[PATCH] drm/panfrost: Make devfreq truly optional

[Ezequiel Garcia]

On Tue, 2019-05-14 at 08:38 -0500, Rob Herring wrote:
> On Mon, May 13, 2019 at 12:56 PM Ezequiel Garcia <ezequiel at collabora.com> wrote:
> > Currently, there is some logic to make devfreq optional,
> > but it fails to cover some cases such as !CONFIG_PM_DEVFREQ.
> 
> Fails how? compiling? runtime? Or just builds extra code?
> 

Well, given we currently don't enforce PM_DEVFREQ, the driver fails
to probe. Specifically,

panfrost_devfreq_init
  devfreq_recommended_opp
    -EINVAL
 
> > Moreover, depending on return codes is not resilient to change,
> > so let's take a different approach, introducing proper
> > stubs and only conditionally compiling the devfreq support.
> 
> The downside here is another build time configuration to test. Isn't
> devfreq essentially going to be required to run the GPU at higher
> frequencies and to not melt it?
> 

Right. So the alternative is to select or depend on PM_DEVFREQ.

Otherwise, it's quite confusing for developers to choose the driver
and have it fail to probe because some other option is not selected.

Let me know what you think and I'll cook a v2.

Thanks,
Eze

> > Signed-off-by: Ezequiel Garcia <ezequiel at collabora.com>
> > ---
> >  drivers/gpu/drm/panfrost/Makefile           |  3 ++-
> >  drivers/gpu/drm/panfrost/panfrost_devfreq.c | 13 ++-----------
> >  drivers/gpu/drm/panfrost/panfrost_devfreq.h | 19 +++++++++++++++++--
> >  3 files changed, 21 insertions(+), 14 deletions(-)
> > 
> > diff --git a/drivers/gpu/drm/panfrost/Makefile b/drivers/gpu/drm/panfrost/Makefile
> > index 6de72d13c58f..8b690672f9d9 100644
> > --- a/drivers/gpu/drm/panfrost/Makefile
> > +++ b/drivers/gpu/drm/panfrost/Makefile
> > @@ -3,10 +3,11 @@
> >  panfrost-y := \
> >         panfrost_drv.o \
> >         panfrost_device.o \
> > -       panfrost_devfreq.o \
> >         panfrost_gem.o \
> >         panfrost_gpu.o \
> >         panfrost_job.o \
> >         panfrost_mmu.o
> > 
> > +panfrost-$(CONFIG_PM_DEVFREQ) += panfrost_devfreq.o
> > +
> >  obj-$(CONFIG_DRM_PANFROST) += panfrost.o
> > diff --git a/drivers/gpu/drm/panfrost/panfrost_devfreq.c b/drivers/gpu/drm/panfrost/panfrost_devfreq.c
> > index 238bd1d89d43..29fcffdf2d57 100644
> > --- a/drivers/gpu/drm/panfrost/panfrost_devfreq.c
> > +++ b/drivers/gpu/drm/panfrost/panfrost_devfreq.c
> > @@ -140,8 +140,8 @@ int panfrost_devfreq_init(struct panfrost_device *pfdev)
> >                 return 0;
> > 
> >         ret = dev_pm_opp_of_add_table(&pfdev->pdev->dev);
> > -       if (ret == -ENODEV) /* Optional, continue without devfreq */
> > -               return 0;
> > +       if (ret)
> > +               return ret;
> > 
> >         panfrost_devfreq_reset(pfdev);
> > 
> > @@ -170,9 +170,6 @@ void panfrost_devfreq_resume(struct panfrost_device *pfdev)
> >  {
> >         int i;
> > 
> > -       if (!pfdev->devfreq.devfreq)
> > -               return;
> > -
> >         panfrost_devfreq_reset(pfdev);
> >         for (i = 0; i < NUM_JOB_SLOTS; i++)
> >                 pfdev->devfreq.slot[i].busy = false;
> > @@ -182,9 +179,6 @@ void panfrost_devfreq_resume(struct panfrost_device *pfdev)
> > 
> >  void panfrost_devfreq_suspend(struct panfrost_device *pfdev)
> >  {
> > -       if (!pfdev->devfreq.devfreq)
> > -               return;
> > -
> >         devfreq_suspend_device(pfdev->devfreq.devfreq);
> >  }
> > 
> > @@ -194,9 +188,6 @@ static void panfrost_devfreq_update_utilization(struct panfrost_device *pfdev, i
> >         ktime_t now;
> >         ktime_t last;
> > 
> > -       if (!pfdev->devfreq.devfreq)
> > -               return;
> > -
> >         now = ktime_get();
> >         last = pfdev->devfreq.slot[slot].time_last_update;
> > 
> > diff --git a/drivers/gpu/drm/panfrost/panfrost_devfreq.h b/drivers/gpu/drm/panfrost/panfrost_devfreq.h
> > index eb999531ed90..76b56a8de6e3 100644
> > --- a/drivers/gpu/drm/panfrost/panfrost_devfreq.h
> > +++ b/drivers/gpu/drm/panfrost/panfrost_devfreq.h
> > @@ -4,11 +4,26 @@
> >  #ifndef __PANFROST_DEVFREQ_H__
> >  #define __PANFROST_DEVFREQ_H__
> > 
> > +#if defined(CONFIG_PM_DEVFREQ)
> >  int panfrost_devfreq_init(struct panfrost_device *pfdev);
> > -
> >  void panfrost_devfreq_resume(struct panfrost_device *pfdev);
> >  void panfrost_devfreq_suspend(struct panfrost_device *pfdev);
> > -
> >  void panfrost_devfreq_record_transition(struct panfrost_device *pfdev, int slot);
> > +#else
> > +static inline int panfrost_devfreq_init(struct panfrost_device *pfdev)
> > +{
> > +       return 0;
> > +}
> > +
> > +static inline void panfrost_devfreq_resume(struct panfrost_device *pfdev)
> > +{}
> > +
> > +static inline void panfrost_devfreq_suspend(struct panfrost_device *pfdev)
> > +{}
> > +
> > +static inline void
> > +panfrost_devfreq_record_transition(struct panfrost_device *pfdev, int slot)
> > +{}
> > +#endif
> > 
> >  #endif /* __PANFROST_DEVFREQ_H__ */
> > --
> > 2.20.1
> >