Re: [PATCH] drm/meson: fix max mode_config height/width

[Jeykumar Sankaran]

Reviving this thread from the context of the below conversion:

https://lore.kernel.org/linux-arm-msm/db26145b-3f64-a334-f698-76f972332881@xxxxxxxxxxxx/T/#u

On 2018-10-05 01:19, Neil Armstrong wrote:
> On 05/10/2018 09:58, Daniel Vetter wrote:
> > On Fri, Oct 5, 2018 at 9:39 AM Neil Armstrong 
> > <narmstrong@xxxxxxxxxxxx> wrote:
> > >
>
> [...]
>
> > > OK, won't this be enough ?
> > > --- a/include/drm/drm_mode_config.h
> > > +++ b/include/drm/drm_mode_config.h
> > > @@ -333,6 +333,8 @@ struct drm_mode_config_funcs {
> > >   * @min_height: minimum fb pixel height on this device
> > >   * @max_width: maximum fb pixel width on this device
> > >   * @max_height: maximum fb pixel height on this device
> > > + * @max_fb_width: maximum fb buffer width if differs from max_width
> > > + * @max_fb_height: maximum fb buffer height if differs from 
> > > max_height
> > >   * @funcs: core driver provided mode setting functions
> > >   * @fb_base: base address of the framebuffer
> > >   * @poll_enabled: track polling support for this device
> > > @@ -508,6 +510,7 @@ struct drm_mode_config {
> > >
> > >         int min_width, min_height;
> > >         int max_width, max_height;
> > > +       int max_fb_width, max_fb_height;
> > >         const struct drm_mode_config_funcs *funcs;
> > >         resource_size_t fb_base;
> > >
> > > --- a/drivers/gpu/drm/drm_framebuffer.c
> > > +++ b/drivers/gpu/drm/drm_framebuffer.c
> > > @@ -283,14 +283,20 @@ drm_internal_framebuffer_create(struct 
> > > drm_device *dev,
> > >                 return ERR_PTR(-EINVAL);
> > >         }
> > >
> > > -       if ((config->min_width > r->width) || (r->width > 
> > > config->max_width)) {
> > > +       if ((config->min_width > r->width) ||
> > > +           (!config->max_fb_width && r->width > config->max_width) 
> > > ||
> > > +           (config->max_fb_width && r->width > 
> > > config->max_fb_width)) {
> > >                 DRM_DEBUG_KMS("bad framebuffer width %d, should be >= 
> > > %d && <= %d\n",
> > > -                         r->width, config->min_width, 
> > > config->max_width);
> > > +                         r->width, config->min_width, 
> > > config->max_fb_width ?
> > > +                         config->max_fb_width : config->max_width);
> > >                 return ERR_PTR(-EINVAL);
> > >         }
> > > -       if ((config->min_height > r->height) || (r->height > 
> > > config->max_height)) {
> > > +       if ((config->min_height > r->height) ||
> > > +           (!config->max_fb_height && r->height > 
> > > config->max_height) ||
> > > +           (config->max_fb_height && r->height > 
> > > config->max_fb_height)) {
> > >                 DRM_DEBUG_KMS("bad framebuffer height %d, should be 
> > > >= %d && <= %d\n",
> > > -                         r->height, config->min_height, 
> > > config->max_height);
> > > +                         r->height, config->min_height, 
> > > config->max_fb_height ?
> > > +                         config->max_fb_height : 
> > > config->max_height);
> > >                 return ERR_PTR(-EINVAL);
> > >         }
> > >
> > > and in the driver :
> > >
> > > +       drm->mode_config.max_width = 4096;
> > > +       drm->mode_config.max_height = 3840;
> > > +       drm->mode_config.max_fb_width = 16384;
> > > +       drm->mode_config.max_fb_height = 8192;
> > >
> > > With this I leave the mode filtering intact.
> >
> > Not enough. See
> > https://dri.freedesktop.org/docs/drm/gpu/drm-kms-helpers.html#c.drm_connector_helper_funcs
> > and scroll down to mode_valid. You need to filter modes both in the
> > detect paths, and the atomic_check paths.
> >
> > Detect is explicitly filtered out, but atomic_check was only
> > implicitly filtered, through the max fb size checks. Ok, you could
> > light up a mode that's bigger than max fb, but in practice, no
> > userspace ever did that.

Daniel, MSM and few other vendor hardware have upscale blocks where the 
driver can expose fb sizes smaller than
the mode resolution and use h/w upscaling to fill the screen. This would 
optimize the fetch bandwidth.

But with your code we're missing crucial
> > validation now, and userspace could fall over that. What I think we
> > need is to add mode filter against mode_config.max_width/height in
> > drm_atomic_helper_check_modeset(). Probably best to stuff that into
> > the mode_valid() function.
Agreed! Since the above patch from Niel is taking care of cases where 
max/min fb values
are not set, by checking against the original max/min values, can we 
separate out this
core change from the driver level mode_valid changes? If Niel couldn't 
find the time, I can
repost the above change.

Thanks and Regards,
Jeykumar S.

> Ok I understood now, thanks for pointer, I'll try to add this.
>
> Neil
>
> > Cheers, Daniel
> > > Neil
> > >
> > >
> > > > -Daniel
> > > >
> > > > > Neil
> > > > >
> > > > > > Bunch of igt to make sure we're not missing anything would be 
> > > > > > sweet on
> > > > > > top, e.g. e.g. trying to set a mode over the limit and making sure 
> > > > > > it
> > > > > > fails.
> > > > > >
> > > > > > Cheers, Daniel
> > > > > >
> > > > > > > ---
> > > > > > >  drivers/gpu/drm/meson/meson_drv.c | 4 ++--
> > > > > > >  1 file changed, 2 insertions(+), 2 deletions(-)
> > > > > > >
> > > > > > > diff --git a/drivers/gpu/drm/meson/meson_drv.c 
> > > > > > > b/drivers/gpu/drm/meson/meson_drv.c
> > > > > > > index d344312..2e29968 100644
> > > > > > > --- a/drivers/gpu/drm/meson/meson_drv.c
> > > > > > > +++ b/drivers/gpu/drm/meson/meson_drv.c
> > > > > > > @@ -243,8 +243,8 @@ static int meson_drv_bind_master(struct 
> > > > > > > device *dev, bool has_components)
> > > > > > >              goto free_drm;
> > > > > > >
> > > > > > >      drm_mode_config_init(drm);
> > > > > > > -    drm->mode_config.max_width = 3840;
> > > > > > > -    drm->mode_config.max_height = 2160;
> > > > > > > +    drm->mode_config.max_width = 16384;
> > > > > > > +    drm->mode_config.max_height = 8192;
> > > > > > >      drm->mode_config.funcs = &meson_mode_config_funcs;
> > > > > > >
> > > > > > >      /* Hardware Initialization */
> > > > > > > --
> > > > > > > 2.7.4
> > > > > > >
> > > > > > > _______________________________________________
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> > > > > > > dri-devel@xxxxxxxxxxxxxxxxxxxxx
> > > > > > > https://lists.freedesktop.org/mailman/listinfo/dri-devel
> > > > >
> > > > > _______________________________________________
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>
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--
Jeykumar S