5.15-stable review patch. If anyone has any objections, please let me know.
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From: Andrew Halaney ahalaney@redhat.com
[ Upstream commit a862fafa263aea0f427d51aca6ff7fd9eeaaa8bd ]
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... Reviewed-by: Manivannan Sadhasivam manivannan.sadhasivam@linaro.org Signed-off-by: Martin K. Petersen martin.petersen@oracle.com Signed-off-by: Sasha Levin sashal@kernel.org --- drivers/scsi/ufs/ufs-qcom.c | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-)
diff --git a/drivers/scsi/ufs/ufs-qcom.c b/drivers/scsi/ufs/ufs-qcom.c index f810b99ef5c51..4809ced13851e 100644 --- a/drivers/scsi/ufs/ufs-qcom.c +++ b/drivers/scsi/ufs/ufs-qcom.c @@ -449,7 +449,7 @@ 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); }
if (ufs_qcom_cap_qunipro(host))