[PATCH 06/13] drm/i915: Retrieve the current mode upon KMS takeover

[Jesse Barnes <jbarnes@virtuousgeek.org>]

From: Chris Wilson <chris@chris-wilson.co.uk>

Read the current hardware state to retrieve the active mode and populate
our CRTC config if that mode matches our presumptions.

Signed-off-by: Chris Wilson <chris@chris-wilson.co.uk>
---
 drivers/gpu/drm/i915/i915_drv.h      |    2 +
 drivers/gpu/drm/i915/intel_crt.c     |   27 +++++++-
 drivers/gpu/drm/i915/intel_display.c |  119 ++++++++++++++++++++++++++--------
 drivers/gpu/drm/i915/intel_dp.c      |   22 +++++++
 drivers/gpu/drm/i915/intel_drv.h     |    7 +-
 drivers/gpu/drm/i915/intel_dvo.c     |   36 ++++++----
 drivers/gpu/drm/i915/intel_hdmi.c    |   22 +++++++
 drivers/gpu/drm/i915/intel_lvds.c    |   27 +++++++-
 drivers/gpu/drm/i915/intel_sdvo.c    |   23 +++++++
 9 files changed, 242 insertions(+), 43 deletions(-)

diff --git a/drivers/gpu/drm/i915/i915_drv.h b/drivers/gpu/drm/i915/i915_drv.h
index 30cf7e6..8473db4 100644
--- a/drivers/gpu/drm/i915/i915_drv.h
+++ b/drivers/gpu/drm/i915/i915_drv.h
@@ -283,6 +283,8 @@ struct drm_i915_display_funcs {
 	void (*update_linetime_wm)(struct drm_device *dev, int pipe,
 				 struct drm_display_mode *mode);
 	void (*modeset_global_resources)(struct drm_device *dev);
+	bool (*crtc_get_mode)(struct drm_crtc *crtc,
+			     struct drm_display_mode *mode);
 	int (*crtc_mode_set)(struct drm_crtc *crtc,
 			     struct drm_display_mode *mode,
 			     struct drm_display_mode *adjusted_mode,
diff --git a/drivers/gpu/drm/i915/intel_crt.c b/drivers/gpu/drm/i915/intel_crt.c
index cfc9687..f1d68e8 100644
--- a/drivers/gpu/drm/i915/intel_crt.c
+++ b/drivers/gpu/drm/i915/intel_crt.c
@@ -81,6 +81,27 @@ static bool intel_crt_get_hw_state(struct intel_encoder *encoder,
 	return true;
 }
 
+static unsigned intel_crt_get_mode_flags(struct intel_encoder *encoder)
+{
+	struct drm_i915_private *dev_priv = encoder->base.dev->dev_private;
+	struct intel_crt *crt = intel_encoder_to_crt(encoder);
+	u32 tmp, flags = 0;
+
+	tmp = I915_READ(crt->adpa_reg);
+
+	if (tmp & ADPA_HSYNC_ACTIVE_HIGH)
+		flags |= DRM_MODE_FLAG_PHSYNC;
+	else
+		flags |= DRM_MODE_FLAG_NHSYNC;
+
+	if (tmp & ADPA_VSYNC_ACTIVE_HIGH)
+		flags |= DRM_MODE_FLAG_PVSYNC;
+	else
+		flags |= DRM_MODE_FLAG_NVSYNC;
+
+	return flags;
+}
+
 static void intel_disable_crt(struct intel_encoder *encoder)
 {
 	struct drm_i915_private *dev_priv = encoder->base.dev->dev_private;
@@ -777,10 +798,12 @@ void intel_crt_init(struct drm_device *dev)
 
 	crt->base.disable = intel_disable_crt;
 	crt->base.enable = intel_enable_crt;
-	if (HAS_DDI(dev))
+	if (HAS_DDI(dev)) {
 		crt->base.get_hw_state = intel_ddi_get_hw_state;
-	else
+	} else {
 		crt->base.get_hw_state = intel_crt_get_hw_state;
+		crt->base.get_mode_flags = intel_crt_get_mode_flags;
+	}
 	intel_connector->get_hw_state = intel_connector_get_hw_state;
 
