PM
>To: Martin K. Petersen
>Cc: Christoph Hellwig; James Bottomley; Sumit Saxena; linux-
>scsi@vger.kernel.org; Hannes Reinecke; Hannes Reinecke
>Subject: [PATCH 5/5] megaraid_sas: add mmio barrier after register writes
>
>The megaraid_sas HBA only has a single register for I/O submission, which
will be
>hit pretty hard with scsi-mq. To ensure that the PCI writes have made it
across we
>need to add a mmio barrier after each write; otherwise I've been seeing
spurious
>command completions and I/O stalls.
>
>Signed-off-by: Hannes Reinecke <hare@suse.com>
Acked-by: Sumit Saxena <sumit.saxena@broadcom.com>

>---
> drivers/scsi/megaraid/megaraid_sas_fusion.c | 1 +
> 1 file changed, 1 insertion(+)
>
>diff --git a/drivers/scsi/megaraid/megaraid_sas_fusion.c
>b/drivers/scsi/megaraid/megaraid_sas_fusion.c
>index aba53c0..729a654 100644
>--- a/drivers/scsi/megaraid/megaraid_sas_fusion.c
>+++ b/drivers/scsi/megaraid/megaraid_sas_fusion.c
>@@ -196,6 +196,7 @@ inline void megasas_return_cmd_fusion(struct
>megasas_instance *instance,
> 			le32_to_cpu(req_desc->u.low));
>
> 	writeq(req_data, &instance->reg_set->inbound_low_queue_port);
>+	mmiowb();
> #else
> 	unsigned long flags;
>
>--
>1.8.5.6