1 // SPDX-License-Identifier: GPL-2.0 2 /* 3 * DisplayPort CEC-Tunneling-over-AUX support 4 * 5 * Copyright 2018 Cisco Systems, Inc. and/or its affiliates. All rights reserved. 6 */ 7 8 #include <linux/kernel.h> 9 #include <linux/module.h> 10 #include <linux/slab.h> 11 12 #include <media/cec.h> 13 14 #include <drm/display/drm_dp_helper.h> 15 #include <drm/drm_connector.h> 16 #include <drm/drm_device.h> 17 18 /* 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 22 * Parade PS176), but they do not wire up the CEC pin, thus making CEC 23 * useless. Note that MegaChips 2900-based adapters appear to have good 24 * support for CEC tunneling. Those adapters that I have tested using 25 * this chipset all have the CEC line connected. 26 * 27 * Sadly there is no way for this driver to know this. What happens is 28 * that a /dev/cecX device is created that is isolated and unable to see 29 * any of the other CEC devices. Quite literally the CEC wire is cut 30 * (or in this case, never connected in the first place). 31 * 32 * The reason so few adapters support this is that this tunneling protocol 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. 35 * 36 * Hopefully by creating this driver it will be easier for vendors to 37 * finally fix their adapters and test the CEC functionality. 38 * 39 * I keep a list of known working adapters here: 40 * 41 * https://hverkuil.home.xs4all.nl/cec-status.txt 42 * 43 * Please mail me (hverkuil@xs4all.nl) if you find an adapter that works 44 * and is not yet listed there. 45 * 46 * Note that the current implementation does not support CEC over an MST hub. 47 * As far as I can see there is no mechanism defined in the DisplayPort 48 * standard to transport CEC interrupts over an MST device. It might be 49 * possible to do this through polling, but I have not been able to get that 50 * to work. 51 */ 52 53 /** 54 * DOC: dp cec helpers 55 * 56 * These functions take care of supporting the CEC-Tunneling-over-AUX 57 * feature of DisplayPort-to-HDMI adapters. 58 */ 59 60 /* 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 64 * short period for one reason or another, and that would cause the CEC adapter 65 * to be removed and added again, even though nothing else changed. 66 * 67 * This module parameter sets a delay in seconds before the CEC adapter is 68 * actually unregistered. Only if the HPD does not return within that time will 69 * the CEC adapter be unregistered. 70 * 71 * If it is set to a value >= NEVER_UNREG_DELAY, then the CEC adapter will never 72 * be unregistered for as long as the connector remains registered. 73 * 74 * If it is set to 0, then the CEC adapter will be unregistered immediately as 75 * soon as the HPD disappears. 76 * 77 * The default is one second to prevent short HPD glitches from unregistering 78 * the CEC adapter. 