drm/i915: clean up pipe bpp confusion

- gen4 and earlier (save for g4x) only really have a 8bpc pipe, with
  the possibility to dither to 6bpc using the panel fitter
- g4x has hdmi, but no 12 bpc pipe ... !? Clamp hdmi accordingly.
- TV/SDVO out are the only connectors available on platforms with
  a pipe bpp != 8, add code to force the pipe to 8bpc unconditionally.

<rant>
The dither handling on gmch platforms is one giant disaster. I'm hoping
somewhat that vlv enabling will fix this up, but given that the 6bpc
handling for edp was simply added with another quick hack, I don't have
high hopes ...
</rant>

v2: Neither vlv nor g4x have 12bpc pipes. Still set pipe_bpp to 12*3,
but let the crtc code clamp things down to 10bpc on these platforms.

v3: Fix a bpc vs. bpp mixup in the gen4 and earlier pipe_bpp limiter
code.

v4: Drop the hunk in intel_hdmi.c about g4x/vlv 12bpc, it was wrong.
Reviewed-by: NJesse Barnes <jbarnes@virtuousgeek.org>
Signed-off-by: NDaniel Vetter <daniel.vetter@ffwll.ch>

drivers/gpu/drm/i915/intel_display.c

@@ -3971,6 +3971,14 @@ static bool intel_crtc_compute_config(struct drm_crtc *crtc,
 		adjusted_mode->hsync_start == adjusted_mode->hdisplay)
 		return false;
 
+	if ((IS_G4X(dev) || IS_VALLEYVIEW(dev)) && pipe_config->pipe_bpp > 10) {
+		pipe_config->pipe_bpp = 10*3; /* 12bpc is gen5+ */
+	} else if (INTEL_INFO(dev)->gen <= 4 && pipe_config->pipe_bpp > 8) {
+		/* only a 8bpc pipe, with 6bpc dither through the panel fitter
+		 * for lvds. */
+		pipe_config->pipe_bpp = 8*3;
+	}
+
 	return true;
 }
 

drivers/gpu/drm/i915/intel_sdvo.c

@@ -1048,6 +1048,9 @@ static bool intel_sdvo_compute_config(struct intel_encoder *encoder,
 	struct drm_display_mode *adjusted_mode = &pipe_config->adjusted_mode;
 	struct drm_display_mode *mode = &pipe_config->requested_mode;
 
+	DRM_DEBUG_KMS("forcing bpc to 8 for SDVO\n");
+	pipe_config->pipe_bpp = 8*3;
+
 	if (HAS_PCH_SPLIT(encoder->base.dev))
 		pipe_config->has_pch_encoder = true;
 

drivers/gpu/drm/i915/intel_tv.c

@@ -905,11 +905,10 @@ intel_tv_mode_valid(struct drm_connector *connector,
 
 
 static bool
-intel_tv_mode_fixup(struct drm_encoder *encoder,
-		    const struct drm_display_mode *mode,
-		    struct drm_display_mode *adjusted_mode)
+intel_tv_compute_config(struct intel_encoder *encoder,
+			struct intel_crtc_config *pipe_config)
 {
-	struct intel_tv *intel_tv = enc_to_intel_tv(encoder);
+	struct intel_tv *intel_tv = enc_to_intel_tv(&encoder->base);
 	const struct tv_mode *tv_mode = intel_tv_mode_find(intel_tv);
 
 	if (!tv_mode)
@@ -918,7 +917,10 @@ intel_tv_mode_fixup(struct drm_encoder *encoder,
 	if (intel_encoder_check_is_cloned(&intel_tv->base))
 		return false;
 
-	adjusted_mode->clock = tv_mode->clock;
+	pipe_config->adjusted_mode.clock = tv_mode->clock;
+	DRM_DEBUG_KMS("forcing bpc to 8 for TV\n");
+	pipe_config->pipe_bpp = 8*3;
+
 	return true;
 }
 
@@ -1485,7 +1487,6 @@ intel_tv_set_property(struct drm_connector *connector, struct drm_property *prop
 }
 
 static const struct drm_encoder_helper_funcs intel_tv_helper_funcs = {
-	.mode_fixup = intel_tv_mode_fixup,
 	.mode_set = intel_tv_mode_set,
 };
 
@@ -1620,6 +1621,7 @@ intel_tv_init(struct drm_device *dev)
 	drm_encoder_init(dev, &intel_encoder->base, &intel_tv_enc_funcs,
 			 DRM_MODE_ENCODER_TVDAC);
 
+	intel_encoder->compute_config = intel_tv_compute_config;
 	intel_encoder->enable = intel_enable_tv;
 	intel_encoder->disable = intel_disable_tv;
 	intel_encoder->get_hw_state = intel_tv_get_hw_state;