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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>
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
Subject: [PATCH RFC v3 06/11] scsi: ufs: cdns-pltfrm: Perform read back after
writing HCLKDIV
Date: Thu, 21 Dec 2023 13:09:52 -0600
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<20231221-ufs-reset-ensure-effect-before-delay-v3-6-2195a1b66d2e@redhat.com>
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|
| Series |
scsi: ufs: Remove overzealous memory barriers
|
expand
|
diff --git a/drivers/ufs/host/cdns-pltfrm.c b/drivers/ufs/host/cdns-pltfrm.c index bb30267da471..66811d8d1929 100644 --- a/drivers/ufs/host/cdns-pltfrm.c +++ b/drivers/ufs/host/cdns-pltfrm.c @@ -136,7 +136,7 @@ static int cdns_ufs_set_hclkdiv(struct ufs_hba *hba) * Make sure the register was updated, * UniPro layer will not work with an incorrect value. */ - mb(); + ufshcd_readl(hba, CDNS_UFS_REG_HCLKDIV); return 0; }
Currently, HCLKDIV is 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 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: d90996dae8e4 ("scsi: ufs: Add UFS platform driver for Cadence UFS") Signed-off-by: Andrew Halaney <ahalaney@redhat.com> --- drivers/ufs/host/cdns-pltfrm.c | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-)