On 2025-09-01 17:33, Melissa Wen wrote:
> Don't update DC stream color components during atomic check. The driver
> will continue validating the new CRTC color state but will not change DC
> stream color components. The DC stream color state will only be
> programmed at commit time in the `atomic_setup_commit` stage.
>
> It fixes gamma LUT loss reported by KDE users when changing brightness
> quickly or changing Display settings (such as overscan) with nightlight
> on and HDR. As KWin can do a test commit with color settings different
> from those that should be applied in a non-test-only commit, if the
> driver changes DC stream color state in atomic check, this state can be
> eventually HW programmed in commit tail, instead of the respective state
> set by the non-blocking commit.
>
> Link: https://gitlab.freedesktop.org/drm/amd/-/issues/4444
> Reported-by: Xaver Hugl <[email protected]>
> Signed-off-by: Melissa Wen <[email protected]>
> ---
> .../gpu/drm/amd/display/amdgpu_dm/amdgpu_dm.c | 2 +-
> .../gpu/drm/amd/display/amdgpu_dm/amdgpu_dm.h | 1 +
> .../amd/display/amdgpu_dm/amdgpu_dm_color.c | 105 +++++++++++++++++-
> 3 files changed, 104 insertions(+), 4 deletions(-)
>
> diff --git a/drivers/gpu/drm/amd/display/amdgpu_dm/amdgpu_dm.c
> b/drivers/gpu/drm/amd/display/amdgpu_dm/amdgpu_dm.c
> index 9bd82e04fe5c..ba40346eaf95 100644
> --- a/drivers/gpu/drm/amd/display/amdgpu_dm/amdgpu_dm.c
> +++ b/drivers/gpu/drm/amd/display/amdgpu_dm/amdgpu_dm.c
> @@ -11125,7 +11125,7 @@ static int dm_update_crtc_state(struct
> amdgpu_display_manager *dm,
> if (dm_new_crtc_state->base.color_mgmt_changed ||
> dm_old_crtc_state->regamma_tf != dm_new_crtc_state->regamma_tf ||
> drm_atomic_crtc_needs_modeset(new_crtc_state)) {
> - ret = amdgpu_dm_update_crtc_color_mgmt(dm_new_crtc_state);
> + ret = amdgpu_dm_check_crtc_color_mgmt(dm_new_crtc_state);
> if (ret)
> goto fail;
> }
> diff --git a/drivers/gpu/drm/amd/display/amdgpu_dm/amdgpu_dm.h
> b/drivers/gpu/drm/amd/display/amdgpu_dm/amdgpu_dm.h
> index ce74125c713e..1cc3d83e377a 100644
> --- a/drivers/gpu/drm/amd/display/amdgpu_dm/amdgpu_dm.h
> +++ b/drivers/gpu/drm/amd/display/amdgpu_dm/amdgpu_dm.h
> @@ -1041,6 +1041,7 @@ void amdgpu_dm_init_color_mod(void);
> int amdgpu_dm_create_color_properties(struct amdgpu_device *adev);
> int amdgpu_dm_verify_lut_sizes(const struct drm_crtc_state *crtc_state);
> int amdgpu_dm_update_crtc_color_mgmt(struct dm_crtc_state *crtc);
> +int amdgpu_dm_check_crtc_color_mgmt(struct dm_crtc_state *crtc);
> int amdgpu_dm_update_plane_color_mgmt(struct dm_crtc_state *crtc,
> struct drm_plane_state *plane_state,
> struct dc_plane_state *dc_plane_state);
> 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 c7387af725d6..a7cfcdba1fc9 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
> @@ -566,12 +566,11 @@ static int __set_output_tf(struct dc_transfer_func
> *func,
> return res ? 0 : -ENOMEM;
> }
>
> -static int amdgpu_dm_set_atomic_regamma(struct dc_stream_state *stream,
> +static int amdgpu_dm_set_atomic_regamma(struct dc_transfer_func *out_tf,
> const struct drm_color_lut *regamma_lut,
> uint32_t regamma_size, bool has_rom,
> enum dc_transfer_func_predefined tf)
> {
> - struct dc_transfer_func *out_tf = &stream->out_transfer_func;
> int ret = 0;
>
> if (regamma_size || tf != TRANSFER_FUNCTION_LINEAR) {
> @@ -969,7 +968,7 @@ int amdgpu_dm_update_crtc_color_mgmt(struct dm_crtc_state
> *crtc)
> return r;
> } else {
> regamma_size = has_regamma ? regamma_size : 0;
> - r = amdgpu_dm_set_atomic_regamma(stream, regamma_lut,
> + r = amdgpu_dm_set_atomic_regamma(&stream->out_transfer_func,
> regamma_lut,
> regamma_size, has_rom, tf);
> if (r)
> return r;
> @@ -1008,6 +1007,106 @@ int amdgpu_dm_update_crtc_color_mgmt(struct
> dm_crtc_state *crtc)
> return 0;
> }
>
> +/**
> + * amdgpu_dm_check_crtc_color_mgmt: Check if DRM color props are
> programmable by DC.
