drm/i915: scramble reset support for DP port CRC on vlv

They've moved the DC balance reset bit around. Again I don't think we
need it, but better safe than sorry and maybe HDMI port CRC will prove
useful for checking infoframes or hdmi audio.

v2: Apply the suggestions from Damien's review.

Reviewed-by: Damien Lespiau <damien.lespiau@intel.com>
Signed-off-by: Daniel Vetter <daniel.vetter@ffwll.ch>

diff --git a/drivers/gpu/drm/i915/i915_debugfs.c b/drivers/gpu/drm/i915/i915_debugfs.c
index 8812516115125bd14b60f7070f8bf4ca2d053f26..82c58eb1aa667b0adea2f50a093054a95134da9b 100644 (file)
--- a/drivers/gpu/drm/i915/i915_debugfs.c
+++ b/drivers/gpu/drm/i915/i915_debugfs.c
@@ -2026,6 +2026,9 @@ static int vlv_pipe_crc_ctl_reg(struct drm_device *dev,
                                enum intel_pipe_crc_source *source,
                                uint32_t *val)
 {
+       struct drm_i915_private *dev_priv = dev->dev_private;
+       bool need_stable_symbols = false;
+
        if (*source == INTEL_PIPE_CRC_SOURCE_AUTO) {
                int ret = i9xx_pipe_crc_auto_source(dev, pipe, source);
                if (ret)
@@ -2038,9 +2041,11 @@ static int vlv_pipe_crc_ctl_reg(struct drm_device *dev,
                break;
        case INTEL_PIPE_CRC_SOURCE_DP_B:
                *val = PIPE_CRC_ENABLE | PIPE_CRC_SOURCE_DP_B_VLV;
+               need_stable_symbols = true;
                break;
        case INTEL_PIPE_CRC_SOURCE_DP_C:
                *val = PIPE_CRC_ENABLE | PIPE_CRC_SOURCE_DP_C_VLV;
+               need_stable_symbols = true;
                break;
        case INTEL_PIPE_CRC_SOURCE_NONE:
                *val = 0;
@@ -2049,6 +2054,29 @@ static int vlv_pipe_crc_ctl_reg(struct drm_device *dev,
                return -EINVAL;
        }
 
+       /*
+        * When the pipe CRC tap point is after the transcoders we need
+        * to tweak symbol-level features to produce a deterministic series of
+        * symbols for a given frame. We need to reset those features only once
+        * a frame (instead of every nth symbol):
+        *   - DC-balance: used to ensure a better clock recovery from the data
+        *     link (SDVO)
+        *   - DisplayPort scrambling: used for EMI reduction
+        */
+       if (need_stable_symbols) {
+               uint32_t tmp = I915_READ(PORT_DFT2_G4X);
+
+               WARN_ON(!IS_G4X(dev));
+
+               tmp |= DC_BALANCE_RESET_VLV;
+               if (pipe == PIPE_A)
+                       tmp |= PIPE_A_SCRAMBLE_RESET;
+               else
+                       tmp |= PIPE_B_SCRAMBLE_RESET;
+
+               I915_WRITE(PORT_DFT2_G4X, tmp);
+       }
+
        return 0;
 }
 
@@ -2128,6 +2156,22 @@ static int i9xx_pipe_crc_ctl_reg(struct drm_device *dev,
        return 0;
 }
 
+static void vlv_undo_pipe_scramble_reset(struct drm_device *dev,
+                                        enum pipe pipe)
+{
+       struct drm_i915_private *dev_priv = dev->dev_private;
+       uint32_t tmp = I915_READ(PORT_DFT2_G4X);
+
+       if (pipe == PIPE_A)
+               tmp &= ~PIPE_A_SCRAMBLE_RESET;
+       else
+               tmp &= ~PIPE_B_SCRAMBLE_RESET;
+       if (!(tmp & PIPE_SCRAMBLE_RESET_MASK))
+               tmp &= ~DC_BALANCE_RESET_VLV;
+       I915_WRITE(PORT_DFT2_G4X, tmp);
+
+}
+
 static void g4x_undo_pipe_scramble_reset(struct drm_device *dev,
                                         enum pipe pipe)
 {
@@ -2267,6 +2311,8 @@ static int pipe_crc_set_source(struct drm_device *dev, enum pipe pipe,
 
                if (IS_G4X(dev))
                        g4x_undo_pipe_scramble_reset(dev, pipe);
+               else if (IS_VALLEYVIEW(dev))
+                       vlv_undo_pipe_scramble_reset(dev, pipe);
        }
 
        return 0;