linux-kernel - Re: [PATCH v5 2/7] scsi: ufs: atomic update for clkgating

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Date:   Wed, 18 Nov 2020 11:54:26 +0800
From:   Can Guo <cang@...eaurora.org>
To:     Jaegeuk Kim <jaegeuk@...nel.org>
Cc:     linux-kernel@...r.kernel.org, linux-scsi@...r.kernel.org,
        kernel-team@...roid.com, alim.akhtar@...sung.com,
        avri.altman@....com, bvanassche@....org,
        martin.petersen@...cle.com, stanley.chu@...iatek.com,
        Jaegeuk Kim <jaegeuk@...gle.com>
Subject: Re: [PATCH v5 2/7] scsi: ufs: atomic update for clkgating_enable

On 2020-11-18 00:58, Jaegeuk Kim wrote:
> From: Jaegeuk Kim <jaegeuk@...gle.com>
> 
> When giving a stress test which enables/disables clkgating, we hit 
> device
> timeout sometimes. This patch avoids subtle racy condition to address 
> it.
> 
> Note that, this requires a patch to address the device stuck by 
> REQ_CLKS_OFF in
> __ufshcd_release().
> 
> The fix is "scsi: ufs: avoid to call REQ_CLKS_OFF to CLKS_OFF".
> 
> Signed-off-by: Jaegeuk Kim <jaegeuk@...gle.com>

Reviewed-by: Can Guo <cang@...eaurora.org>

> ---
>  drivers/scsi/ufs/ufshcd.c | 12 ++++++------
>  1 file changed, 6 insertions(+), 6 deletions(-)
> 
> diff --git a/drivers/scsi/ufs/ufshcd.c b/drivers/scsi/ufs/ufshcd.c
> index cc8d5f0c3fdc..6c9269bffcbd 100644
> --- a/drivers/scsi/ufs/ufshcd.c
> +++ b/drivers/scsi/ufs/ufshcd.c
> @@ -1808,19 +1808,19 @@ static ssize_t
> ufshcd_clkgate_enable_store(struct device *dev,
>  		return -EINVAL;
> 
>  	value = !!value;
> +
> +	spin_lock_irqsave(hba->host->host_lock, flags);
>  	if (value == hba->clk_gating.is_enabled)
>  		goto out;
> 
> -	if (value) {
> -		ufshcd_release(hba);
> -	} else {
> -		spin_lock_irqsave(hba->host->host_lock, flags);
> +	if (value)
> +		__ufshcd_release(hba);
> +	else
>  		hba->clk_gating.active_reqs++;
> -		spin_unlock_irqrestore(hba->host->host_lock, flags);
> -	}
> 
>  	hba->clk_gating.is_enabled = value;
>  out:
> +	spin_unlock_irqrestore(hba->host->host_lock, flags);
>  	return count;
>  }