drm/i915: use GMBUS to manage i2c links

Use the GMBUS interface rather than direct bit banging to grab the EDID
over DDC (and for other forms of auxiliary communication with external
display controllers). The hope is that this method will be much faster
and more reliable than bit banging for fetching EDIDs from buggy monitors
or through switches, though we still preserve the bit banging as a
fallback in case GMBUS fails.

Based on an original patch by Jesse Barnes.

Cc: Jesse Barnes <jbarnes@virtuousgeek.org>
Signed-off-by: Chris Wilson <chris@chris-wilson.co.uk>

1 files changed, 4 insertions, 12 deletions

diff --git a/drivers/gpu/drm/i915/intel_modes.c b/drivers/gpu/drm/i915/intel_modes.c
index 1138aa9..f70b7cf 100644
--- a/drivers/gpu/drm/i915/intel_modes.c
+++ b/drivers/gpu/drm/i915/intel_modes.c
@@ -1,6 +1,6 @@
 /*
  * Copyright (c) 2007 Dave Airlie <airlied@linux.ie>
- * Copyright (c) 2007 Intel Corporation
+ * Copyright (c) 2007, 2010 Intel Corporation
  *   Jesse Barnes <jesse.barnes@intel.com>
  *
  * Permission is hereby granted, free of charge, to any person obtaining a
@@ -34,11 +34,11 @@
  * intel_ddc_probe
  *
  */
-bool intel_ddc_probe(struct intel_encoder *intel_encoder)
+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];
-	int ret;
 	struct i2c_msg msgs[] = {
 		{
 			.addr = 0x50,
@@ -54,13 +54,7 @@ bool intel_ddc_probe(struct intel_encoder *intel_encoder)
 		}
 	};
 
-	intel_i2c_quirk_set(intel_encoder->base.dev, true);
-	ret = i2c_transfer(intel_encoder->ddc_bus, msgs, 2);
-	intel_i2c_quirk_set(intel_encoder->base.dev, false);
-	if (ret == 2)
-		return true;
-
-	return false;
+	return i2c_transfer(&dev_priv->gmbus[ddc_bus].adapter, msgs, 2) == 2;
 }
 
 /**
@@ -76,9 +70,7 @@ int intel_ddc_get_modes(struct drm_connector *connector,
 	struct edid *edid;
 	int ret = 0;
 
-	intel_i2c_quirk_set(connector->dev, true);
 	edid = drm_get_edid(connector, adapter);
-	intel_i2c_quirk_set(connector->dev, false);
 	if (edid) {
 		drm_mode_connector_update_edid_property(connector, edid);
 		ret = drm_add_edid_modes(connector, edid);