1 // SPDX-License-Identifier: GPL-2.0
3  * DisplayPort CEC-Tunneling-over-AUX support
20  * Unfortunately it turns out that we have a chicken-and-egg situation
21  * here. Quite a few active (mini-)DP-to-HDMI or USB-C-to-HDMI adapters
22  * have a converter chip that supports CEC-Tunneling-over-AUX (usually the
24  * useless. Note that MegaChips 2900-based adapters appear to have good
28  * Sadly there is no way for this driver to know this. What happens is
34  * was never supported by any OS. So there was no easy way of testing it,
35  * and no incentive to correctly wire up the CEC pin.
42  * https://hverkuil.home.xs4all.nl/cec-status.txt
48  * As far as I can see there is no mechanism defined in the DisplayPort
57  * These functions take care of supporting the CEC-Tunneling-over-AUX
58  * feature of DisplayPort-to-HDMI adapters.
62  * When the EDID is unset because the HPD went low, then the CEC DPCD registers
63  * typically can no longer be read (true for a DP-to-HDMI adapter since it is
64  * powered by the HPD). However, some displays toggle the HPD off and on for a
69  * actually unregistered. Only if the HPD does not return within that time will
76  * soon as the HPD disappears.
78  * The default is one second to prevent short HPD glitches from unregistering
82  * registers remain available even if the HPD goes low since it is not powered
83  * by the HPD. In that case the CEC adapter will never be unregistered during
91 		 "CEC unregister delay in seconds, 0: no delay, >= 1000: never unregister");
112 		la_mask |= adap->log_addrs.log_addr_mask | (1 << addr);  in drm_dp_cec_adap_log_addr()
123 	unsigned int retries = min(5, attempts - 1);  in drm_dp_cec_adap_transmit()
127 				msg->msg, msg->len);  in drm_dp_cec_adap_transmit()
132 				 (msg->len - 1) | (retries << 4) |  in drm_dp_cec_adap_transmit()
144 	if (!(adap->capabilities & CEC_CAP_MONITOR_ALL))  in drm_dp_cec_adap_monitor_all_enable()
168 		   (int)sizeof(id->oui), id->oui);  in drm_dp_cec_adap_status()
170 		   (int)strnlen(id->device_id, sizeof(id->device_id)),  in drm_dp_cec_adap_status()
171 		   id->device_id);  in drm_dp_cec_adap_status()
172 	seq_printf(file, "HW Rev: %d.%d\n", id->hw_rev >> 4, id->hw_rev & 0xf);  in drm_dp_cec_adap_status()
178 		   id->sw_major_rev, id->sw_minor_rev,  in drm_dp_cec_adap_status()
179 		   id->sw_major_rev, id->sw_minor_rev);  in drm_dp_cec_adap_status()
192 	struct cec_adapter *adap = aux->cec.adap;  in drm_dp_cec_received()
215 	struct cec_adapter *adap = aux->cec.adap;  in drm_dp_cec_handle_irq()
237  * drm_dp_cec_irq() - handle CEC interrupt, if any
240  * Should be called when handling an IRQ_HPD request. If CEC-tunneling-over-AUX
248 	/* No transfer function was set, so not a DP connector */  in drm_dp_cec_irq()
249 	if (!aux->transfer)  in drm_dp_cec_irq()
252 	mutex_lock(&aux->cec.lock);  in drm_dp_cec_irq()
253 	if (!aux->cec.adap)  in drm_dp_cec_irq()
264 	mutex_unlock(&aux->cec.lock);  in drm_dp_cec_irq()
281  * Called if the HPD was low for more than drm_dp_cec_unregister_delay
289 	mutex_lock(&aux->cec.lock);  in drm_dp_cec_unregister_work()
290 	cec_unregister_adapter(aux->cec.adap);  in drm_dp_cec_unregister_work()
291 	aux->cec.adap = NULL;  in drm_dp_cec_unregister_work()
292 	mutex_unlock(&aux->cec.lock);  in drm_dp_cec_unregister_work()
