From 4bfc22dbf7bd2d707be1bb1511b4722c11423508 Mon Sep 17 00:00:00 2001 From: Andrew Halaney Date: Fri, 29 Mar 2024 15:46:48 -0500 Subject: scsi: ufs: cdns-pltfrm: Perform read back after writing HCLKDIV [ Upstream commit b715c55daf598aac8fa339048e4ca8a0916b332e ] Currently, HCLKDIV is written to and then completed with an mb(). mb() ensures 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: d90996dae8e4 ("scsi: ufs: Add UFS platform driver for Cadence UFS") Reviewed-by: Manivannan Sadhasivam Signed-off-by: Andrew Halaney Link: https://lore.kernel.org/r/20240329-ufs-reset-ensure-effect-before-delay-v5-6-181252004586@redhat.com Reviewed-by: Bart Van Assche Signed-off-by: Martin K. Petersen Signed-off-by: Sasha Levin --- drivers/ufs/host/cdns-pltfrm.c | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-) (limited to 'drivers/ufs') diff --git a/drivers/ufs/host/cdns-pltfrm.c b/drivers/ufs/host/cdns-pltfrm.c index bb30267da471..66811d8d1929 100644 --- a/drivers/ufs/host/cdns-pltfrm.c +++ b/drivers/ufs/host/cdns-pltfrm.c @@ -136,7 +136,7 @@ static int cdns_ufs_set_hclkdiv(struct ufs_hba *hba) * Make sure the register was updated, * UniPro layer will not work with an incorrect value. */ - mb(); + ufshcd_readl(hba, CDNS_UFS_REG_HCLKDIV); return 0; } -- cgit v1.2.3