linux-kernel - Re: [PATCH v2 3/3] scsi: ufs: Let resume callback return -EBUSY after ufshcd

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Message-ID: <bf5b8bc409af22f32c4fc5f5de769058@codeaurora.org>
Date:   Tue, 05 Jan 2021 09:10:05 +0800
From:   Can Guo <cang@...eaurora.org>
To:     Bean Huo <huobean@...il.com>
Cc:     alim.akhtar@...sung.com, avri.altman@....com,
        asutoshd@...eaurora.org, jejb@...ux.ibm.com,
        martin.petersen@...cle.com, stanley.chu@...iatek.com,
        beanhuo@...ron.com, bvanassche@....org, tomas.winkler@...el.com,
        linux-scsi@...r.kernel.org, linux-kernel@...r.kernel.org,
        rjw@...ysocki.net
Subject: Re: [PATCH v2 3/3] scsi: ufs: Let resume callback return -EBUSY after
 ufshcd_shutdown

On 2020-12-25 01:20, Bean Huo wrote:
> From: Bean Huo <beanhuo@...ron.com>
> 
> After ufshcd_shutdown(), both UFS device and UFS LINk are powered off,
> return '0' will mislead the upper PM layer since the device has not 
> been
> successfully resumed yet. This will let pm_runtime_get_sync() caller
> mistakenly believe the device/LINK has been resumed, which leads to
> request processing timeout that was en-queued later.
> 
> To fix this, let ufshcd_system/runtimie_resume() return -EBUSY in case 
> of
> hba->is_powered == false.

This change won't work as you expect...

During/after shutdown, for UFS's case only,
pm_runtime_get_sync(hba->dev) will most likely return 0,
because it is already RUNTIME_ACTIVE, pm_runtime_get_sync()
will directly return 0... meaning your change won't even be
exercised.

Check Stanley's change -
https://lore.kernel.org/patchwork/patch/1341389/

Can Guo.

> 
> Signed-off-by: Bean Huo <beanhuo@...ron.com>
> ---
>  drivers/scsi/ufs/ufshcd.c | 12 ++++++++----
>  1 file changed, 8 insertions(+), 4 deletions(-)
> 
> diff --git a/drivers/scsi/ufs/ufshcd.c b/drivers/scsi/ufs/ufshcd.c
> index e221add25a7e..e1bcac51c01f 100644
> --- a/drivers/scsi/ufs/ufshcd.c
> +++ b/drivers/scsi/ufs/ufshcd.c
> @@ -8950,14 +8950,16 @@ int ufshcd_system_resume(struct ufs_hba *hba)
>  		return -EINVAL;
>  	}
> 
> -	if (!hba->is_powered || pm_runtime_suspended(hba->dev))
> +	if (!hba->is_powered || pm_runtime_suspended(hba->dev)) {
>  		/*
>  		 * Let the runtime resume take care of resuming
>  		 * if runtime suspended.
>  		 */
> +		ret = -EBUSY;
>  		goto out;
> -	else
> +	} else {
>  		ret = ufshcd_resume(hba, UFS_SYSTEM_PM);
> +	}
>  out:
>  	trace_ufshcd_system_resume(dev_name(hba->dev), ret,
>  		ktime_to_us(ktime_sub(ktime_get(), start)),
> @@ -9026,10 +9028,12 @@ int ufshcd_runtime_resume(struct ufs_hba *hba)
>  	if (!hba)
>  		return -EINVAL;
> 
> -	if (!hba->is_powered)
> +	if (!hba->is_powered) {
> +		ret = -EBUSY;
>  		goto out;
> -	else
> +	} else {
>  		ret = ufshcd_resume(hba, UFS_RUNTIME_PM);
> +	}
>  out:
>  	trace_ufshcd_runtime_resume(dev_name(hba->dev), ret,
>  		ktime_to_us(ktime_sub(ktime_get(), start)),