Hello As discussed in this thread http://lists.freedesktop.org/archives/dri-devel/2013-April/037411.html GMBUS based DVO transmitter detection seems to be unreliable which could result in an unusable DVO port. The attached patch fixes this by falling back to bit banging mode for the time DVO transmitter detection is in progress.
Signed-off-by: David Müller <d.mueller@xxxxxxxxx> Tested-by: David Müller <d.mueller@xxxxxxxxx> --- 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;
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