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authorAndrew Halaney <ahalaney@redhat.com>2024-03-29 23:46:44 +0300
committerMartin K. Petersen <martin.petersen@oracle.com>2024-04-06 04:06:28 +0300
commita862fafa263aea0f427d51aca6ff7fd9eeaaa8bd (patch)
tree8bcc3ee186e36d4a0a0140955628bb6cf79a5738
parentc4d28e06b0c94636f6e35d003fa9ebac0a94e1ae (diff)
downloadlinux-a862fafa263aea0f427d51aca6ff7fd9eeaaa8bd.tar.xz
scsi: ufs: qcom: Perform read back after writing REG_UFS_SYS1CLK_1US
Currently after writing to REG_UFS_SYS1CLK_1US a mb() is used to ensure that write has gone through to the device. 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: f06fcc7155dc ("scsi: ufs-qcom: add QUniPro hardware support and power optimizations") Reviewed-by: Can Guo <quic_cang@quicinc.com> Signed-off-by: Andrew Halaney <ahalaney@redhat.com> Link: https://lore.kernel.org/r/20240329-ufs-reset-ensure-effect-before-delay-v5-2-181252004586@redhat.com Reviewed-by: Manivannan Sadhasivam <manivannan.sadhasivam@linaro.org> Signed-off-by: Martin K. Petersen <martin.petersen@oracle.com>
-rw-r--r--drivers/ufs/host/ufs-qcom.c2
1 files changed, 1 insertions, 1 deletions
diff --git a/drivers/ufs/host/ufs-qcom.c b/drivers/ufs/host/ufs-qcom.c
index 8d68bd21ae73..46f8a74e5037 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;