Patch "scsi: ufs: core: Perform read back after disabling interrupts" has been added to the 5.4-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 disabling interrupts

to the 5.4-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-disabling-inte.patch
and it can be found in the queue-5.4 subdirectory.

If you, or anyone else, feels it should not be added to the stable tree,
please let <stable@xxxxxxxxxxxxxxx> know about it.



commit e1add71f89e133a5db62153542b3e019d434c193
Author: Andrew Halaney <ahalaney@xxxxxxxxxx>
Date:   Fri Mar 29 15:46:50 2024 -0500

    scsi: ufs: core: Perform read back after disabling interrupts
    
    [ Upstream commit e4a628877119bd40164a651d20321247b6f94a8b ]
    
    Currently, interrupts are cleared and disabled prior to registering the
    interrupt. An mb() is used to complete the clear/disable writes before the
    interrupt is registered.
    
    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 these 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: 199ef13cac7d ("scsi: ufs: avoid spurious UFS host controller interrupts")
    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-v5-8-181252004586@xxxxxxxxxx
    Signed-off-by: Martin K. Petersen <martin.petersen@xxxxxxxxxx>
    Signed-off-by: Sasha Levin <sashal@xxxxxxxxxx>

diff --git a/drivers/scsi/ufs/ufshcd.c b/drivers/scsi/ufs/ufshcd.c
index 363adf489079a..ea6148ee27835 100644
--- a/drivers/scsi/ufs/ufshcd.c
+++ b/drivers/scsi/ufs/ufshcd.c
@@ -8424,7 +8424,7 @@ int ufshcd_init(struct ufs_hba *hba, void __iomem *mmio_base, unsigned int irq)
 	 * Make sure that UFS interrupts are disabled and any pending interrupt
 	 * status is cleared before registering UFS interrupt handler.
 	 */
-	mb();
+	ufshcd_readl(hba, REG_INTERRUPT_ENABLE);
 
 	/* IRQ registration */
 	err = devm_request_irq(dev, irq, ufshcd_intr, IRQF_SHARED, UFSHCD, hba);




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