[PATCH] gpu/drm/i915: Don't disable panel for modesetting if pfit hasn't changed

[Matthew Garrett <mjg@redhat.com>]

It seems to be possible to program a new mode without disabling the panel
if the panel fitter setup doesn't change. Add support for that.

Signed-off-by: Matthew Garrett <mjg@redhat.com>
---
 drivers/gpu/drm/i915/intel_lvds.c |   22 ++++++++++++++++++++--
 1 files changed, 20 insertions(+), 2 deletions(-)

diff --git a/drivers/gpu/drm/i915/intel_lvds.c b/drivers/gpu/drm/i915/intel_lvds.c
index b66806a..1da0030 100644
--- a/drivers/gpu/drm/i915/intel_lvds.c
+++ b/drivers/gpu/drm/i915/intel_lvds.c
@@ -84,6 +84,16 @@ static u32 intel_lvds_get_max_backlight(struct drm_device *dev)
 		BACKLIGHT_MODULATION_FREQ_SHIFT) * 2;
 }
 
+static void intel_lvds_lock_panel(struct drm_device *dev, bool lock)
+{
+	struct drm_i915_private *dev_priv = dev->dev_private;
+
+	if (lock)
+		I915_WRITE(PP_CONTROL, I915_READ(PP_CONTROL) & 0x3);
+	else
+		I915_WRITE(PP_CONTROL, I915_READ(PP_CONTROL) | (0xabcd << 16));
+}
+
 /**
  * Sets the power state for the panel.
  */
@@ -555,6 +565,8 @@ static void intel_lvds_prepare(struct drm_encoder *encoder)
 {
 	struct drm_device *dev = encoder->dev;
 	struct drm_i915_private *dev_priv = dev->dev_private;
+	struct intel_encoder *intel_encoder = enc_to_intel_encoder(encoder);
+	struct intel_lvds_priv *lvds_priv = intel_encoder->dev_priv;
 	u32 reg;
 
 	if (HAS_PCH_SPLIT(dev))
@@ -566,7 +578,10 @@ static void intel_lvds_prepare(struct drm_encoder *encoder)
 	dev_priv->backlight_duty_cycle = (dev_priv->saveBLC_PWM_CTL &
 				       BACKLIGHT_DUTY_CYCLE_MASK);
 
-	intel_lvds_set_power(dev, false);
+	if (lvds_priv->pfit_control == I915_READ(PFIT_CONTROL))
+		intel_lvds_lock_panel(dev, false);
+	else
+		intel_lvds_set_power(dev, false);
 }
 
 static void intel_lvds_commit( struct drm_encoder *encoder)
@@ -578,7 +593,10 @@ static void intel_lvds_commit( struct drm_encoder *encoder)
 		dev_priv->backlight_duty_cycle =
 			intel_lvds_get_max_backlight(dev);
 
-	intel_lvds_set_power(dev, true);
+	if ((I915_READ(PP_CONTROL) & (0xabcd << 16)) == (0xabcd << 16))
+		intel_lvds_lock_panel(dev, true);
+	else
+		intel_lvds_set_power(dev, true);
 }
 
 static void intel_lvds_mode_set(struct drm_encoder *encoder,
-- 
1.6.5.2