79 * 80 * Note that for integrated HDMI branch devices that support CEC the DPCD 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 83 * the life time of the connector. At least, this is the theory since I do not 84 * have hardware with an integrated HDMI branch device that supports CEC. 85 */ 86 #define NEVER_UNREG_DELAY 1000 87 static unsigned int drm_dp_cec_unregister_delay = 1; 88 module_param(drm_dp_cec_unregister_delay, uint, 0600); 89 MODULE_PARM_DESC(drm_dp_cec_unregister_delay, 90 "CEC unregister delay in seconds, 0: no delay, >= 1000: never unregister"); 91 92 static int drm_dp_cec_adap_enable(struct cec_adapter *adap, bool enable) 93 { 94 struct drm_dp_aux *aux = cec_get_drvdata(adap); 95 u32 val = enable ? DP_CEC_TUNNELING_ENABLE : 0; 96 ssize_t err = 0; 97 98 err = drm_dp_dpcd_writeb(aux, DP_CEC_TUNNELING_CONTROL, val); 99 return (enable && err < 0) ? err : 0; 100 } 101 102 static int drm_dp_cec_adap_log_addr(struct cec_adapter *adap, u8 addr) 103 { 104 struct drm_dp_aux *aux = cec_get_drvdata(adap); 105 /* Bit 15 (logical address 15) should always be set */ 106 u16 la_mask = 1 << CEC_LOG_ADDR_BROADCAST; 107 u8 mask[2]; 108 ssize_t err; 109 110 if (addr != CEC_LOG_ADDR_INVALID) 111 la_mask |= adap->log_addrs.log_addr_mask | (1 << addr); 112 mask[0] = la_mask & 0xff; 113 mask[1] = la_mask >> 8; 114 err = drm_dp_dpcd_write(aux, DP_CEC_LOGICAL_ADDRESS_MASK, mask, 2); 115 return (addr != CEC_LOG_ADDR_INVALID && err < 0) ? err : 0; 116 } 117 118 static int drm_dp_cec_adap_transmit(struct cec_adapter *adap, u8 attempts, 119 u32 signal_free_time, struct cec_msg *msg) 120 { 121 struct drm_dp_aux *aux = cec_get_drvdata(adap); 122 unsigned int retries = min(5, attempts - 1); 123 ssize_t err; 124 125 err = drm_dp_dpcd_write(aux, DP_CEC_TX_MESSAGE_BUFFER, 126 msg->msg, msg->len); 127 if (err < 0) 128 return err; 129 130 err = drm_dp_dpcd_writeb(aux, DP_CEC_TX_MESSAGE_INFO, 131 (msg->len - 1) | (retries << 4) | 132 DP_CEC_TX_MESSAGE_SEND); 133 return err < 0 ? err : 0; 134 } 135 136 static int drm_dp_cec_adap_monitor_all_enable(struct cec_adapter *adap, 137 bool enable) 138 { 139 struct drm_dp_aux *aux = cec_get_drvdata(adap); 140 ssize_t err; 141 u8 val; 142 143 if (!(adap->capabilities & CEC_CAP_MONITOR_ALL)) 144 return 0; 145 146 err = drm_dp_dpcd_readb(aux, DP_CEC_TUNNELING_CONTROL, &val); 147 if (err >= 0) { 148 if (enable) 149 val |= DP_CEC_SNOOPING_ENABLE; 150 else 151 val &= ~DP_CEC_SNOOPING_ENABLE; 152 err = drm_dp_dpcd_writeb(aux, DP_CEC_TUNNELING_CONTROL, val); 153 } 154 return (enable && err < 0) ? err : 0; 155 } 156 157 static void drm_dp_cec_adap_status(struct cec_adapter *adap, 158 struct seq_file *file) 159 { 160 struct drm_dp_aux *aux = cec_get_drvdata(adap); 161 struct drm_dp_desc desc; 162 struct drm_dp_dpcd_ident *id = &desc.ident; 163 164 if (drm_dp_read_desc(aux, &desc, true)) 165 return; 166 seq_printf(file, "OUI: %*phD\n", 167 (int)sizeof(id->oui), id->oui); 168 seq_printf(file, "ID: %*pE\n", 169 (int)strnlen(id->device_id, sizeof(id->device_id)), 170 id->device_id); 171 seq_printf(file, "HW Rev: %d.%d\n", id->hw_rev >> 4, id->hw_rev & 0xf); 172 /* 173 * Show this both in decimal and hex: at least one vendor 174 * always reports this in hex. 175 */ 176 seq_printf(file, "FW/SW Rev: %d.