 	drm_encoder_helper_add(&crt->base.base, &crt_encoder_funcs);
diff --git a/drivers/gpu/drm/i915/intel_display.c b/drivers/gpu/drm/i915/intel_display.c
index 9793e66..e19b637 100644
--- a/drivers/gpu/drm/i915/intel_display.c
+++ b/drivers/gpu/drm/i915/intel_display.c
@@ -6618,11 +6618,12 @@ void intel_release_load_detect_pipe(struct drm_connector *connector,
 }
 
 /* Returns the clock of the currently programmed mode of the given pipe. */
-static int intel_crtc_clock_get(struct drm_device *dev, struct drm_crtc *crtc)
+static int i9xx_crtc_clock_get(struct drm_crtc *crtc)
 {
+	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;
+	enum pipe pipe = intel_crtc->pipe;
 	u32 dpll = I915_READ(DPLL(pipe));
 	u32 fp;
 	intel_clock_t clock;
@@ -6705,35 +6706,84 @@ static int intel_crtc_clock_get(struct drm_device *dev, struct drm_crtc *crtc)
 }
 
 /** Returns the currently programmed mode of the given pipe. */
-struct drm_display_mode *intel_crtc_mode_get(struct drm_device *dev,
-					     struct drm_crtc *crtc)
+static bool i9xx_crtc_get_mode(struct drm_crtc *crtc,
+			       struct drm_display_mode *mode)
 {
-	struct drm_i915_private *dev_priv = dev->dev_private;
+	struct drm_i915_private *dev_priv = crtc->dev->dev_private;
 	struct intel_crtc *intel_crtc = to_intel_crtc(crtc);
 	enum transcoder cpu_transcoder = intel_crtc->cpu_transcoder;
-	struct drm_display_mode *mode;
-	int htot = I915_READ(HTOTAL(cpu_transcoder));
-	int hsync = I915_READ(HSYNC(cpu_transcoder));
-	int vtot = I915_READ(VTOTAL(cpu_transcoder));
-	int vsync = I915_READ(VSYNC(cpu_transcoder));
+	u32 tmp;
 
-	mode = kzalloc(sizeof(*mode), GFP_KERNEL);
-	if (!mode)
-		return NULL;
+	memset(mode, 0, sizeof(*mode));
+
+	tmp = I915_READ(HTOTAL(cpu_transcoder));
+	mode->hdisplay = (tmp & 0xffff) + 1;
+	mode->htotal = ((tmp & 0xffff0000) >> 16) + 1;
+
+	tmp = I915_READ(HSYNC(cpu_transcoder));
+	mode->hsync_start = (tmp & 0xffff) + 1;
+	mode->hsync_end = ((tmp & 0xffff0000) >> 16) + 1;
+
+	tmp = I915_READ(VTOTAL(cpu_transcoder));
+	mode->vdisplay = (tmp & 0xffff) + 1;
+	mode->vtotal = ((tmp & 0xffff0000) >> 16) + 1;
+
+	tmp = I915_READ(VSYNC(cpu_transcoder));
+	mode->vsync_start = (tmp & 0xffff) + 1;
+	mode->vsync_end = ((tmp & 0xffff0000) >> 16) + 1;
+
+	mode->clock = i9xx_crtc_clock_get(crtc);
+
+	drm_mode_set_name(mode);
+
+	return true;
+}
+
+static bool ironlake_crtc_get_mode(struct drm_crtc *crtc,
+				   struct drm_display_mode *mode)
+{
+	struct drm_i915_private *dev_priv = crtc->dev->dev_private;
+	struct intel_crtc *intel_crtc = to_intel_crtc(crtc);
+	enum transcoder cpu_transcoder = intel_crtc->cpu_transcoder;
+	u32 tmp;
+
+	memset(mode, 0, sizeof(*mode));
+
+	tmp = I915_READ(HTOTAL(cpu_transcoder));
+	mode->hdisplay = (tmp & 0xffff) + 1;
+	mode->htotal = ((tmp & 0xffff0000) >> 16) + 1;
+
+	tmp = I915_READ(HSYNC(cpu_transcoder));
+	mode->hsync_start = (tmp & 0xffff) + 1;
+	mode->hsync_end = ((tmp & 0xffff0000) >> 16) + 1;
+
+	tmp = I915_READ(VTOTAL(cpu_transcoder));
+	mode->vdisplay = (tmp & 0xffff) + 1;
+	mode->vtotal = ((tmp & 0xffff0000) >> 16) + 1;
 
