Re: [RFC v5 2/8] drm: Add Plane Degamma properties

[Matt Roper <matthew.d.roper@intel.com>]

On Sun, Sep 16, 2018 at 01:45:25PM +0530, Uma Shankar wrote:
> Add Plane Degamma as a blob property and plane degamma size as
> a range property.
> 
> 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
> 
> v5: Added "Display Color Hardware Pipeline" flow to kernel
> documentation as suggested by "Ville Syrjala" and "Brian Starkey".
> Moved the property creation to drm_color_mgmt.c file to consolidate
> all color operations at one place.
> 
> Signed-off-by: Uma Shankar <uma.shankar@intel.com>
> Reviewed-by: Alexandru Gheorghe <alexandru-cosmin.gheorghe@arm.com>
> ---
>  Documentation/gpu/drm-kms.rst       | 90 +++++++++++++++++++++++++++++++++++++
>  drivers/gpu/drm/drm_atomic.c        | 13 ++++++
>  drivers/gpu/drm/drm_atomic_helper.c |  6 +++
>  drivers/gpu/drm/drm_color_mgmt.c    | 44 ++++++++++++++++--
>  include/drm/drm_plane.h             | 24 ++++++++++
>  5 files changed, 174 insertions(+), 3 deletions(-)
> 
> diff --git a/Documentation/gpu/drm-kms.rst b/Documentation/gpu/drm-kms.rst
> index f8f5bf1..253d546 100644
> --- a/Documentation/gpu/drm-kms.rst
> +++ b/Documentation/gpu/drm-kms.rst
> @@ -551,12 +551,102 @@ Plane Composition Properties
>  Color Management Properties
>  ---------------------------
>  
> +Below is how a typical hardware pipeline for color
> +will look like:
> +
> +.. kernel-render:: DOT
> +   :alt: Display Color Pipeline
> +   :caption: Display Color Pipeline Overview
> +
> +   digraph "KMS" {
> +      node [shape=box]
> +
> +      subgraph cluster_static {
> +          style=dashed
> +          label="Display Color Hardware Blocks"
> +
> +          node [bgcolor=grey style=filled]
> +          "Plane Degamma A" -> "Plane CSC/CTM A"
> +          "Plane CSC/CTM A" -> "Plane Gamma A"
> +          "Pipe Blender" [color=lightblue,style=filled, width=5.25, height=0.75];
> +          "Plane Gamma A" -> "Pipe Blender"
> +	  "Pipe Blender" -> "Pipe DeGamma"
> +          "Pipe DeGamma" -> "Pipe CSC/CTM"
> +          "Pipe CSC/CTM" -> "Pipe Gamma"
> +          "Pipe Gamma" -> "Pipe Output"
> +      }
> +
> +      subgraph cluster_static {
> +          style=dashed
> +
> +          node [shape=box]
> +          "Plane Degamma B" -> "Plane CSC/CTM B"
> +          "Plane CSC/CTM B" -> "Plane Gamma B"
> +          "Plane Gamma B" -> "Pipe Blender"
> +      }
> +
> +      subgraph cluster_static {
> +          style=dashed
> +
> +          node [shape=box]
> +          "Plane Degamma C" -> "Plane CSC/CTM C"
> +          "Plane CSC/CTM C" -> "Plane Gamma C"
> +          "Plane Gamma C" -> "Pipe Blender"
> +      }
> +
> +      subgraph cluster_fb {
> +          style=dashed
> +          label="RAM"
> +
> +          node [shape=box width=1.7 height=0.2]
> +
> +          "FB 1" -> "Plane Degamma A"
> +          "FB 2" -> "Plane Degamma B"
> +          "FB 3" -> "Plane Degamma C"
> +      }
> +   }
> +
> +In real world usecases,
> +
> +1. Plane Degamma can be used to linearize a non linear gamma
> +encoded framebuffer. This is needed to do any linear math like
> +color space conversion. For ex, linearize frames encoded in SRGB
> +or by HDR curve.
> +
> +2. Later Plane CTM block can convert the content to some different
> +colorspace. For ex, SRGB to BT2020 etc.
> +
> +3. Plane Gamma block can be used later to re-apply the non-linear
> +curve. This can also be used to apply Tone Mapping for HDR usecases.
> +
> +All the layers or framebuffers need to be converted to same color
> +space and format before blending. The plane color hardware blocks
> +can help with this. Once the Data is blended, similar color processing
> +can be done on blended output using pipe color hardware blocks.
> +
> +DRM Properties have been created to define and expose all these
> +hardware blocks to userspace. A userspace application (compositor
> +or any color app) can use these interfaces and define policies to
