RE: [Intel-gfx] [RFC v4 3/8] drm: Add Plane CTM property

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>-----Original Message-----
>From: Ville Syrjälä [mailto:ville.syrjala@xxxxxxxxxxxxxxx]
>Sent: Wednesday, August 22, 2018 6:36 PM
>To: Brian Starkey <brian.starkey@xxxxxxx>
>Cc: Lankhorst, Maarten <maarten.lankhorst@xxxxxxxxx>;
>dcastagna@xxxxxxxxxxxx; intel-gfx@xxxxxxxxxxxxxxxxxxxxx; dri-
>devel@xxxxxxxxxxxxxxxxxxxxx; Shankar, Uma <uma.shankar@xxxxxxxxx>;
>seanpaul@xxxxxxxxxxxx; Syrjala, Ville <ville.syrjala@xxxxxxxxx>
>Subject: Re: [Intel-gfx] [RFC v4 3/8] drm: Add Plane CTM property
>
>On Wed, Aug 22, 2018 at 12:11:42PM +0100, Brian Starkey wrote:
>> 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@xxxxxxxxx>
>> >> > ---
>> >> >  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?).
>
>So far the idea has been that the internal pipeline is assumed to be full range RGB.
>If/when someone needs something else they can try to design a new API for it. If
>we had tried to deal with ycbcr passthrough and whatnot when adding the
>encoding/range props we probably still wouldn't have landed anything.
>

I agree, blending limited range layers with Full range is slightly tricky as of
now. I believe we need to convert the Limited range to full range explicitly and then
flip to display (atleast when we want all the color hardware blocks to come in play)

>But yeah, the docs should of course explicitly state this fact.
>

>From the pipeline perspective, Ville is right (ycbcr->rgb -> degamma -> ctm -> gamma )
and that's how it works. I will try to document these as part of kernel docs under
color management to give more clarity and avoid any kind of ambiguity.

Regards,
Uma Shankar

>--
>Ville Syrjälä
>Intel
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