This is an RFC because I'm not all the confident in this topic. UFS has
a lot of mb() variants used, most with comments saying "ensure this
takes effect before continuing". mb()'s aren't really the way to
guarantee that, a read back is the best method.
Some of these though I think could go a step further and remove the mb()
variant without a read back. As far as I can tell there's no real reason
to ensure it takes effect in most cases (there's no delay() or anything
afterwards, and eventually another readl()/writel() happens which is by
definition ordered). Some of the patches in this series do that if I was
confident it was safe (or a reviewer pointed out prior that they thought
it was safe to do so).
Thanks in advance for the help,
Andrew
Signed-off-by: Andrew Halaney <ahalaney@xxxxxxxxxx>
---
Changes in v4:
- Collected Reviewed-by tags
- Changed patches 3, 4, 10, and 11 to drop the read back && mb():
- Please note all of those patches got reviewed-by tags by either
Can, Mani, or Bart, but one of the three pointed out that they
thought it could be dropped altogether (some of Mani's comments
are on my foobar'ed v2). After some consideration I
agree. Therefore I'd appreciate re-review on those patches by
you three to make sure that's appropriate
- Link to v3: https://lore.kernel.org/r/20231221-ufs-reset-ensure-effect-before-delay-v3-0-2195a1b66d2e@xxxxxxxxxx
Changes in v3:
- Nothing changed, I just failed to send with b4 (resulting in 2 half
sent v2 series on list)
- Link to v2: https://lore.kernel.org/r/pnwsdz3i2liivjxvtfwq6tijotgh5adyqipjjb5wdvo4jpu7yv@j6fkshm5ipue
Changes in v2:
- Added review tags for original patch
- Added new patches to address all other memory barriers used
- Link to v1: https://lore.kernel.org/r/20231208-ufs-reset-ensure-effect-before-delay-v1-1-8a0f82d7a09e@xxxxxxxxxx
---
Andrew Halaney (11):
scsi: ufs: qcom: Perform read back after writing reset bit
scsi: ufs: qcom: Perform read back after writing REG_UFS_SYS1CLK_1US
scsi: ufs: qcom: Remove unnecessary mb() after writing testbus config
scsi: ufs: qcom: Perform read back after writing unipro mode
scsi: ufs: qcom: Perform read back after writing CGC enable
scsi: ufs: cdns-pltfrm: Perform read back after writing HCLKDIV
scsi: ufs: core: Perform read back after writing UTP_TASK_REQ_LIST_BASE_H
scsi: ufs: core: Perform read back after disabling interrupts
scsi: ufs: core: Perform read back after disabling UIC_COMMAND_COMPL
scsi: ufs: core: Remove unnecessary wmb() after ringing doorbell
scsi: ufs: core: Remove unnecessary wmb() prior to writing run/stop regs
drivers/ufs/core/ufshcd.c | 15 +++------------
drivers/ufs/host/cdns-pltfrm.c | 2 +-
drivers/ufs/host/ufs-qcom.c | 12 ++----------
drivers/ufs/host/ufs-qcom.h | 12 ++++++------
4 files changed, 12 insertions(+), 29 deletions(-)
---
base-commit: 319fbd8fc6d339e0a1c7b067eed870c518a13a02
change-id: 20231208-ufs-reset-ensure-effect-before-delay-6e06899d5419
Best regards,
--
Andrew Halaney <ahalaney@xxxxxxxxxx>