-	mode->clock = intel_crtc_clock_get(dev, crtc);
-	mode->hdisplay = (htot & 0xffff) + 1;
-	mode->htotal = ((htot & 0xffff0000) >> 16) + 1;
-	mode->hsync_start = (hsync & 0xffff) + 1;
-	mode->hsync_end = ((hsync & 0xffff0000) >> 16) + 1;
-	mode->vdisplay = (vtot & 0xffff) + 1;
-	mode->vtotal = ((vtot & 0xffff0000) >> 16) + 1;
-	mode->vsync_start = (vsync & 0xffff) + 1;
-	mode->vsync_end = ((vsync & 0xffff0000) >> 16) + 1;
+	tmp = I915_READ(VSYNC(cpu_transcoder));
+	mode->vsync_start = (tmp & 0xffff) + 1;
+	mode->vsync_end = ((tmp & 0xffff0000) >> 16) + 1;
+
+	//mode->clock = i9xx_crtc_clock_get(crtc);
+	//mode->clock = 69300;
 
 	drm_mode_set_name(mode);
 
-	return mode;
+	return false; /* XXX mode->clock unset */
+}
+
+static __maybe_unused bool no_crtc_get_mode(struct drm_crtc *crtc,
+					    struct drm_display_mode *mode)
+{
+	return false;
+}
+
+bool intel_crtc_get_mode(struct drm_crtc *crtc,
+			 struct drm_display_mode *mode)
+{
+	struct drm_i915_private *dev_priv = crtc->dev->dev_private;
+	return dev_priv->display.crtc_get_mode(crtc, mode);
 }
 
 static void intel_increase_pllclock(struct drm_crtc *crtc)
@@ -8515,20 +8565,25 @@ static void intel_init_display(struct drm_device *dev)
 {
 	struct drm_i915_private *dev_priv = dev->dev_private;
 
+	dev_priv->display.crtc_get_mode = no_crtc_get_mode;
+
 	/* We always want a DPMS function */
 	if (HAS_DDI(dev)) {
+		dev_priv->display.crtc_get_mode = ironlake_crtc_get_mode;
 		dev_priv->display.crtc_mode_set = haswell_crtc_mode_set;
 		dev_priv->display.crtc_enable = haswell_crtc_enable;
 		dev_priv->display.crtc_disable = haswell_crtc_disable;
 		dev_priv->display.off = haswell_crtc_off;
 		dev_priv->display.update_plane = ironlake_update_plane;
 	} else if (HAS_PCH_SPLIT(dev)) {
+		dev_priv->display.crtc_get_mode = ironlake_crtc_get_mode;
 		dev_priv->display.crtc_mode_set = ironlake_crtc_mode_set;
 		dev_priv->display.crtc_enable = ironlake_crtc_enable;
 		dev_priv->display.crtc_disable = ironlake_crtc_disable;
 		dev_priv->display.off = ironlake_crtc_off;
 		dev_priv->display.update_plane = ironlake_update_plane;
 	} else {
+		dev_priv->display.crtc_get_mode = i9xx_crtc_get_mode;
 		dev_priv->display.crtc_mode_set = i9xx_crtc_mode_set;
 		dev_priv->display.crtc_enable = i9xx_crtc_enable;
 		dev_priv->display.crtc_disable = i9xx_crtc_disable;
@@ -9068,6 +9123,14 @@ void intel_modeset_setup_hw_state(struct drm_device *dev,
 		DRM_DEBUG_KMS("[CRTC:%d] hw state readout: %s\n",
 			      crtc->base.base.id,
 			      crtc->active ? "enabled" : "disabled");
+
+
+		if (crtc->base.enabled)
+			crtc->mode_valid = intel_crtc_get_mode(&crtc->base, &crtc->base.mode);
+		if (crtc->mode_valid) {
+			DRM_DEBUG_KMS("found active mode: ");
+			drm_mode_debug_printmodeline(&crtc->base.mode);
+		}
 	}
 
