Commit 408e2808 authored by Andrew Halaney's avatar Andrew Halaney Committed by Martin K. Petersen
Browse files

scsi: ufs: core: Perform read back after writing UTP_TASK_REQ_LIST_BASE_H 

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: 88441a8d ("scsi: ufs: core: Add hibernation callbacks")
Reviewed-by: default avatarManivannan Sadhasivam <manivannan.sadhasivam@linaro.org>
Reviewed-by: default avatarBart Van Assche <bvanassche@acm.org>
Reviewed-by: default avatarCan Guo <quic_cang@quicinc.com>
Signed-off-by: default avatarAndrew Halaney <ahalaney@redhat.com>
Link: https://lore.kernel.org/r/20240329-ufs-reset-ensure-effect-before-delay-v5-7-181252004586@redhat.com


Signed-off-by: default avatarMartin K. Petersen <martin.petersen@oracle.com>
parent b715c55d

drivers/ufs/core/ufshcd.c

+1 −1
Original line number Diff line number Diff line
@@ -10395,7 +10395,7 @@ 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);