CHV/BSW supports Degamma color correction, which linearizes all
the non-linear color values. This will be applied before Color
Transformation.

This patch does the following:
1. Attach deGamma property to CRTC
2. Add the core function to program DeGamma correction values for
   CHV/BSW platform
2. Add 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/i915_reg.h            |  6 ++
 drivers/gpu/drm/i915/intel_color_manager.c | 92 ++++++++++++++++++++++++++++++
 drivers/gpu/drm/i915/intel_color_manager.h |  5 ++
 3 files changed, 103 insertions(+)

diff --git a/drivers/gpu/drm/i915/i915_reg.h b/drivers/gpu/drm/i915/i915_reg.h
index 45ddd84..1e46562 100644
--- a/drivers/gpu/drm/i915/i915_reg.h
+++ b/drivers/gpu/drm/i915/i915_reg.h
@@ -8160,4 +8160,10 @@ enum skl_disp_power_wells {
 #define _PIPE_GAMMA_BASE(pipe) \
        (_PIPE3(pipe, PIPEA_CGM_GAMMA, PIPEB_CGM_GAMMA, PIPEC_CGM_GAMMA))
 
+#define PIPEA_CGM_DEGAMMA                      (VLV_DISPLAY_BASE + 0x66000)
+#define PIPEB_CGM_DEGAMMA                      (VLV_DISPLAY_BASE + 0x68000)
+#define PIPEC_CGM_DEGAMMA                      (VLV_DISPLAY_BASE + 0x6A000)
+#define _PIPE_DEGAMMA_BASE(pipe) \
+       (_PIPE3(pipe, PIPEA_CGM_DEGAMMA, PIPEB_CGM_DEGAMMA, PIPEC_CGM_DEGAMMA))
+
 #endif /* _I915_REG_H_ */
diff --git a/drivers/gpu/drm/i915/intel_color_manager.c 
b/drivers/gpu/drm/i915/intel_color_manager.c
index acb9647..aa815a5 100644
--- a/drivers/gpu/drm/i915/intel_color_manager.c
+++ b/drivers/gpu/drm/i915/intel_color_manager.c
@@ -27,6 +27,92 @@
 
 #include "intel_color_manager.h"
 
+static int chv_set_degamma(struct drm_device *dev,
+       struct drm_property_blob *blob, struct drm_crtc *crtc)
+{
+       u16 red_fract, green_fract, blue_fract;
+       u32 red, green, blue;
+       u32 num_samples;
+       u32 word = 0;
+       u32 count, cgm_control_reg, cgm_degamma_reg;
+       enum pipe pipe;
+       struct drm_palette *degamma_data;
+       struct drm_i915_private *dev_priv = dev->dev_private;
+       struct drm_r32g32b32 *correction_values = NULL;
+       struct drm_crtc_state *state = crtc->state;
+
+       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 functionality on Pipe - CGM Block */
+               cgm_control_reg = I915_READ(_PIPE_CGM_CONTROL(pipe));
+               cgm_control_reg &= ~CGM_DEGAMMA_EN;
+               state->palette_before_ctm_blob = NULL;
+
+               I915_WRITE(_PIPE_CGM_CONTROL(pipe), cgm_control_reg);
+               DRM_DEBUG_DRIVER("DeGamma disabled on Pipe %c\n",
+                               pipe_name(pipe));
+               break;
+
+       case CHV_DEGAMMA_MAX_VALS:
+               cgm_degamma_reg = _PIPE_DEGAMMA_BASE(pipe);
+               count = 0;
+               correction_values = (struct drm_r32g32b32 *)&degamma_data->lut;
+               while (count < CHV_DEGAMMA_MAX_VALS) {
+                       blue = correction_values[count].b32;
+                       green = correction_values[count].g32;
+                       red = correction_values[count].r32;
+
+                       if (blue > CHV_MAX_GAMMA)
+                               blue = CHV_MAX_GAMMA;
+
+                       if (green > CHV_MAX_GAMMA)
+                               green = CHV_MAX_GAMMA;
+
+                       if (red > CHV_MAX_GAMMA)
+                               red = CHV_MAX_GAMMA;
+
+                       blue_fract = GET_BITS(blue, 8, 14);
+                       green_fract = GET_BITS(green, 8, 14);
+                       red_fract = GET_BITS(red, 8, 14);
+
+                       /* Green (29:16) and Blue (13:0) in DWORD1 */
+                       SET_BITS(word, green_fract, 16, 14);
+                       SET_BITS(word, blue_fract, 0, 14);
+                       I915_WRITE(cgm_degamma_reg, word);
+                       cgm_degamma_reg += 4;
+
+                       /* Red (13:0) to be written to DWORD2 */
+                       word = red_fract;
+                       I915_WRITE(cgm_degamma_reg, word);
+                       cgm_degamma_reg += 4;
+                       count++;
+               }
+
+               DRM_DEBUG_DRIVER("DeGamma LUT loaded for Pipe %c\n",
+                               pipe_name(pipe));
+
+               /* Enable DeGamma on Pipe */
+               I915_WRITE(_PIPE_CGM_CONTROL(pipe),
+                       I915_READ(_PIPE_CGM_CONTROL(pipe)) | CGM_DEGAMMA_EN);
+
+               DRM_DEBUG_DRIVER("DeGamma correction enabled on Pipe %c\n",
+                               pipe_name(pipe));
+               break;
+
+       default:
+               DRM_ERROR("Invalid number of samples for DeGamma LUT\n");
+               return -EINVAL;
+       }
+       return 0;
+}
+
 static int chv_set_gamma(struct drm_device *dev, struct drm_property_blob 
*blob,
                struct drm_crtc *crtc)
 {
@@ -155,4 +241,10 @@ void intel_attach_color_properties_to_crtc(struct 
drm_device *dev,
                DRM_DEBUG_DRIVER("gamma property attached to CRTC\n");
        }
 
+       /* Degamma correction */
+       if (config->cm_palette_before_ctm_property) {
+               drm_object_attach_property(mode_obj,
+                       config->cm_palette_before_ctm_property, 0);
+               DRM_DEBUG_DRIVER("degamma property attached to CRTC\n");
+       }
 }
diff --git a/drivers/gpu/drm/i915/intel_color_manager.h 
b/drivers/gpu/drm/i915/intel_color_manager.h
index de706d9..77a2119 100644
--- a/drivers/gpu/drm/i915/intel_color_manager.h
+++ b/drivers/gpu/drm/i915/intel_color_manager.h
@@ -63,5 +63,10 @@
 #define CHV_GAMMA_SHIFT_GREEN                  16
 #define CHV_MAX_GAMMA                          ((1 << 24) - 1)
 
+/* Degamma on CHV */
+#define CHV_DEGAMMA_MSB_SHIFT                  2
+#define CHV_DEGAMMA_GREEN_SHIFT                16
+
 /* CHV CGM Block */
 #define CGM_GAMMA_EN                           (1 << 2)
+#define CGM_DEGAMMA_EN                         (1 << 0)
-- 
1.9.1

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