diff mbox

[v4,3/7] scsi: dpt_i2o: eliminate duplicate barriers on weakly-ordered archs

Message ID 1521514207-10695-4-git-send-email-okaya@codeaurora.org (mailing list archive)
State New, archived
Headers show

Commit Message

Sinan Kaya March 20, 2018, 2:50 a.m. UTC 
Code includes barrier() 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 <okaya@codeaurora.org>
---
 drivers/scsi/dpt_i2o.c | 6 +++---
 1 file changed, 3 insertions(+), 3 deletions(-)

Comments

Christoph Hellwig March 20, 2018, 10:23 a.m. UTC | #1 
This is a basically unmaintained driver for historic hardware, and not the
right place for micro-optimizations.
Sinan Kaya March 20, 2018, 12:13 p.m. UTC | #2 
On 2018-03-20 06:23, Christoph Hellwig wrote:
> This is a basically unmaintained driver for historic hardware, and not 
> the
> right place for micro-optimizations.

Sure, I can drop this on the next version.
diff mbox

Patch

diff --git a/drivers/scsi/dpt_i2o.c b/drivers/scsi/dpt_i2o.c
index fd172b0..3c1e64a 100644
--- a/drivers/scsi/dpt_i2o.c
+++ b/drivers/scsi/dpt_i2o.c
@@ -1300,7 +1300,7 @@  static s32 adpt_i2o_post_this(adpt_hba* pHba, u32* data, int len)
 	wmb();
 
 	//post message
-	writel(m, pHba->post_port);
+	writel_relaxed(m, pHba->post_port);
 	wmb();
 
 	return 0;
@@ -1390,7 +1390,7 @@  static s32 adpt_i2o_reset_hba(adpt_hba* pHba)
 
 	memcpy_toio(pHba->msg_addr_virt+m, msg, sizeof(msg));
 	wmb();
-	writel(m, pHba->post_port);
+	writel_relaxed(m, pHba->post_port);
 	wmb();
 
 	while(*status == 0){
@@ -2797,7 +2797,7 @@  static s32 adpt_send_nop(adpt_hba*pHba,u32 m)
 	writel( 0,&msg[2]);
 	wmb();
 
-	writel(m, pHba->post_port);
+	writel_relaxed(m, pHba->post_port);
 	wmb();
 	return 0;
 }