On 2025-09-11 13:21, 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.
>
> Closes: https://gitlab.freedesktop.org/drm/amd/-/issues/4444
> Reported-by: Xaver Hugl <xaver.h...@gmail.com>
> Reviewed-by: Harry Wentland <harry.wentl...@amd.com> #v2
> Signed-off-by: Melissa Wen <m...@igalia.com>
> ---
> .../gpu/drm/amd/display/amdgpu_dm/amdgpu_dm.c | 2 +-
> .../gpu/drm/amd/display/amdgpu_dm/amdgpu_dm.h | 2 +
> .../amd/display/amdgpu_dm/amdgpu_dm_color.c | 86 ++++++++++++++-----
> 3 files changed, 66 insertions(+), 24 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 f6462ff7251f..50b3bd0e32dd 100644
> --- a/drivers/gpu/drm/amd/display/amdgpu_dm/amdgpu_dm.c
> +++ b/drivers/gpu/drm/amd/display/amdgpu_dm/amdgpu_dm.c
> @@ -11118,7 +11118,7 @@ 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, true);
> 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..69125c3f08d5 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 +1041,8 @@ 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,
> + bool check_only);
> 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..427bf8877df7 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) {
> @@ -885,33 +884,33 @@ int amdgpu_dm_verify_lut_sizes(const struct
> drm_crtc_state *crtc_state)
> }
>
> /**
> - * amdgpu_dm_update_crtc_color_mgmt: Maps DRM color management to DC stream.
> + * amdgpu_dm_check_crtc_color_mgmt: Check if DRM color props are
> programmable by DC.
> * @crtc: amdgpu_dm crtc state
> + * @check_only: only check color state without update dc stream
> *
> - * With no plane level color management properties we're free to use any
> - * of the HW blocks as long as the CRTC CTM always comes before the
> - * CRTC RGM and after the CRTC DGM.
> - *
> - * - The CRTC RGM block will be placed in the RGM LUT block if it is
> non-linear.
> - * - The CRTC DGM block will be placed in the DGM LUT block if it is
> non-linear.
> - * - The CRTC CTM will be placed in the gamut remap block if it is
> non-linear.
> + * 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 CRTC properties
> - * or blend adjustments together.
> + * 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 setup fails.
> + * 0 on success. Error code if validation fails.
> */
> -int amdgpu_dm_update_crtc_color_mgmt(struct dm_crtc_state *crtc)
> +
> +int amdgpu_dm_check_crtc_color_mgmt(struct dm_crtc_state *crtc,
> + bool check_only)
> {
> struct dc_stream_state *stream = crtc->stream;
> struct amdgpu_device *adev = drm_to_adev(crtc->base.state->dev);
> bool has_rom = adev->asic_type <= CHIP_RAVEN;
> - struct drm_color_ctm *ctm = NULL;
> + struct dc_transfer_func *out_tf;
> const struct drm_color_lut *degamma_lut, *regamma_lut;
> uint32_t degamma_size, regamma_size;
> bool has_regamma, has_degamma;
> @@ -940,6 +939,14 @@ int amdgpu_dm_update_crtc_color_mgmt(struct
> dm_crtc_state *crtc)
> crtc->cm_has_degamma = false;
> crtc->cm_is_degamma_srgb = false;
>
> + if (check_only) {
> + out_tf = kvzalloc(sizeof(*out_tf), GFP_KERNEL);
> + if (!out_tf)
> + return -ENOMEM;
> + } else {
> + out_tf = &stream->out_transfer_func;
> + }
> +
> /* Setup regamma and degamma. */
> if (is_legacy) {
> /*
> @@ -954,8 +961,8 @@ int amdgpu_dm_update_crtc_color_mgmt(struct dm_crtc_state
> *crtc)
> * inverse color ramp in legacy userspace.
> */
> crtc->cm_is_degamma_srgb = true;
> - stream->out_transfer_func.type = TF_TYPE_DISTRIBUTED_POINTS;
> - stream->out_transfer_func.tf = TRANSFER_FUNCTION_SRGB;
> + 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
> @@ -963,16 +970,12 @@ int amdgpu_dm_update_crtc_color_mgmt(struct
> dm_crtc_state *crtc)
> *
> * See more in mod_color_calculate_regamma_params()
> */
> - r = __set_legacy_tf(&stream->out_transfer_func, regamma_lut,
> + r = __set_legacy_tf(out_tf, regamma_lut,
> regamma_size, has_rom);
> - if (r)
> - 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(out_tf, regamma_lut,
> regamma_size, has_rom, tf);
> - if (r)
> - return r;
> }
>
> /*
> @@ -981,6 +984,43 @@ int amdgpu_dm_update_crtc_color_mgmt(struct
> dm_crtc_state *crtc)
> * have to place the CTM in the OCSC in that case.
> */
> crtc->cm_has_degamma = has_degamma;
> + if (check_only)
> + kvfree(out_tf);
> +
> + return r;
> +}
> +
> +/**
> + * amdgpu_dm_update_crtc_color_mgmt: Maps DRM color management to DC stream.
> + * @crtc: amdgpu_dm crtc state
> + *
> + * With no plane level color management properties we're free to use any
> + * of the HW blocks as long as the CRTC CTM always comes before the
> + * CRTC RGM and after the CRTC DGM.
> + *
> + * - The CRTC RGM block will be placed in the RGM LUT block if it is
> non-linear.
> + * - The CRTC DGM block will be placed in the DGM LUT block if it is
> non-linear.
> + * - The CRTC CTM will be placed in the gamut remap block if it is
> non-linear.
> + *
> + * 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 CRTC properties
> + * or blend adjustments together.
> + *
> + * Returns:
> + * 0 on success. Error code if setup fails.
> + */
> +int amdgpu_dm_update_crtc_color_mgmt(struct dm_crtc_state *crtc)
> +{
> + struct dc_stream_state *stream = crtc->stream;
> + struct drm_color_ctm *ctm = NULL;
> + int ret;
> +
> + ret = amdgpu_dm_check_crtc_color_mgmt(crtc, false);
> + if (ret)
> + return ret;
Thanks. I like it.
Reviewed-by: Harry Wentland <harry.wentl...@amd.com>
Harry
>
> /* Setup CRTC CTM. */
> if (crtc->base.ctm) {
