Re: [Freedreno] [PATCH] drm/msm/dpu: ensure device suspend happens during PM sleep

[kalyan_t]

On 2020-03-31 00:25, Doug Anderson wrote:
> Hi,
>
> On Mon, Mar 30, 2020 at 2:04 AM Kalyan Thota <kalyan_t@xxxxxxxxxxxxxx> 
> wrote:
> > "The PM core always increments the runtime usage counter
> > before calling the ->suspend() callback and decrements it
> > after calling the ->resume() callback"
> >
> > DPU and DSI are managed as runtime devices. When
> > suspend is triggered, PM core adds a refcount on all the
> > devices and calls device suspend, since usage count is
> > already incremented, runtime suspend was not getting called
> > and it kept the clocks on which resulted in target not
> > entering into XO shutdown.
> >
> > Add changes to manage runtime devices during pm sleep.
> >
> > Changes in v1:
> >  - Remove unnecessary checks in the function
> >    _dpu_kms_disable_dpu (Rob Clark).
> >
> > Changes in v2:
> >  - Avoid using suspend_late to reset the usagecount
> >    as suspend_late might not be called during suspend
> >    call failures (Doug).
> >
> > Signed-off-by: Kalyan Thota <kalyan_t@xxxxxxxxxxxxxx>
> > ---
> >  drivers/gpu/drm/msm/disp/dpu1/dpu_kms.c | 33 
> > +++++++++++++++++++++++++++++++++
> >  drivers/gpu/drm/msm/msm_drv.c           |  4 ++++
> >  drivers/gpu/drm/msm/msm_kms.h           |  2 ++
> >  3 files changed, 39 insertions(+)
>
> I am still 100% baffled by your patch and I never did quite understand
> your response to my previous comments [1].  I think you're saying that
> the problem you were facing is that if you call "suspend" but never
> called "runtime_suspend" that the device stays active.  Is that right?
>  If that's true, did you try something like this suggestion I made?
>
> SET_SYSTEM_SLEEP_PM_OPS(pm_runtime_force_suspend, 
> pm_runtime_force_resume)
>
>
> > diff --git a/drivers/gpu/drm/msm/disp/dpu1/dpu_kms.c 
> > b/drivers/gpu/drm/msm/disp/dpu1/dpu_kms.c
> > index ce19f1d..2343cbd 100644
> > --- a/drivers/gpu/drm/msm/disp/dpu1/dpu_kms.c
> > +++ b/drivers/gpu/drm/msm/disp/dpu1/dpu_kms.c
> > @@ -26,6 +26,7 @@
> >  #include "dpu_encoder.h"
> >  #include "dpu_plane.h"
> >  #include "dpu_crtc.h"
> > +#include "dsi.h"
> >
> >  #define CREATE_TRACE_POINTS
> >  #include "dpu_trace.h"
> > @@ -325,6 +326,37 @@ static void dpu_kms_disable_commit(struct msm_kms 
> > *kms)
> >         pm_runtime_put_sync(&dpu_kms->pdev->dev);
> >  }
> >
> > +static void _dpu_kms_disable_dpu(struct msm_kms *kms)
> > +{
> > +       struct dpu_kms *dpu_kms = to_dpu_kms(kms);
> > +       struct drm_device *dev = dpu_kms->dev;
> > +       struct msm_drm_private *priv = dev->dev_private;
> > +       struct msm_dsi *dsi;
> > +       int i;
> > +
> > +       dpu_kms_disable_commit(kms);
> > +
> > +       for (i = 0; i < ARRAY_SIZE(priv->dsi); i++) {
> > +               if (!priv->dsi[i])
> > +                       continue;
> > +               dsi = priv->dsi[i];
> > +               pm_runtime_put_sync(&dsi->pdev->dev);
> > +       }
> > +       pm_runtime_put_sync(dev->dev);
> > +
> > +       /* Increment the usagecount without triggering a resume */
> > +       pm_runtime_get_noresume(dev->dev);
> > +
> > +       pm_runtime_get_noresume(&dpu_kms->pdev->dev);
> > +
> > +       for (i = 0; i < ARRAY_SIZE(priv->dsi); i++) {
> > +               if (!priv->dsi[i])
> > +                       continue;
> > +               dsi = priv->dsi[i];
> > +               pm_runtime_get_noresume(&dsi->pdev->dev);
> > +       }
> > +}
>
> My pm_runtime knowledge is pretty weak sometimes, but the above
> function looks crazy.  Maybe it's just me not understanding, but can
> you please summarize what you're trying to accomplish?
-- I was trying to get the runtime callbacks via controlling the device 
usage_count
Since the usage_count was already incremented by PM core, i was 
decrementing and incrementing (without resume)
so that callbacks are triggered.

I have taken your suggestion on forcing the suspend instead of managing 
it via usage_count.
i'll follow it up in the next patchset.

> -Doug
>
> [1] 
> https://lore.kernel.org/r/114130f68c494f83303c51157e2c5bfa@xxxxxxxxxxxxxx
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