diff options
Diffstat (limited to 'drivers/gpu/drm/drm_dp_cec.c')
| -rw-r--r-- | drivers/gpu/drm/drm_dp_cec.c | 428 |
1 files changed, 428 insertions, 0 deletions
diff --git a/drivers/gpu/drm/drm_dp_cec.c b/drivers/gpu/drm/drm_dp_cec.c new file mode 100644 index 000000000000..988513346e9c --- /dev/null +++ b/drivers/gpu/drm/drm_dp_cec.c @@ -0,0 +1,428 @@ +// SPDX-License-Identifier: GPL-2.0 +/* + * DisplayPort CEC-Tunneling-over-AUX support + * + * Copyright 2018 Cisco Systems, Inc. and/or its affiliates. All rights reserved. + */ + +#include <linux/kernel.h> +#include <linux/module.h> +#include <linux/slab.h> +#include <drm/drm_dp_helper.h> +#include <media/cec.h> + +/* + * Unfortunately it turns out that we have a chicken-and-egg situation + * here. Quite a few active (mini-)DP-to-HDMI or USB-C-to-HDMI adapters + * have a converter chip that supports CEC-Tunneling-over-AUX (usually the + * Parade PS176), but they do not wire up the CEC pin, thus making CEC + * useless. + * + * Sadly there is no way for this driver to know this. What happens is + * that a /dev/cecX device is created that is isolated and unable to see + * any of the other CEC devices. Quite literally the CEC wire is cut + * (or in this case, never connected in the first place). + * + * The reason so few adapters support this is that this tunneling protocol + * was never supported by any OS. So there was no easy way of testing it, + * and no incentive to correctly wire up the CEC pin. + * + * Hopefully by creating this driver it will be easier for vendors to + * finally fix their adapters and test the CEC functionality. + * + * I keep a list of known working adapters here: + * + * https://hverkuil.home.xs4all.nl/cec-status.txt + * + * Please mail me (hverkuil@xs4all.nl) if you find an adapter that works + * and is not yet listed there. + * + * Note that the current implementation does not support CEC over an MST hub. + * As far as I can see there is no mechanism defined in the DisplayPort + * standard to transport CEC interrupts over an MST device. It might be + * possible to do this through polling, but I have not been able to get that + * to work. + */ + +/** + * DOC: dp cec helpers + * + * These functions take care of supporting the CEC-Tunneling-over-AUX + * feature of DisplayPort-to-HDMI adapters. + */ + +/* + * When the EDID is unset because the HPD went low, then the CEC DPCD registers + * typically can no longer be read (true for a DP-to-HDMI adapter since it is + * powered by the HPD). However, some displays toggle the HPD off and on for a + * short period for one reason or another, and that would cause the CEC adapter + * to be removed and added again, even though nothing else changed. + * + * This module parameter sets a delay in seconds before the CEC adapter is + * actually unregistered. Only if the HPD does not return within that time will + * the CEC adapter be unregistered. + * + * If it is set to a value >= NEVER_UNREG_DELAY, then the CEC adapter will never + * be unregistered for as long as the connector remains registered. + * + * If it is set to 0, then the CEC adapter will be unregistered immediately as + * soon as the HPD disappears. + * + * The default is one second to prevent short HPD glitches from unregistering + * the CEC adapter. + * + * Note that for integrated HDMI branch devices that support CEC the DPCD + * registers remain available even if the HPD goes low since it is not powered + * by the HPD. In