Re: [v7 00/16] Add Plane Color Properties

["Ville Syrjälä" <ville.syrjala@linux.intel.com>]

On Wed, Jun 19, 2019 at 10:18:18AM -0300, Ezequiel Garcia wrote:
> On Wed, 2019-06-19 at 06:20 +0000, Shankar, Uma wrote:
> > > -----Original Message-----
> > > From: dri-devel [mailto:dri-devel-bounces@lists.freedesktop.org] On Behalf Of
> > > Ezequiel Garcia
> > > Sent: Friday, June 14, 2019 9:48 PM
> > > To: Shankar, Uma <uma.shankar@intel.com>
> > > Cc: Emil Velikov <emil.l.velikov@gmail.com>; intel-gfx@lists.freedesktop.org; Syrjala,
> > > Ville <ville.syrjala@intel.com>; Lankhorst, Maarten <maarten.lankhorst@intel.com>;
> > > dri-devel <dri-devel@lists.freedesktop.org>
> > > Subject: Re: [v7 00/16] Add Plane Color Properties
> > > 
> > > On Thu, 28 Mar 2019 at 16:50, 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, CSC used for gamut
> > > > conversion, and gamma 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.
> > > > 
> > > > Usersapce 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 just add the property interfaces and enable helper
> > > > functions.
> > > > 
> > > > This series adds Intel Gen9 specific plane gamma feature. We can build
> > > > up and add other platform/hardware specific implementation on top of
> > > > this series
> > > > 
> > > > Note: This is just to get a design feedback whether these interfaces
> > > > look ok. Based on community feedback on interfaces, we will implement
> > > > IGT tests to validate plane color features. This is un-tested currently.
> > > > 
> > > > Userspace implementation using these properties have been done in drm
> > > > hwcomposer by "Alexandru-Cosmin Gheorghe Alexandru-
> > > Cosmin.Gheorghe@arm.com"
> > > > from ARM. A merge request has been opened by Alexandru for
> > > > drm_hwcomposer, implementing the property changes for the same. Please review
> > > that as well:
> > > > https://gitlab.freedesktop.org/drm-hwcomposer/drm-hwcomposer/merge_req
> > > > uests/25
> > > > 
> > > > v2: Dropped legacy gamma table for plane as suggested by Maarten.
> > > > Added Gen9/BDW plane gamma feature and rebase on tot.
> > > > 
> > > > v3: Added a new drm_color_lut_ext structure to accommodate 32 bit
> > > > precision entries, pointed to by Brian, Starkey for HDR usecases.
> > > > Addressed Sean,Paul comments and moved plane color properties to
> > > > drm_plane instead of mode_config. Added property documentation as suggested by
> > > Daniel, Vetter.
> > > > Fixed a rebase fumble which occurred in v2, pointed by Emil Velikov.
> > > > 
> > > > v4: Rebase
> > > > 
> > > > v5: Added "Display Color Hardware Pipeline" flow to kernel
> > > > documentation as suggested by "Ville Syrjala" and "Brian Starkey".
> > > > Moved the property creation to drm_color_mgmt.c file to consolidate
> > > > all color operations at one place. Addressed Alexandru's review comments.
> > > > 
> > > > v6: Rebase. Added support for ICL Color features. Enhanced Lut
> > > > precision to accept input values in u32.32 format. This is needed for
> > > > higher precision required in HDR data processing.
> > > > 
> > > > v7: Fixed Lut roundup and extraction function in patch 1 and address
> > > > definitions for Degamma index in patch 10. Rest of the patches are
> > > > just rebased.
> > > > 
> > > 
> > > I can't find any comments on this one.
> > > 
> > > What's the status of this?
> > 
> > Hi Eze,
> > This was blocked due to lack of a userspace consumer. Since its adds a new UAPI, we need a userspace
> > consumer using this for it to get merge. We have some folks signed up in Intel who can help here.
> > Hopefully we can see some movement on this soon.
> > 
> 
> Hi Uma,
> 
> Thanks a lot for your reply.
> 
> We do have a userspace consumer in chromeos [1]. This is being shipped
> since some time now, and I have been (perhaps too silently) waiting
> for this series to be merged.

I don't think the proposed uapi will be good enough and instead we
need something like the gamma_mode prop for planes as well. Eg. even
bunch of Intel platforms have plane gamma where the input points are
not evenly spaced, so we again have the problem of either lying to
userspace and throwing away a bunch of the user provided LUT entries,
or we add the gamma_mode prop that actually describes the LUT
capabilities.

Another idea that was thrown around was supporting hardware that
supports only hardcoded gamma curves. We need to describe those
somehow and let userspace select the right one.

-- 
Ville Syrjälä
Intel
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