drm/i915: Use an I2C algo to do the flip to SDVO DDC bus.

Previously, we would set the control bus switch before calls were made
to request EDID information over DDC.  But recently the DDC code started
doing multiple I2C transfers to get the EDID extensions as well.  This
tripped up SDVO, because the control bus switch is only in effect until
the next STOP after a START.  By doing our own algo, we can wrap each i2c
transaction on the DDC I2C bus with the control bus switch it requires.

freedesktop.org bug #21042

Signed-off-by: Ma Ling <ling.ma@intel.com>
[anholt: Hand application for conflict, fixed error path]
Signed-off-by: Eric Anholt <eric@anholt.net>

drivers/gpu/drm/i915/intel_sdvo.c

@@ -1402,10 +1402,8 @@ static enum drm_connector_status intel_sdvo_detect(struct drm_connector *connect
 static void intel_sdvo_get_ddc_modes(struct drm_connector *connector)
 {
 	struct intel_output *intel_output = to_intel_output(connector);
-	struct intel_sdvo_priv *sdvo_priv = intel_output->dev_priv;
 
 	/* set the bus switch and get the modes */
-	intel_sdvo_set_control_bus_switch(intel_output, sdvo_priv->ddc_bus);
 	intel_ddc_get_modes(intel_output);
 
 #if 0
@@ -1601,6 +1599,9 @@ static void intel_sdvo_destroy(struct drm_connector *connector)
 
 	if (intel_output->i2c_bus)
 		intel_i2c_destroy(intel_output->i2c_bus);
+	if (intel_output->ddc_bus)
+		intel_i2c_destroy(intel_output->ddc_bus);
+
 	drm_sysfs_connector_remove(connector);
 	drm_connector_cleanup(connector);
 	kfree(intel_output);
@@ -1697,12 +1698,56 @@ intel_sdvo_get_digital_encoding_mode(struct intel_output *output)
 	return true;
 }
 
+static struct intel_output *
+intel_sdvo_chan_to_intel_output(struct intel_i2c_chan *chan)
+{
+	struct drm_device *dev = chan->drm_dev;
+	struct drm_connector *connector;
+	struct intel_output *intel_output = NULL;
+
+	list_for_each_entry(connector,
+			&dev->mode_config.connector_list, head) {
+		if (to_intel_output(connector)->ddc_bus == chan) {
+			intel_output = to_intel_output(connector);
+			break;
+		}
+	}
+	return intel_output;
+}
+
+static int intel_sdvo_master_xfer(struct i2c_adapter *i2c_adap,
+				  struct i2c_msg msgs[], int num)
+{
+	struct intel_output *intel_output;
+	struct intel_sdvo_priv *sdvo_priv;
+	struct i2c_algo_bit_data *algo_data;
+	struct i2c_algorithm *algo;
+
+	algo_data = (struct i2c_algo_bit_data *)i2c_adap->algo_data;
+	intel_output =
+		intel_sdvo_chan_to_intel_output(
+				(struct intel_i2c_chan *)(algo_data->data));
+	if (intel_output == NULL)
+		return -EINVAL;
+
+	sdvo_priv = intel_output->dev_priv;
+	algo = (struct i2c_algorithm *)intel_output->i2c_bus->adapter.algo;
+
+	intel_sdvo_set_control_bus_switch(intel_output, sdvo_priv->ddc_bus);
+	return algo->master_xfer(i2c_adap, msgs, num);
+}
+
+static struct i2c_algorithm intel_sdvo_i2c_bit_algo = {
+	.master_xfer	= intel_sdvo_master_xfer,
+};
+
 bool intel_sdvo_init(struct drm_device *dev, int output_device)
 {
 	struct drm_connector *connector;
 	struct intel_output *intel_output;
 	struct intel_sdvo_priv *sdvo_priv;
 	struct intel_i2c_chan *i2cbus = NULL;
+	struct intel_i2c_chan *ddcbus = NULL;
 	int connector_type;
 	u8 ch[0x40];
 	int i;
@@ -1748,6 +1793,20 @@ bool intel_sdvo_init(struct drm_device *dev, int output_device)
 		}
 	}
 
+	/* setup the DDC bus. */
+	if (output_device == SDVOB)
+		ddcbus = intel_i2c_create(dev, GPIOE, "SDVOB DDC BUS");
+	else
+		ddcbus = intel_i2c_create(dev, GPIOE, "SDVOC DDC BUS");
+
+	if (ddcbus == NULL)
+		goto err_i2c;
+
+	intel_sdvo_i2c_bit_algo.functionality =
+		intel_output->i2c_bus->adapter.algo->functionality;
+	ddcbus->adapter.algo = &intel_sdvo_i2c_bit_algo;
+	intel_output->ddc_bus = ddcbus;
+
 	/* In defaut case sdvo lvds is false */
 	sdvo_priv->is_lvds = false;
 	intel_sdvo_get_capabilities(intel_output, &sdvo_priv->caps);
@@ -1862,11 +1921,11 @@ bool intel_sdvo_init(struct drm_device *dev, int output_device)
 		  sdvo_priv->caps.output_flags &
 			(SDVO_OUTPUT_TMDS1 | SDVO_OUTPUT_RGB1) ? 'Y' : 'N');
 
-	intel_output->ddc_bus = i2cbus;
-
 	return true;
 
 err_i2c:
+	if (ddcbus != NULL)
+		intel_i2c_destroy(intel_output->ddc_bus);
 	intel_i2c_destroy(intel_output->i2c_bus);
 err_inteloutput:
 	kfree(intel_output);