[PATCH v2 08/26] qedf: Correct the memory barriers in qedf_ring_doorbell.

[Saurav Kashyap]

From: Andrew Vasquez <andr...@marvell.com>

- Correct memory barriers to make sure all cmnds are
flushed.

Signed-off-by: Andrew Vasquez <andr...@marvell.com>
Signed-off-by: Saurav Kashyap <skash...@marvell.com>
---
 drivers/scsi/qedf/qedf_io.c | 12 ++++++++++--
 1 file changed, 10 insertions(+), 2 deletions(-)

diff --git a/drivers/scsi/qedf/qedf_io.c b/drivers/scsi/qedf/qedf_io.c
index 58257ec..ab67056 100644
--- a/drivers/scsi/qedf/qedf_io.c
+++ b/drivers/scsi/qedf/qedf_io.c
@@ -773,10 +773,18 @@ void qedf_ring_doorbell(struct qedf_rport *fcport)
            FCOE_DB_DATA_AGG_VAL_SEL_SHIFT;
 
        dbell.sq_prod = fcport->fw_sq_prod_idx;
+       /* wmb makes sure that the BDs data is updated before updating the
+        * producer, otherwise FW may read old data from the BDs.
+        */
+       wmb();
+       barrier();
        writel(*(u32 *)&dbell, fcport->p_doorbell);
-       /* Make sure SQ index is updated so f/w prcesses requests in order */
+       /*
+        * Fence required to flush the write combined buffer, since another
+        * CPU may write to the same doorbell address and data may be lost
+        * due to relaxed order nature of write combined bar.
+        */
        wmb();
-       mmiowb();
 }
 
 static void qedf_trace_io(struct qedf_rport *fcport, struct qedf_ioreq *io_req,
-- 
1.8.3.1