[PATCH 2/2] Check if the bus is valid prior to discovering edid.

[Eugeni Dodonov <eugeni.dodonov@intel.com>]

This adds a new function intel_drm_get_valid_edid, which attempts to detect
EDID values from available devices and returns quickly in case no connection
is present.  We detect non-existing devices by checking the i2c_transfer
status, and if it fails with the -ENXIO result, we know that the
i2c_algo_bit was unable to locate the hardware, so we give up on further
edid discovery.

This should improve the edid detection timeouts by about 10-30% in most
cases, and by a much larger margin in case of broken or phantom outputs
https://bugs.freedesktop.org/show_bug.cgi?id=41059.

This also removes intel_ddc_probe, whose functionality is now done by
intel_drm_get_valid_edid.

Signed-off-by: Eugeni Dodonov <eugeni.dodonov@intel.com>
---
 drivers/gpu/drm/i915/intel_crt.c   |   46 ++++++++++++++++++------------------
 drivers/gpu/drm/i915/intel_dp.c    |    4 +-
 drivers/gpu/drm/i915/intel_drv.h   |    3 +-
 drivers/gpu/drm/i915/intel_hdmi.c  |    4 +-
 drivers/gpu/drm/i915/intel_i2c.c   |   42 ++++++++++++++++++++++++++++++++
 drivers/gpu/drm/i915/intel_lvds.c  |    2 +-
 drivers/gpu/drm/i915/intel_modes.c |   29 +----------------------
 drivers/gpu/drm/i915/intel_sdvo.c  |    4 +-
 8 files changed, 75 insertions(+), 59 deletions(-)

diff --git a/drivers/gpu/drm/i915/intel_crt.c b/drivers/gpu/drm/i915/intel_crt.c
index 0979d88..3b55fdf 100644
--- a/drivers/gpu/drm/i915/intel_crt.c
+++ b/drivers/gpu/drm/i915/intel_crt.c
@@ -273,36 +273,36 @@ static bool intel_crt_detect_ddc(struct drm_connector *connector)
 {
 	struct intel_crt *crt = intel_attached_crt(connector);
 	struct drm_i915_private *dev_priv = crt->base.base.dev->dev_private;
+	struct edid *edid = NULL;
+	bool is_digital = false;
 
 	/* CRT should always be at 0, but check anyway */
 	if (crt->base.type != INTEL_OUTPUT_ANALOG)
 		return false;
 
-	if (intel_ddc_probe(&crt->base, dev_priv->crt_ddc_pin)) {
-		struct edid *edid;
-		bool is_digital = false;
+	edid = intel_drm_get_valid_edid(connector,
+		&dev_priv->gmbus[dev_priv->crt_ddc_pin].adapter);
+	if (!edid)
+		return false;
 
-		edid = drm_get_edid(connector,
-			&dev_priv->gmbus[dev_priv->crt_ddc_pin].adapter);
-		/*
-		 * This may be a DVI-I connector with a shared DDC
-		 * link between analog and digital outputs, so we
-		 * have to check the EDID input spec of the attached device.
-		 *
-		 * On the other hand, what should we do if it is a broken EDID?
-		 */
-		if (edid != NULL) {
-			is_digital = edid->input & DRM_EDID_INPUT_DIGITAL;
-			connector->display_info.raw_edid = NULL;
-			kfree(edid);
-		}
+	/*
+	 * This may be a DVI-I connector with a shared DDC
+	 * link between analog and digital outputs, so we
+	 * have to check the EDID input spec of the attached device.
+	 *
+	 * On the other hand, what should we do if it is a broken EDID?
+	 */
+	if (edid != NULL) {
+		is_digital = edid->input & DRM_EDID_INPUT_DIGITAL;
+		connector->display_info.raw_edid = NULL;
+		kfree(edid);
+	}
 
