From: Andrew Halaney Date: Fri, 29 Mar 2024 20:46:48 +0000 (-0500) Subject: scsi: ufs: cdns-pltfrm: Perform read back after writing HCLKDIV X-Git-Tag: v6.10-rc1~156^2~34^2~5 X-Git-Url: http://git.ipfire.org/?a=commitdiff_plain;h=b715c55daf598aac8fa339048e4ca8a0916b332e;p=thirdparty%2Fkernel%2Flinux.git scsi: ufs: cdns-pltfrm: Perform read back after writing HCLKDIV 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 --- diff --git a/drivers/ufs/host/cdns-pltfrm.c b/drivers/ufs/host/cdns-pltfrm.c index bb30267da4711..66811d8d1929c 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; }