Re: [RFC v4 3/8] drm: Add Plane CTM property

[Brian Starkey <brian.starkey@arm.com>]

Hi,

On Wed, Aug 22, 2018 at 12:53:58PM +0300, Ville Syrjälä wrote:
>On Wed, Aug 22, 2018 at 08:40:19AM +0000, Lankhorst, Maarten wrote:
>> fre 2018-08-17 klockan 19:48 +0530 skrev Uma Shankar:
>> > Add a blob property for plane CSC usage.
>> >
>> > v2: Rebase
>> >
>> > v3: Fixed Sean, Paul's review comments. Moved the property from
>> > mode_config to drm_plane. Created a helper function to instantiate
>> > these properties and removed from drm_mode_create_standard_properties
>> > Added property documentation as suggested by Daniel, Vetter.
>> >
>> > v4: Rebase
>> >
>> > Signed-off-by: Uma Shankar <uma.shankar@intel.com>
>> > ---
>> >  Documentation/gpu/drm-kms.rst       |  3 +++
>> >  drivers/gpu/drm/drm_atomic.c        | 10 ++++++++++
>> >  drivers/gpu/drm/drm_atomic_helper.c |  4 ++++
>> >  drivers/gpu/drm/drm_plane.c         | 12 ++++++++++++
>> >  include/drm/drm_plane.h             | 15 +++++++++++++++
>> >  5 files changed, 44 insertions(+)
>> >
>> > diff --git a/Documentation/gpu/drm-kms.rst b/Documentation/gpu/drm-
>> > kms.rst
>> > index 8b10b12..16d6d8d 100644
>> > --- a/Documentation/gpu/drm-kms.rst
>> > +++ b/Documentation/gpu/drm-kms.rst
>> > @@ -560,6 +560,9 @@ Plane Color Management Properties
>> >  .. kernel-doc:: drivers/gpu/drm/drm_plane.c
>> >     :doc: degamma_lut_size_property
>> >
>> > +.. kernel-doc:: drivers/gpu/drm/drm_plane.c
>> > +   :doc: ctm_property
>> > +
>> >  Tile Group Property
>> >  -------------------
>> >
>> > diff --git a/drivers/gpu/drm/drm_atomic.c
>> > b/drivers/gpu/drm/drm_atomic.c
>> > index f8cad9b..ddda935 100644
>> > --- a/drivers/gpu/drm/drm_atomic.c
>> > +++ b/drivers/gpu/drm/drm_atomic.c
>> > @@ -917,6 +917,14 @@ static int drm_atomic_plane_set_property(struct
>> > drm_plane *plane,
>> >  					&replaced);
>> >  		state->color_mgmt_changed |= replaced;
>> >  		return ret;
>> > +	} else if (property == plane->ctm_property) {
>> > +		ret = drm_atomic_replace_property_blob_from_id(dev,
>> > +					&state->ctm,
>> > +					val,
>> > +					sizeof(struct
>> > drm_color_ctm), -1,
>> > +					&replaced);
>> > +		state->color_mgmt_changed |= replaced;
>> > +		return ret;
>> >  	} else if (plane->funcs->atomic_set_property) {
>> >  		return plane->funcs->atomic_set_property(plane,
>> > state,
>> >  				property, val);
>> > @@ -988,6 +996,8 @@ static int drm_atomic_plane_set_property(struct
>> > drm_plane *plane,
>> >  	} else if (property == plane->degamma_lut_property) {
>> >  		*val = (state->degamma_lut) ?
>> >  			state->degamma_lut->base.id : 0;
>> > +	} else if (property == plane->ctm_property) {
>> > +		*val = (state->ctm) ? state->ctm->base.id : 0;
>> >  	} else if (plane->funcs->atomic_get_property) {
>> >  		return plane->funcs->atomic_get_property(plane,
>> > state, property, val);
>> >  	} else {
>> > diff --git a/drivers/gpu/drm/drm_atomic_helper.c
>> > b/drivers/gpu/drm/drm_atomic_helper.c
>> > index 67c5b51..866181f 100644
>> > --- a/drivers/gpu/drm/drm_atomic_helper.c
>> > +++ b/drivers/gpu/drm/drm_atomic_helper.c
>> > @@ -3616,6 +3616,9 @@ void
>> > __drm_atomic_helper_plane_duplicate_state(struct drm_plane *plane,
>> >
>> >  	if (state->degamma_lut)
>> >  		drm_property_blob_get(state->degamma_lut);
>> > +	if (state->ctm)
>> > +		drm_property_blob_get(state->ctm);
>> > +
>> >  	state->color_mgmt_changed = false;
>> >  }
>> >  EXPORT_SYMBOL(__drm_atomic_helper_plane_duplicate_state);
>> > @@ -3663,6 +3666,7 @@ void
>> > __drm_atomic_helper_plane_destroy_state(struct drm_plane_state
>> > *state)