 	if (HAS_DDI(dev))
@@ -9075,12 +9138,14 @@ void intel_modeset_setup_hw_state(struct drm_device *dev,
 
 	list_for_each_entry(encoder, &dev->mode_config.encoder_list,
 			    base.head) {
-		pipe = 0;
+		pipe = -1;
 
 		if (encoder->get_hw_state(encoder, &pipe)) {
-			encoder->base.crtc =
-				dev_priv->pipe_to_crtc_mapping[pipe];
-		} else {
+			crtc = to_intel_crtc(dev_priv->pipe_to_crtc_mapping[pipe]);
+			if (crtc->mode_valid && encoder->get_mode_flags)
+				crtc->base.mode.flags |= encoder->get_mode_flags(encoder);
+			encoder->base.crtc = &crtc->base;
+		} else
 			encoder->base.crtc = NULL;
 		}
 
diff --git a/drivers/gpu/drm/i915/intel_dp.c b/drivers/gpu/drm/i915/intel_dp.c
index 7b8bfe8..e84d4dd 100644
--- a/drivers/gpu/drm/i915/intel_dp.c
+++ b/drivers/gpu/drm/i915/intel_dp.c
@@ -1411,6 +1411,27 @@ static bool intel_dp_get_hw_state(struct intel_encoder *encoder,
 	return true;
 }
 
+static unsigned intel_dp_get_mode_flags(struct intel_encoder *encoder)
+{
+	struct intel_dp *intel_dp = enc_to_intel_dp(&encoder->base);
+	struct drm_i915_private *dev_priv = encoder->base.dev->dev_private;
+	u32 tmp, flags = 0;
+
+	tmp = I915_READ(intel_dp->output_reg);
+
+	if (tmp & DP_SYNC_HS_HIGH)
+		flags |= DRM_MODE_FLAG_PHSYNC;
+	else
+		flags |= DRM_MODE_FLAG_NHSYNC;
+
+	if (tmp & DP_SYNC_VS_HIGH)
+		flags |= DRM_MODE_FLAG_PVSYNC;
+	else
+		flags |= DRM_MODE_FLAG_NVSYNC;
+
+	return flags;
+}
+
 static void intel_disable_dp(struct intel_encoder *encoder)
 {
 	struct intel_dp *intel_dp = enc_to_intel_dp(&encoder->base);
@@ -2966,6 +2987,7 @@ intel_dp_init(struct drm_device *dev, int output_reg, enum port port)
 	intel_encoder->disable = intel_disable_dp;
 	intel_encoder->post_disable = intel_post_disable_dp;
 	intel_encoder->get_hw_state = intel_dp_get_hw_state;
+	intel_encoder->get_mode_flags = intel_dp_get_mode_flags;
 
 	intel_dig_port->port = port;
 	intel_dig_port->dp.output_reg = output_reg;
diff --git a/drivers/gpu/drm/i915/intel_drv.h b/drivers/gpu/drm/i915/intel_drv.h
index 9cf794f..de8928b 100644
--- a/drivers/gpu/drm/i915/intel_drv.h
+++ b/drivers/gpu/drm/i915/intel_drv.h
@@ -176,6 +176,9 @@ struct intel_encoder {
 	 * the encoder is active. If the encoder is enabled it also set the pipe
 	 * it is connected to in the pipe parameter. */
 	bool (*get_hw_state)(struct intel_encoder *, enum pipe *pipe);
+	/* Reconstructs the equivalent mode flags for the current hardware
+	 * state. */
+	unsigned (*get_mode_flags)(struct intel_encoder *);
 	int crtc_mask;
 };
 
