1 // SPDX-License-Identifier: GPL-2.0
3  * DisplayPort CEC-Tunneling-over-AUX support
19  * Unfortunately it turns out that we have a chicken-and-egg situation
20  * here. Quite a few active (mini-)DP-to-HDMI or USB-C-to-HDMI adapters
21  * have a converter chip that supports CEC-Tunneling-over-AUX (usually the
23  * useless. Note that MegaChips 2900-based adapters appear to have good
27  * Sadly there is no way for this driver to know this. What happens is
33  * was never supported by any OS. So there was no easy way of testing it,
34  * and no incentive to correctly wire up the CEC pin.
41  * https://hverkuil.home.xs4all.nl/cec-status.txt
47  * As far as I can see there is no mechanism defined in the DisplayPort
56  * These functions take care of supporting the CEC-Tunneling-over-AUX
57  * feature of DisplayPort-to-HDMI adapters.
61  * When the EDID is unset because the HPD went low, then the CEC DPCD registers
62  * typically can no longer be read (true for a DP-to-HDMI adapter since it is
63  * powered by the HPD). However, some displays toggle the HPD off and on for a
68  * actually unregistered. Only if the HPD does not return within that time will
75  * soon as the HPD disappears.
77  * The default is one second to prevent short HPD glitches from unregistering
81  * registers remain available even if the HPD goes low since it is not powered
82  * by the HPD. In that case the CEC adapter will never be unregistered during
90 		 "CEC unregister delay in seconds, 0: no delay, >= 1000: never unregister");
111 		la_mask |= adap->log_addrs.log_addr_mask | (1 << addr);  in drm_dp_cec_adap_log_addr()
122 	unsigned int retries = min(5, attempts - 1);  in drm_dp_cec_adap_transmit()
126 				msg->msg, msg->len);  in drm_dp_cec_adap_transmit()
131 				 (msg->len - 1) | (retries << 4) |  in drm_dp_cec_adap_transmit()
143 	if (!(adap->capabilities & CEC_CAP_MONITOR_ALL))  in drm_dp_cec_adap_monitor_all_enable()
167 		   (int)sizeof(id->oui), id->oui);  in drm_dp_cec_adap_status()
169 		   (int)strnlen(id->device_id, sizeof(id->device_id)),  in drm_dp_cec_adap_status()
170 		   id->device_id);  in drm_dp_cec_adap_status()
171 	seq_printf(file, "HW Rev: %d.%d\n", id->hw_rev >> 4, id->hw_rev & 0xf);  in drm_dp_cec_adap_status()
177 		   id->sw_major_rev, id->sw_minor_rev,  in drm_dp_cec_adap_status()
178 		   id->sw_major_rev, id->sw_minor_rev);  in drm_dp_cec_adap_status()
191 	struct cec_adapter *adap = aux->cec.adap;  in drm_dp_cec_received()
214 	struct cec_adapter *adap = aux->cec.adap;  in drm_dp_cec_handle_irq()
236  * drm_dp_cec_irq() - handle CEC interrupt, if any
239  * Should be called when handling an IRQ_HPD request. If CEC-tunneling-over-AUX
247 	/* No transfer function was set, so not a DP connector */  in drm_dp_cec_irq()
248 	if (!aux->transfer)  in drm_dp_cec_irq()
251 	mutex_lock(&aux->cec.lock);  in drm_dp_cec_irq()
252 	if (!aux->cec.adap)  in drm_dp_cec_irq()
263 	mutex_unlock(&aux->cec.lock);  in drm_dp_cec_irq()
280  * Called if the HPD was low for more than drm_dp_cec_unregister_delay
288 	mutex_lock(&aux->cec.lock);  in drm_dp_cec_unregister_work()
289 	cec_unregister_adapter(aux->cec.adap);  in drm_dp_cec_unregister_work()
