linux-kernel - Re: [PATCH v2 31/34] drm/amd/display: set stream gamut remap matrix to MPC for DCN301

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Message-ID: <20230828112041.16eb5827.pekka.paalanen@collabora.com>
Date:   Mon, 28 Aug 2023 11:20:41 +0300
From:   Pekka Paalanen <pekka.paalanen@...labora.com>
To:     Melissa Wen <mwen@...lia.com>
Cc:     amd-gfx@...ts.freedesktop.org,
        Harry Wentland <harry.wentland@....com>,
        Rodrigo Siqueira <Rodrigo.Siqueira@....com>,
        sunpeng.li@....com, Alex Deucher <alexander.deucher@....com>,
        dri-devel@...ts.freedesktop.org, christian.koenig@....com,
        Xinhui.Pan@....com, airlied@...il.com, daniel@...ll.ch,
        Joshua Ashton <joshua@...ggi.es>,
        Sebastian Wick <sebastian.wick@...hat.com>,
        Xaver Hugl <xaver.hugl@...il.com>,
        Shashank Sharma <Shashank.Sharma@....com>,
        Nicholas Kazlauskas <nicholas.kazlauskas@....com>,
        sungjoon.kim@....com, Alex Hung <alex.hung@....com>,
        Simon Ser <contact@...rsion.fr>, kernel-dev@...lia.com,
        linux-kernel@...r.kernel.org
Subject: Re: [PATCH v2 31/34] drm/amd/display: set stream gamut remap matrix
 to MPC for DCN301

On Fri, 25 Aug 2023 13:37:08 -0100
Melissa Wen <mwen@...lia.com> wrote:

> On 08/22, Pekka Paalanen wrote:
> > On Thu, 10 Aug 2023 15:03:11 -0100
> > Melissa Wen <mwen@...lia.com> wrote:
> >   
> > > dc->caps.color.mpc.gamut_remap says there is a post-blending color block
> > > for gamut remap matrix for DCN3 HW family and newer versions. However,
> > > those drivers still follow DCN10 programming that remap stream
> > > gamut_remap_matrix to DPP (pre-blending).  
> > 
> > That's ok only as long as CRTC degamma is pass-through. Blending itself
> > is a linear operation, so it doesn't matter if a matrix is applied to
> > the blending result or to all blending inputs. But you cannot move a
> > matrix operation to the other side of a non-linear operation, and you
> > cannot move a non-linear operation across blending.  
> 
> Oh, I'm not moving it, what I'm doing here is the opposite and fixing
> it. This patch puts each pre- and post-blending CTM in their right
> place, since we have the HW caps for it on DCN3+... Or are you just
> pointing out the implementation mistake on old driver versions?

It's just the old mistake.

I hope no-one complains, forcing you to revert this fix as a regression.


Thanks,
pq


> > > To enable pre-blending and post-blending gamut_remap matrix supports at
> > > the same time, set stream gamut_remap to MPC and plane gamut_remap to
> > > DPP for DCN301 that support both.
> > > 
> > > It was tested using IGT KMS color tests for DRM CRTC CTM property and it
> > > preserves test results.
> > > 
> > > Signed-off-by: Melissa Wen <mwen@...lia.com>
> > > ---
> > >  .../drm/amd/display/dc/dcn30/dcn30_hwseq.c    | 37 +++++++++++++++++++
> > >  .../drm/amd/display/dc/dcn30/dcn30_hwseq.h    |  3 ++
> > >  .../drm/amd/display/dc/dcn301/dcn301_init.c   |  2 +-
> > >  3 files changed, 41 insertions(+), 1 deletion(-)

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