On 08/22, Pekka Paalanen wrote:
> On Thu, 10 Aug 2023 15:02:59 -0100
> Melissa Wen <mwen@xxxxxxxxxx> wrote:
>
> > The next patch adds pre-blending degamma to AMD color mgmt pipeline, but
> > pre-blending degamma caps (DPP) is currently in use to provide DRM CRTC
> > atomic degamma or implict degamma on legacy gamma. Detach degamma usage
> > regarging CRTC color properties to manage plane and CRTC color
> > correction combinations.
> >
> > Reviewed-by: Harry Wentland <harry.wentland@xxxxxxx>
> > Signed-off-by: Melissa Wen <mwen@xxxxxxxxxx>
> > ---
> > .../amd/display/amdgpu_dm/amdgpu_dm_color.c | 59 +++++++++++++------
> > 1 file changed, 41 insertions(+), 18 deletions(-)
> >
> > diff --git a/drivers/gpu/drm/amd/display/amdgpu_dm/amdgpu_dm_color.c b/drivers/gpu/drm/amd/display/amdgpu_dm/amdgpu_dm_color.c
> > index 68e9f2c62f2e..74eb02655d96 100644
> > --- a/drivers/gpu/drm/amd/display/amdgpu_dm/amdgpu_dm_color.c
> > +++ b/drivers/gpu/drm/amd/display/amdgpu_dm/amdgpu_dm_color.c
> > @@ -764,20 +764,9 @@ int amdgpu_dm_update_crtc_color_mgmt(struct dm_crtc_state *crtc)
> > return 0;
> > }
> >
> > -/**
> > - * amdgpu_dm_update_plane_color_mgmt: Maps DRM color management to DC plane.
> > - * @crtc: amdgpu_dm crtc state
> > - * @dc_plane_state: target DC surface
> > - *
> > - * Update the underlying dc_stream_state's input transfer function (ITF) in
> > - * preparation for hardware commit. The transfer function used depends on
> > - * the preparation done on the stream for color management.
> > - *
> > - * Returns:
> > - * 0 on success. -ENOMEM if mem allocation fails.
> > - */
> > -int amdgpu_dm_update_plane_color_mgmt(struct dm_crtc_state *crtc,
> > - struct dc_plane_state *dc_plane_state)
> > +static int
> > +map_crtc_degamma_to_dc_plane(struct dm_crtc_state *crtc,
> > + struct dc_plane_state *dc_plane_state)
> > {
> > const struct drm_color_lut *degamma_lut;
> > enum dc_transfer_func_predefined tf = TRANSFER_FUNCTION_SRGB;
> > @@ -800,8 +789,7 @@ int amdgpu_dm_update_plane_color_mgmt(struct dm_crtc_state *crtc,
> > °amma_size);
> > ASSERT(degamma_size == MAX_COLOR_LUT_ENTRIES);
> >
> > - dc_plane_state->in_transfer_func->type =
> > - TF_TYPE_DISTRIBUTED_POINTS;
> > + dc_plane_state->in_transfer_func->type = TF_TYPE_DISTRIBUTED_POINTS;
> >
> > /*
> > * This case isn't fully correct, but also fairly
> > @@ -837,7 +825,7 @@ int amdgpu_dm_update_plane_color_mgmt(struct dm_crtc_state *crtc,
> > degamma_lut, degamma_size);
> > if (r)
> > return r;
> > - } else if (crtc->cm_is_degamma_srgb) {
> > + } else {
> > /*
> > * For legacy gamma support we need the regamma input
> > * in linear space. Assume that the input is sRGB.
> > @@ -847,8 +835,43 @@ int amdgpu_dm_update_plane_color_mgmt(struct dm_crtc_state *crtc,
> >
> > if (tf != TRANSFER_FUNCTION_SRGB &&
> > !mod_color_calculate_degamma_params(NULL,
> > - dc_plane_state->in_transfer_func, NULL, false))
> > + dc_plane_state->in_transfer_func,
> > + NULL, false))
> > return -ENOMEM;
> > + }
> > +
> > + return 0;
> > +}
> > +
> > +/**
> > + * amdgpu_dm_update_plane_color_mgmt: Maps DRM color management to DC plane.
> > + * @crtc: amdgpu_dm crtc state
> > + * @dc_plane_state: target DC surface
> > + *
> > + * Update the underlying dc_stream_state's input transfer function (ITF) in
> > + * preparation for hardware commit. The transfer function used depends on
> > + * the preparation done on the stream for color management.
> > + *
> > + * Returns:
> > + * 0 on success. -ENOMEM if mem allocation fails.
> > + */
> > +int amdgpu_dm_update_plane_color_mgmt(struct dm_crtc_state *crtc,
> > + struct dc_plane_state *dc_plane_state)
> > +{
> > + bool has_crtc_cm_degamma;
> > + int ret;
> > +
> > + has_crtc_cm_degamma = (crtc->cm_has_degamma || crtc->cm_is_degamma_srgb);
> > + if (has_crtc_cm_degamma){
> > + /* AMD HW doesn't have post-blending degamma caps. When DRM
> > + * CRTC atomic degamma is set, we maps it to DPP degamma block
> > + * (pre-blending) or, on legacy gamma, we use DPP degamma to
> > + * linearize (implicit degamma) from sRGB/BT709 according to
> > + * the input space.
>
> Uhh, you can't just move degamma before blending if KMS userspace
> wants it after blending. That would be incorrect behaviour. If you
> can't implement it correctly, reject it.
>
> I hope that magical unexpected linearization is not done with atomic,
> either.
>
> Or maybe this is all a lost cause, and only the new color-op pipeline
> UAPI will actually work across drivers.
I agree that crtc degamma is an optional property and should be not
exposed if not available. I did something in this line for DCE that has
no degamma block[1]. Then, AMD DDX driver stopped to advertise atomic
API for DCE, that was not correct too[2].
But I see it as a lost cause that will only be fixed in a new generic
color API. I don't think we should change it using the current DRM CRTC
API with driver-specific props.
[1] https://lore.kernel.org/amd-gfx/20221103184500.14450-1-mwen@xxxxxxxxxx/
[2] https://gitlab.freedesktop.org/xorg/driver/xf86-video-amdgpu/-/issues/67
>
>
> Thanks,
> pq
>
> > + */
> > + ret = map_crtc_degamma_to_dc_plane(crtc, dc_plane_state);
> > + if (ret)
> > + return ret;
> > } else {
> > /* ...Otherwise we can just bypass the DGM block. */
> > dc_plane_state->in_transfer_func->type = TF_TYPE_BYPASS;
>
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