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

Commit Message

Saurav Kashyap March 5, 2019, 10:58 a.m. UTC

From: Andrew Vasquez <[e-mail]>

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

Signed-off-by: Andrew Vasquez <[e-mail]>
Signed-off-by: Saurav Kashyap <[e-mail]>
---
 drivers/scsi/qedf/qedf_io.c | 12 ++++++++++--
 1 file changed, 10 insertions(+), 2 deletions(-)

Patch

diff --git a/drivers/scsi/qedf/qedf_io.c b/drivers/scsi/qedf/qedf_io.c
index 1a36ab5..f04191f 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,