6.9-stable review patch. If anyone has any objections, please let me know.
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From: Andrew Halaney ahalaney@redhat.com
[ Upstream commit 823150ecf04f958213cf3bf162187cd1a91c885c ]
Currently, the QUNIPRO_SEL bit is written to and then an mb() is used to ensure that completes before continuing.
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
But, there's really no reason to even ensure completion before continuing. The only requirement here is that this write is ordered to this endpoint (which readl()/writel() guarantees already). For that reason the mb() can be dropped altogether without anything forcing completion.
Fixes: f06fcc7155dc ("scsi: ufs-qcom: add QUniPro hardware support and power optimizations") Signed-off-by: Andrew Halaney ahalaney@redhat.com Link: https://lore.kernel.org/r/20240329-ufs-reset-ensure-effect-before-delay-v5-4... 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/ufs/host/ufs-qcom.c | 3 --- 1 file changed, 3 deletions(-)
diff --git a/drivers/ufs/host/ufs-qcom.c b/drivers/ufs/host/ufs-qcom.c index bb3445e5efa8b..004a0f6b1fffa 100644 --- a/drivers/ufs/host/ufs-qcom.c +++ b/drivers/ufs/host/ufs-qcom.c @@ -284,9 +284,6 @@ static void ufs_qcom_select_unipro_mode(struct ufs_qcom_host *host)
if (host->hw_ver.major >= 0x05) ufshcd_rmwl(host->hba, QUNIPRO_G4_SEL, 0, REG_UFS_CFG0); - - /* make sure above configuration is applied before we return */ - mb(); }
/*