drm/dp: add a hw mutex around the transfer functions. (v2)

This should avoid races between connector probing and HPD
irqs in the future, currently mode_config.mutex blocks this
possibility.
Reviewed-by: Daniel Vetter <daniel.vetter@ffwll.ch>
Signed-off-by: Dave Airlie <airlied@redhat.com>

drivers/gpu/drm/drm_dp_helper.c

@@ -216,7 +216,7 @@ i2c_dp_aux_prepare_bus(struct i2c_adapter *adapter)
  *
  * IMPORTANT:
  * This interface is deprecated, please switch to the new dp aux helpers and
- * drm_dp_aux_register_i2c_bus().
+ * drm_dp_aux_register().
  */
 int
 i2c_dp_aux_add_bus(struct i2c_adapter *adapter)
@@ -382,7 +382,10 @@ static int drm_dp_dpcd_access(struct drm_dp_aux *aux, u8 request,
 	 * transactions.
 	 */
 	for (retry = 0; retry < 7; retry++) {
+
+		mutex_lock(&aux->hw_mutex);
 		err = aux->transfer(aux, &msg);
+		mutex_unlock(&aux->hw_mutex);
 		if (err < 0) {
 			if (err == -EBUSY)
 				continue;
@@ -596,7 +599,9 @@ static int drm_dp_i2c_do_msg(struct drm_dp_aux *aux, struct drm_dp_aux_msg *msg)
 	 * before giving up the AUX transaction.
 	 */
 	for (retry = 0; retry < 7; retry++) {
+		mutex_lock(&aux->hw_mutex);
 		err = aux->transfer(aux, msg);
+		mutex_unlock(&aux->hw_mutex);
 		if (err < 0) {
 			if (err == -EBUSY)
 				continue;
@@ -729,13 +734,15 @@ static const struct i2c_algorithm drm_dp_i2c_algo = {
 };
 
 /**
- * drm_dp_aux_register_i2c_bus() - register an I2C adapter for I2C-over-AUX
+ * drm_dp_aux_register() - initialise and register aux channel
  * @aux: DisplayPort AUX channel
  *
  * Returns 0 on success or a negative error code on failure.
  */
-int drm_dp_aux_register_i2c_bus(struct drm_dp_aux *aux)
+int drm_dp_aux_register(struct drm_dp_aux *aux)
 {
+	mutex_init(&aux->hw_mutex);
+
 	aux->ddc.algo = &drm_dp_i2c_algo;
 	aux->ddc.algo_data = aux;
 	aux->ddc.retries = 3;
@@ -750,14 +757,14 @@ int drm_dp_aux_register_i2c_bus(struct drm_dp_aux *aux)
 
 	return i2c_add_adapter(&aux->ddc);
 }
-EXPORT_SYMBOL(drm_dp_aux_register_i2c_bus);
+EXPORT_SYMBOL(drm_dp_aux_register);
 
 /**
- * drm_dp_aux_unregister_i2c_bus() - unregister an I2C-over-AUX adapter
+ * drm_dp_aux_unregister() - unregister an AUX adapter
  * @aux: DisplayPort AUX channel
  */
-void drm_dp_aux_unregister_i2c_bus(struct drm_dp_aux *aux)
+void drm_dp_aux_unregister(struct drm_dp_aux *aux)
 {
 	i2c_del_adapter(&aux->ddc);
 }
-EXPORT_SYMBOL(drm_dp_aux_unregister_i2c_bus);
+EXPORT_SYMBOL(drm_dp_aux_unregister);

drivers/gpu/drm/i915/intel_dp.c

@@ -702,9 +702,9 @@ intel_dp_aux_init(struct intel_dp *intel_dp, struct intel_connector *connector)
 	DRM_DEBUG_KMS("registering %s bus for %s\n", name,
 		      connector->base.kdev->kobj.name);
 
-	ret = drm_dp_aux_register_i2c_bus(&intel_dp->aux);
+	ret = drm_dp_aux_register(&intel_dp->aux);
 	if (ret < 0) {
-		DRM_ERROR("drm_dp_aux_register_i2c_bus() for %s failed (%d)\n",
+		DRM_ERROR("drm_dp_aux_register() for %s failed (%d)\n",
 			  name, ret);
 		return;
 	}
@@ -714,7 +714,7 @@ intel_dp_aux_init(struct intel_dp *intel_dp, struct intel_connector *connector)
 				intel_dp->aux.ddc.dev.kobj.name);
 	if (ret < 0) {
 		DRM_ERROR("sysfs_create_link() for %s failed (%d)\n", name, ret);
-		drm_dp_aux_unregister_i2c_bus(&intel_dp->aux);
+		drm_dp_aux_unregister(&intel_dp->aux);
 	}
 }
 
@@ -3662,7 +3662,7 @@ void intel_dp_encoder_destroy(struct drm_encoder *encoder)
 	struct intel_dp *intel_dp = &intel_dig_port->dp;
 	struct drm_device *dev = intel_dp_to_dev(intel_dp);
 