@@ -581,8 +584,8 @@ extern void intel_connector_attach_encoder(struct intel_connector *connector,
 					   struct intel_encoder *encoder);
 extern struct drm_encoder *intel_best_encoder(struct drm_connector *connector);
 
-extern struct drm_display_mode *intel_crtc_mode_get(struct drm_device *dev,
-						    struct drm_crtc *crtc);
+extern bool intel_crtc_get_mode(struct drm_crtc *crtc,
+				struct drm_display_mode *mode);
 int intel_get_pipe_from_crtc_id(struct drm_device *dev, void *data,
 				struct drm_file *file_priv);
 extern enum transcoder
diff --git a/drivers/gpu/drm/i915/intel_dvo.c b/drivers/gpu/drm/i915/intel_dvo.c
index 15da995..46b549e 100644
--- a/drivers/gpu/drm/i915/intel_dvo.c
+++ b/drivers/gpu/drm/i915/intel_dvo.c
@@ -129,6 +129,22 @@ static bool intel_dvo_get_hw_state(struct intel_encoder *encoder,
 	return true;
 }
 
+static unsigned
+intel_dvo_get_mode_flags(struct intel_encoder *encoder)
+{
+	struct drm_i915_private *dev_priv = encoder->base.dev->dev_private;
+	struct intel_dvo *intel_dvo = enc_to_intel_dvo(&encoder->base);
+	u32 tmp, flags = 0;
+
+	tmp = I915_READ(intel_dvo->dev.dvo_reg);
+	if (tmp & DVO_HSYNC_ACTIVE_HIGH)
+		flags |= DRM_MODE_FLAG_PHSYNC;
+	if (tmp & DVO_VSYNC_ACTIVE_HIGH)
+		flags |= DRM_MODE_FLAG_PVSYNC;
+
+	return flags;
+}
+
 static void intel_disable_dvo(struct intel_encoder *encoder)
 {
 	struct drm_i915_private *dev_priv = encoder->base.dev->dev_private;
@@ -390,29 +406,26 @@ intel_dvo_get_current_mode(struct drm_connector *connector)
 	struct drm_i915_private *dev_priv = dev->dev_private;
 	struct intel_dvo *intel_dvo = intel_attached_dvo(connector);
 	uint32_t dvo_val = I915_READ(intel_dvo->dev.dvo_reg);
-	struct drm_display_mode *mode = NULL;
+	struct drm_display_mode *fixed_mode = NULL;
 
 	/* If the DVO port is active, that'll be the LVDS, so we can pull out
 	 * its timings to get how the BIOS set up the panel.
 	 */
 	if (dvo_val & DVO_ENABLE) {
+		struct drm_display_mode mode;
 		struct drm_crtc *crtc;
 		int pipe = (dvo_val & DVO_PIPE_B_SELECT) ? 1 : 0;
 
 		crtc = intel_get_crtc_for_pipe(dev, pipe);
-		if (crtc) {
-			mode = intel_crtc_mode_get(dev, crtc);
-			if (mode) {
-				mode->type |= DRM_MODE_TYPE_PREFERRED;
-				if (dvo_val & DVO_HSYNC_ACTIVE_HIGH)
-					mode->flags |= DRM_MODE_FLAG_PHSYNC;
-				if (dvo_val & DVO_VSYNC_ACTIVE_HIGH)
-					mode->flags |= DRM_MODE_FLAG_PVSYNC;
-			}
+		if (intel_crtc_get_mode(crtc, &mode))
+			fixed_mode = drm_mode_duplicate(dev, &mode);
+		if (fixed_mode) {
+			fixed_mode->type |= DRM_MODE_TYPE_PREFERRED;
+			fixed_mode->flags = intel_dvo_get_mode_flags(&intel_dvo->base);
 		}
 	}
 
