Re: [RFC v1 3/7] drm/i915: Add Support for Multi Segment Gamma Mode

["Ville Syrjälä" <ville.syrjala@intel.com>]

On Tue, Mar 19, 2019 at 10:46:27AM +0200, Lankhorst, Maarten wrote:
> tis 2019-03-19 klockan 14:00 +0530 skrev Uma Shankar:
> > Multi Segment Gamma Mode is added in Gen11+ platforms.
> > Added a property interface to enable that.
> > 
> > Signed-off-by: Uma Shankar <uma.shankar@intel.com>
> > ---
> >  drivers/gpu/drm/i915/i915_drv.h    |  1 +
> >  drivers/gpu/drm/i915/intel_color.c | 23 +++++++++++++++++++++++
> >  include/uapi/drm/i915_drm.h        | 14 ++++++++++++++
> >  3 files changed, 38 insertions(+)
> > 
> > diff --git a/drivers/gpu/drm/i915/i915_drv.h
> > b/drivers/gpu/drm/i915/i915_drv.h
> > index 02231ae..f20d418 100644
> > --- a/drivers/gpu/drm/i915/i915_drv.h
> > +++ b/drivers/gpu/drm/i915/i915_drv.h
> > @@ -1736,6 +1736,7 @@ struct drm_i915_private {
> >  	struct drm_property *force_audio_property;
> >  
> >  	struct drm_property *gamma_mode_property;
> > +	struct drm_property *multi_segment_gamma_mode_property;
> 
> Seems to me both properties should be part of drm core?
> 
> >  	/* hda/i915 audio component */
> >  	struct i915_audio_component *audio_component;
> > diff --git a/drivers/gpu/drm/i915/intel_color.c
> > b/drivers/gpu/drm/i915/intel_color.c
> > index 9d43d19..399d63d 100644
> > --- a/drivers/gpu/drm/i915/intel_color.c
> > +++ b/drivers/gpu/drm/i915/intel_color.c
> > @@ -149,6 +149,26 @@ static bool crtc_state_is_legacy_gamma(const
> > struct intel_crtc_state *crtc_state
> >  	drm_object_attach_property(&crtc->base.base, prop, 0);
> >  }
> >  
> > +void
> > +intel_attach_multi_segment_gamma_mode_property(struct intel_crtc
> > *crtc)
> > +{
> > +	struct drm_device *dev = crtc->base.dev;
> > +	struct drm_i915_private *dev_priv = to_i915(dev);
> > +	struct drm_property *prop;
> > +
> > +	prop = dev_priv->multi_segment_gamma_mode_property;
> > +	if (!prop) {
> > +		prop = drm_property_create(dev, DRM_MODE_PROP_BLOB,
> > +					   "Multi-segment Gamma",
> > 0);
> > +		if (!prop)
> > +			return;
> > +
> > +		dev_priv->multi_segment_gamma_mode_property = prop;
> > +	}
> > +
> > +	drm_object_attach_property(&crtc->base.base, prop, 0);
> > +}
> > +
> >  /*
> >   * When using limited range, multiply the matrix given by userspace
> > by
> >   * the matrix that we would use for the limited range.
> > @@ -953,4 +973,7 @@ void intel_color_init(struct intel_crtc *crtc)
> >  					   INTEL_INFO(dev_priv)-
> > >color.gamma_lut_size);
> >  
> >  	intel_attach_gamma_mode_property(crtc);
> > +
> > +	if (INTEL_GEN(dev_priv) >= 11)
> > +		intel_attach_multi_segment_gamma_mode_property(crtc)
> > ;
> >  }
> > diff --git a/include/uapi/drm/i915_drm.h
> > b/include/uapi/drm/i915_drm.h
> > index aa2d4c7..8f1974e 100644
> > --- a/include/uapi/drm/i915_drm.h
> > +++ b/include/uapi/drm/i915_drm.h
> > @@ -1842,6 +1842,20 @@ struct drm_i915_query_topology_info {
> >  	__u8 data[];
> >  };
> >  
> > +/*
> > + * Structure for muti segmented gamma lut
> > + */
> > +struct multi_segment_gamma_lut {
> > +	/* Number of Lut Segments */
> > +	__u8 segment_cnt;
> > +	/* Precison of LUT entries in bits */
> > +	__u8 precision_bits;
> > +	/* Pointer having number of LUT elements in each segment */
> > +	__u32 *segment_lut_cnt_ptr;
> > +	/* Pointer to store exact lut values for each segment */
> > +	__u32 *segment_lut_ptr;
> > +};
> > 
> And perhaps a variation of this as description for all gamma mode
> types.

This is my old idea how to represent fancier LUTs:
https://github.com/vsyrjala/linux/commit/1aab7625dca77b831e05e32af17904c21300ff95
https://github.com/vsyrjala/linux/commit/74ffa5d441702c53830f6d71bb687bb0ae5aa58f

Each distinct segment of the curve would be just described by
a fixed size range descriptor, and the entire blob would be made up
of however many of those are needed.

That way we don't even need any multi-segment uapi for setting up 
the LUT. The blob for that would just contain as many entries as the
LUT needs in that specific mode.

-- 
Ville Syrjälä
Intel
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