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

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On 2021-06-02 4:22 p.m., Shankar, Uma wrote:
> 
> 
>> -----Original Message-----
>> From: Pekka Paalanen <ppaalanen@xxxxxxxxx>
>> Sent: Wednesday, June 2, 2021 2:59 PM
>> To: Shankar, Uma <uma.shankar@xxxxxxxxx>
>> Cc: intel-gfx@xxxxxxxxxxxxxxxxxxxxx; dri-devel@xxxxxxxxxxxxxxxxxxxxx; Modem,
>> Bhanuprakash <bhanuprakash.modem@xxxxxxxxx>; Harry Wentland
>> <harry.wentland@xxxxxxx>
>> 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@xxxxxxxxx> 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.
> 

Just wanted to let you know that I've seen and read through both of Shankar's patchsets
and had some thoughts but haven't found the time to respond. I will respond soon.

I very much agree with Pekka. We need to make sure this all plays well together and is
well documented. Maybe a library to deal with DRM KMS color management/HDR would even
be helpful. Not sure yet how I feel about that.

Harry

> 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(-)
>>>
> 




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