From: Bart Van Assche <bvanassche@acm.org>
To: Andrew Halaney <ahalaney@redhat.com>,
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>,
Can Guo <quic_cang@quicinc.com>
Cc: Will Deacon <will@kernel.org>,
linux-arm-msm@vger.kernel.org, linux-scsi@vger.kernel.org,
linux-kernel@vger.kernel.org
Subject: Re: [PATCH RFC v3 11/11] scsi: ufs: core: Perform read back before writing run/stop regs
Date: Thu, 21 Dec 2023 11:25:47 -0800 [thread overview]
Message-ID: <d4e9bf6c-0a71-49d1-a74b-76eba3af6a51@acm.org> (raw)
In-Reply-To: <20231221-ufs-reset-ensure-effect-before-delay-v3-11-2195a1b66d2e@redhat.com>
On 12/21/23 11:09, Andrew Halaney wrote:
> Currently a wmb() is used to ensure that writes to the
> UTP_TASK_REQ_LIST_BASE* regs are completed prior to following writes to
> the run/stop registers.
>
> wmb() ensure that the write completes, but completion doesn't mean that
> it isn't stored in a buffer somewhere. The recommendation for
> ensuring the 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 wmb()'s
> purpose wasn't to add extra ordering (on top of the ordering guaranteed
> by writel()/readl()), it can safely be removed.
Reviewed-by: Bart Van Assche <bvanassche@acm.org>
next prev parent reply other threads:[~2023-12-21 19:25 UTC|newest]
Thread overview: 31+ messages / expand[flat|nested] mbox.gz Atom feed top
2023-12-21 19:09 [PATCH RFC v3 00/11] scsi: ufs: Remove overzealous memory barriers Andrew Halaney
2023-12-21 19:09 ` [PATCH RFC v3 01/11] scsi: ufs: qcom: Perform read back after writing reset bit Andrew Halaney
2023-12-22 8:18 ` Can Guo
2023-12-21 19:09 ` [PATCH RFC v3 02/11] scsi: ufs: qcom: Perform read back after writing REG_UFS_SYS1CLK_1US Andrew Halaney
2023-12-22 8:18 ` Can Guo
2023-12-21 19:09 ` [PATCH RFC v3 03/11] scsi: ufs: qcom: Perform read back after writing testbus config Andrew Halaney
2023-12-22 8:20 ` Can Guo
2023-12-21 19:09 ` [PATCH RFC v3 04/11] scsi: ufs: qcom: Perform read back after writing unipro mode Andrew Halaney
2023-12-22 8:23 ` Can Guo
2023-12-21 19:09 ` [PATCH RFC v3 05/11] scsi: ufs: qcom: Perform read back after writing CGC enable Andrew Halaney
2023-12-22 8:25 ` Can Guo
2023-12-21 19:09 ` [PATCH RFC v3 06/11] scsi: ufs: cdns-pltfrm: Perform read back after writing HCLKDIV Andrew Halaney
2023-12-21 19:09 ` [PATCH RFC v3 07/11] scsi: ufs: core: Perform read back after writing UTP_TASK_REQ_LIST_BASE_H Andrew Halaney
2023-12-21 19:30 ` Bart Van Assche
2023-12-22 8:26 ` Can Guo
2023-12-21 19:09 ` [PATCH RFC v3 08/11] scsi: ufs: core: Perform read back after disabling interrupts Andrew Halaney
2023-12-21 19:30 ` Bart Van Assche
2023-12-22 8:26 ` Can Guo
2023-12-21 19:09 ` [PATCH RFC v3 09/11] scsi: ufs: core: Perform read back after disabling UIC_COMMAND_COMPL Andrew Halaney
2023-12-21 19:29 ` Bart Van Assche
2023-12-22 8:26 ` Can Guo
2023-12-27 6:16 ` Manivannan Sadhasivam
2023-12-21 19:09 ` [PATCH RFC v3 10/11] scsi: ufs: core: Perform read back to commit doorbell Andrew Halaney
2023-12-21 19:28 ` Bart Van Assche
2023-12-22 8:27 ` Can Guo
2023-12-27 6:18 ` Manivannan Sadhasivam
2023-12-21 19:09 ` [PATCH RFC v3 11/11] scsi: ufs: core: Perform read back before writing run/stop regs Andrew Halaney
2023-12-21 19:25 ` Bart Van Assche [this message]
2023-12-22 8:27 ` Can Guo
2023-12-27 6:21 ` Manivannan Sadhasivam
2023-12-21 19:13 ` [PATCH RFC v3 00/11] scsi: ufs: Remove overzealous memory barriers Konrad Dybcio
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