> +efficiently use the display hardware for such color operations.
> +
> +Pipe Color Management Properties
> +---------------------------------
> +
>  .. kernel-doc:: drivers/gpu/drm/drm_color_mgmt.c
>     :doc: overview
>  
>  .. kernel-doc:: drivers/gpu/drm/drm_color_mgmt.c
>     :export:
>  
> +Plane Color Management Properties
> +---------------------------------
> +
> +.. kernel-doc:: drivers/gpu/drm/drm_color_mgmt.c
> +   :doc: Plane Color Properties
> +
> +.. kernel-doc:: drivers/gpu/drm/drm_color_mgmt.c
> +   :doc: export
> +
>  Tile Group Property
>  -------------------
>  
> diff --git a/drivers/gpu/drm/drm_atomic.c b/drivers/gpu/drm/drm_atomic.c
> index d0478ab..e716614 100644
> --- a/drivers/gpu/drm/drm_atomic.c
> +++ b/drivers/gpu/drm/drm_atomic.c
> @@ -857,6 +857,8 @@ static int drm_atomic_plane_set_property(struct drm_plane *plane,
>  {
>  	struct drm_device *dev = plane->dev;
>  	struct drm_mode_config *config = &dev->mode_config;
> +	bool replaced = false;
> +	int ret;
>  
>  	if (property == config->prop_fb_id) {
>  		struct drm_framebuffer *fb = drm_framebuffer_lookup(dev, NULL, val);
> @@ -910,6 +912,13 @@ static int drm_atomic_plane_set_property(struct drm_plane *plane,
>  		state->color_encoding = val;
>  	} else if (property == plane->color_range_property) {
>  		state->color_range = val;
> +	} else if (property == plane->degamma_lut_property) {
> +		ret = drm_atomic_replace_property_blob_from_id(dev,
> +					&state->degamma_lut,
> +					val, -1, sizeof(struct drm_color_lut),
> +					&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);
> @@ -980,6 +989,9 @@ static int drm_atomic_plane_set_property(struct drm_plane *plane,
>  		*val = state->color_encoding;
>  	} else if (property == plane->color_range_property) {
>  		*val = state->color_range;
> +	} else if (property == plane->degamma_lut_property) {
> +		*val = (state->degamma_lut) ?
> +			state->degamma_lut->base.id : 0;
>  	} else if (plane->funcs->atomic_get_property) {
>  		return plane->funcs->atomic_get_property(plane, state, property, val);
>  	} else {
> @@ -1120,6 +1132,7 @@ static void drm_atomic_plane_print_state(struct drm_printer *p,
>  		   drm_get_color_encoding_name(state->color_encoding));
>  	drm_printf(p, "\tcolor-range=%s\n",
>  		   drm_get_color_range_name(state->color_range));
> +	drm_printf(p, "\tcolor_mgmt_changed=%d\n", state->color_mgmt_changed);
>  
>  	if (plane->funcs->atomic_print_state)
>  		plane->funcs->atomic_print_state(p, state);
> diff --git a/drivers/gpu/drm/drm_atomic_helper.c b/drivers/gpu/drm/drm_atomic_helper.c
> index 2c23a48..203137e 100644
> --- a/drivers/gpu/drm/drm_atomic_helper.c
> +++ b/drivers/gpu/drm/drm_atomic_helper.c
> @@ -3614,6 +3614,10 @@ void __drm_atomic_helper_plane_duplicate_state(struct drm_plane *plane,
>  
>  	state->fence = NULL;
>  	state->commit = NULL;
> +
> +	if (state->degamma_lut)
> +		drm_property_blob_get(state->degamma_lut);
> +	state->color_mgmt_changed = false;
>  }
>  EXPORT_SYMBOL(__drm_atomic_helper_plane_duplicate_state);
>  
> @@ -3658,6 +3662,8 @@ void __drm_atomic_helper_plane_destroy_state(struct drm_plane_state *state)
>  
>  	if (state->commit)
>  		drm_crtc_commit_put(state->commit);
> +
> +	drm_property_blob_put(state->degamma_lut);
>  }
>  EXPORT_SYMBOL(__drm_atomic_helper_plane_destroy_state);
>  
> diff --git a/drivers/gpu/drm/drm_color_mgmt.c b/drivers/gpu/drm/drm_color_mgmt.c
> index 1bdcc1a..d8a9e8b 100644
> --- a/drivers/gpu/drm/drm_color_mgmt.c
> +++ b/drivers/gpu/drm/drm_color_mgmt.c
> @@ -29,11 +29,11 @@
>  /**
>   * DOC: overview
>   *
> - * Color management or color space adjustments is supported through a set of 5
> - * properties on the &drm_crtc object. They are set up by calling
> + * Pipe Color management or color space adjustments is supported through a
> + * set of 5 properties on the &drm_crtc object. They are set up by calling
>   * drm_crtc_enable_color_mgmt().
>   *
> - * "DEGAMMA_LUT”:
> + * "DEGAMMA_LUT

