Re: [Nouveau] [PATCH 4/5] drm/nouveau: Grab RPM ref when i2c bus is in use

[Ben Skeggs <skeggsb@gmail.com>]

On Tue, 17 Jul 2018 at 20:18, Karol Herbst <kherbst@redhat.com> wrote:
>
> mhh, we shouldn't call to Linux APIs from within of nvkm. Rather gaurd
> the Linux glue code to the i2c stuff instead, but this is all done
> from inside of nvkm. I think we should move it out into
> drm/nouveau/nouveau_i2c.c and do the handling there.
Huh?  No, this is completely fine.

>
> On Tue, Jul 17, 2018 at 1:59 AM, Lyude Paul <lyude@redhat.com> wrote:
> > The i2c bus can be both accessed by DRM itself, along with any of it's
> > devnodes (/sys/class/i2c). So, we need to make sure that all codepaths
> > using the i2c bus keep the GPU resumed.
> >
> > Signed-off-by: Lyude Paul <lyude@redhat.com>
> > Cc: Karol Herbst <karolherbst@gmail.com>
> > Cc: stable@vger.kernel.org
> > ---
> >  drivers/gpu/drm/nouveau/nvkm/subdev/i2c/bus.c | 12 +++++++++++-
> >  1 file changed, 11 insertions(+), 1 deletion(-)
> >
> > diff --git a/drivers/gpu/drm/nouveau/nvkm/subdev/i2c/bus.c b/drivers/gpu/drm/nouveau/nvkm/subdev/i2c/bus.c
> > index 807a2b67bd64..1de48c990b80 100644
> > --- a/drivers/gpu/drm/nouveau/nvkm/subdev/i2c/bus.c
> > +++ b/drivers/gpu/drm/nouveau/nvkm/subdev/i2c/bus.c
> > @@ -119,18 +119,28 @@ nvkm_i2c_bus_release(struct nvkm_i2c_bus *bus)
> >         BUS_TRACE(bus, "release");
> >         nvkm_i2c_pad_release(pad);
> >         mutex_unlock(&bus->mutex);
> > +       pm_runtime_put_autosuspend(pad->i2c->subdev.device->dev);
> >  }
> >
> >  int
> >  nvkm_i2c_bus_acquire(struct nvkm_i2c_bus *bus)
> >  {
> >         struct nvkm_i2c_pad *pad = bus->pad;
> > +       struct device *dev = pad->i2c->subdev.device->dev;
> >         int ret;
> > +
> >         BUS_TRACE(bus, "acquire");
> > +
> > +       ret = pm_runtime_get_sync(dev);
> > +       if (ret < 0 && ret != -EACCES)
> > +               return ret;
> > +
> >         mutex_lock(&bus->mutex);
> >         ret = nvkm_i2c_pad_acquire(pad, NVKM_I2C_PAD_I2C);
> > -       if (ret)
> > +       if (ret) {
> >                 mutex_unlock(&bus->mutex);
> > +               pm_runtime_put_autosuspend(dev);
> > +       }
> >         return ret;
> >  }
> >
> > --
> > 2.17.1
> >
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