linux-kernel - Re: [PATCH] scsi: ufs: Make sure clk scaling happens only when hba is runtime ACTIVE

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Message-ID: <67c4ae5998765daa674a4df696d8d673@codeaurora.org>
Date:   Tue, 20 Oct 2020 10:35:53 +0800
From:   Can Guo <cang@...eaurora.org>
To:     asutoshd@...eaurora.org, nguyenb@...eaurora.org,
        hongwus@...eaurora.org, rnayak@...eaurora.org,
        linux-scsi@...r.kernel.org, kernel-team@...roid.com,
        saravanak@...gle.com, salyzyn@...gle.com, cang@...eaurora.org
Cc:     Alim Akhtar <alim.akhtar@...sung.com>,
        Avri Altman <avri.altman@....com>,
        "James E.J. Bottomley" <jejb@...ux.ibm.com>,
        "Martin K. Petersen" <martin.petersen@...cle.com>,
        Stanley Chu <stanley.chu@...iatek.com>,
        Bean Huo <beanhuo@...ron.com>,
        Bart Van Assche <bvanassche@....org>,
        linux-kernel@...r.kernel.org
Subject: Re: [PATCH] scsi: ufs: Make sure clk scaling happens only when hba is
 runtime ACTIVE

Hi Stanley,

On 2020-09-22 15:09, Can Guo wrote:
> If someone plays with the UFS clk scaling devfreq governor through 
> sysfs,
> ufshcd_devfreq_scale may be called even when hba is not runtime ACTIVE,
> which can lead to unexpected error. We cannot just protect it by 
> calling
> pm_runtime_get_sync, because that may cause racing problem since hba
> runtime suspend ops needs to suspend clk scaling. In order to fix it, 
> call
> pm_runtime_get_noresume and check hba's runtime status, then only 
> proceed
> if hba is runtime ACTIVE, otherwise just bail.
> 
> governor_store
>  devfreq_performance_handler
>   update_devfreq
>    devfreq_set_target
>     ufshcd_devfreq_target
>      ufshcd_devfreq_scale
> 
> Signed-off-by: Can Guo <cang@...eaurora.org>
> 
> diff --git a/drivers/scsi/ufs/ufshcd.c b/drivers/scsi/ufs/ufshcd.c
> index e4cb994..847f355 100644
> --- a/drivers/scsi/ufs/ufshcd.c
> +++ b/drivers/scsi/ufs/ufshcd.c
> @@ -1294,8 +1294,15 @@ static int ufshcd_devfreq_target(struct device 
> *dev,
>  	}
>  	spin_unlock_irqrestore(hba->host->host_lock, irq_flags);
> 
> +	pm_runtime_get_noresume(hba->dev);
> +	if (!pm_runtime_active(hba->dev)) {
> +		pm_runtime_put_noidle(hba->dev);
> +		ret = -EAGAIN;
> +		goto out;
> +	}
>  	start = ktime_get();
>  	ret = ufshcd_devfreq_scale(hba, scale_up);
> +	pm_runtime_put(hba->dev);
> 
>  	trace_ufshcd_profile_clk_scaling(dev_name(hba->dev),
>  		(scale_up ? "up" : "down"),

Could you please review this one since we may be the only two
users of clk scaling?

Thanks,

Can Guo.