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() ensure 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>
---
drivers/ufs/core/ufshcd.c | 2 +-
1 file changed, 1 insertion(+), 1 deletion(-)
diff --git a/drivers/ufs/core/ufshcd.c b/drivers/ufs/core/ufshcd.c
index e30fd125988d..a89887878d98 100644
--- a/drivers/ufs/core/ufshcd.c
+++ b/drivers/ufs/core/ufshcd.c
@@ -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);
--
2.44.0
