Re: [RFC PATCH v4 00/42] Color Pipeline API w/ VKMS

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On 2/26/24 21:10, Harry Wentland wrote:
This is an RFC set for a color pipeline API, along with a sample
implementation in VKMS. All the key API bits are here. VKMS now
supports two named transfer function colorops and two matrix
colorops. We have IGT tests that check all four of these colorops
with a pixel-by-pixel comparison that checks that these colorops
do what we expect them to do with a +/- 1 8 bpc code point margin.

The big new change with v4 is the addition of an amdgpu color
pipeline, for all AMD GPUs with DCN 3 and newer. Amdgpu now support
the following:

1. 1D Curve EOTF
2. 3x4 CTM
3. Multiplier
4. 1D Curve Inverse EOTF
5. 1D LUT
6. 1D Curve EOTF
7. 1D LUT

The supported curves for the 1D Curve type are:
- sRGB EOTF and its inverse
- PQ EOTF, scaled to [0.0, 125.0] and its inverse
- BT.2020/BT.709 OETF and its inverse

Note that the 1st and 5th colorops take the EOTF or Inverse
OETF while the 3rd colorop takes the Inverse EOTF or OETF.

We are working on two more ops for amdgpu, the HDR multiplier
and the 3DLUT, which will give us this:

1. 1D Curve EOTF
2. 3x4 CTM
3. HDR Multiplier
4. 1D Curve Inverse EOTF
5. 1D LUT
6. 3D LUT
7. 1D Curve EOTF
8. 1D LUT

This, essentially mirrors the color pipeline used by gamescope
and presented by Melissa Wen, with the exception of the DEGAM
LUT, which is not currently used. See

After this we'd like to also add the following ops:
- Scaler (Informational only)

Why informational only? Having NEAREST and in general custom taps should be possible on AMDGPU right?

We don't have to solve this now, but I just want to make sure that we aren't locking this to info only.


- Joshie 🐸✨

- Color Encoding, to replace drm_plane's COLOR_ENCODING
- Color Range, to replace drm_plane's COLOR_RANGE

This patchset is grouped as follows:
  - Patches 1-3: couple general patches/fixes
  - Patches 4-7: introduce kunit to VKMS
  - Patch 7: description of motivation and details behind the
             Color Pipeline API. If you're reading nothing else
             but are interested in the topic I highly recommend
             you take a look at this.
  - Patches 7-27: DRM core and VKMS changes for color pipeline API
  - Patches 28-40: DRM core and amdgpu changes for color pipeline API

VKMS patches could still be improved in a few ways, though the
payoff might be limited and I would rather focus on other work
at the moment. The most obvious thing to improve would be to
eliminate the hard-coded LUTs for identity, and sRGB, and replace
them with fixed-point math instead.

There are plenty of things that I would like to see here but
haven't had a chance to look at. These will (hopefully) be
addressed in future iterations, either in VKMS or amdgpu:
  - Clear documentation for each drm_colorop_type
  - Add custom LUT colorops to VKMS
  - Add pre-blending 3DLUT
  - How to support HW which can't bypass entire pipeline?
  - Add ability to create colorops that don't have BYPASS
  - Can we do a LOAD / COMMIT model for LUTs (and other properties)?
  - read-only scaling colorop which defines scaling taps and position
  - read-only color format colorop to define supported color formats
    for a pipeline
  - named matrices, for things like converting YUV to RGB

IGT tests can be found at

IGT patches are also being sent to the igt-dev mailing list.

If you prefer a gitlab MR for review you can find it at

  - Add amdgpu color pipeline (WIP)
  - Don't block setting of deprecated properties, instead pass client cap
    to atomic check so drivers can ignore these props
  - Drop IOCTL definitions (Pekka)
  - Use enum property for colorop TYPE (Pekka)
  - A few cleanups to the docs (Pekka)
  - Rework the TYPE enum to name relation to avoid code duplication (Pekka)
  - Add missing function declarations (Chaitanya Kumar Borah)
  - Allow setting of NEXT property to NULL in _set_ function (Chaitanya Kumar Borah)
  - Add helper for creation of pipeline drm_plane property (Pekka)
  - Always create Bypass pipeline (Pekka)
  - A bunch of changes to VKMS kunit tests (Pekka)
  - Fix index in CTM doc (Pekka)

  - Abandon IOCTLs and discover colorops as clients iterate the pipeline
  - Remove need for libdrm
  - Add color_pipeline client cap and make mutually exclusive with
  - add CTM colorop to VKMS
  - Use include way for kunit testing static functions (Arthur)
  - Make TYPE a range property
  - Move enum drm_colorop_type to uapi header
  - and a bunch of smaller bits that are highlighted in the relevant commit