-		if (!is_digital) {
-			DRM_DEBUG_KMS("CRT detected via DDC:0x50 [EDID]\n");
-			return true;
-		} else {
-			DRM_DEBUG_KMS("CRT not detected via DDC:0x50 [EDID reports a digital panel]\n");
-		}
+	if (!is_digital) {
+		DRM_DEBUG_KMS("CRT detected via DDC:0x50 [EDID]\n");
+		return true;
+	} else {
+		DRM_DEBUG_KMS("CRT not detected via DDC:0x50 [EDID reports a digital panel]\n");
 	}
 
 	return false;
diff --git a/drivers/gpu/drm/i915/intel_dp.c b/drivers/gpu/drm/i915/intel_dp.c
index 44fef5e..dd0d8b1 100644
--- a/drivers/gpu/drm/i915/intel_dp.c
+++ b/drivers/gpu/drm/i915/intel_dp.c
@@ -1715,7 +1715,7 @@ intel_dp_detect(struct drm_connector *connector, bool force)
 	if (intel_dp->force_audio) {
 		intel_dp->has_audio = intel_dp->force_audio > 0;
 	} else {
-		edid = drm_get_edid(connector, &intel_dp->adapter);
+		edid = intel_drm_get_valid_edid(connector, &intel_dp->adapter);
 		if (edid) {
 			intel_dp->has_audio = drm_detect_monitor_audio(edid);
 			connector->display_info.raw_edid = NULL;
@@ -1772,7 +1772,7 @@ intel_dp_detect_audio(struct drm_connector *connector)
 	struct edid *edid;
 	bool has_audio = false;
 
-	edid = drm_get_edid(connector, &intel_dp->adapter);
+	edid = intel_drm_get_valid_edid(connector, &intel_dp->adapter);
 	if (edid) {
 		has_audio = drm_detect_monitor_audio(edid);
 
diff --git a/drivers/gpu/drm/i915/intel_drv.h b/drivers/gpu/drm/i915/intel_drv.h
index fe1099d..0e4b823 100644
--- a/drivers/gpu/drm/i915/intel_drv.h
+++ b/drivers/gpu/drm/i915/intel_drv.h
@@ -264,8 +264,9 @@ struct intel_fbc_work {
 	int interval;
 };
 
+struct edid * intel_drm_get_valid_edid(struct drm_connector *connector,
+		struct i2c_adapter *adapter);
 int intel_ddc_get_modes(struct drm_connector *c, struct i2c_adapter *adapter);
-extern bool intel_ddc_probe(struct intel_encoder *intel_encoder, int ddc_bus);
 
 extern void intel_attach_force_audio_property(struct drm_connector *connector);
 extern void intel_attach_broadcast_rgb_property(struct drm_connector *connector);
diff --git a/drivers/gpu/drm/i915/intel_hdmi.c b/drivers/gpu/drm/i915/intel_hdmi.c
index 226ba83..714f2fb 100644
--- a/drivers/gpu/drm/i915/intel_hdmi.c
+++ b/drivers/gpu/drm/i915/intel_hdmi.c
@@ -329,7 +329,7 @@ intel_hdmi_detect(struct drm_connector *connector, bool force)
 
 	intel_hdmi->has_hdmi_sink = false;
 	intel_hdmi->has_audio = false;
-	edid = drm_get_edid(connector,
+	edid = intel_drm_get_valid_edid(connector,
 			    &dev_priv->gmbus[intel_hdmi->ddc_bus].adapter);
 
 	if (edid) {
@@ -371,7 +371,7 @@ intel_hdmi_detect_audio(struct drm_connector *connector)
 	struct edid *edid;
 	bool has_audio = false;
 
