From: Manivannan Sadhasivam <mani@kernel.org>
To: Andrew Halaney <ahalaney@redhat.com>
Cc: Andy Gross <agross@kernel.org>,
Bjorn Andersson <andersson@kernel.org>,
Konrad Dybcio <konrad.dybcio@linaro.org>,
"James E.J. Bottomley" <jejb@linux.ibm.com>,
"Martin K. Petersen" <martin.petersen@oracle.com>,
Yaniv Gardi <ygardi@codeaurora.org>,
Dov Levenglick <dovl@codeaurora.org>,
Hannes Reinecke <hare@suse.de>,
Subhash Jadavani <subhashj@codeaurora.org>,
Gilad Broner <gbroner@codeaurora.org>,
Venkat Gopalakrishnan <venkatg@codeaurora.org>,
Janek Kotas <jank@cadence.com>,
Alim Akhtar <alim.akhtar@samsung.com>,
Avri Altman <avri.altman@wdc.com>,
Bart Van Assche <bvanassche@acm.org>,
Anjana Hari <quic_ahari@quicinc.com>,
Dolev Raviv <draviv@codeaurora.org>,
Can Guo <quic_cang@quicinc.com>, 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 v2 05/11] scsi: ufs: qcom: Perform read back after writing CGC enable'
Date: Wed, 27 Dec 2023 11:34:48 +0530 [thread overview]
Message-ID: <20231227060448.GC2814@thinkpad> (raw)
In-Reply-To: <20231221-ufs-reset-ensure-effect-before-delay-v2-5-75af2a9bae51@redhat.com>
On Thu, Dec 21, 2023 at 12:25:22PM -0600, Andrew Halaney wrote:
> Currently, the CGC enable bit is written and then an mb() is used to
> ensure that completes before continuing.
>
> mb() ensure that the write completes, but completion doesn't mean that
> it isn't stored in a buffer somewhere. The recommendation for
> ensuring this bit has 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 bit hits 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: 81c0fc51b7a7 ("ufs-qcom: add support for Qualcomm Technologies Inc platforms")
> Signed-off-by: Andrew Halaney <ahalaney@redhat.com>
For this patch, a read back would make sense since I'm not sure if the ICE block
getting enabled afterwards is in the same domain or not.
Reviewed-by: Manivannan Sadhasivam <manivannan.sadhasivam@linaro.org>
- Mani
> ---
> drivers/ufs/host/ufs-qcom.c | 2 +-
> 1 file changed, 1 insertion(+), 1 deletion(-)
>
> diff --git a/drivers/ufs/host/ufs-qcom.c b/drivers/ufs/host/ufs-qcom.c
> index ab1ff7432d11..3db19591d008 100644
> --- a/drivers/ufs/host/ufs-qcom.c
> +++ b/drivers/ufs/host/ufs-qcom.c
> @@ -409,7 +409,7 @@ static void ufs_qcom_enable_hw_clk_gating(struct ufs_hba *hba)
> REG_UFS_CFG2);
>
> /* Ensure that HW clock gating is enabled before next operations */
> - mb();
> + ufshcd_readl(hba, REG_UFS_CFG2);
> }
>
> static int ufs_qcom_hce_enable_notify(struct ufs_hba *hba,
>
> --
> 2.43.0
>
--
மணிவண்ணன் சதாசிவம்
next prev parent reply other threads:[~2023-12-27 6:05 UTC|newest]
Thread overview: 16+ messages / expand[flat|nested] mbox.gz Atom feed top
2023-12-21 18:25 [PATCH RFC v2 00/11] scsi: ufs: Remove overzealous memory barriers Andrew Halaney
2023-12-21 18:25 ` [PATCH RFC v2 01/11] scsi: ufs: qcom: Perform read back after writing reset bit Andrew Halaney
2023-12-21 18:25 ` [PATCH RFC v2 02/11] scsi: ufs: qcom: Perform read back after writing REG_UFS_SYS1CLK_1US Andrew Halaney
2023-12-21 18:25 ` [PATCH RFC v2 03/11] scsi: ufs: qcom: Perform read back after writing testbus config Andrew Halaney
2023-12-27 5:47 ` Manivannan Sadhasivam
2023-12-21 18:25 ` [PATCH RFC v2 04/11] scsi: ufs: qcom: Perform read back after writing unipro mode Andrew Halaney
2023-12-27 6:01 ` [PATCH RFC v2 04/11] scsi: ufs: qcom: Perform read back after writing unipro mode' Manivannan Sadhasivam
2023-12-21 18:25 ` [PATCH RFC v2 05/11] scsi: ufs: qcom: Perform read back after writing CGC enable Andrew Halaney
2023-12-27 6:04 ` Manivannan Sadhasivam [this message]
2023-12-21 18:25 ` [PATCH RFC v2 06/11] scsi: ufs: cdns-pltfrm: Perform read back after writing HCLKDIV Andrew Halaney
2023-12-27 6:06 ` Manivannan Sadhasivam
2023-12-21 18:25 ` [PATCH RFC v2 07/11] scsi: ufs: core: Perform read back after writing UTP_TASK_REQ_LIST_BASE_H Andrew Halaney
2023-12-27 6:10 ` Manivannan Sadhasivam
2023-12-21 18:25 ` [PATCH RFC v2 08/11] scsi: ufs: core: Perform read back after disabling interrupts Andrew Halaney
2023-12-27 6:13 ` Manivannan Sadhasivam
2023-12-21 18:31 ` [PATCH RFC v2 00/11] scsi: ufs: Remove overzealous memory barriers Andrew Halaney
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