[PATCH v2 1/5] drm: add legacy support for using degamma for gamma

[Laurent Pinchart]

Hi Tomi,

Thank you for the patch.

On Tue, Nov 03, 2020 at 10:03:06AM +0200, Tomi Valkeinen wrote:
> We currently have drm_atomic_helper_legacy_gamma_set() helper which can
> be used to handle legacy gamma-set ioctl.
> drm_atomic_helper_legacy_gamma_set() sets GAMMA_LUT, and clears
> CTM and DEGAMMA_LUT. This works fine on HW where we have either:
> 
> degamma -> ctm -> gamma -> out
> 
> or
> 
> ctm -> gamma -> out
> 
> However, if the HW has gamma table before ctm, the atomic property
> should be DEGAMMA_LUT, and thus we have:
> 
> degamma -> ctm -> out
> 
> This is fine for userspace which sets gamma table using the properties,
> as the userspace can check for the existence of gamma & degamma, but the
> legacy gamma-set ioctl does not work.
> 
> This patch adds a new helper, drm_atomic_helper_legacy_degamma_set(),
> which can be used instead of drm_atomic_helper_legacy_gamma_set() when
> the DEGAMMA_LUT is the underlying property that needs to be set.
> 
> Signed-off-by: Tomi Valkeinen <tomi.valkeinen at ti.com>
> Reviewed-by: Pekka Paalanen <pekka.paalanen at collabora.com>
> ---
>  drivers/gpu/drm/drm_atomic_helper.c | 81 ++++++++++++++++++++++-------
>  include/drm/drm_atomic_helper.h     |  4 ++
>  2 files changed, 65 insertions(+), 20 deletions(-)
> 
> diff --git a/drivers/gpu/drm/drm_atomic_helper.c b/drivers/gpu/drm/drm_atomic_helper.c
> index ddd0e3239150..23cbed541dc7 100644
> --- a/drivers/gpu/drm/drm_atomic_helper.c
> +++ b/drivers/gpu/drm/drm_atomic_helper.c
> @@ -3499,24 +3499,11 @@ int drm_atomic_helper_page_flip_target(struct drm_crtc *crtc,
>  }
>  EXPORT_SYMBOL(drm_atomic_helper_page_flip_target);
>  
> -/**
> - * drm_atomic_helper_legacy_gamma_set - set the legacy gamma correction table
> - * @crtc: CRTC object
> - * @red: red correction table
> - * @green: green correction table
> - * @blue: green correction table
> - * @size: size of the tables
> - * @ctx: lock acquire context
> - *
> - * Implements support for legacy gamma correction table for drivers
> - * that support color management through the DEGAMMA_LUT/GAMMA_LUT
> - * properties. See drm_crtc_enable_color_mgmt() and the containing chapter for
> - * how the atomic color management and gamma tables work.
> - */
> -int drm_atomic_helper_legacy_gamma_set(struct drm_crtc *crtc,
> -				       u16 *red, u16 *green, u16 *blue,
> -				       uint32_t size,
> -				       struct drm_modeset_acquire_ctx *ctx)
> +static int legacy_gamma_degamma_set(struct drm_crtc *crtc,
> +				    u16 *red, u16 *green, u16 *blue,
> +				    uint32_t size,
> +				    struct drm_modeset_acquire_ctx *ctx,
> +				    bool use_degamma)
>  {
>  	struct drm_device *dev = crtc->dev;
>  	struct drm_atomic_state *state;
> @@ -3555,9 +3542,11 @@ int drm_atomic_helper_legacy_gamma_set(struct drm_crtc *crtc,
>  	}
>  
>  	/* Reset DEGAMMA_LUT and CTM properties. */
> -	replaced  = drm_property_replace_blob(&crtc_state->degamma_lut, NULL);
> +	replaced  = drm_property_replace_blob(&crtc_state->degamma_lut,
> +					      use_degamma ? blob : NULL);
>  	replaced |= drm_property_replace_blob(&crtc_state->ctm, NULL);
> -	replaced |= drm_property_replace_blob(&crtc_state->gamma_lut, blob);
> +	replaced |= drm_property_replace_blob(&crtc_state->gamma_lut,
> +					      use_degamma ? NULL : blob);
>  	crtc_state->color_mgmt_changed |= replaced;
>  
>  	ret = drm_atomic_commit(state);
> @@ -3567,8 +3556,60 @@ int drm_atomic_helper_legacy_gamma_set(struct drm_crtc *crtc,
>  	drm_property_blob_put(blob);
>  	return ret;
>  }
> +
> +/**
> + * drm_atomic_helper_legacy_gamma_set - set the legacy gamma correction table using gamma_lut
> + * @crtc: CRTC object
> + * @red: red correction table
> + * @green: green correction table
> + * @blue: green correction table
> + * @size: size of the tables
> + * @ctx: lock acquire context
> + *
> + * Implements support for legacy gamma correction table for drivers
> + * that support color management through the DEGAMMA_LUT/GAMMA_LUT
> + * properties. See drm_crtc_enable_color_mgmt() and the containing chapter for
> + * how the atomic color management and gamma tables work.
> + *
> + * This function uses GAMMA_LUT property for the gamma table. This function