-	edid = drm_get_edid(connector,
+	edid = intel_drm_get_valid_edid(connector,
 			    &dev_priv->gmbus[intel_hdmi->ddc_bus].adapter);
 	if (edid) {
 		if (edid->input & DRM_EDID_INPUT_DIGITAL)
diff --git a/drivers/gpu/drm/i915/intel_i2c.c b/drivers/gpu/drm/i915/intel_i2c.c
index d98cee6..b3a6eda 100644
--- a/drivers/gpu/drm/i915/intel_i2c.c
+++ b/drivers/gpu/drm/i915/intel_i2c.c
@@ -470,3 +470,45 @@ void intel_teardown_gmbus(struct drm_device *dev)
 	kfree(dev_priv->gmbus);
 	dev_priv->gmbus = NULL;
 }
+
+/**
+ * intel_drm_get_valid_edid - gets edid from existent adapters only
+ * @connector: DRM connector device to use
+ * @adapter: i2c adapter
+ *
+ * Verifies if the i2c adapter is responding to our queries before
+ * attempting to do proper communication with it. If it does,
+ * retreive the EDID with help of drm_get_edid
+ */
+struct edid *
+intel_drm_get_valid_edid(struct drm_connector *connector,
+		struct i2c_adapter *adapter)
+{
+	int ret;
+	u8 out_buf[] = { 0x0, 0x0};
+	u8 buf[2];
+	struct i2c_msg msgs[] = {
+		{
+			.addr = 0x50,
+			.flags = 0,
+			.len = 1,
+			.buf = out_buf,
+		},
+		{
+			.addr = 0x50,
+			.flags = I2C_M_RD,
+			.len = 1,
+			.buf = buf,
+		}
+	};
+
+	/* We just check for -ENXIO - drm_get_edid checks if the transfer
+	 * works and manages the remaining parts of the EDID */
+	ret = i2c_transfer(adapter, msgs, 2);
+	if (ret == -ENXIO) {
+		DRM_DEBUG_KMS("i915: adapter %s not responding: %d\n",
+				adapter->name, ret);
+		return NULL;
+	}
+	return drm_get_edid(connector, adapter);
+}
diff --git a/drivers/gpu/drm/i915/intel_lvds.c b/drivers/gpu/drm/i915/intel_lvds.c
index 31da77f..8f59a8e 100644
--- a/drivers/gpu/drm/i915/intel_lvds.c
+++ b/drivers/gpu/drm/i915/intel_lvds.c
@@ -921,7 +921,7 @@ bool intel_lvds_init(struct drm_device *dev)
 	 * Attempt to get the fixed panel mode from DDC.  Assume that the
 	 * preferred mode is the right one.
 	 */
-	intel_lvds->edid = drm_get_edid(connector,
+	intel_lvds->edid = intel_drm_get_valid_edid(connector,
 					&dev_priv->gmbus[pin].adapter);
 	if (intel_lvds->edid) {
 		if (drm_add_edid_modes(connector,
diff --git a/drivers/gpu/drm/i915/intel_modes.c b/drivers/gpu/drm/i915/intel_modes.c
index 3b26a3b..ae1a989 100644
--- a/drivers/gpu/drm/i915/intel_modes.c
+++ b/drivers/gpu/drm/i915/intel_modes.c
@@ -31,33 +31,6 @@
 #include "i915_drv.h"
 
 /**
- * intel_ddc_probe
- *
- */
-bool intel_ddc_probe(struct intel_encoder *intel_encoder, int ddc_bus)
-{
-	struct drm_i915_private *dev_priv = intel_encoder->base.dev->dev_private;
-	u8 out_buf[] = { 0x0, 0x0};
-	u8 buf[2];
-	struct i2c_msg msgs[] = {
-		{
-			.addr = 0x50,
-			.flags = 0,
-			.len = 1,
-			.buf = out_buf,
-		},
-		{
-			.addr = 0x50,
-			.flags = I2C_M_RD,
-			.len = 1,
-			.buf = buf,
-		}
-	};
-
-	return i2c_transfer(&dev_priv->gmbus[ddc_bus].adapter, msgs, 2) == 2;
-}
-
-/**
  * intel_ddc_get_modes - get modelist from monitor
  * @connector: DRM connector device to use
  * @adapter: i2c adapter
@@ -70,7 +43,7 @@ int intel_ddc_get_modes(struct drm_connector *connector,
 	struct edid *edid;
 	int ret = 0;
 
-	edid = drm_get_edid(connector, adapter);
+	edid = intel_drm_get_valid_edid(connector, adapter);
 	if (edid) {
 		drm_mode_connector_update_edid_property(connector, edid);
 		ret = drm_add_edid_modes(connector, edid);
diff --git a/drivers/gpu/drm/i915/intel_sdvo.c b/drivers/gpu/drm/i915/intel_sdvo.c
index 6348c49..8b4ac61 100644
--- a/drivers/gpu/drm/i915/intel_sdvo.c
+++ b/drivers/gpu/drm/i915/intel_sdvo.c
@@ -1240,7 +1240,7 @@ static struct edid *
 intel_sdvo_get_edid(struct drm_connector *connector)
 {
 	struct intel_sdvo *sdvo = intel_attached_sdvo(connector);
-	return drm_get_edid(connector, &sdvo->ddc);
+	return intel_drm_get_valid_edid(connector, &sdvo->ddc);
 }
 
 /* Mac mini hack -- use the same DDC as the analog connector */
@@ -1249,7 +1249,7 @@ intel_sdvo_get_analog_edid(struct drm_connector *connector)
 {
 	struct drm_i915_private *dev_priv = connector->dev->dev_private;
 
-	return drm_get_edid(connector,
+	return intel_drm_get_valid_edid(connector,
 			    &dev_priv->gmbus[dev_priv->crt_ddc_pin].adapter);
 }
 
-- 
1.7.7