[v5,1/3] RDMA/bnxt_re: Eliminate duplicate barriers on weakly-ordered archs

Commit Message

Sinan Kaya March 22, 2018, 4:26 p.m. UTC

Code includes wmb() followed by writel(). writel() already has a barrier on
some architectures like arm64.

This ends up CPU observing two barriers back to back before executing the
register write.

Since code already has an explicit barrier call, changing writel() to
writel_relaxed().

Signed-off-by: Sinan Kaya <[e-mail]>
---
 drivers/infiniband/hw/bnxt_re/qplib_rcfw.c | 9 +++++----
 1 file changed, 5 insertions(+), 4 deletions(-)

Patch

diff --git a/drivers/infiniband/hw/bnxt_re/qplib_rcfw.c b/drivers/infiniband/hw/bnxt_re/qplib_rcfw.c
index 8329ec6..10f9a26 100644
--- a/drivers/infiniband/hw/bnxt_re/qplib_rcfw.c
+++ b/drivers/infiniband/hw/bnxt_re/qplib_rcfw.c
@@ -181,10 +181,11 @@  static int __send_message(struct bnxt_qplib_rcfw *rcfw, struct cmdq_base *req,
 
 	/* ring CMDQ DB */
 	wmb();
-	writel(cmdq_prod, rcfw->cmdq_bar_reg_iomem +
-	       rcfw->cmdq_bar_reg_prod_off);
-	writel(RCFW_CMDQ_TRIG_VAL, rcfw->cmdq_bar_reg_iomem +
-	       rcfw->cmdq_bar_reg_trig_off);
+	writel_relaxed(cmdq_prod, rcfw->cmdq_bar_reg_iomem +
+		       rcfw->cmdq_bar_reg_prod_off);
+	writel_relaxed(RCFW_CMDQ_TRIG_VAL, rcfw->cmdq_bar_reg_iomem +
+		       rcfw->cmdq_bar_reg_trig_off);
+	mmiowb();
 done:
 	spin_unlock_irqrestore(&cmdq->lock, flags);
 	/* Return the CREQ response pointer */