  - Rebased on drm-misc-next
  - Introduce a VKMS Kunit so we can test LUT functionality in vkms_composer
  - Incorporate feedback in color_pipeline.rst doc
  - Add support for sRGB inverse EOTF
  - Add 2nd enumerated TF colorop to VKMS
  - Fix LUTs and some issues with applying LUTs in VKMS

Cc: Ville Syrjala <ville.syrjala@xxxxxxxxxxxxxxx>
Cc: Pekka Paalanen <pekka.paalanen@xxxxxxxxxxxxx>
Cc: Simon Ser <contact@xxxxxxxxxxx>
Cc: Harry Wentland <harry.wentland@xxxxxxx>
Cc: Melissa Wen <mwen@xxxxxxxxxx>
Cc: Jonas Ådahl <jadahl@xxxxxxxxxx>
Cc: Sebastian Wick <sebastian.wick@xxxxxxxxxx>
Cc: Shashank Sharma <shashank.sharma@xxxxxxx>
Cc: Alexander Goins <agoins@xxxxxxxxxx>
Cc: Joshua Ashton <joshua@xxxxxxxxx>
Cc: Michel Dänzer <mdaenzer@xxxxxxxxxx>
Cc: Aleix Pol <aleixpol@xxxxxxx>
Cc: Xaver Hugl <xaver.hugl@xxxxxxxxx>
Cc: Victoria Brekenfeld <victoria@xxxxxxxxxxxx>
Cc: Sima <daniel@xxxxxxxx>
Cc: Uma Shankar <uma.shankar@xxxxxxxxx>
Cc: Naseer Ahmed <quic_naseer@xxxxxxxxxxx>
Cc: Christopher Braga <quic_cbraga@xxxxxxxxxxx>
Cc: Abhinav Kumar <quic_abhinavk@xxxxxxxxxxx>
Cc: Arthur Grillo <arthurgrillo@xxxxxxxxxx>
Cc: Hector Martin <marcan@xxxxxxxxx>
Cc: Liviu Dudau <Liviu.Dudau@xxxxxxx>
Cc: Sasha McIntosh <sashamcintosh@xxxxxxxxxx>
Cc: Chaitanya Kumar Borah <chaitanya.kumar.borah@xxxxxxxxx>

Alex Hung (10):
   drm/colorop: define a new macro for_each_new_colorop_in_state
   drm/amd/display: Skip color pipeline initialization for cursor plane
   drm/amd/display: Add support for sRGB EOTF in DEGAM block
   drm/amd/display: Add support for sRGB Inverse EOTF in SHAPER block
   drm/amd/display: Add support for sRGB EOTF in BLND block
   drm/colorop: Add 1D Curve Custom LUT type
   drm/amd/display: add shaper and blend colorops for 1D Curve Custom LUT
   drm/amd/display: add 3x4 matrix colorop
   drm/colorop: Add mutliplier type
   drm/amd/display: add multiplier colorop

Harry Wentland (32):
   drm: Don't treat 0 as -1 in drm_fixp2int_ceil
   drm: Add helper for conversion from signed-magnitude
   drm: Correctly round for fixp2int_round
   drm/vkms: Round fixp2int conversion in lerp_u16
   drm/vkms: Create separate Kconfig file for VKMS
   drm/vkms: Add kunit tests for VKMS LUT handling
   drm/vkms: Avoid reading beyond LUT array
   drm/doc/rfc: Describe why prescriptive color pipeline is needed
   drm/colorop: Introduce new drm_colorop mode object
   drm/colorop: Add TYPE property
   drm/colorop: Add 1D Curve subtype
   drm/colorop: Add BYPASS property
   drm/colorop: Add NEXT property
   drm/colorop: Add atomic state print for drm_colorop
   drm/plane: Add COLOR PIPELINE property
   drm/colorop: Add NEXT to colorop state print
   drm/vkms: Add enumerated 1D curve colorop
   drm/vkms: Add kunit tests for linear and sRGB LUTs
   drm/colorop: Add 3x4 CTM type
   drm/vkms: Pull apply_colorop out of pre_blend_color_transform
   drm/vkms: Use s32 for internal color pipeline precision
   drm/vkms: add 3x4 matrix in color pipeline
   drm/tests: Add a few tests around drm_fixed.h
   drm/vkms: Add tests for CTM handling
   drm/colorop: pass plane_color_pipeline client cap to atomic check
   drm/amd/display: Ignore deprecated props when plane_color_pipeline set
   drm/amd/display: Add bypass COLOR PIPELINE
   drm/colorop: Add PQ 125 EOTF and its inverse
   drm/amd/display: Enable support for PQ 125 EOTF and Inverse
   drm/colorop: add BT2020/BT709 OETF and Inverse OETF
   drm/amd/display: Add support for BT.709 and BT.2020 TFs

