From: Konrad Dybcio <konrad.dybcio@linaro.org>
To: Andrew Halaney <ahalaney@redhat.com>,
Andy Gross <agross@kernel.org>,
Bjorn Andersson <andersson@kernel.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: 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 00/11] scsi: ufs: Remove overzealous memory barriers
Date: Thu, 21 Dec 2023 20:13:17 +0100 [thread overview]
Message-ID: <2382ff87-0635-4ab2-bacb-1624d8238e32@linaro.org> (raw)
In-Reply-To: <20231221-ufs-reset-ensure-effect-before-delay-v3-0-2195a1b66d2e@redhat.com>
On 21.12.2023 20:09, Andrew Halaney wrote:
> 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).
If I understand this correctly - and I'm no expert - it's probably good
practice to read it back in critical places, so that if the code around
it changes, the most crucial writes arrive when expected.
Konrad
prev parent reply other threads:[~2023-12-21 19:13 UTC|newest]
Thread overview: 31+ messages / expand[flat|nested] mbox.gz Atom feed top
2023-12-21 19:09 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
2023-12-22 8:27 ` Can Guo
2023-12-27 6:21 ` Manivannan Sadhasivam
2023-12-21 19:13 ` Konrad Dybcio [this message]
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