drm/i915: Implement pipe CSC based limited range RGB output

HSW no longer has the PIPECONF bit for limited range RGB output.
Instead the pipe CSC unit must be used to perform that task.

The CSC pre offset are set to 0, since the incoming data is full
[0:255] range RGB, the coefficients are programmed to compress the
data into [0:219] range, and then we use either the CSC_MODE black
screen offset bit, or the CSC post offsets to shift the data to
the correct [16:235] range.

Also have to change the confiuration of all planes so that the
data is sent through the pipe CSC unit. For simplicity send the
plane data through the pipe CSC unit always, and in case full
range output is requested, the pipe CSC unit is set up with an
identity transform to pass the plane data through unchanged.

I've been told by some hardware people that the use of the pipe
CSC unit shouldn't result in any measurable increase in power
consumption numbers.

Signed-off-by: Ville Syrjälä <ville.syrjala@linux.intel.com>
Reviewed-by: Paulo Zanoni <paulo.r.zanoni@intel.com>
Signed-off-by: Daniel Vetter <daniel.vetter@ffwll.ch>

1 files changed, 70 insertions, 1 deletions

diff --git a/drivers/gpu/drm/i915/intel_display.c b/drivers/gpu/drm/i915/intel_display.c
index ba1d9131a5d6..6eb3882ba9bf 100644
--- a/drivers/gpu/drm/i915/intel_display.c
+++ b/drivers/gpu/drm/i915/intel_display.c
@@ -5126,6 +5126,71 @@ static void ironlake_set_pipeconf(struct drm_crtc *crtc,
         POSTING_READ(PIPECONF(pipe));
 }
 
+/*
+ * Set up the pipe CSC unit.
+ *
+ * Currently only full range RGB to limited range RGB conversion
+ * is supported, but eventually this should handle various
+ * RGB<->YCbCr scenarios as well.
+ */
+static void intel_set_pipe_csc(struct drm_crtc *crtc,
+                               const struct drm_display_mode *adjusted_mode)
+{
+        struct drm_device *dev = crtc->dev;
+        struct drm_i915_private *dev_priv = dev->dev_private;
+        struct intel_crtc *intel_crtc = to_intel_crtc(crtc);
+        int pipe = intel_crtc->pipe;
+        uint16_t coeff = 0x7800; /* 1.0 */
+
+        /*
+         * TODO: Check what kind of values actually come out of the pipe
+         * with these coeff/postoff values and adjust to get the best
+         * accuracy. Perhaps we even need to take the bpc value into
+         * consideration.
+         */
+
+        if (adjusted_mode->private_flags & INTEL_MODE_LIMITED_COLOR_RANGE)
+                coeff = ((235 - 16) * (1 << 12) / 255) & 0xff8; /* 0.xxx... */
+
+        /*
+         * GY/GU and RY/RU should be the other way around according
+         * to BSpec, but reality doesn't agree. Just set them up in
+         * a way that results in the correct picture.
+         */
+        I915_WRITE(PIPE_CSC_COEFF_RY_GY(pipe), coeff << 16);
+        I915_WRITE(PIPE_CSC_COEFF_BY(pipe), 0);
+
+        I915_WRITE(PIPE_CSC_COEFF_RU_GU(pipe), coeff);
+        I915_WRITE(PIPE_CSC_COEFF_BU(pipe), 0);
+
+        I915_WRITE(PIPE_CSC_COEFF_RV_GV(pipe), 0);
+        I915_WRITE(PIPE_CSC_COEFF_BV(pipe), coeff << 16);
+
+        I915_WRITE(PIPE_CSC_PREOFF_HI(pipe), 0);
+        I915_WRITE(PIPE_CSC_PREOFF_ME(pipe), 0);
+        I915_WRITE(PIPE_CSC_PREOFF_LO(pipe), 0);
+
+        if (INTEL_INFO(dev)->gen > 6) {
+                uint16_t postoff = 0;
+
+                if (adjusted_mode->private_flags & INTEL_MODE_LIMITED_COLOR_RANGE)
+                        postoff = (16 * (1 << 13) / 255) & 0x1fff;
+
+                I915_WRITE(PIPE_CSC_POSTOFF_HI(pipe), postoff);
+                I915_WRITE(PIPE_CSC_POSTOFF_ME(pipe), postoff);
+                I915_WRITE(PIPE_CSC_POSTOFF_LO(pipe), postoff);
+
+                I915_WRITE(PIPE_CSC_MODE(pipe), 0);
+        } else {
+                uint32_t mode = CSC_MODE_YUV_TO_RGB;
+
+                if (adjusted_mode->private_flags & INTEL_MODE_LIMITED_COLOR_RANGE)
+                        mode |= CSC_BLACK_SCREEN_OFFSET;
+
+                I915_WRITE(PIPE_CSC_MODE(pipe), mode);
+        }
+}
+
 static void haswell_set_pipeconf(struct drm_crtc *crtc,
                                  struct drm_display_mode *adjusted_mode,
                                  bool dither)
@@ -5714,8 +5779,10 @@ static int haswell_crtc_mode_set(struct drm_crtc *crtc,
 
         haswell_set_pipeconf(crtc, adjusted_mode, dither);
 
+        intel_set_pipe_csc(crtc, adjusted_mode);
+
         /* Set up the display plane register */
-        I915_WRITE(DSPCNTR(plane), DISPPLANE_GAMMA_ENABLE);
+        I915_WRITE(DSPCNTR(plane), DISPPLANE_GAMMA_ENABLE | DISPPLANE_PIPE_CSC_ENABLE);
         POSTING_READ(DSPCNTR(plane));
 
         ret = intel_pipe_set_base(crtc, x, y, fb);
@@ -6120,6 +6187,8 @@ static void ivb_update_cursor(struct drm_crtc *crtc, u32 base)
                         cntl &= ~(CURSOR_MODE | MCURSOR_GAMMA_ENABLE);
                         cntl |= CURSOR_MODE_DISABLE;
                 }
+                if (IS_HASWELL(dev))
+                        cntl |= CURSOR_PIPE_CSC_ENABLE;
                 I915_WRITE(CURCNTR_IVB(pipe), cntl);
 
                 intel_crtc->cursor_visible = visible;