BDW/SKL/BXT supports Degamma color correction feature, which
linearizes the non-linearity due to gamma encoded color values.
This will be applied before Color Transformation.

This patch does the following:
1. Adds the core function to program DeGamma correction values for
   BDW/SKL/BXT platform
2. Adds DeGamma correction macros/defines

Signed-off-by: Shashank Sharma <shashank.sha...@intel.com>
Signed-off-by: Kausal Malladi <kausalmall...@gmail.com>
---
 drivers/gpu/drm/i915/intel_color_manager.c | 59 ++++++++++++++++++++++++++++++
 1 file changed, 59 insertions(+)

diff --git a/drivers/gpu/drm/i915/intel_color_manager.c 
b/drivers/gpu/drm/i915/intel_color_manager.c
index 44f99be..3d792b2 100644
--- a/drivers/gpu/drm/i915/intel_color_manager.c
+++ b/drivers/gpu/drm/i915/intel_color_manager.c
@@ -306,6 +306,63 @@ static int bdw_set_gamma(struct drm_device *dev, struct 
drm_property_blob *blob,
        return 0;
 }
 
+static int bdw_set_degamma(struct drm_device *dev,
+       struct drm_property_blob *blob, struct drm_crtc *crtc)
+{
+       enum pipe pipe;
+       int num_samples;
+       u32 index, mode;
+       u32 pal_prec_index, pal_prec_data;
+       struct drm_palette *degamma_data;
+       struct drm_crtc_state *state = crtc->state;
+       struct drm_i915_private *dev_priv = dev->dev_private;
+       struct drm_r32g32b32 *correction_values = NULL;
+
+       if (WARN_ON(!blob))
+               return -EINVAL;
+
+       degamma_data = (struct drm_palette *)blob->data;
+       pipe = to_intel_crtc(crtc)->pipe;
+       num_samples = blob->length / sizeof(struct drm_r32g32b32);
+
+       switch (num_samples) {
+       case GAMMA_DISABLE_VALS:
+               /* Disable degamma on Pipe */
+               mode = I915_READ(GAMMA_MODE(pipe)) & ~GAMMA_MODE_MODE_MASK;
+               I915_WRITE(GAMMA_MODE(pipe), mode | GAMMA_MODE_MODE_8BIT);
+
+               state->palette_before_ctm_blob = NULL;
+               DRM_DEBUG_DRIVER("Disabling degamma on Pipe %c\n",
+                       pipe_name(pipe));
+               break;
+
+       case BDW_SPLITGAMMA_MAX_VALS:
+               pal_prec_index = _PREC_PAL_INDEX(pipe);
+               pal_prec_data = _PREC_PAL_DATA(pipe);
+               correction_values = degamma_data->lut;
+
+               index = I915_READ(pal_prec_index);
+               index |= BDW_INDEX_AUTO_INCREMENT | BDW_INDEX_SPLIT_MODE;
+               I915_WRITE(pal_prec_index, index);
+
+               bdw_write_10bit_gamma_precision(dev, correction_values,
+               pal_prec_data, BDW_SPLITGAMMA_MAX_VALS);
+
+               /* Enable degamma on Pipe */
+               mode = I915_READ(GAMMA_MODE(pipe));
+               mode &= ~GAMMA_MODE_MODE_MASK;
+               I915_WRITE(GAMMA_MODE(pipe), mode | GAMMA_MODE_MODE_SPLIT);
+               DRM_DEBUG_DRIVER("degamma correction enabled on Pipe %c\n",
+                       pipe_name(pipe));
+               break;
+
+       default:
+               DRM_ERROR("Invalid number of samples\n");
+               return -EINVAL;
+       }
+       return 0;
+}
+
 static s32 chv_prepare_csc_coeff(s64 csc_value)
 {
        s32 csc_int_value;
@@ -596,6 +653,8 @@ void intel_color_manager_crtc_commit(struct drm_device *dev,
                /* Degamma correction */
                if (IS_CHERRYVIEW(dev))
                        ret = chv_set_degamma(dev, blob, crtc);
+               else if (IS_BROADWELL(dev) || IS_GEN9(dev))
+                       ret = bdw_set_degamma(dev, blob, crtc);
 
                if (ret)
                        DRM_ERROR("set degamma correction failed\n");
-- 
1.9.1

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