[RFC,v4,07/11] scsi: ufs: core: Perform read back after writing UTP_TASK_REQ_LIST_BASE_H
Message ID | 20240122-ufs-reset-ensure-effect-before-delay-v4-7-90a54c832508@redhat.com |
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State | New |
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Mon, 22 Jan 2024 09:24:38 -0800 (PST) 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> 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 RFC v4 07/11] scsi: ufs: core: Perform read back after writing UTP_TASK_REQ_LIST_BASE_H Date: Mon, 22 Jan 2024 11:24:03 -0600 Message-ID: <20240122-ufs-reset-ensure-effect-before-delay-v4-7-90a54c832508@redhat.com> X-Mailer: git-send-email 2.43.0 In-Reply-To: <20240122-ufs-reset-ensure-effect-before-delay-v4-0-90a54c832508@redhat.com> References: <20240122-ufs-reset-ensure-effect-before-delay-v4-0-90a54c832508@redhat.com> Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: <linux-kernel.vger.kernel.org> List-Subscribe: <mailto:linux-kernel+subscribe@vger.kernel.org> List-Unsubscribe: <mailto:linux-kernel+unsubscribe@vger.kernel.org> MIME-Version: 1.0 Content-Type: text/plain; charset="utf-8" X-Mailer: b4 0.12.3 Content-Transfer-Encoding: quoted-printable X-getmail-retrieved-from-mailbox: INBOX X-GMAIL-THRID: 1788814757743278819 X-GMAIL-MSGID: 1788814757743278819 |
Series |
scsi: ufs: Remove overzealous memory barriers
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Commit Message
Andrew Halaney
Jan. 22, 2024, 5:24 p.m. UTC
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@linaro.org> Reviewed-by: Bart Van Assche <bvanassche@acm.org> Reviewed-by: Can Guo <quic_cang@quicinc.com> Signed-off-by: Andrew Halaney <ahalaney@redhat.com> --- drivers/ufs/core/ufshcd.c | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-) -- 2.43.0
diff --git a/drivers/ufs/core/ufshcd.c b/drivers/ufs/core/ufshcd.c index 029d017fc1b6..e2e6002fe46a 100644 --- a/drivers/ufs/core/ufshcd.c +++ b/drivers/ufs/core/ufshcd.c @@ -10347,7 +10347,7 @@ 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);