that case the CEC adapter will never be unregistered during + * the life time of the connector. At least, this is the theory since I do not + * have hardware with an integrated HDMI branch device that supports CEC. + */ +#define NEVER_UNREG_DELAY 1000 +static unsigned int drm_dp_cec_unregister_delay = 1; +module_param(drm_dp_cec_unregister_delay, uint, 0600); +MODULE_PARM_DESC(drm_dp_cec_unregister_delay, + "CEC unregister delay in seconds, 0: no delay, >= 1000: never unregister"); + +static int drm_dp_cec_adap_enable(struct cec_adapter *adap, bool enable) +{ + struct drm_dp_aux *aux = cec_get_drvdata(adap); + u32 val = enable ? DP_CEC_TUNNELING_ENABLE : 0; + ssize_t err = 0; + + err = drm_dp_dpcd_writeb(aux, DP_CEC_TUNNELING_CONTROL, val); + return (enable && err < 0) ? err : 0; +} + +static int drm_dp_cec_adap_log_addr(struct cec_adapter *adap, u8 addr) +{ + struct drm_dp_aux *aux = cec_get_drvdata(adap); + /* Bit 15 (logical address 15) should always be set */ + u16 la_mask = 1 << CEC_LOG_ADDR_BROADCAST; + u8 mask[2]; + ssize_t err; + + if (addr != CEC_LOG_ADDR_INVALID) + la_mask |= adap->log_addrs.log_addr_mask | (1 << addr); + mask[0] = la_mask & 0xff; + mask[1] = la_mask >> 8; + err = drm_dp_dpcd_write(aux, DP_CEC_LOGICAL_ADDRESS_MASK, mask, 2); + return (addr != CEC_LOG_ADDR_INVALID && err < 0) ? err : 0; +} + +static int drm_dp_cec_adap_transmit(struct cec_adapter *adap, u8 attempts, + u32 signal_free_time, struct cec_msg *msg) +{ + struct drm_dp_aux *aux = cec_get_drvdata(adap); + unsigned int retries = min(5, attempts - 1); + ssize_t err; + + err = drm_dp_dpcd_write(aux, DP_CEC_TX_MESSAGE_BUFFER, + msg->msg, msg->len); + if (err < 0) + return err; + + err = drm_dp_dpcd_writeb(aux, DP_CEC_TX_MESSAGE_INFO, + (msg->len - 1) | (retries << 4) | + DP_CEC_TX_MESSAGE_SEND); + return err < 0 ? err : 0; +} + +static int drm_dp_cec_adap_monitor_all_enable(struct cec_adapter *adap, + bool enable) +{ + struct drm_dp_aux *aux = cec_get_drvdata(adap); + ssize_t err; + u8 val; + + if (!(adap->capabilities & CEC_CAP_MONITOR_ALL)) + return 0; + + err = drm_dp_dpcd_readb(aux, DP_CEC_TUNNELING_CONTROL, &val); + if (err >= 0) { + if (enable) + val |= DP_CEC_SNOOPING_ENABLE; + else + val &= ~DP_CEC_SNOOPING_ENABLE; + err = drm_dp_dpcd_writeb(aux, DP_CEC_TUNNELING_CONTROL, val); + } + return (enable && err < 0) ? err : 0; +} + +static void drm_dp_cec_adap_status(struct cec_adapter *adap, + struct seq_file *file) +{ + struct drm_dp_aux *aux = cec_get_drvdata(adap); + struct drm_dp_desc desc; + struct drm_dp_dpcd_ident *id = &desc.ident; + + if (drm_dp_read_desc(aux, &desc, true)) + return; + seq_printf(file, "OUI: %*phD\n", + (int)sizeof(id->oui), id->oui); + seq_printf(file, "ID: %*pE\n", + (int)strnlen(id->device_id, sizeof(id->device_id)), + id->device_id); + seq_printf(file, "HW Rev: %d.%d\n", id->hw_rev >> 4, id->hw_rev & 0xf); + /* + * Show this both in decimal and hex: at least one vendor + * always reports this in hex. + */ + seq_printf(file, "FW/SW Rev: %d.%d (0x%02x.0x%02x)\n", + id->sw_major_rev, id->sw_minor_rev, + id->sw_major_rev, id->sw_minor_rev); +} + +static const struct cec_adap_ops drm_dp_cec_adap_ops = { + .adap_enable = drm_dp_cec_adap_enable, + .adap_log_addr = drm_dp_cec_adap_log_addr, + .adap_transmit = drm_dp_cec_adap_transmit, + .adap_monitor_all_enable = drm_dp_cec_adap_monitor_all_enable, + .adap_status = drm_dp_cec_adap_status, +}; + +static int drm_dp_cec_received(struct drm_dp_aux *aux) +{ + struct cec_adapter *adap = aux->cec.adap; + struct cec_msg msg; + u8 rx_msg_info; + ssize_t err; + + err = drm_dp_dpcd_readb(aux, DP_CEC_RX_MESSAGE_INFO, &rx_msg_info); + if (err < 0) + return err; + + if (!