296  * A new EDID is set. If there is no CEC adapter, then create one. If
303 	struct drm_connector *connector = aux->cec.connector;  in drm_dp_cec_attach()
310 	/* No transfer function was set, so not a DP connector */  in drm_dp_cec_attach()
311 	if (!aux->transfer)  in drm_dp_cec_attach()
314 	cancel_delayed_work_sync(&aux->cec.unregister_work);  in drm_dp_cec_attach()
316 	mutex_lock(&aux->cec.lock);  in drm_dp_cec_attach()
319 		cec_unregister_adapter(aux->cec.adap);  in drm_dp_cec_attach()
320 		aux->cec.adap = NULL;  in drm_dp_cec_attach()
329 	if (aux->cec.adap) {  in drm_dp_cec_attach()
331 		if ((aux->cec.adap->capabilities & CEC_CAP_MONITOR_ALL) ==  in drm_dp_cec_attach()
333 		    aux->cec.adap->available_log_addrs == num_las) {  in drm_dp_cec_attach()
335 			cec_s_phys_addr(aux->cec.adap, source_physical_address, false);  in drm_dp_cec_attach()
342 		cec_unregister_adapter(aux->cec.adap);  in drm_dp_cec_attach()
346 	aux->cec.adap = cec_allocate_adapter(&drm_dp_cec_adap_ops,  in drm_dp_cec_attach()
347 					     aux, connector->name, cec_caps,  in drm_dp_cec_attach()
349 	if (IS_ERR(aux->cec.adap)) {  in drm_dp_cec_attach()
350 		aux->cec.adap = NULL;  in drm_dp_cec_attach()
355 	cec_s_conn_info(aux->cec.adap, &conn_info);  in drm_dp_cec_attach()
357 	if (cec_register_adapter(aux->cec.adap, connector->dev->dev)) {  in drm_dp_cec_attach()
358 		cec_delete_adapter(aux->cec.adap);  in drm_dp_cec_attach()
359 		aux->cec.adap = NULL;  in drm_dp_cec_attach()
366 		cec_s_phys_addr(aux->cec.adap, source_physical_address, false);  in drm_dp_cec_attach()
369 	mutex_unlock(&aux->cec.lock);  in drm_dp_cec_attach()
375  * connector->display_info.source_physical_address if possible.
381 	if (edid && edid->extensions)  in drm_dp_cec_set_edid()
383 					    EDID_LENGTH * (edid->extensions + 1), NULL);  in drm_dp_cec_set_edid()
390  * The EDID disappeared (likely because of the HPD going down).
394 	/* No transfer function was set, so not a DP connector */  in drm_dp_cec_unset_edid()
395 	if (!aux->transfer)  in drm_dp_cec_unset_edid()
398 	cancel_delayed_work_sync(&aux->cec.unregister_work);  in drm_dp_cec_unset_edid()
400 	mutex_lock(&aux->cec.lock);  in drm_dp_cec_unset_edid()
401 	if (!aux->cec.adap)  in drm_dp_cec_unset_edid()
404 	cec_phys_addr_invalidate(aux->cec.adap);  in drm_dp_cec_unset_edid()
415 		 * seconds. This to debounce short HPD off-and-on cycles from  in drm_dp_cec_unset_edid()
418 		schedule_delayed_work(&aux->cec.unregister_work,  in drm_dp_cec_unset_edid()
422 	mutex_unlock(&aux->cec.lock);  in drm_dp_cec_unset_edid()
427  * drm_dp_cec_register_connector() - register a new connector
439 	WARN_ON(aux->cec.adap);  in drm_dp_cec_register_connector()
440 	if (WARN_ON(!aux->transfer))  in drm_dp_cec_register_connector()
442 	aux->cec.connector = connector;  in drm_dp_cec_register_connector()
443 	INIT_DELAYED_WORK(&aux->cec.unregister_work,  in drm_dp_cec_register_connector()
449  * drm_dp_cec_unregister_connector() - unregister the CEC adapter, if any
454 	if (!aux->cec.adap)  in drm_dp_cec_unregister_connector()
456 	cancel_delayed_work_sync(&aux->cec.unregister_work);  in drm_dp_cec_unregister_connector()
457 	cec_unregister_adapter(aux->cec.adap);  in drm_dp_cec_unregister_connector()
458 	aux->cec.adap = NULL;  in drm_dp_cec_unregister_connector()