On 12/25/19 2:31 AM, Can Guo wrote:
On 2019-12-25 06:02, Bart Van Assche wrote:
Calling wmb() after having written to a doorbell slows down code and does
not help to commit the doorbell write faster. Hence remove such wmb()
calls. Note: detailed information about the semantics of writel() is
available in Documentation/driver-api/device-io.rst.
Cc: Bean Huo <beanhuo@xxxxxxxxxx>
Cc: Can Guo <cang@xxxxxxxxxxxxxx>
Cc: Avri Altman <avri.altman@xxxxxxx>
Cc: Stanley Chu <stanley.chu@xxxxxxxxxxxx>
Cc: Tomas Winkler <tomas.winkler@xxxxxxxxx>
Signed-off-by: Bart Van Assche <bvanassche@xxxxxxx>
---
drivers/scsi/ufs/ufshcd.c | 4 ----
1 file changed, 4 deletions(-)
diff --git a/drivers/scsi/ufs/ufshcd.c b/drivers/scsi/ufs/ufshcd.c
index 4d9bb1932b39..edcc137c436b 100644
--- a/drivers/scsi/ufs/ufshcd.c
+++ b/drivers/scsi/ufs/ufshcd.c
@@ -1879,8 +1879,6 @@ void ufshcd_send_command(struct ufs_hba *hba,
unsigned int task_tag)
ufshcd_clk_scaling_start_busy(hba);
__set_bit(task_tag, &hba->outstanding_reqs);
ufshcd_writel(hba, 1 << task_tag, REG_UTP_TRANSFER_REQ_DOOR_BELL);
- /* Make sure that doorbell is committed immediately */
- wmb();
}
/**
@@ -5766,8 +5764,6 @@ static int __ufshcd_issue_tm_cmd(struct ufs_hba
*hba,
wmb();
ufshcd_writel(hba, 1 << free_slot, REG_UTP_TASK_REQ_DOOR_BELL);
- /* Make sure that doorbell is committed immediately */
- wmb();
spin_unlock_irqrestore(host->host_lock, flags);
Hi Bart,
Three wmb()s were added in commit ad1a1b9cd because we did see instances on
which OCS=3(MISMATCH_DATA_BUFFER_SIZE) error were observed in large scale
test. Commit ad1a1b9cd fixed the error and we had confirmed it through
large amount of tests. I am not sure removing the 2 wmb()s here would cause
regression or not.
Hi Can,
Thank you for having reported this. I will drop this patch.
Bart.
