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From: Andrew Halaney <ahalaney@redhat.com>
To: Andy Gross <agross@kernel.org>,
	Bjorn Andersson <andersson@kernel.org>,
	Konrad Dybcio <konrad.dybcio@linaro.org>,
	Manivannan Sadhasivam <mani@kernel.org>,
	"James E.J. Bottomley" <jejb@linux.ibm.com>,
	"Martin K. Petersen" <martin.petersen@oracle.com>,
	Hannes Reinecke <hare@suse.de>,
	Janek Kotas <jank@cadence.com>,
	Alim Akhtar <alim.akhtar@samsung.com>,
	Avri Altman <avri.altman@wdc.com>,
	Bart Van Assche <bvanassche@acm.org>,
	Can Guo <quic_cang@quicinc.com>,
	Anjana Hari <quic_ahari@quicinc.com>
Cc: Andrew Halaney <ahalaney@redhat.com>,
	Will Deacon <will@kernel.org>,
	linux-arm-msm@vger.kernel.org,
	linux-scsi@vger.kernel.org,
	linux-kernel@vger.kernel.org,
	Manivannan Sadhasivam <manivannan.sadhasivam@linaro.org>
Subject: [PATCH v5 00/11] scsi: ufs: Remove overzealous memory barriers
Date: Fri, 29 Mar 2024 15:46:42 -0500
Message-ID: <20240329-ufs-reset-ensure-effect-before-delay-v5-0-181252004586@redhat.com>
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Please review with care as I'm not all that confident in this subject.=0D
UFS has a lot of mb() variants used, most with comments saying "ensure this=
=0D
takes effect before continuing". mb()'s aren't really the way to=0D
guarantee that, a read back is the best method.=0D
=0D
Some of these though I think could go a step further and remove the mb()=0D
variant without a read back. As far as I can tell there's no real reason=0D
to ensure it takes effect in most cases (there's no delay() or anything=0D
afterwards, and eventually another readl()/writel() happens which is by=0D
definition ordered). Some of the patches in this series do that if I was=0D
confident it was safe (or a reviewer pointed out prior that they thought=0D
it was safe to do so).=0D
=0D
Thanks in advance for the help,=0D
Andrew=0D
=0D
To: Andy Gross <agross@kernel.org>=0D
To: Bjorn Andersson <andersson@kernel.org>=0D
To: Konrad Dybcio <konrad.dybcio@linaro.org>=0D
To: Manivannan Sadhasivam <mani@kernel.org>=0D
To: James E.J. Bottomley <jejb@linux.ibm.com>=0D
To: Martin K. Petersen <martin.petersen@oracle.com>=0D
To: Hannes Reinecke <hare@suse.de>=0D
To: Janek Kotas <jank@cadence.com>=0D
To: Alim Akhtar <alim.akhtar@samsung.com>=0D
To: Avri Altman <avri.altman@wdc.com>=0D
To: Bart Van Assche <bvanassche@acm.org>=0D
To: Can Guo <quic_cang@quicinc.com>=0D
To: Anjana Hari <quic_ahari@quicinc.com>=0D
Cc: Will Deacon <will@kernel.org>=0D
Cc: linux-arm-msm@vger.kernel.org=0D
Cc: linux-scsi@vger.kernel.org=0D
Cc: linux-kernel@vger.kernel.org=0D
Signed-off-by: Andrew Halaney <ahalaney@redhat.com>=0D
=0D
Changes in v5:=0D
- Rebased on top of next-20240327=0D
- v4 changes need review, so please pay attention to that bit=0D
  still :)=0D
- Link to v4: https://lore.kernel.org/r/20240122-ufs-reset-ensure-effect-be=
fore-delay-v4-0-6c48432151cc@redhat.com=0D
=0D
Changes in v4:=0D
- Collected Reviewed-by tags=0D
- Changed patches 3, 4, 10, and 11 to drop the read back && mb():=0D
    - Please note all of those patches got reviewed-by tags by either=0D
      Can, Mani, or Bart, but one of the three pointed out that they=0D
      thought it could be dropped altogether (some of Mani's comments=0D
      are on my foobar'ed v2). After some consideration I=0D
      agree. Therefore I'd appreciate re-review on those patches by=0D
      you three to make sure that's appropriate=0D
- Link to v3: https://lore.kernel.org/r/20231221-ufs-reset-ensure-effect-be=
fore-delay-v3-0-2195a1b66d2e@redhat.com=0D
=0D
Changes in v3:=0D
- Nothing changed, I just failed to send with b4 (resulting in 2 half=0D
  sent v2 series on list)=0D
- Link to v2: https://lore.kernel.org/r/pnwsdz3i2liivjxvtfwq6tijotgh5adyqip=
jjb5wdvo4jpu7yv@j6fkshm5ipue=0D
=0D
Changes in v2:=0D
- Added review tags for original patch=0D
- Added new patches to address all other memory barriers used=0D
=0D
- Link to v1: https://lore.kernel.org/r/20231208-ufs-reset-ensure-effect-be=
fore-delay-v1-1-8a0f82d7a09e@redhat.com=0D
=0D
---=0D
Andrew Halaney (11):=0D
      scsi: ufs: qcom: Perform read back after writing reset bit=0D
      scsi: ufs: qcom: Perform read back after writing REG_UFS_SYS1CLK_1US=
=0D
      scsi: ufs: qcom: Remove unnecessary mb() after writing testbus config=
=0D
      scsi: ufs: qcom: Perform read back after writing unipro mode=0D
      scsi: ufs: qcom: Perform read back after writing CGC enable=0D
      scsi: ufs: cdns-pltfrm: Perform read back after writing HCLKDIV=0D
      scsi: ufs: core: Perform read back after writing UTP_TASK_REQ_LIST_BA=
SE_H=0D
      scsi: ufs: core: Perform read back after disabling interrupts=0D
      scsi: ufs: core: Perform read back after disabling UIC_COMMAND_COMPL=
=0D
      scsi: ufs: core: Remove unnecessary wmb() after ringing doorbell=0D
      scsi: ufs: core: Remove unnecessary wmb() prior to writing run/stop r=
egs=0D
=0D
 drivers/ufs/core/ufshcd.c      | 15 +++------------=0D
 drivers/ufs/host/cdns-pltfrm.c |  2 +-=0D
 drivers/ufs/host/ufs-qcom.c    | 12 ++----------=0D
 drivers/ufs/host/ufs-qcom.h    | 12 ++++++------=0D
 4 files changed, 12 insertions(+), 29 deletions(-)=0D
---=0D
base-commit: 26074e1be23143b2388cacb36166766c235feb7c=0D
change-id: 20231208-ufs-reset-ensure-effect-before-delay-6e06899d5419=0D
=0D
Best regards,=0D
-- =0D
Andrew Halaney <ahalaney@redhat.com>=0D
=0D