-	return mode;
+	return fixed_mode;
 }
 
 void intel_dvo_init(struct drm_device *dev)
@@ -441,6 +454,7 @@ void intel_dvo_init(struct drm_device *dev)
 	intel_encoder->disable = intel_disable_dvo;
 	intel_encoder->enable = intel_enable_dvo;
 	intel_encoder->get_hw_state = intel_dvo_get_hw_state;
+	intel_encoder->get_mode_flags = intel_dvo_get_mode_flags;
 	intel_connector->get_hw_state = intel_dvo_connector_get_hw_state;
 
 	/* Now, try to find a controller */
diff --git a/drivers/gpu/drm/i915/intel_hdmi.c b/drivers/gpu/drm/i915/intel_hdmi.c
index 5a6138c..005b9f9 100644
--- a/drivers/gpu/drm/i915/intel_hdmi.c
+++ b/drivers/gpu/drm/i915/intel_hdmi.c
@@ -656,6 +656,27 @@ static bool intel_hdmi_get_hw_state(struct intel_encoder *encoder,
 	return true;
 }
 
+static unsigned intel_hdmi_get_mode_flags(struct intel_encoder *encoder)
+{
+	struct intel_hdmi *intel_hdmi = enc_to_intel_hdmi(&encoder->base);
+	struct drm_i915_private *dev_priv = encoder->base.dev->dev_private;
+	u32 tmp, flags = 0;
+
+	tmp = I915_READ(intel_hdmi->sdvox_reg);
+
+	if (tmp & SDVO_HSYNC_ACTIVE_HIGH)
+		flags |= DRM_MODE_FLAG_PHSYNC;
+	else
+		flags |= DRM_MODE_FLAG_NHSYNC;
+
+	if (tmp & SDVO_VSYNC_ACTIVE_HIGH)
+		flags |= DRM_MODE_FLAG_PVSYNC;
+	else
+		flags |= DRM_MODE_FLAG_NVSYNC;
+
+	return flags;
+}
+
 static void intel_enable_hdmi(struct intel_encoder *encoder)
 {
 	struct drm_device *dev = encoder->base.dev;
@@ -1102,6 +1123,7 @@ void intel_hdmi_init(struct drm_device *dev, int sdvox_reg, enum port port)
 	intel_encoder->enable = intel_enable_hdmi;
 	intel_encoder->disable = intel_disable_hdmi;
 	intel_encoder->get_hw_state = intel_hdmi_get_hw_state;
+	intel_encoder->get_mode_flags = intel_hdmi_get_mode_flags;
 
 	intel_encoder->type = INTEL_OUTPUT_HDMI;
 	intel_encoder->crtc_mask = (1 << 0) | (1 << 1) | (1 << 2);
diff --git a/drivers/gpu/drm/i915/intel_lvds.c b/drivers/gpu/drm/i915/intel_lvds.c
index c7154bf..400afa4 100644
--- a/drivers/gpu/drm/i915/intel_lvds.c
+++ b/drivers/gpu/drm/i915/intel_lvds.c
@@ -88,6 +88,26 @@ static bool intel_lvds_get_hw_state(struct intel_encoder *encoder,
 	return true;
 }
 