This change seems unrelated/unwanted.

>   *	Blob property to set the degamma lookup table (LUT) mapping pixel data
>   *	from the framebuffer before it is given to the transformation matrix.
>   *	The data is interpreted as an array of &struct drm_color_lut elements.
> @@ -491,3 +491,41 @@ int drm_plane_create_color_properties(struct drm_plane *plane,
>  	return 0;
>  }
>  EXPORT_SYMBOL(drm_plane_create_color_properties);
> +
> +/**
> + * DOC: Plane Color Properties
> + *
> + * Plane Color management or color space adjustments is supported
> + * through a set of 5 properties on the &drm_plane object.
> + *
> + * degamma_lut_property:
> + *     Blob property which allows a userspace to provide LUT values
> + *     to apply degamma curve using the h/w plane degamma processing
> + *     engine, thereby making the content as linear for further color
> + *     processing.
> + *
> + * degamma_lut_size_property:
> + *     Range Property to indicate size of the plane degamma LUT.

Elsewhere we're documenting the string name for the property, which is
part of the ABI (e.g., "DEGAMMA_LUT") but here you're documenting the
property variable name in the code.

I think there was also discussion at one point of having a more complex
LUT interface that deals with things like non-linear ranges and such.
If that's still planned, would it be layered on top of these properties,
or would it be a completely separate, replacement ABI down the road?

> + */
> +int drm_plane_color_create_prop(struct drm_device *dev,
> +				struct drm_plane *plane)
> +{
> +	struct drm_property *prop;
> +
> +	prop = drm_property_create(dev,
> +			DRM_MODE_PROP_BLOB,
> +			"PLANE_DEGAMMA_LUT", 0);
> +	if (!prop)
> +		return -ENOMEM;
> +	plane->degamma_lut_property = prop;
> +
> +	prop = drm_property_create_range(dev,
> +			DRM_MODE_PROP_IMMUTABLE,
> +			"PLANE_DEGAMMA_LUT_SIZE", 0, UINT_MAX);
> +	if (!prop)
> +		return -ENOMEM;

If this fails, should we try to clean up the earlier property?  It looks
the i915 callsite for this function (in patch #6 of the series) doesn't
check the return value, so even if we return -ENOMEM, the driver will
continue with some properties created and some not.

Actually, aside from using names "PLANE_FOO" instead of "FOO," is there
a reason why we need to create new properties for planes?  I think we
could still attach the same properties we're already using for CRTC's
(dev->mode_config.degamma_lut_property and such) since afaik there isn't
anything that prevents us from attaching the same property to different
kinds of drm_object's.


Matt

> +	plane->degamma_lut_size_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 16f5b666..7f0d961 100644
> --- a/include/drm/drm_plane.h
> +++ b/include/drm/drm_plane.h
> @@ -182,6 +182,14 @@ struct drm_plane_state {
>  	 */
>  	bool visible;
>  
> +	/* @degamma_lut:
> +	 *
> +	 * Lookup table for converting framebuffer pixel data before apply the
> +	 * color conversion matrix @ctm. See drm_plane_enable_color_mgmt(). The
> +	 * blob (if not NULL) is an array of &struct drm_color_lut_ext.
> +	 */
> +	struct drm_property_blob *degamma_lut;
> +
>  	/**
>  	 * @commit: Tracks the pending commit to prevent use-after-free conditions,
>  	 * and for async plane updates.
> @@ -192,6 +200,8 @@ struct drm_plane_state {
>  
>  	/** @state: backpointer to global drm_atomic_state */
>  	struct drm_atomic_state *state;
> +
> +	u8 color_mgmt_changed : 1;
>  };
>  
>  static inline struct drm_rect
> @@ -692,6 +702,18 @@ struct drm_plane {
>  	 * See drm_plane_create_color_properties().
>  	 */
>  	struct drm_property *color_range_property;
> +
> +	/**
> +	 * @degamma_lut_property: Optional Plane property to set the LUT
> +	 * used to convert the framebuffer's colors to linear gamma.
> +	 */
> +	struct drm_property *degamma_lut_property;
> +
> +	/**
> +	 * @degamma_lut_size_property: Optional Plane property for the
> +	 * size of the degamma LUT as supported by the driver (read-only).
> +	 */
> +	struct drm_property *degamma_lut_size_property;
>  };
>  
>  #define obj_to_plane(x) container_of(x, struct drm_plane, base)
> @@ -741,6 +763,8 @@ static inline u32 drm_plane_mask(const struct drm_plane *plane)
>  int drm_mode_plane_set_obj_prop(struct drm_plane *plane,
>  				       struct drm_property *property,
>  				       uint64_t value);
> +int drm_plane_color_create_prop(struct drm_device *dev,
> +				struct drm_plane *plane);
>  
>  /**
>   * drm_plane_find - find a &drm_plane
> -- 
> 1.9.1
> 
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-- 
Matt Roper
Graphics Software Engineer
IoTG Platform Enabling & Development
Intel Corporation
(916) 356-2795
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