Re: [PATCH 00/21] Add Support for Plane Color Lut and CSC features

[Pekka Paalanen <ppaalanen@gmail.com>]

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On Tue,  1 Jun 2021 16:21:57 +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

Hi,

this is an excellent picture. I have long been wanting schematics like
that in the DRM UAPI documentation. Another note on that:
https://lists.freedesktop.org/archives/dri-devel/2021-May/307310.html

But the schematic for DRM UAPI documentation needs to be written in
terms of the abstract KMS pipeline with property names spelled out,
like in what Ville sketched in that email.

> 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.

This is very much welcome!

There is also the thread:
https://lists.freedesktop.org/archives/dri-devel/2021-May/306726.html

Everything mentioned will interact with each other by changing what the
abstract KMS pixel pipeline does. I think you and Harry should probably
look at each others' suggestions and see how to fit them all into a
single abstract KMS pipeline.

People are adding new pieces into KMS left and right, and I fear we
lose sight of how everything will actually work together when all KMS
properties are supposed to be generic and potentially present
simultaneously. This is why I would very much like to have that *whole*
abstract KMS pipeline documented with *everything*. Otherwise it is
coming really hard fast to figure out how generic userspace should use
all these KMS properties together.

Or if there cannot be a single abstract KMS pipeline, then sure, have
multiple, as long as they are documented and how userspace will know
which pipeline it is dealing with, and what things are mutually
exclusive so we can avoid writing userspace code for combinations that
will never exist.


Thanks,
pq

> 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. We
> will notify the list once we have that ready for review.
> 
> ToDo: State readout for this feature will be added next.
> 
> Uma Shankar (21):
>   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 +++
>  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 ++
>  15 files changed, 1170 insertions(+), 6 deletions(-)
> 


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