s/uses/uses the/
s/This function$/It/

Same below.

> + * can be used when the driver exposes either only GAMMA_LUT or both GAMMA_LUT
> + * and DEGAMMA_LUT.
> + */
> +int drm_atomic_helper_legacy_gamma_set(struct drm_crtc *crtc,
> +				       u16 *red, u16 *green, u16 *blue,
> +				       uint32_t size,
> +				       struct drm_modeset_acquire_ctx *ctx)
> +{
> +	return legacy_gamma_degamma_set(crtc, red, green, blue, size, ctx, false);
> +}

I wonder, would it make sense to make this automatic by setting the
degamma LUT when only the DEGAMMA_LUT property exists, and the gamma LUT
otherwise ? Are there use cases for drm_atomic_helper_legacy_degamma_set
for drivers that support both gamma and degamma ?

>  EXPORT_SYMBOL(drm_atomic_helper_legacy_gamma_set);
>  
> +/**
> + * drm_atomic_helper_legacy_degamma_set - set the legacy gamma correction table using degamma_lut
> + * @crtc: CRTC object
> + * @red: red correction table
> + * @green: green correction table
> + * @blue: green correction table
> + * @size: size of the tables
> + * @ctx: lock acquire context
> + *
> + * Implements support for legacy gamma correction table for drivers
> + * that support color management through the DEGAMMA_LUT/GAMMA_LUT
> + * properties. See drm_crtc_enable_color_mgmt() and the containing chapter for
> + * how the atomic color management and gamma tables work.
> + *
> + * This function uses DEGAMMA_LUT property for the gamma table. This function
> + * can be used when the driver exposes only DEGAMNMA_LUT.
> + */
> +int drm_atomic_helper_legacy_degamma_set(struct drm_crtc *crtc,
> +					 u16 *red, u16 *green, u16 *blue,
> +					 uint32_t size,
> +					 struct drm_modeset_acquire_ctx *ctx)
> +{
> +	return legacy_gamma_degamma_set(crtc, red, green, blue, size, ctx, true);
> +}
> +EXPORT_SYMBOL(drm_atomic_helper_legacy_degamma_set);
> +
>  /**
>   * drm_atomic_helper_bridge_propagate_bus_fmt() - Propagate output format to
>   *						  the input end of a bridge
> diff --git a/include/drm/drm_atomic_helper.h b/include/drm/drm_atomic_helper.h
> index 85df04c8e62f..561c78680388 100644
> --- a/include/drm/drm_atomic_helper.h
> +++ b/include/drm/drm_atomic_helper.h
> @@ -151,6 +151,10 @@ int drm_atomic_helper_legacy_gamma_set(struct drm_crtc *crtc,
>  				       u16 *red, u16 *green, u16 *blue,
>  				       uint32_t size,
>  				       struct drm_modeset_acquire_ctx *ctx);
> +int drm_atomic_helper_legacy_degamma_set(struct drm_crtc *crtc,
> +					 u16 *red, u16 *green, u16 *blue,
> +					 uint32_t size,
> +					 struct drm_modeset_acquire_ctx *ctx);
>  
>  /**
>   * drm_atomic_crtc_for_each_plane - iterate over planes currently attached to CRTC

-- 
Regards,

Laurent Pinchart