(rx_msg_info & DP_CEC_RX_MESSAGE_ENDED)) + return 0; + + msg.len = (rx_msg_info & DP_CEC_RX_MESSAGE_LEN_MASK) + 1; + err = drm_dp_dpcd_read(aux, DP_CEC_RX_MESSAGE_BUFFER, msg.msg, msg.len); + if (err < 0) + return err; + + cec_received_msg(adap, &msg); + return 0; +} + +static void drm_dp_cec_handle_irq(struct drm_dp_aux *aux) +{ + struct cec_adapter *adap = aux->cec.adap; + u8 flags; + + if (drm_dp_dpcd_readb(aux, DP_CEC_TUNNELING_IRQ_FLAGS, &flags) < 0) + return; + + if (flags & DP_CEC_RX_MESSAGE_INFO_VALID) + drm_dp_cec_received(aux); + + if (flags & DP_CEC_TX_MESSAGE_SENT) + cec_transmit_attempt_done(adap, CEC_TX_STATUS_OK); + else if (flags & DP_CEC_TX_LINE_ERROR) + cec_transmit_attempt_done(adap, CEC_TX_STATUS_ERROR | + CEC_TX_STATUS_MAX_RETRIES); + else if (flags & + (DP_CEC_TX_ADDRESS_NACK_ERROR | DP_CEC_TX_DATA_NACK_ERROR)) + cec_transmit_attempt_done(adap, CEC_TX_STATUS_NACK | + CEC_TX_STATUS_MAX_RETRIES); + drm_dp_dpcd_writeb(aux, DP_CEC_TUNNELING_IRQ_FLAGS, flags); +} + +/** + * drm_dp_cec_irq() - handle CEC interrupt, if any + * @aux: DisplayPort AUX channel + * + * Should be called when handling an IRQ_HPD request. If CEC-tunneling-over-AUX + * is present, then it will check for a CEC_IRQ and handle it accordingly. + */ +void drm_dp_cec_irq(struct drm_dp_aux *aux) +{ + u8 cec_irq; + int ret; + + mutex_lock(&aux->cec.lock); + if (!aux->cec.adap) + goto unlock; + + ret = drm_dp_dpcd_readb(aux, DP_DEVICE_SERVICE_IRQ_VECTOR_ESI1, + &cec_irq); + if (ret < 0 || !(cec_irq & DP_CEC_IRQ)) + goto unlock; + + drm_dp_cec_handle_irq(aux); + drm_dp_dpcd_writeb(aux, DP_DEVICE_SERVICE_IRQ_VECTOR_ESI1, DP_CEC_IRQ); +unlock: + mutex_unlock(&aux->cec.lock); +} +EXPORT_SYMBOL(drm_dp_cec_irq); + +static bool drm_dp_cec_cap(struct drm_dp_aux *aux, u8 *cec_cap) +{ + u8 cap = 0; + + if (drm_dp_dpcd_readb(aux, DP_CEC_TUNNELING_CAPABILITY, &cap) != 1 || + !(cap & DP_CEC_TUNNELING_CAPABLE)) + return false; + if (cec_cap) + *cec_cap = cap; + return true; +} + +/* + * Called if the HPD was low for more than drm_dp_cec_unregister_delay + * seconds. This unregisters the CEC adapter. + */ +static void drm_dp_cec_unregister_work(struct work_struct *work) +{ + struct drm_dp_aux *aux = container_of(work, struct drm_dp_aux, + cec.unregister_work.work); + + mutex_lock(&aux->cec.lock); + cec_unregister_adapter(aux->cec.adap); + aux->cec.adap = NULL; + mutex_unlock(&aux->cec.lock); +} + +/* + * A new EDID is set. If there is no CEC adapter, then create one. If + * there was a CEC adapter, then check if the CEC adapter properties + * were unchanged and just update the CEC physical address. Otherwise + * unregister the old CEC adapter and create a new one. + */ +void drm_dp_cec_set_edid(struct drm_dp_aux *aux, const struct edid *edid) +{ + u32 cec_caps = CEC_CAP_DEFAULTS | CEC_CAP_NEEDS_HPD; + unsigned int num_las = 1; + u8 cap; + +#ifndef CONFIG_MEDIA_CEC_RC + /* + * CEC_CAP_RC is part of CEC_CAP_DEFAULTS, but it is stripped by + * cec_allocate_adapter() if CONFIG_MEDIA_CEC_RC is undefined. + * + * Do this here as well to ensure the tests against cec_caps are + * correct. + */ + cec_caps &= ~CEC_CAP_RC; +#endif + cancel_delayed_work_sync(&aux->cec.unregister_work); + + mutex_lock(&aux->cec.lock); + if (!drm_dp_cec_cap(aux, &cap)) { + /* CEC is not supported, unregister any existing adapter */ + cec_unregister_adapter(aux->cec.adap); + aux->cec.adap = NULL; + goto unlock; + } + + if (cap & DP_CEC_SNOOPING_CAPABLE) + cec_caps |= CEC_CAP_MONITOR_ALL; + if (cap & DP_CEC_MULTIPLE_LA_CAPABLE) + num_las = CEC_MAX_LOG_ADDRS; + + if (aux->cec.adap) { + if (aux->cec.adap->capabilities == cec_caps && + aux->cec.adap->available_log_addrs == num_las) { + /* Unchanged, so just set the phys addr */ + cec_s_phys_addr_from_edid(aux->cec.adap, edid); + goto unlock; + } + /* + * The capabilities changed, so unregister the old + * adapter first. + */ + cec_unregister_adapter(aux->cec.adap); + } + + /* Create a new adapter */ + aux->cec.adap = cec_allocate_adapter(&drm_dp_cec_adap_ops, + aux, aux->cec.name, cec_caps, + num_las); + if (IS_ERR(aux->cec.adap)) { + aux->cec.adap = NULL; + goto unlock; + } + if (cec_register_adapter(aux->cec.adap, aux->cec.parent)) { + cec_delete_adapter(aux->cec.adap); + aux->cec.adap = NULL; + } else { + /* + * Update the phys addr for the new CEC adapter. When called + * from drm_dp_cec_register_connector() edid == NULL, so in + * that case the phys addr is just invalidated. + */ + cec_s_phys_addr_from_edid(aux->cec.adap, edid); + } +unlock: + mutex_unlock(&aux->cec.lock); +} +EXPORT_SYMBOL(drm_dp_cec_set_edid); + +/* + * The EDID disappeared (likely because of the HPD going down). + */ +void drm_dp_cec_unset_edid(struct drm_dp_aux *aux) +{ + cancel_delayed_work_sync(&aux->cec.unregister_work); + + mutex_lock(&aux->cec.lock); + if (!aux->cec.adap) + goto unlock; + + cec_phys_addr_invalidate(aux->cec.adap); + /* + * We're done if we want to keep the CEC device + * (drm_dp_cec_unregister_delay is >= NEVER_UNREG_DELAY) or if the + * DPCD still indicates the CEC capability (expected for an integrated + * HDMI branch device). + */ + if (drm_dp_cec_unregister_delay < NEVER_UNREG_DELAY && + !drm_dp_cec_cap(aux, NULL)) { + /* + * Unregister the CEC adapter after drm_dp_cec_unregister_delay + * seconds. This to debounce short HPD off-and-on cycles from + * displays. + */ + schedule_delayed_work(&aux->cec.unregister_work, + drm_dp_cec_unregister_delay * HZ); + } +unlock: + mutex_unlock(&aux->cec.lock); +} +EXPORT_SYMBOL(drm_dp_cec_unset_edid); + +/** + * drm_dp_cec_register_connector() - register a new connector + * @aux: DisplayPort AUX channel + * @name: name of the CEC device + * @parent: parent device + * + * A new connector was registered with associated CEC adapter name and + * CEC adapter parent device. After registering the name and parent + * drm_dp_cec_set_edid() is called to check if the connector supports + * CEC and to register a CEC adapter if that is the case. + */ +void drm_dp_cec_register_connector(struct drm_dp_aux *aux, const char *name, + struct device *parent) +{ + WARN_ON(aux->cec.adap); + aux->cec.name = name; + aux->cec.parent = parent; + INIT_DELAYED_WORK(&aux->cec.unregister_work, + drm_dp_cec_unregister_work); + + drm_dp_cec_set_edid(aux, NULL); +} +EXPORT_SYMBOL(drm_dp_cec_register_connector); + +/** + * drm_dp_cec_unregister_connector() - unregister the CEC adapter, if any + * @aux: DisplayPort AUX channel + */ +void drm_dp_cec_unregister_connector(struct drm_dp_aux *aux) +{ + if (!aux->cec.adap) + return; + cancel_delayed_work_sync(&aux->cec.unregister_work); + cec_unregister_adapter(aux->cec.adap); + aux->cec.adap = NULL; +} +EXPORT_SYMBOL(drm_dp_cec_unregister_connector); |