> + * @crtc: amdgpu_dm crtc state
> + *
> + * This function just verifies CRTC LUT sizes, if there is enough space for
> + * output transfer function and if its parameters can be calculated by AMD
> + * color module. It also adjusts some settings for programming CRTC degamma
> at
> + * plane stage, using plane DGM block.
> + *
> + * The RGM block is typically more fully featured and accurate across
> + * all ASICs - DCE can't support a custom non-linear CRTC DGM.
> + *
> + * For supporting both plane level color management and CRTC level color
> + * management at once we have to either restrict the usage of some CRTC
> + * properties or blend adjustments together.
> + *
> + * Returns:
> + * 0 on success. Error code if validation fails.
> + */
> +
> +int amdgpu_dm_check_crtc_color_mgmt(struct dm_crtc_state *crtc)
This function is almost a duplicate of amdgpu_dm_update_crtc_color_mgmt,
without the part that sets the stream->out_transfer_func and without
the "Setup CRTC CTM" bits. I wonder whether it would make sense to
combine them in a way where the "update" function would look like:
int amdgpu_dm_update_crtc_color_mgmt(...)
{
amdgpu_dm_check_crtc_color_mgmt(...);
update stream->out_transfer_func based on out_tf computed in check
do the "Setup CRTC CTM bits
}
Either way, great find, and really good change. The series is
Reviewed-by: Harry Wentland <[email protected]>
Harry
> +{
> + struct amdgpu_device *adev = drm_to_adev(crtc->base.state->dev);
> + bool has_rom = adev->asic_type <= CHIP_RAVEN;
> + const struct drm_color_lut *degamma_lut, *regamma_lut;
> + uint32_t degamma_size, regamma_size;
> + bool has_regamma, has_degamma;
> + struct dc_transfer_func *out_tf;
> + enum dc_transfer_func_predefined tf = TRANSFER_FUNCTION_LINEAR;
> + bool is_legacy;
> + int r;
> +
> + tf = amdgpu_tf_to_dc_tf(crtc->regamma_tf);
> +
> + r = amdgpu_dm_verify_lut_sizes(&crtc->base);
> + if (r)
> + return r;
> +
> + degamma_lut = __extract_blob_lut(crtc->base.degamma_lut, °amma_size);
> + regamma_lut = __extract_blob_lut(crtc->base.gamma_lut, ®amma_size);
> +
> + has_degamma =
> + degamma_lut && !__is_lut_linear(degamma_lut, degamma_size);
> +
> + has_regamma =
> + regamma_lut && !__is_lut_linear(regamma_lut, regamma_size);
> +
> + is_legacy = regamma_size == MAX_COLOR_LEGACY_LUT_ENTRIES;
> +
> + /* Reset all adjustments. */
> + crtc->cm_has_degamma = false;
> + crtc->cm_is_degamma_srgb = false;
> +
> + out_tf = kzalloc(sizeof(*out_tf), GFP_KERNEL);
> + if (!out_tf)
> + return -ENOMEM;
> +
> + /* Setup regamma and degamma. */
> + if (is_legacy) {
> + /*
> + * Legacy regamma forces us to use the sRGB RGM as a base.
> + * This also means we can't use linear DGM since DGM needs
> + * to use sRGB as a base as well, resulting in incorrect CRTC
> + * DGM and CRTC CTM.
> + *
> + * TODO: Just map this to the standard regamma interface
> + * instead since this isn't really right. One of the cases
> + * where this setup currently fails is trying to do an
> + * inverse color ramp in legacy userspace.
> + */
> + crtc->cm_is_degamma_srgb = true;
> + out_tf->type = TF_TYPE_DISTRIBUTED_POINTS;
> + out_tf->tf = TRANSFER_FUNCTION_SRGB;
> + /*
> + * Note: although we pass has_rom as parameter here, we never
> + * actually use ROM because the color module only takes the ROM
> + * path if transfer_func->type == PREDEFINED.
> + *
> + * See more in mod_color_calculate_regamma_params()
> + */
> + r = __set_legacy_tf(out_tf, regamma_lut,
> + regamma_size, has_rom);
> + } else {
> + regamma_size = has_regamma ? regamma_size : 0;
> + r = amdgpu_dm_set_atomic_regamma(out_tf, regamma_lut,
> + regamma_size, has_rom, tf);
> + }
> +
> + /*
> + * CRTC DGM goes into DGM LUT. It would be nice to place it
> + * into the RGM since it's a more featured block but we'd
> + * have to place the CTM in the OCSC in that case.
> + */
> + crtc->cm_has_degamma = has_degamma;
> + dc_transfer_func_release(out_tf);
> +
> + return r;
> +}
> +
> +
> static int
> map_crtc_degamma_to_dc_plane(struct dm_crtc_state *crtc,
> struct dc_plane_state *dc_plane_state,
