Re: [PATCH 1/2] scsi: ufs: Protect some contexts from unexpected clock scaling

[Can Guo]

On 2020-12-11 01:34, Bean Huo wrote:
> Hi Can
>
> On Wed, 2020-12-09 at 05:35 -0800, Can Guo wrote:
> > @@ -1160,6 +1166,7 @@ static void
> > ufshcd_clock_scaling_unprepare(struct ufs_hba *hba)
> >  {
> >  	up_write(&hba->clk_scaling_lock);
> >  	ufshcd_scsi_unblock_requests(hba);
> > +	ufshcd_release(hba);
> >  }
> >
> >  /**
> > @@ -1175,12 +1182,9 @@ static int ufshcd_devfreq_scale(struct ufs_hba
> > *hba, bool scale_up)
> >  {
> >  	int ret = 0;
> >
> > -	/* let's not get into low power until clock scaling is
> > completed */
> > -	ufshcd_hold(hba, false);
> > -
> >  	ret = ufshcd_clock_scaling_prepare(hba);
> >  	if (ret)
> > -		goto out;
> > +		return ret;
> >
> >  	/* scale down the gear before scaling down clocks */
> >  	if (!scale_up) {
> > @@ -1212,8 +1216,6 @@ static int ufshcd_devfreq_scale(struct ufs_hba
> > *hba, bool scale_up)
> >
> >  out_unprepare:
> >  	ufshcd_clock_scaling_unprepare(hba);
> > -out:
> > -	ufshcd_release(hba);
> >  	return ret;
> >  }
>
> I didn't understand why moving ufshcd_hold/ufshcd_release into
> ufshcd_clock_scaling_prepare()/ufshcd_clock_scaling_unprepare().

Say you change devfreq's governor to performance after UFS host
has entered runtime suspend.

governor_store
 devfreq_performance_handler
  update_devfreq
   devfreq_set_target
    ufshcd_devfreq_target
     ufshcd_devfreq_scale

When ufshcd_devfreq_scale() calls ufshcd_hold() when host is already
runtime suspended, guess what, NoC issues. So clk_scaling.is_allowed
should be checked first.

Regards,

Can Guo.

> > @@ -1294,15 +1296,8 @@ 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);
>
> which branch are you working on?  I didn't see this part codes in the
> branch 5.11/scsi-queue and 5.11/scsi-staging.
>
> Bean