[PATCH 19/19] drm/i915: use pipe_config for lvds dithering

[Daniel Vetter <daniel.vetter@ffwll.ch>]

Up to now we've relied on the bios to get this right for us. Let's try
out whether our code has improved a bit, since we should dither
always when the output bpp doesn't match the plane bpp.
- gen5+ should be fine, since we only use the bios hint as an upgrade.
- gen4 changes, since here dithering is still controlled in the lvds
  register.
- gen2/3 has implicit dithering depeding upon whether you use 2 or 3
  lvds pairs (which makes sense, since it only supports 8bpc pipe
  outpu configurations).
- hsw doesn't support lvds.

Signed-off-by: Daniel Vetter <daniel.vetter@ffwll.ch>
---
 drivers/gpu/drm/i915/intel_display.c | 25 +++++++------------------
 drivers/gpu/drm/i915/intel_drv.h     |  4 ++++
 drivers/gpu/drm/i915/intel_lvds.c    |  4 +++-
 3 files changed, 14 insertions(+), 19 deletions(-)

diff --git a/drivers/gpu/drm/i915/intel_display.c b/drivers/gpu/drm/i915/intel_display.c
index 98abd75..41fb397 100644
--- a/drivers/gpu/drm/i915/intel_display.c
+++ b/drivers/gpu/drm/i915/intel_display.c
@@ -4841,8 +4841,7 @@ static int ironlake_get_refclk(struct drm_crtc *crtc)
 }
 
 static void ironlake_set_pipeconf(struct drm_crtc *crtc,
-				  struct drm_display_mode *adjusted_mode,
-				  bool dither)
+				  struct drm_display_mode *adjusted_mode)
 {
 	struct drm_i915_private *dev_priv = crtc->dev->dev_private;
 	struct intel_crtc *intel_crtc = to_intel_crtc(crtc);
@@ -4871,7 +4870,7 @@ static void ironlake_set_pipeconf(struct drm_crtc *crtc,
 	}
 
 	val &= ~(PIPECONF_DITHER_EN | PIPECONF_DITHER_TYPE_MASK);
-	if (dither)
+	if (intel_crtc->config.dither)
 		val |= (PIPECONF_DITHER_EN | PIPECONF_DITHER_TYPE_SP);
 
 	val &= ~PIPECONF_INTERLACE_MASK;
@@ -4890,8 +4889,7 @@ static void ironlake_set_pipeconf(struct drm_crtc *crtc,
 }
 
 static void haswell_set_pipeconf(struct drm_crtc *crtc,
-				 struct drm_display_mode *adjusted_mode,
-				 bool dither)
+				 struct drm_display_mode *adjusted_mode)
 {
 	struct drm_i915_private *dev_priv = crtc->dev->dev_private;
 	struct intel_crtc *intel_crtc = to_intel_crtc(crtc);
@@ -4901,7 +4899,7 @@ static void haswell_set_pipeconf(struct drm_crtc *crtc,
 	val = I915_READ(PIPECONF(cpu_transcoder));
 
 	val &= ~(PIPECONF_DITHER_EN | PIPECONF_DITHER_TYPE_MASK);
-	if (dither)
+	if (intel_crtc->config.dither)
 		val |= (PIPECONF_DITHER_EN | PIPECONF_DITHER_TYPE_SP);
 
 	val &= ~PIPECONF_INTERLACE_MASK_HSW;
@@ -5253,7 +5251,7 @@ static int ironlake_crtc_mode_set(struct drm_crtc *crtc,
 	bool is_lvds = false;
 	struct intel_encoder *encoder;
 	int ret;
-	bool dither, fdi_config_ok;
+	bool fdi_config_ok;
 
 	for_each_encoder_on_crtc(dev, crtc, encoder) {
 		switch (encoder->type) {
@@ -5288,11 +5286,6 @@ static int ironlake_crtc_mode_set(struct drm_crtc *crtc,
 	/* Ensure that the cursor is valid for the new mode before changing... */
 	intel_crtc_update_cursor(crtc, true);
 
