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

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Message-ID: <1603768211.2104.8.camel@mtkswgap22>
Date:   Tue, 27 Oct 2020 11:10:11 +0800
From:   Stanley Chu <stanley.chu@...iatek.com>
To:     Can Guo <cang@...eaurora.org>
CC:     <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>,
        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>,
        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 Can,

On Tue, 2020-10-20 at 10:35 +0800, Can Guo wrote:
> 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?
> 

Looks good to me.

Reviewed-by: Stanley Chu <stanley.chu@...iatek.com>