%d (0x%02x.0x%02x)\n", 177 id->sw_major_rev, id->sw_minor_rev, 178 id->sw_major_rev, id->sw_minor_rev); 179 } 180 181 static const struct cec_adap_ops drm_dp_cec_adap_ops = { 182 .adap_enable = drm_dp_cec_adap_enable, 183 .adap_log_addr = drm_dp_cec_adap_log_addr, 184 .adap_transmit = drm_dp_cec_adap_transmit, 185 .adap_monitor_all_enable = drm_dp_cec_adap_monitor_all_enable, 186 .adap_status = drm_dp_cec_adap_status, 187 }; 188 189 static int drm_dp_cec_received(struct drm_dp_aux *aux) 190 { 191 struct cec_adapter *adap = aux->cec.adap; 192 struct cec_msg msg; 193 u8 rx_msg_info; 194 ssize_t err; 195 196 err = drm_dp_dpcd_readb(aux, DP_CEC_RX_MESSAGE_INFO, &rx_msg_info); 197 if (err < 0) 198 return err; 199 200 if (!(rx_msg_info & DP_CEC_RX_MESSAGE_ENDED)) 201 return 0; 202 203 msg.len = (rx_msg_info & DP_CEC_RX_MESSAGE_LEN_MASK) + 1; 204 err = drm_dp_dpcd_read(aux, DP_CEC_RX_MESSAGE_BUFFER, msg.msg, msg.len); 205 if (err < 0) 206 return err; 207 208 cec_received_msg(adap, &msg); 209 return 0; 210 } 211 212 static void drm_dp_cec_handle_irq(struct drm_dp_aux *aux) 213 { 214 struct cec_adapter *adap = aux->cec.adap; 215 u8 flags; 216 217 if (drm_dp_dpcd_readb(aux, DP_CEC_TUNNELING_IRQ_FLAGS, &flags) < 0) 218 return; 219 220 if (flags & DP_CEC_RX_MESSAGE_INFO_VALID) 221 drm_dp_cec_received(aux); 222 223 if (flags & DP_CEC_TX_MESSAGE_SENT) 224 cec_transmit_attempt_done(adap, CEC_TX_STATUS_OK); 225 else if (flags & DP_CEC_TX_LINE_ERROR) 226 cec_transmit_attempt_done(adap, CEC_TX_STATUS_ERROR | 227 CEC_TX_STATUS_MAX_RETRIES); 228 else if (flags & 229 (DP_CEC_TX_ADDRESS_NACK_ERROR | DP_CEC_TX_DATA_NACK_ERROR)) 230 cec_transmit_attempt_done(adap, CEC_TX_STATUS_NACK | 231 CEC_TX_STATUS_MAX_RETRIES); 232 drm_dp_dpcd_writeb(aux, DP_CEC_TUNNELING_IRQ_FLAGS, flags); 233 } 234 235 /** 236 * drm_dp_cec_irq() - handle CEC interrupt, if any 237 * @aux: DisplayPort AUX channel 238 * 239 * Should be called when handling an IRQ_HPD request. If CEC-tunneling-over-AUX 240 * is present, then it will check for a CEC_IRQ and handle it accordingly. 241 */ 242 void drm_dp_cec_irq(struct drm_dp_aux *aux) 243 { 244 u8 cec_irq; 245 int ret; 246 247 /* No transfer function was set, so not a DP connector */ 248 if (!aux->transfer) 249 return; 250 251 mutex_lock(&aux->cec.lock); 252 if (!aux->cec.adap) 253 goto unlock; 254 255 ret = drm_dp_dpcd_readb(aux, DP_DEVICE_SERVICE_IRQ_VECTOR_ESI1, 256 &cec_irq); 257 if (ret < 0 || !(cec_irq & DP_CEC_IRQ)) 258 goto unlock; 259 260 drm_dp_cec_handle_irq(aux); 261 drm_dp_dpcd_writeb(aux, DP_DEVICE_SERVICE_IRQ_VECTOR_ESI1, DP_CEC_IRQ); 262 unlock: 263 mutex_unlock(&aux->cec.lock); 264 } 265 EXPORT_SYMBOL(drm_dp_cec_irq); 266 267 static bool drm_dp_cec_cap(struct drm_dp_aux *aux, u8 *cec_cap) 268 { 269 u8 cap = 0; 270 271 if (drm_dp_dpcd_readb(aux, DP_CEC_TUNNELING_CAPABILITY, &cap) != 1 || 272 !(cap & DP_CEC_TUNNELING_CAPABLE)) 273 return false; 274 if (cec_cap) 275 *cec_cap = cap; 276 return true; 277 } 278 279 /* 280 * Called if the HPD was low for more than drm_dp_cec_unregister_delay 281 * seconds. This unregisters the CEC adapter. 