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authorAndrew Halaney <ahalaney@redhat.com>2024-03-29 15:46:48 -0500
committerMartin K. Petersen <martin.petersen@oracle.com>2024-04-05 21:06:29 -0400
commitb715c55daf598aac8fa339048e4ca8a0916b332e (patch)
tree0aa8ff9af25397f012aec56d59d1763fb1ce392f /drivers/ufs/host/cdns-pltfrm.c
parentd9488511b3ac7eb48a91bc5eded7027525525e03 (diff)
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 <manivannan.sadhasivam@linaro.org> Signed-off-by: Andrew Halaney <ahalaney@redhat.com> Link: https://lore.kernel.org/r/20240329-ufs-reset-ensure-effect-before-delay-v5-6-181252004586@redhat.com Reviewed-by: Bart Van Assche <bvanassche@acm.org> Signed-off-by: Martin K. Petersen <martin.petersen@oracle.com>
Diffstat (limited to 'drivers/ufs/host/cdns-pltfrm.c')
-rw-r--r--drivers/ufs/host/cdns-pltfrm.c2
1 files changed, 1 insertions, 1 deletions
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;
}