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Subject: Re: [PATCH v2 3/3] scsi: ufs: Let resume callback return -EBUSY
 after ufshcd_shutdown
From:   Bean Huo <huobean@gmail.com>
To:     rjw@rjwysocki.net
Cc:     linux-scsi@vger.kernel.org, linux-kernel@vger.kernel.org,
        rjw@rjwysocki.net, alim.akhtar@samsung.com, avri.altman@wdc.com,
        asutoshd@codeaurora.org, jejb@linux.ibm.com,
        martin.petersen@oracle.com, stanley.chu@mediatek.com,
        beanhuo@micron.com, bvanassche@acm.org, tomas.winkler@intel.com,
        cang@codeaurora.org
Date:   Mon, 04 Jan 2021 20:26:25 +0100
In-Reply-To: <20201224172010.10701-4-huobean@gmail.com>
References: <20201224172010.10701-1-huobean@gmail.com>
         <20201224172010.10701-4-huobean@gmail.com>
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Hi Rafael

Would you please help to review this patch assoociated with PM resume
callback implementation?
 
Original code that ufshcd_system/runtime_resume returns '0' in case
resume failed due to the UFS device and UFS LINk are powered off(hba-
>is_powered == false).

In the patch 2/3 Add handling of the return value of
pm_runtime_get_sync() is to fix race exists between shudown path and
device access through sysfs node.


Thanks,
Bean


On Thu, 2020-12-24 at 18:20 +0100, Bean Huo wrote:
> From: Bean Huo <beanhuo@micron.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.
> 
> Signed-off-by: Bean Huo <beanhuo@micron.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)),