  Documentation/gpu/rfc/color_pipeline.rst      | 360 ++++++++
  drivers/gpu/drm/Kconfig                       |  14 +-
  drivers/gpu/drm/Makefile                      |   1 +
  .../gpu/drm/amd/display/amdgpu_dm/Makefile    |   3 +-
  .../gpu/drm/amd/display/amdgpu_dm/amdgpu_dm.c |   4 +
  .../amd/display/amdgpu_dm/amdgpu_dm_color.c   | 352 ++++++++
  .../amd/display/amdgpu_dm/amdgpu_dm_colorop.c | 160 ++++
  .../amd/display/amdgpu_dm/amdgpu_dm_colorop.h |  36 +
  .../amd/display/amdgpu_dm/amdgpu_dm_plane.c   |  32 +
  drivers/gpu/drm/drm_atomic.c                  | 161 +++-
  drivers/gpu/drm/drm_atomic_helper.c           |  12 +
  drivers/gpu/drm/drm_atomic_state_helper.c     |   5 +
  drivers/gpu/drm/drm_atomic_uapi.c             | 158 ++++
  drivers/gpu/drm/drm_colorop.c                 | 411 +++++++++
  drivers/gpu/drm/drm_ioctl.c                   |   7 +
  drivers/gpu/drm/drm_mode_config.c             |   7 +
  drivers/gpu/drm/drm_plane.c                   |  52 ++
  drivers/gpu/drm/tests/Makefile                |   3 +-
  drivers/gpu/drm/tests/drm_fixp_test.c         |  69 ++
  drivers/gpu/drm/vkms/Kconfig                  |  20 +
  drivers/gpu/drm/vkms/Makefile                 |   4 +-
  drivers/gpu/drm/vkms/tests/.kunitconfig       |   4 +
  drivers/gpu/drm/vkms/tests/vkms_color_tests.c | 449 ++++++++++
  drivers/gpu/drm/vkms/vkms_colorop.c           | 100 +++
  drivers/gpu/drm/vkms/vkms_composer.c          | 135 ++-
  drivers/gpu/drm/vkms/vkms_drv.h               |   8 +
  drivers/gpu/drm/vkms/vkms_luts.c              | 802 ++++++++++++++++++
  drivers/gpu/drm/vkms/vkms_luts.h              |  12 +
  drivers/gpu/drm/vkms/vkms_plane.c             |   2 +
  include/drm/drm_atomic.h                      | 122 +++
  include/drm/drm_atomic_uapi.h                 |   3 +
  include/drm/drm_colorop.h                     | 301 +++++++
  include/drm/drm_file.h                        |   7 +
  include/drm/drm_fixed.h                       |  35 +-
  include/drm/drm_mode_config.h                 |  18 +
  include/drm/drm_plane.h                       |  13 +
  include/uapi/drm/drm.h                        |  16 +
  include/uapi/drm/drm_mode.h                   |  14 +
  38 files changed, 3882 insertions(+), 30 deletions(-)
  create mode 100644 Documentation/gpu/rfc/color_pipeline.rst
  create mode 100644 drivers/gpu/drm/amd/display/amdgpu_dm/amdgpu_dm_colorop.c
  create mode 100644 drivers/gpu/drm/amd/display/amdgpu_dm/amdgpu_dm_colorop.h
  create mode 100644 drivers/gpu/drm/drm_colorop.c
  create mode 100644 drivers/gpu/drm/tests/drm_fixp_test.c
  create mode 100644 drivers/gpu/drm/vkms/Kconfig
  create mode 100644 drivers/gpu/drm/vkms/tests/.kunitconfig
  create mode 100644 drivers/gpu/drm/vkms/tests/vkms_color_tests.c
  create mode 100644 drivers/gpu/drm/vkms/vkms_colorop.c
  create mode 100644 drivers/gpu/drm/vkms/vkms_luts.c
  create mode 100644 drivers/gpu/drm/vkms/vkms_luts.h
  create mode 100644 include/drm/drm_colorop.h


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