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

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

[Can Guo]

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@codeaurora.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"),
-- 
Qualcomm Innovation Center, Inc. is a member of Code Aurora Forum, a Linux Foundation Collaborative Project.

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

[Can Guo]

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@codeaurora.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.

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

[Stanley Chu]

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@codeaurora.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@mediatek.com>

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

[Martin K. Petersen]

On Tue, 22 Sep 2020 00:09:04 -0700, 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.
> 
> [...]

Applied to 5.10/scsi-fixes, thanks!

[1/1] scsi: ufs: Make sure clk scaling happens only when HBA is runtime ACTIVE
      https://git.kernel.org/mkp/scsi/c/73cc291c2702

-- 
Martin K. Petersen	Oracle Linux Engineering