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.
Create a new wrapper function with relaxed write operator. Use the new
wrapper when a write is following a barrier().
Signed-off-by: Sinan Kaya <ok...@codeaurora.org>
---
drivers/scsi/csiostor/csio_hw.h | 4 ++++
drivers/scsi/csiostor/csio_wr.c | 2 +-
2 files changed, 5 insertions(+), 1 deletion(-)
diff --git a/drivers/scsi/csiostor/csio_hw.h b/drivers/scsi/csiostor/csio_hw.h
index 30f5f52..9fd8b00 100644
--- a/drivers/scsi/csiostor/csio_hw.h
+++ b/drivers/scsi/csiostor/csio_hw.h
@@ -512,6 +512,10 @@ struct csio_hw {
csio_reg((_h)->regstart, (_r)))
#define csio_wr_reg16(_h, _v, _r) writew((_v), \
csio_reg((_h)->regstart, (_r)))
+
+#define csio_wr_reg32_relaxed(_h, _v, _r) \
+ writel_relaxed((_v), csio_reg((_h)->regstart, (_r)))
+
#define csio_wr_reg32(_h, _v, _r) writel((_v), \
csio_reg((_h)->regstart, (_r)))
#define csio_wr_reg64(_h, _v, _r) writeq((_v), \
diff --git a/drivers/scsi/csiostor/csio_wr.c b/drivers/scsi/csiostor/csio_wr.c
index c0a1778..db26222 100644
--- a/drivers/scsi/csiostor/csio_wr.c
+++ b/drivers/scsi/csiostor/csio_wr.c
@@ -984,7 +984,7 @@ csio_wr_issue(struct csio_hw *hw, int qidx, bool prio)
wmb();
/* Ring SGE Doorbell writing q->pidx into it */
- csio_wr_reg32(hw, DBPRIO_V(prio) | QID_V(q->un.eq.physeqid) |
+ csio_wr_reg32_relaxed(hw, DBPRIO_V(prio) | QID_V(q->un.eq.physeqid) |
PIDX_T5_V(q->inc_idx) | DBTYPE_F,
MYPF_REG(SGE_PF_KDOORBELL_A));
q->inc_idx = 0;
--
2.7.4
