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Bottomley" , "Martin K. Petersen" , Hannes Reinecke , Janek Kotas , Alim Akhtar , Avri Altman , Bart Van Assche , Can Guo Cc: Andrew Halaney , Will Deacon , linux-arm-msm@vger.kernel.org, linux-scsi@vger.kernel.org, linux-kernel@vger.kernel.org, Manivannan Sadhasivam Subject: [PATCH RFC v4 09/11] scsi: ufs: core: Perform read back after disabling UIC_COMMAND_COMPL Date: Mon, 22 Jan 2024 11:24:05 -0600 Message-ID: <20240122-ufs-reset-ensure-effect-before-delay-v4-9-90a54c832508@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: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Type: text/plain; charset="utf-8" X-Mailer: b4 0.12.3 Content-Transfer-Encoding: quoted-printable Currently, the UIC_COMMAND_COMPL interrupt is disabled and a wmb() is=0D used to complete the register write before any following writes.=0D =0D wmb() ensures the writes complete in that order, but completion doesn't=0D mean that it isn't stored in a buffer somewhere. The recommendation for=0D ensuring this bit has taken effect on the device is to perform a read=0D back to force it to make it all the way to the device. This is=0D documented in device-io.rst and a talk by Will Deacon on this can=0D be seen over here:=0D =0D https://youtu.be/i6DayghhA8Q?si=3DMiyxB5cKJXSaoc01&t=3D1678=0D =0D Let's do that to ensure the bit hits the device. Because the wmb()'s=0D purpose wasn't to add extra ordering (on top of the ordering guaranteed=0D by writel()/readl()), it can safely be removed.=0D =0D Fixes: d75f7fe495cf ("scsi: ufs: reduce the interrupts for power mode chang= e requests")=0D Reviewed-by: Bart Van Assche =0D Reviewed-by: Can Guo =0D Reviewed-by: Manivannan Sadhasivam =0D Signed-off-by: Andrew Halaney =0D ---=0D drivers/ufs/core/ufshcd.c | 2 +-=0D 1 file changed, 1 insertion(+), 1 deletion(-)=0D =0D diff --git a/drivers/ufs/core/ufshcd.c b/drivers/ufs/core/ufshcd.c=0D index 9b6355555897..9bf490bb8eed 100644=0D --- a/drivers/ufs/core/ufshcd.c=0D +++ b/drivers/ufs/core/ufshcd.c=0D @@ -4240,7 +4240,7 @@ static int ufshcd_uic_pwr_ctrl(struct ufs_hba *hba, s= truct uic_command *cmd)=0D * Make sure UIC command completion interrupt is disabled before=0D * issuing UIC command.=0D */=0D - wmb();=0D + ufshcd_readl(hba, REG_INTERRUPT_ENABLE);=0D reenable_intr =3D true;=0D }=0D spin_unlock_irqrestore(hba->host->host_lock, flags);=0D =0D -- =0D 2.43.0=0D =0D