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Commit bffce907 authored by Jani Nikula's avatar Jani Nikula
Browse files

drm/i915: abstract i2c bit banging fallback in gmbus xfer 



Choose between i2c bit banging and gmbus in a new higher level function,
and let the i2c core retry the first time we fall back to bit banging.

The i2c core imposes a timeout on -EAGAIN, but it defaults to 1 second,
and shouldn't be a problem for us.

Reviewed-by: default avatarVille Syrjälä <ville.syrjala@linux.intel.com>
Signed-off-by: default avatarJani Nikula <jani.nikula@intel.com>
Link: http://patchwork.freedesktop.org/patch/msgid/1448980166-23055-2-git-send-email-jani.nikula@intel.com
parent 0aeb9048

drivers/gpu/drm/i915/intel_i2c.c

+25 −14
Original line number Diff line number Diff line
@@ -472,9 +472,7 @@ gmbus_xfer_index_read(struct drm_i915_private *dev_priv, struct i2c_msg *msgs) 
}



static int

gmbus_xfer(struct i2c_adapter *adapter,

	   struct i2c_msg *msgs,

	   int num)

do_gmbus_xfer(struct i2c_adapter *adapter, struct i2c_msg *msgs, int num)

{

	struct intel_gmbus *bus = container_of(adapter,

					       struct intel_gmbus,
@@ -483,14 +481,6 @@ gmbus_xfer(struct i2c_adapter *adapter, 
	int i = 0, inc, try = 0;

	int ret = 0;



	intel_display_power_get(dev_priv, POWER_DOMAIN_GMBUS);

	mutex_lock(&dev_priv->gmbus_mutex);



	if (bus->force_bit) {

		ret = i2c_bit_algo.master_xfer(adapter, msgs, num);

		goto out;

	}



retry:

	I915_WRITE(GMBUS0, bus->reg0);
@@ -585,13 +575,34 @@ gmbus_xfer(struct i2c_adapter *adapter, 
		 bus->adapter.name, bus->reg0 & 0xff);

	I915_WRITE(GMBUS0, 0);



	/* Hardware may not support GMBUS over these pins? Try GPIO bitbanging instead. */

	/*

	 * Hardware may not support GMBUS over these pins? Try GPIO bitbanging

	 * instead. Use EAGAIN to have i2c core retry.

	 */

	bus->force_bit = 1;

	ret = i2c_bit_algo.master_xfer(adapter, msgs, num);

	ret = -EAGAIN;



out:

	mutex_unlock(&dev_priv->gmbus_mutex);

	return ret;

}



static int

gmbus_xfer(struct i2c_adapter *adapter, struct i2c_msg *msgs, int num)

{

	struct intel_gmbus *bus = container_of(adapter, struct intel_gmbus,

					       adapter);

	struct drm_i915_private *dev_priv = bus->dev_priv;

	int ret;



	intel_display_power_get(dev_priv, POWER_DOMAIN_GMBUS);

	mutex_lock(&dev_priv->gmbus_mutex);



	if (bus->force_bit)

		ret = i2c_bit_algo.master_xfer(adapter, msgs, num);

	else

		ret = do_gmbus_xfer(adapter, msgs, num);



	mutex_unlock(&dev_priv->gmbus_mutex);

	intel_display_power_put(dev_priv, POWER_DOMAIN_GMBUS);



	return ret;