-	/* determine panel color depth */
-	dither = intel_crtc->config.dither;
-	if (is_lvds && dev_priv->lvds_dither)
-		dither = true;
-
 	fp = clock.n << 16 | clock.m1 << 8 | clock.m2;
 	if (has_reduced_clock)
 		fp2 = reduced_clock.n << 16 | reduced_clock.m1 << 8 |
@@ -5358,7 +5351,7 @@ static int ironlake_crtc_mode_set(struct drm_crtc *crtc,
 
 	fdi_config_ok = ironlake_check_fdi_lanes(intel_crtc);
 
-	ironlake_set_pipeconf(crtc, adjusted_mode, dither);
+	ironlake_set_pipeconf(crtc, adjusted_mode);
 
 	intel_wait_for_vblank(dev, pipe);
 
@@ -5437,7 +5430,6 @@ static int haswell_crtc_mode_set(struct drm_crtc *crtc,
 	bool is_cpu_edp = false;
 	struct intel_encoder *encoder;
 	int ret;
-	bool dither;
 
 	for_each_encoder_on_crtc(dev, crtc, encoder) {
 		switch (encoder->type) {
@@ -5468,9 +5460,6 @@ static int haswell_crtc_mode_set(struct drm_crtc *crtc,
 	/* Ensure that the cursor is valid for the new mode before changing... */
 	intel_crtc_update_cursor(crtc, true);
 
-	/* determine panel color depth */
-	dither = intel_crtc->config.dither;
-
 	DRM_DEBUG_KMS("Mode for pipe %d:\n", pipe);
 	drm_mode_debug_printmodeline(mode);
 
@@ -5484,7 +5473,7 @@ static int haswell_crtc_mode_set(struct drm_crtc *crtc,
 	if (intel_crtc->config.has_pch_encoder)
 		ironlake_fdi_set_m_n(crtc);
 
-	haswell_set_pipeconf(crtc, adjusted_mode, dither);
+	haswell_set_pipeconf(crtc, adjusted_mode);
 
 	/* Set up the display plane register */
 	I915_WRITE(DSPCNTR(plane), DISPPLANE_GAMMA_ENABLE);
diff --git a/drivers/gpu/drm/i915/intel_drv.h b/drivers/gpu/drm/i915/intel_drv.h
index 987679b..208debc 100644
--- a/drivers/gpu/drm/i915/intel_drv.h
+++ b/drivers/gpu/drm/i915/intel_drv.h
@@ -187,6 +187,10 @@ struct intel_crtc_config {
 	/* DP has a bunch of special case unfortunately, so mark the pipe
 	 * accordingly. */
 	bool has_dp_encoder;
+	/*
+	 * Enable dithering, used when the selected pipe bpp doesn't match the
+	 * plane bpp.
+	 */
 	bool dither;
 
 	/*
diff --git a/drivers/gpu/drm/i915/intel_lvds.c b/drivers/gpu/drm/i915/intel_lvds.c
index 47ff403..b5cc74d 100644
--- a/drivers/gpu/drm/i915/intel_lvds.c
+++ b/drivers/gpu/drm/i915/intel_lvds.c
@@ -136,7 +136,7 @@ static void intel_pre_pll_enable_lvds(struct intel_encoder *encoder)
 	 * special lvds dither control bit on pch-split platforms, dithering is
 	 * only controlled through the PIPECONF reg. */
 	if (INTEL_INFO(dev)->gen == 4) {
-		if (dev_priv->lvds_dither)
+		if (intel_crtc->config.dither)
 			temp |= LVDS_ENABLE_DITHER;
 		else
 			temp &= ~LVDS_ENABLE_DITHER;
@@ -332,6 +332,8 @@ static bool intel_lvds_compute_config(struct intel_encoder *intel_encoder,
 			      pipe_config->pipe_bpp, lvds_bpp);
 		pipe_config->pipe_bpp = lvds_bpp;
 	}
+
+	pipe_config->dither = dev_priv->lvds_dither;
 	/*
 	 * We have timings from the BIOS for the panel, put them in
 	 * to the adjusted mode.  The CRTC will be set up for this mode,
-- 
1.7.11.7