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

["Shankar, Uma" <uma.shankar@intel.com>]

> -----Original Message-----
> From: Pekka Paalanen <ppaalanen@gmail.com>
> Sent: Wednesday, June 2, 2021 2:59 PM
> To: Shankar, Uma <uma.shankar@intel.com>
> Cc: intel-gfx@lists.freedesktop.org; dri-devel@lists.freedesktop.org; Modem,
> Bhanuprakash <bhanuprakash.modem@intel.com>; Harry Wentland
> <harry.wentland@amd.com>
> Subject: Re: [PATCH 00/21] Add Support for Plane Color Lut and CSC features
> 
> 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.

Sure Pekka, I can add that.

> > 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.

This is a good suggestion to have the whole pipeline and properties documented along with
the exact usages. We may end with 2 properties almost doing similar work but needed due to
underlying hardware, but we can get that properly documented and defined. 

I will discuss with Harry and Ville as well to define this.

Regards,
Uma Shankar
> 
> 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(-)
> >