This is a note to let you know that I've just added the patch titled
scsi: ufs: core: Perform read back after writing UTP_TASK_REQ_LIST_BASE_H
to the 6.6-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-core-perform-read-back-after-writing-utp_ta.patch
and it can be found in the queue-6.6 subdirectory.
If you, or anyone else, feels it should not be added to the stable tree,
please let <stable@xxxxxxxxxxxxxxx> know about it.
commit 52f8beaea74a18a297c67063828ba2d25a1ff215
Author: Andrew Halaney <ahalaney@xxxxxxxxxx>
Date: Fri Mar 29 15:46:49 2024 -0500
scsi: ufs: core: Perform read back after writing UTP_TASK_REQ_LIST_BASE_H
[ Upstream commit 408e28086f1c7a6423efc79926a43d7001902fae ]
Currently, the UTP_TASK_REQ_LIST_BASE_L/UTP_TASK_REQ_LIST_BASE_H regs are
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 these
bits have 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 bits hit 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: 88441a8d355d ("scsi: ufs: core: Add hibernation callbacks")
Reviewed-by: Manivannan Sadhasivam <manivannan.sadhasivam@xxxxxxxxxx>
Reviewed-by: Bart Van Assche <bvanassche@xxxxxxx>
Reviewed-by: Can Guo <quic_cang@xxxxxxxxxxx>
Signed-off-by: Andrew Halaney <ahalaney@xxxxxxxxxx>
Link: https://lore.kernel.org/r/20240329-ufs-reset-ensure-effect-before-delay-v5-7-181252004586@xxxxxxxxxx
Signed-off-by: Martin K. Petersen <martin.petersen@xxxxxxxxxx>
Signed-off-by: Sasha Levin <sashal@xxxxxxxxxx>
diff --git a/drivers/ufs/core/ufshcd.c b/drivers/ufs/core/ufshcd.c
index 344806330be16..cd1b9db8543dc 100644
--- a/drivers/ufs/core/ufshcd.c
+++ b/drivers/ufs/core/ufshcd.c
@@ -10152,7 +10152,7 @@ int ufshcd_system_restore(struct device *dev)
* are updated with the latest queue addresses. Only after
* updating these addresses, we can queue the new commands.
*/
- mb();
+ ufshcd_readl(hba, REG_UTP_TASK_REQ_LIST_BASE_H);
/* Resuming from hibernate, assume that link was OFF */
ufshcd_set_link_off(hba);
