Signed-off-by: David Müller <d.mueller@elsoft.ch>
Tested-by: David Müller <d.mueller@elsoft.ch>

---
diff -dpurN a/drivers/gpu/drm/i915/intel_dvo.c b/drivers/gpu/drm/i915/intel_dvo.c
--- a/drivers/gpu/drm/i915/intel_dvo.c	2012-12-11 10:09:35.113446850 +0100
+++ b/drivers/gpu/drm/i915/intel_dvo.c	2013-04-19 07:21:54.054546365 +0200
@@ -449,6 +449,7 @@ void intel_dvo_init(struct drm_device *d
 		const struct intel_dvo_device *dvo = &intel_dvo_devices[i];
 		struct i2c_adapter *i2c;
 		int gpio;
+		bool dvoinit;
 
 		/* Allow the I2C driver info to specify the GPIO to be used in
 		 * special cases, but otherwise default to what's defined
@@ -468,7 +469,17 @@ void intel_dvo_init(struct drm_device *d
 		i2c = intel_gmbus_get_adapter(dev_priv, gpio);
 
 		intel_dvo->dev = *dvo;
-		if (!dvo->dev_ops->init(&intel_dvo->dev, i2c))
+
+		/* GMBUS NAK handling seems to be unstable, hence let the
+		 * transmitter detection run in bit banging mode for now.
+		 */
+		intel_gmbus_force_bit(i2c, true);
+
+		dvoinit = dvo->dev_ops->init(&intel_dvo->dev, i2c);
+
+		intel_gmbus_force_bit(i2c, false);
+
+		if (!dvoinit)
 			continue;
 
 		intel_encoder->type = INTEL_OUTPUT_DVO;