linux-kernel - Re: [PATCH v1 1/1] scsi: ufs: Increase the UIC command timeout to 5 seconds

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Message-ID: <20220419151320.GA8699@thinkpad>
Date:   Tue, 19 Apr 2022 20:43:20 +0530
From:   Manivannan Sadhasivam <manivannan.sadhasivam@...aro.org>
To:     "Bao D. Nguyen" <quic_nguyenb@...cinc.com>
Cc:     quic_cang@...cinc.com, quic_asutoshd@...cinc.com,
        martin.petersen@...cle.com, linux-scsi@...r.kernel.org,
        linux-arm-msm@...r.kernel.org,
        Alim Akhtar <alim.akhtar@...sung.com>,
        Avri Altman <avri.altman@....com>,
        "James E.J. Bottomley" <jejb@...ux.ibm.com>,
        Bart Van Assche <bvanassche@....org>,
        Bean Huo <beanhuo@...ron.com>,
        Daejun Park <daejun7.park@...sung.com>,
        Adrian Hunter <adrian.hunter@...el.com>,
        Can Guo <cang@...eaurora.org>,
        Asutosh Das <asutoshd@...eaurora.org>,
        open list <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH v1 1/1] scsi: ufs: Increase the UIC command timeout to 5
 seconds

On Mon, Apr 18, 2022 at 06:36:05PM -0700, Bao D. Nguyen wrote:
> Increase the UIC command timeout to avoid false and unnecessary
> UFS errors printout. There are increasing number of false UIC command
> timeout error events where the actual cause of the issues is interrupt
> starvation. When looking into these issues closely, it was clear that
> the UIC command completed successfully, but the CPUs were hogged by other
> subsystems for more than 500ms, causing a false UIC command timeout.
> 

UFS irq handler is a hardirq. Not sure how CPU starving can happen here.
Unless all CPUs are occupied by hardirq handlers from other subsystems.

Thanks,
Mani

> Increase the UIC command timeout to 5 seconds to avoid false and
> time consuming support calls so that we can shift the focus to where
> the real issue would be.
> 
> Signed-off-by: Bao D. Nguyen <quic_nguyenb@...cinc.com>
> ---
>  drivers/scsi/ufs/ufshcd.c | 2 +-
>  1 file changed, 1 insertion(+), 1 deletion(-)
> 
> diff --git a/drivers/scsi/ufs/ufshcd.c b/drivers/scsi/ufs/ufshcd.c
> index 3f9caaf..806acf4 100644
> --- a/drivers/scsi/ufs/ufshcd.c
> +++ b/drivers/scsi/ufs/ufshcd.c
> @@ -35,7 +35,7 @@
>  				 UTP_TASK_REQ_COMPL |\
>  				 UFSHCD_ERROR_MASK)
>  /* UIC command timeout, unit: ms */
> -#define UIC_CMD_TIMEOUT	500
> +#define UIC_CMD_TIMEOUT	5000
>  
>  /* NOP OUT retries waiting for NOP IN response */
>  #define NOP_OUT_RETRIES    10
> -- 
> The Qualcomm Innovation Center, Inc. is a member of the Code Aurora Forum,
> a Linux Foundation Collaborative Project
>