[PATCH v2 14/15] scsi: ufs: commit descriptors before setting the doorbell

From: Yaniv Gardi
Date: Thu Aug 27 2015 - 08:42:21 EST

Add a write memory barrier to make sure descriptors prepared are actually
written to memory before ringing the doorbell. We have also added the
write memory barrier after ringing the doorbell register so that
controller sees the new request immediately.

Signed-off-by: Gilad Broner <gbroner@xxxxxxxxxxxxxx>
Signed-off-by: Subhash Jadavani <subhashj@xxxxxxxxxxxxxx>
Signed-off-by: Yaniv Gardi <ygardi@xxxxxxxxxxxxxx>

drivers/scsi/ufs/ufshcd.c | 6 ++++++
1 file changed, 6 insertions(+)

diff --git a/drivers/scsi/ufs/ufshcd.c b/drivers/scsi/ufs/ufshcd.c
index 298511a..024cc86 100644
--- a/drivers/scsi/ufs/ufshcd.c
+++ b/drivers/scsi/ufs/ufshcd.c
@@ -833,6 +833,8 @@ void ufshcd_send_command(struct ufs_hba *hba, unsigned int task_tag)
__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();

@@ -1418,6 +1420,8 @@ static int ufshcd_queuecommand(struct Scsi_Host *host, struct scsi_cmnd *cmd)
goto out;

+ /* Make sure descriptors are ready before ringing the doorbell */
+ wmb();
/* issue command to the controller */
spin_lock_irqsave(hba->host->host_lock, flags);
ufshcd_send_command(hba, tag);
@@ -1627,6 +1631,8 @@ static int ufshcd_exec_dev_cmd(struct ufs_hba *hba,

hba->dev_cmd.complete = &wait;

+ /* Make sure descriptors are ready before ringing the doorbell */
+ wmb();
spin_lock_irqsave(hba->host->host_lock, flags);
ufshcd_send_command(hba, tag);
spin_unlock_irqrestore(hba->host->host_lock, flags);

QUALCOMM ISRAEL, on behalf of Qualcomm Innovation Center, Inc. is a member of Code Aurora Forum, hosted by The Linux Foundation
To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
the body of a message to majordomo@xxxxxxxxxxxxxxx
More majordomo info at http://vger.kernel.org/majordomo-info.html
Please read the FAQ at http://www.tux.org/lkml/