Currently after writing to REG_UFS_SYS1CLK_1US a mb() is used to ensure
that write has gone through to the device.
mb() ensure that the write completes, but completion doesn't mean that
it isn't stored in a buffer somewhere. The recommendation for
ensuring this bit has taken effect on the device is to perform a read
back to force it to make it all the way to the device. This is
documented in device-io.rst and a talk by Will Deacon on this can
be seen over here:
https://youtu.be/i6DayghhA8Q?si=MiyxB5cKJXSaoc01&t=1678
Let's do that to ensure the bit hits the device. Because the mb()'s
purpose wasn't to add extra ordering (on top of the ordering guaranteed
by writel()/readl()), it can safely be removed.
Fixes: f06fcc7155dc ("scsi: ufs-qcom: add QUniPro hardware support and power optimizations")
Reviewed-by: Can Guo <quic_cang@xxxxxxxxxxx>
Signed-off-by: Andrew Halaney <ahalaney@xxxxxxxxxx>
---
drivers/ufs/host/ufs-qcom.c | 2 +-
1 file changed, 1 insertion(+), 1 deletion(-)
diff --git a/drivers/ufs/host/ufs-qcom.c b/drivers/ufs/host/ufs-qcom.c
index 39eef470f8fa..0603a07a23a2 100644
--- a/drivers/ufs/host/ufs-qcom.c
+++ b/drivers/ufs/host/ufs-qcom.c
@@ -501,7 +501,7 @@ static int ufs_qcom_cfg_timers(struct ufs_hba *hba, u32 gear,
* make sure above write gets applied before we return from
* this function.
*/
- mb();
+ ufshcd_readl(hba, REG_UFS_SYS1CLK_1US);
}
return 0;
--
2.43.0