>> >  		drm_crtc_commit_put(state->commit);
>> >
>> >  	drm_property_blob_put(state->degamma_lut);
>> > +	drm_property_blob_put(state->ctm);
>> >  }
>> >  EXPORT_SYMBOL(__drm_atomic_helper_plane_destroy_state);
>> >
>> > diff --git a/drivers/gpu/drm/drm_plane.c
>> > b/drivers/gpu/drm/drm_plane.c
>> > index 03e0560..97520b1 100644
>> > --- a/drivers/gpu/drm/drm_plane.c
>> > +++ b/drivers/gpu/drm/drm_plane.c
>> > @@ -489,6 +489,11 @@ int drm_mode_plane_set_obj_prop(struct drm_plane
>> > *plane,
>> >   *
>> >   * degamma_lut_size_property:
>> >   *	Range Property to indicate size of the plane degamma LUT.
>> > + *
>> > + * ctm_property:
>> > + *	Blob property which allows a userspace to provide CTM
>> > coefficients
>> > + *	to do color space conversion or any other enhancement by
>> > doing a
>> > + *	matrix multiplication using the h/w CTM processing engine
>> >   */
>> >  int drm_plane_color_create_prop(struct drm_device *dev,
>> >  				struct drm_plane *plane)
>> > @@ -509,6 +514,13 @@ int drm_plane_color_create_prop(struct
>> > drm_device *dev,
>> >  		return -ENOMEM;
>> >  	plane->degamma_lut_size_property = prop;
>> >
>> > +	prop = drm_property_create(dev,
>> > +			DRM_MODE_PROP_BLOB,
>> > +			"PLANE_CTM", 0);
>> > +	if (!prop)
>> > +		return -ENOMEM;
>> > +	plane->ctm_property = prop;
>> > +
>> >  	return 0;
>> >  }
>> >  EXPORT_SYMBOL(drm_plane_color_create_prop);
>> > diff --git a/include/drm/drm_plane.h b/include/drm/drm_plane.h
>> > index 28357ac..5143277 100644
>> > --- a/include/drm/drm_plane.h
>> > +++ b/include/drm/drm_plane.h
>> > @@ -183,6 +183,14 @@ struct drm_plane_state {
>> >  	struct drm_property_blob *degamma_lut;
>> >
>> >  	/**
>> > +	 * @ctm:
>> > +	 *
>> > +	 * Color transformation matrix. See
>> > drm_plane_enable_color_mgmt(). The
>> > +	 * blob (if not NULL) is a &struct drm_color_ctm.
>> > +	 */
>> > +	struct drm_property_blob *ctm;
>> > +
>> > +	/**
>> >  	 * @commit: Tracks the pending commit to prevent use-after-
>> > free conditions,
>> >  	 * and for async plane updates.
>> >  	 *
>> > @@ -698,6 +706,13 @@ struct drm_plane {
>> >  	 * size of the degamma LUT as supported by the driver (read-
>> > only).
>> >  	 */
>> >  	struct drm_property *degamma_lut_size_property;
>> > +
>> > +	/**
>> > +	 * @plane_ctm_property: Optional Plane property to set the
>> > +	 * matrix used to convert colors after the lookup in the
>> > +	 * degamma LUT.
>> > +	 */
>> > +	struct drm_property *ctm_property;
>> >
>> I'm assuming degamma is done before converting with CTM.
>>
>> But how does this interact with YUV formats? I'm not sure this is
>> explicitly defined. I'm assuming R->Cr G -> Y, B = Cb for degamma
>> tables.
>
>The pipeline is (or at least should be IMO):
>ycbcr->rgb -> degamma -> ctm -> gamma
>

That's what I'm expecting too.

>We should document the full pipeline (including the crtc portions) in
>some docs.

I fully agree with Ville here, we've been around this loop a few
times, so the full pipeline and expectations need to be captured
in docs (IMO before the properties can be decided).

It's slightly unfortunate that the merged ycbcr->rgb properties only
describe the format of the incoming buffer, without any specification
of what the driver is meant to do with that information (what
conversion is meant to be performed?). Without that, this new CTM
property is somewhat useless, because generic userspace can't tell
what the input data to the matrix is in YUV cases - so we need to
decide and document that too (or change/enhance the API).

Thanks,
-Brian

>
>-- 
>Ville Syrjälä
>Intel
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