This is a note to let you know that I've just added the patch titled
scsi: ufs: qcom: Perform read back after writing unipro mode
to the 6.9-stable tree which can be found at:
http://www.kernel.org/git/?p=linux/kernel/git/stable/stable-queue.git;a=summary
The filename of the patch is:
scsi-ufs-qcom-perform-read-back-after-writing-unipro.patch
and it can be found in the queue-6.9 subdirectory.
If you, or anyone else, feels it should not be added to the stable tree,
please let <stable@xxxxxxxxxxxxxxx> know about it.
commit 0a540ccb4bb8f1b5c6fcb4d5d949a40144ca6b9c
Author: Andrew Halaney <ahalaney@xxxxxxxxxx>
Date: Fri Mar 29 15:46:46 2024 -0500
scsi: ufs: qcom: Perform read back after writing unipro mode
[ 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@xxxxxxxxxx>
Link: https://lore.kernel.org/r/20240329-ufs-reset-ensure-effect-before-delay-v5-4-181252004586@xxxxxxxxxx
Reviewed-by: Manivannan Sadhasivam <manivannan.sadhasivam@xxxxxxxxxx>
Signed-off-by: Martin K. Petersen <martin.petersen@xxxxxxxxxx>
Signed-off-by: Sasha Levin <sashal@xxxxxxxxxx>
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();
}
/*
