[PATCH v2] gpu/drm/msm: fix shutdown hook in case GPU components failed to bind

[Rob Clark]

On Wed, Mar 24, 2021 at 6:49 PM Stephen Boyd <swboyd at chromium.org> wrote:
>
> Quoting Dmitry Baryshkov (2021-03-18 13:05:44)
> > if GPU components have failed to bind, shutdown callback would fail with
> > the following backtrace. Add safeguard check to stop that oops from
> > happening and allow the board to reboot.
> [...]
> > diff --git a/drivers/gpu/drm/msm/msm_drv.c b/drivers/gpu/drm/msm/msm_drv.c
> > index 94525ac76d4e..fd2ac54caf9f 100644
> > --- a/drivers/gpu/drm/msm/msm_drv.c
> > +++ b/drivers/gpu/drm/msm/msm_drv.c
> > @@ -1311,6 +1311,10 @@ static int msm_pdev_remove(struct platform_device *pdev)
> >  static void msm_pdev_shutdown(struct platform_device *pdev)
> >  {
> >         struct drm_device *drm = platform_get_drvdata(pdev);
> > +       struct msm_drm_private *priv = drm ? drm->dev_private : NULL;
> > +
> > +       if (!priv || !priv->kms)
> > +               return;
> >
>
> I see a problem where if I don't get a backlight probing then my
> graphics card doesn't appear but this driver is still bound. I was
> hoping this patch would fix it but it doesn't. I have slab poisoning
> enabled so sometimes the 'priv' pointer is 0x6b6b6b6b6b6b6b6b meaning it
> got all freed.
>
> I found that the 'drm' pointer here is pointing at junk. The
> msm_drm_init() function calls drm_dev_put() on the error path and that
> will destroy the drm pointer but it doesn't update this platform drivers
> drvdata. Do we need another patch that sets the drvdata to NULL on
> msm_drm_init() failing? One last note, I'm seeing this on 5.4 so maybe I
> missed something and the drvdata has been set to NULL somewhere else
> upstream. I sort of doubt it though.

the hw that I guess you are running on should work pretty well w/
upstream kernel.. but I don't think there is any important delta
between upstream and the 5.4 based kernel that you are running that
would fix this..

so *probably* you are right..

BR,
-R

>
> ---8<----
> diff --git a/drivers/gpu/drm/msm/msm_drv.c b/drivers/gpu/drm/msm/msm_drv.c
> index c842a270806d..895d74aa8834 100644
> --- a/drivers/gpu/drm/msm/msm_drv.c
> +++ b/drivers/gpu/drm/msm/msm_drv.c
> @@ -577,6 +577,7 @@ static int msm_drm_init(struct device *dev, struct drm_driver *drv)
>         kfree(priv);
>  err_put_drm_dev:
>         drm_dev_put(ddev);
> +       platform_set_drvdata(pdev, NULL);
>         return ret;
>  }