[PATCH 1/2] drm/amdgpu: Add "max_bpc" connector property

[Alex Deucher]

On Wed, Nov 7, 2018 at 11:09 AM Kazlauskas, Nicholas
<Nicholas.Kazlauskas at amd.com> wrote:
>
> On 11/7/18 10:40 AM, Deucher, Alexander wrote:
> > FWIW there is a common property patch:
> >
> > https://patchwork.kernel.org/patch/10606697/
> >
> > When should try and be compatible so we can transition.
> >
> >
> > Alex
>
> Thanks for the heads up. I remember seeing the i915 patch but I missed
> the common property one. It's a shame that this isn't already in.
>
> Sharing the same property name might work for compatibility ("max bpc").
> The implementation relies on the same min/max range, the only thing that
> would change with that would be swapping out the attach with
> drm_connector_attach_max_bpc_property down the line.

I defer to you.  Just wanted to give you a heads up.  Sounds like
Intel is in the same situation so the end results should be similar.

Alex

>
> >
> > ------------------------------------------------------------------------
> > *From:* amd-gfx <amd-gfx-bounces at lists.freedesktop.org> on behalf of
> > Nicholas Kazlauskas <nicholas.kazlauskas at amd.com>
> > *Sent:* Wednesday, November 7, 2018 9:56:54 AM
> > *To:* amd-gfx at lists.freedesktop.org
> > *Cc:* Kazlauskas, Nicholas
> > *Subject:* [PATCH 1/2] drm/amdgpu: Add "max_bpc" connector property
> > [Why]
> > Many panels support more than 8bpc but some modes are unavailable while
> > running at greater than 8bpc due to DP/HDMI bandwidth constraints.
> >
> > Support for more than 8bpc was added recently in the driver but it's
> > defaults to the maximum supported bpc - locking out these modes.
> >
> > This should be a user configurable option such that the user can select
> > what bpc configuration they would like.
> >
> > [How]
> > Introduce the "max_bpc" connector property so the user can limit the
> > maximum bpc for the panel. It ranges from 8 to 16.
> >
> > This doesn't directly set the preferred bpc for the panel but this
> > convetion is already in use for other drivers.
> >
> > Signed-off-by: Nicholas Kazlauskas <nicholas.kazlauskas at amd.com>
> > ---
> >   drivers/gpu/drm/amd/amdgpu/amdgpu_display.c | 5 +++++
> >   drivers/gpu/drm/amd/amdgpu/amdgpu_mode.h    | 2 ++
> >   2 files changed, 7 insertions(+)
> >
> > diff --git a/drivers/gpu/drm/amd/amdgpu/amdgpu_display.c
> > b/drivers/gpu/drm/amd/amdgpu/amdgpu_display.c
> > index 7d6a36bca9dd..83dadf5b85e0 100644
> > --- a/drivers/gpu/drm/amd/amdgpu/amdgpu_display.c
> > +++ b/drivers/gpu/drm/amd/amdgpu/amdgpu_display.c
> > @@ -626,6 +626,11 @@ int amdgpu_display_modeset_create_props(struct
> > amdgpu_device *adev)
> >                                            "dither",
> >                                            amdgpu_dither_enum_list, sz);
> >
> > +       adev->mode_info.max_bpc_property =
> > +               drm_property_create_range(adev->ddev, 0, "max_bpc", 8, 16);
> > +       if (!adev->mode_info.max_bpc_property)
> > +               return -ENOMEM;
> > +
> >           if (amdgpu_device_has_dc_support(adev)) {
> >                   adev->mode_info.freesync_property =
> >                           drm_property_create_bool(adev->ddev, 0,
> > "freesync");
> > diff --git a/drivers/gpu/drm/amd/amdgpu/amdgpu_mode.h
> > b/drivers/gpu/drm/amd/amdgpu/amdgpu_mode.h
> > index 1627dd3413c7..c39af5d79608 100644
> > --- a/drivers/gpu/drm/amd/amdgpu/amdgpu_mode.h
> > +++ b/drivers/gpu/drm/amd/amdgpu/amdgpu_mode.h
> > @@ -338,6 +338,8 @@ struct amdgpu_mode_info {
> >           struct drm_property *audio_property;
> >           /* FMT dithering */
> >           struct drm_property *dither_property;
> > +       /* maximum number of bits per channel for monitor color */
> > +       struct drm_property *max_bpc_property;
> >           /* it is used to allow enablement of freesync mode */
> >           struct drm_property *freesync_property;
> >           /* it is used to know about display capability of freesync mode */
> > --
> > 2.17.1
> >
> > _______________________________________________
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>
> Nicholas Kazlauskas
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