Patch "scsi: ufs: core: Perform read back after writing UTP_TASK_REQ_LIST_BASE_H" has been added to the 6.6-stable tree

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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);




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