+static unsigned intel_lvds_get_mode_flags(struct intel_encoder *encoder)
+{
+	struct drm_device *dev = encoder->base.dev;
+	struct drm_i915_private *dev_priv = dev->dev_private;
+	u32 lvds_reg, tmp, flags = 0;
+
+	if (HAS_PCH_SPLIT(dev))
+		lvds_reg = PCH_LVDS;
+	else
+		lvds_reg = LVDS;
+
+	tmp = I915_READ(lvds_reg);
+	if (tmp & LVDS_HSYNC_POLARITY)
+		flags |= DRM_MODE_FLAG_NHSYNC;
+	if (tmp & LVDS_VSYNC_POLARITY)
+		flags |= DRM_MODE_FLAG_NVSYNC;
+
+	return flags;
+}
+
 /* The LVDS pin pair needs to be on before the DPLLs are enabled.
  * This is an exception to the general rule that mode_set doesn't turn
  * things on.
@@ -1105,6 +1125,7 @@ bool intel_lvds_init(struct drm_device *dev)
 	intel_encoder->pre_pll_enable = intel_pre_pll_enable_lvds;
 	intel_encoder->disable = intel_disable_lvds;
 	intel_encoder->get_hw_state = intel_lvds_get_hw_state;
+	intel_encoder->get_mode_flags = intel_lvds_get_mode_flags;
 	intel_connector->get_hw_state = intel_connector_get_hw_state;
 
 	intel_connector_attach_encoder(intel_connector, intel_encoder);
@@ -1216,11 +1237,15 @@ bool intel_lvds_init(struct drm_device *dev)
 	crtc = intel_get_crtc_for_pipe(dev, pipe);
 
 	if (crtc && (lvds & LVDS_PORT_EN)) {
-		fixed_mode = intel_crtc_mode_get(dev, crtc);
+		struct drm_display_mode mode;
+
+		if (intel_crtc_get_mode(crtc, &mode))
+			fixed_mode = drm_mode_duplicate(dev, &mode);
 		if (fixed_mode) {
 			DRM_DEBUG_KMS("using current (BIOS) mode: ");
 			drm_mode_debug_printmodeline(fixed_mode);
 			fixed_mode->type |= DRM_MODE_TYPE_PREFERRED;
+			fixed_mode->flags = intel_lvds_get_mode_flags(intel_encoder);
 			goto out;
 		}
 	}
diff --git a/drivers/gpu/drm/i915/intel_sdvo.c b/drivers/gpu/drm/i915/intel_sdvo.c
index f01063a..918c269 100644
--- a/drivers/gpu/drm/i915/intel_sdvo.c
+++ b/drivers/gpu/drm/i915/intel_sdvo.c
@@ -1250,6 +1250,27 @@ static bool intel_sdvo_get_hw_state(struct intel_encoder *encoder,
 	return true;
 }
 
+static unsigned intel_sdvo_get_mode_flags(struct intel_encoder *encoder)
+{
+	struct intel_sdvo *intel_sdvo = to_intel_sdvo(&encoder->base);
+	struct drm_i915_private *dev_priv = encoder->base.dev->dev_private;
+	u32 tmp, flags = 0;
+
+	tmp = I915_READ(intel_sdvo->sdvo_reg);
+
+	if (tmp & SDVO_HSYNC_ACTIVE_HIGH)
+		flags |= DRM_MODE_FLAG_PHSYNC;
+	else
+		flags |= DRM_MODE_FLAG_NHSYNC;
+
+	if (tmp & SDVO_VSYNC_ACTIVE_HIGH)
+		flags |= DRM_MODE_FLAG_PVSYNC;
+	else
+		flags |= DRM_MODE_FLAG_NVSYNC;
+
+	return flags;
+}
+
 static void intel_disable_sdvo(struct intel_encoder *encoder)
 {
 	struct drm_i915_private *dev_priv = encoder->base.dev->dev_private;
@@ -2785,6 +2806,8 @@ bool intel_sdvo_init(struct drm_device *dev, uint32_t sdvo_reg, bool is_sdvob)
 	intel_encoder->disable = intel_disable_sdvo;
 	intel_encoder->enable = intel_enable_sdvo;
 	intel_encoder->get_hw_state = intel_sdvo_get_hw_state;
+	if (INTEL_INFO(dev)->gen >= 4)
+		intel_encoder->get_mode_flags = intel_sdvo_get_mode_flags;
 
 	/* In default case sdvo lvds is false */
 	if (!intel_sdvo_get_capabilities(intel_sdvo, &intel_sdvo->caps))
-- 
1.7.9.5