-	drm_dp_aux_unregister_i2c_bus(&intel_dp->aux);
+	drm_dp_aux_unregister(&intel_dp->aux);
 	drm_encoder_cleanup(encoder);
 	if (is_edp(intel_dp)) {
 		cancel_delayed_work_sync(&intel_dp->panel_vdd_work);
@@ -4244,7 +4244,7 @@ intel_dp_init_connector(struct intel_digital_port *intel_dig_port,
 	intel_dp->psr_setup_done = false;
 
 	if (!intel_edp_init_connector(intel_dp, intel_connector, &power_seq)) {
-		drm_dp_aux_unregister_i2c_bus(&intel_dp->aux);
+		drm_dp_aux_unregister(&intel_dp->aux);
 		if (is_edp(intel_dp)) {
 			cancel_delayed_work_sync(&intel_dp->panel_vdd_work);
 			mutex_lock(&dev->mode_config.connection_mutex);

drivers/gpu/drm/radeon/atombios_dp.c

@@ -222,11 +222,12 @@ void radeon_dp_aux_init(struct radeon_connector *radeon_connector)
 	radeon_connector->ddc_bus->rec.hpd = radeon_connector->hpd.hpd;
 	radeon_connector->ddc_bus->aux.dev = radeon_connector->base.kdev;
 	radeon_connector->ddc_bus->aux.transfer = radeon_dp_aux_transfer;
-	ret = drm_dp_aux_register_i2c_bus(&radeon_connector->ddc_bus->aux);
+
+	ret = drm_dp_aux_register(&radeon_connector->ddc_bus->aux);
 	if (!ret)
 		radeon_connector->ddc_bus->has_aux = true;
 
-	WARN(ret, "drm_dp_aux_register_i2c_bus() failed with error %d\n", ret);
+	WARN(ret, "drm_dp_aux_register() failed with error %d\n", ret);
 }
 
 /***** general DP utility functions *****/

drivers/gpu/drm/radeon/radeon_i2c.c

@@ -988,7 +988,7 @@ void radeon_i2c_destroy(struct radeon_i2c_chan *i2c)
 		return;
 	i2c_del_adapter(&i2c->adapter);
 	if (i2c->has_aux)
-		drm_dp_aux_unregister_i2c_bus(&i2c->aux);
+		drm_dp_aux_unregister(&i2c->aux);
 	kfree(i2c);
 }
 

drivers/gpu/drm/tegra/dpaux.c

@@ -332,7 +332,7 @@ static int tegra_dpaux_probe(struct platform_device *pdev)
 	dpaux->aux.transfer = tegra_dpaux_transfer;
 	dpaux->aux.dev = &pdev->dev;
 
-	err = drm_dp_aux_register_i2c_bus(&dpaux->aux);
+	err = drm_dp_aux_register(&dpaux->aux);
 	if (err < 0)
 		return err;
 
@@ -355,7 +355,7 @@ static int tegra_dpaux_remove(struct platform_device *pdev)
 {
 	struct tegra_dpaux *dpaux = platform_get_drvdata(pdev);
 
-	drm_dp_aux_unregister_i2c_bus(&dpaux->aux);
+	drm_dp_aux_unregister(&dpaux->aux);
 
 	mutex_lock(&dpaux_lock);
 	list_del(&dpaux->list);

include/drm/drm_dp_helper.h

@@ -514,6 +514,7 @@ struct drm_dp_aux_msg {
  * @name: user-visible name of this AUX channel and the I2C-over-AUX adapter
  * @ddc: I2C adapter that can be used for I2C-over-AUX communication
  * @dev: pointer to struct device that is the parent for this AUX channel
+ * @hw_mutex: internal mutex used for locking transfers
  * @transfer: transfers a message representing a single AUX transaction
  *
  * The .dev field should be set to a pointer to the device that implements
@@ -546,7 +547,7 @@ struct drm_dp_aux {
 	const char *name;
 	struct i2c_adapter ddc;
 	struct device *dev;
-
+	struct mutex hw_mutex;
 	ssize_t (*transfer)(struct drm_dp_aux *aux,
 			    struct drm_dp_aux_msg *msg);
 };
@@ -605,7 +606,7 @@ int drm_dp_link_probe(struct drm_dp_aux *aux, struct drm_dp_link *link);
 int drm_dp_link_power_up(struct drm_dp_aux *aux, struct drm_dp_link *link);
 int drm_dp_link_configure(struct drm_dp_aux *aux, struct drm_dp_link *link);
 
-int drm_dp_aux_register_i2c_bus(struct drm_dp_aux *aux);
-void drm_dp_aux_unregister_i2c_bus(struct drm_dp_aux *aux);
+int drm_dp_aux_register(struct drm_dp_aux *aux);
+void drm_dp_aux_unregister(struct drm_dp_aux *aux);
 
 #endif /* _DRM_DP_HELPER_H_ */