290 	aux->cec.adap = NULL;  in drm_dp_cec_unregister_work()
291 	mutex_unlock(&aux->cec.lock);  in drm_dp_cec_unregister_work()
295  * A new EDID is set. If there is no CEC adapter, then create one. If
302 	struct drm_connector *connector = aux->cec.connector;  in drm_dp_cec_set_edid()
309 	/* No transfer function was set, so not a DP connector */  in drm_dp_cec_set_edid()
310 	if (!aux->transfer)  in drm_dp_cec_set_edid()
323 	cancel_delayed_work_sync(&aux->cec.unregister_work);  in drm_dp_cec_set_edid()
325 	mutex_lock(&aux->cec.lock);  in drm_dp_cec_set_edid()
328 		cec_unregister_adapter(aux->cec.adap);  in drm_dp_cec_set_edid()
329 		aux->cec.adap = NULL;  in drm_dp_cec_set_edid()
338 	if (aux->cec.adap) {  in drm_dp_cec_set_edid()
339 		if (aux->cec.adap->capabilities == cec_caps &&  in drm_dp_cec_set_edid()
340 		    aux->cec.adap->available_log_addrs == num_las) {  in drm_dp_cec_set_edid()
342 			cec_s_phys_addr_from_edid(aux->cec.adap, edid);  in drm_dp_cec_set_edid()
349 		cec_unregister_adapter(aux->cec.adap);  in drm_dp_cec_set_edid()
353 	aux->cec.adap = cec_allocate_adapter(&drm_dp_cec_adap_ops,  in drm_dp_cec_set_edid()
354 					     aux, connector->name, cec_caps,  in drm_dp_cec_set_edid()
356 	if (IS_ERR(aux->cec.adap)) {  in drm_dp_cec_set_edid()
357 		aux->cec.adap = NULL;  in drm_dp_cec_set_edid()
362 	cec_s_conn_info(aux->cec.adap, &conn_info);  in drm_dp_cec_set_edid()
364 	if (cec_register_adapter(aux->cec.adap, connector->dev->dev)) {  in drm_dp_cec_set_edid()
365 		cec_delete_adapter(aux->cec.adap);  in drm_dp_cec_set_edid()
366 		aux->cec.adap = NULL;  in drm_dp_cec_set_edid()
373 		cec_s_phys_addr_from_edid(aux->cec.adap, edid);  in drm_dp_cec_set_edid()
376 	mutex_unlock(&aux->cec.lock);  in drm_dp_cec_set_edid()
381  * The EDID disappeared (likely because of the HPD going down).
385 	/* No transfer function was set, so not a DP connector */  in drm_dp_cec_unset_edid()
386 	if (!aux->transfer)  in drm_dp_cec_unset_edid()
389 	cancel_delayed_work_sync(&aux->cec.unregister_work);  in drm_dp_cec_unset_edid()
391 	mutex_lock(&aux->cec.lock);  in drm_dp_cec_unset_edid()
392 	if (!aux->cec.adap)  in drm_dp_cec_unset_edid()
395 	cec_phys_addr_invalidate(aux->cec.adap);  in drm_dp_cec_unset_edid()
406 		 * seconds. This to debounce short HPD off-and-on cycles from  in drm_dp_cec_unset_edid()
409 		schedule_delayed_work(&aux->cec.unregister_work,  in drm_dp_cec_unset_edid()
413 	mutex_unlock(&aux->cec.lock);  in drm_dp_cec_unset_edid()
418  * drm_dp_cec_register_connector() - register a new connector
430 	WARN_ON(aux->cec.adap);  in drm_dp_cec_register_connector()
431 	if (WARN_ON(!aux->transfer))  in drm_dp_cec_register_connector()
433 	aux->cec.connector = connector;  in drm_dp_cec_register_connector()
434 	INIT_DELAYED_WORK(&aux->cec.unregister_work,  in drm_dp_cec_register_connector()
440  * drm_dp_cec_unregister_connector() - unregister the CEC adapter, if any
445 	if (!aux->cec.adap)  in drm_dp_cec_unregister_connector()
447 	cancel_delayed_work_sync(&aux->cec.unregister_work);  in drm_dp_cec_unregister_connector()
448 	cec_unregister_adapter(aux->cec.adap);  in drm_dp_cec_unregister_connector()
449 	aux->cec.adap = NULL;  in drm_dp_cec_unregister_connector()