Re: [RFC v2 00/22] Add Support for Plane Color Lut and CSC features

[Pekka Paalanen <ppaalanen@gmail.com>]

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On Tue,  7 Sep 2021 03:08:42 +0530
Uma Shankar <uma.shankar@intel.com> wrote:

> This is how a typical display color hardware pipeline looks like:
>  +-------------------------------------------+
>  |                RAM                        |
>  |  +------+    +---------+    +---------+   |
>  |  | FB 1 |    |  FB 2   |    | FB N    |   |
>  |  +------+    +---------+    +---------+   |
>  +-------------------------------------------+
>        |  Plane Color Hardware Block |
>  +--------------------------------------------+
>  | +---v-----+   +---v-------+   +---v------+ |
>  | | Plane A |   | Plane B   |   | Plane N  | |
>  | | DeGamma |   | Degamma   |   | Degamma  | |
>  | +---+-----+   +---+-------+   +---+------+ |
>  |     |             |               |        |
>  | +---v-----+   +---v-------+   +---v------+ |
>  | |Plane A  |   | Plane B   |   | Plane N  | |
>  | |CSC/CTM  |   | CSC/CTM   |   | CSC/CTM  | |
>  | +---+-----+   +----+------+   +----+-----+ |
>  |     |              |               |       |
>  | +---v-----+   +----v------+   +----v-----+ |
>  | | Plane A |   | Plane B   |   | Plane N  | |
>  | | Gamma   |   | Gamma     |   | Gamma    | |
>  | +---+-----+   +----+------+   +----+-----+ |
>  |     |              |               |       |
>  +--------------------------------------------+
> +------v--------------v---------------v-------|
> ||                                           ||
> ||           Pipe Blender                    ||
> +--------------------+------------------------+
> |                    |                        |
> |        +-----------v----------+             |
> |        |  Pipe DeGamma        |             |
> |        |                      |             |
> |        +-----------+----------+             |
> |                    |            Pipe Color  |
> |        +-----------v----------+ Hardware    |
> |        |  Pipe CSC/CTM        |             |
> |        |                      |             |
> |        +-----------+----------+             |
> |                    |                        |
> |        +-----------v----------+             |
> |        |  Pipe Gamma          |             |
> |        |                      |             |
> |        +-----------+----------+             |
> |                    |                        |
> +---------------------------------------------+
>                      |
>                      v
>                Pipe Output
> 
> This patch series adds properties for plane color features. It adds
> properties for degamma used to linearize data and CSC used for gamut
> conversion. It also includes Gamma support used to again non-linearize
> data as per panel supported color space. These can be utilize by user
> space to convert planes from one format to another, one color space to
> another etc.
> 
> Userspace can take smart blending decisions and utilize these hardware
> supported plane color features to get accurate color profile. The same
> can help in consistent color quality from source to panel taking
> advantage of advanced color features in hardware.
> 
> These patches add the property interfaces and enable helper functions.
> This series adds Intel's XE_LPD hw specific plane gamma feature. We
> can build up and add other platform/hardware specific implementation
> on top of this series.
> 
> Credits: Special mention and credits to Ville Syrjala for coming up
> with a design for this feature and inputs. This series is based on
> his original design and idea.
> 
> Note: Userspace support for this new UAPI will be done on Chrome in
> alignment with weston and general opensource community.
> Discussion ongoing with Harry Wentland, Pekka and community on color
> pipeline and UAPI design. Harry's RFC below:
> https://patchwork.freedesktop.org/series/89506/
> We need to converge on a common UAPI interface which caters to
> all the modern color hardware pipelines. 
> 
> ToDo: State readout for this feature will be added next.
> 
> v2: Added UAPI description and added change in the rfc section of
> kernel Documentation folder

Hi,

thank you for this. I do believe the KMS UAPI should expose what
hardware can do (prescribed operations) rather than how they would be
often used (to realize a conversion from one space description to
another). This proposal fits quite nicely with what I have envisioned
for Weston.

I mainly went over the big picture by commenting in detail on the
proposal document, and not looking too carefully at the other
documentation or UAPI details at this time.

Unfortunately I was unable to decipher how userspace is supposed to use
the XE_LPD special gamma features.


Thanks,
pq

> 
> Uma Shankar (22):
>   drm: RFC for Plane Color Hardware Pipeline
>   drm: Add Enhanced Gamma and color lut range attributes
>   drm: Add Plane Degamma Mode property
>   drm: Add Plane Degamma Lut property
>   drm/i915/xelpd: Define Degamma Lut range struct for HDR planes
>   drm/i915/xelpd: Add register definitions for Plane Degamma
>   drm/i915/xelpd: Enable plane color features
>   drm/i915/xelpd: Add color capabilities of SDR planes
>   drm/i915/xelpd: Program Plane Degamma Registers
>   drm/i915/xelpd: Add plane color check to glk_plane_color_ctl
>   drm/i915/xelpd: Initialize plane color features
>   drm/i915/xelpd: Load plane color luts from atomic flip
>   drm: Add Plane CTM property
>   drm: Add helper to attach Plane ctm property
>   drm/i915/xelpd: Define Plane CSC Registers
>   drm/i915/xelpd: Enable Plane CSC
>   drm: Add Plane Gamma Mode property
>   drm: Add Plane Gamma Lut property
>   drm/i915/xelpd: Define and Initialize Plane Gamma Lut range
>   drm/i915/xelpd: Add register definitions for Plane Gamma
>   drm/i915/xelpd: Program Plane Gamma Registers
>   drm/i915/xelpd: Enable plane gamma
> 
>  Documentation/gpu/drm-kms.rst                 |  90 +++
>  Documentation/gpu/rfc/drm_color_pipeline.rst  | 167 ++++++
>  drivers/gpu/drm/drm_atomic.c                  |   1 +
>  drivers/gpu/drm/drm_atomic_state_helper.c     |  12 +
>  drivers/gpu/drm/drm_atomic_uapi.c             |  38 ++
>  drivers/gpu/drm/drm_color_mgmt.c              | 177 +++++-
>  .../gpu/drm/i915/display/intel_atomic_plane.c |   6 +
>  .../gpu/drm/i915/display/intel_atomic_plane.h |   2 +
>  drivers/gpu/drm/i915/display/intel_color.c    | 513 ++++++++++++++++++
>  drivers/gpu/drm/i915/display/intel_color.h    |   2 +
>  .../drm/i915/display/skl_universal_plane.c    |  15 +-
>  drivers/gpu/drm/i915/i915_drv.h               |   3 +
>  drivers/gpu/drm/i915/i915_reg.h               | 176 +++++-
>  include/drm/drm_mode_object.h                 |   2 +-
>  include/drm/drm_plane.h                       |  81 +++
>  include/uapi/drm/drm_mode.h                   |  58 ++
>  16 files changed, 1337 insertions(+), 6 deletions(-)
>  create mode 100644 Documentation/gpu/rfc/drm_color_pipeline.rst
> 


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