282 */ 283 static void drm_dp_cec_unregister_work(struct work_struct *work) 284 { 285 struct drm_dp_aux *aux = container_of(work, struct drm_dp_aux, 286 cec.unregister_work.work); 287 288 mutex_lock(&aux->cec.lock); 289 cec_unregister_adapter(aux->cec.adap); 290 aux->cec.adap = NULL; 291 mutex_unlock(&aux->cec.lock); 292 } 293 294 /* 295 * A new EDID is set. If there is no CEC adapter, then create one. If 296 * there was a CEC adapter, then check if the CEC adapter properties 297 * were unchanged and just update the CEC physical address. Otherwise 298 * unregister the old CEC adapter and create a new one. 299 */ 300 void drm_dp_cec_set_edid(struct drm_dp_aux *aux, const struct edid *edid) 301 { 302 struct drm_connector *connector = aux->cec.connector; 303 u32 cec_caps = CEC_CAP_DEFAULTS | CEC_CAP_NEEDS_HPD | 304 CEC_CAP_CONNECTOR_INFO; 305 struct cec_connector_info conn_info; 306 unsigned int num_las = 1; 307 u8 cap; 308 309 /* No transfer function was set, so not a DP connector */ 310 if (!aux->transfer) 311 return; 312 313 #ifndef CONFIG_MEDIA_CEC_RC 314 /* 315 * CEC_CAP_RC is part of CEC_CAP_DEFAULTS, but it is stripped by 316 * cec_allocate_adapter() if CONFIG_MEDIA_CEC_RC is undefined. 317 * 318 * Do this here as well to ensure the tests against cec_caps are 319 * correct. 320 */ 321 cec_caps &= ~CEC_CAP_RC; 322 #endif 323 cancel_delayed_work_sync(&aux->cec.unregister_work); 324 325 mutex_lock(&aux->cec.lock); 326 if (!drm_dp_cec_cap(aux, &cap)) { 327 /* CEC is not supported, unregister any existing adapter */ 328 cec_unregister_adapter(aux->cec.adap); 329 aux->cec.adap = NULL; 330 goto unlock; 331 } 332 333 if (cap & DP_CEC_SNOOPING_CAPABLE) 334 cec_caps |= CEC_CAP_MONITOR_ALL; 335 if (cap & DP_CEC_MULTIPLE_LA_CAPABLE) 336 num_las = CEC_MAX_LOG_ADDRS; 337 338 if (aux->cec.adap) { 339 if (aux->cec.adap->capabilities == cec_caps && 340 aux->cec.adap->available_log_addrs == num_las) { 341 /* Unchanged, so just set the phys addr */ 342 cec_s_phys_addr_from_edid(aux->cec.adap, edid); 343 goto unlock; 344 } 345 /* 346 * The capabilities changed, so unregister the old 347 * adapter first. 348 */ 349 cec_unregister_adapter(aux->cec.adap); 350 } 351 352 /* Create a new adapter */ 353 aux->cec.adap = cec_allocate_adapter(&drm_dp_cec_adap_ops, 354 aux, connector->name, cec_caps, 355 num_las); 356 if (IS_ERR(aux->cec.adap)) { 357 aux->cec.adap = NULL; 358 goto unlock; 359 } 360 361 cec_fill_conn_info_from_drm(&conn_info, connector); 362 cec_s_conn_info(aux->cec.adap, &conn_info); 363 364 if (cec_register_adapter(aux->cec.adap, connector->dev->dev)) { 365 cec_delete_adapter(aux->cec.adap); 366 aux->cec.adap = NULL; 367 } else { 368 /* 369 * Update the phys addr for the new CEC adapter. When called 370 * from drm_dp_cec_register_connector() edid == NULL, so in 371 * that case the phys addr is just invalidated. 372 */ 373 cec_s_phys_addr_from_edid(aux->cec.adap, edid); 374 } 375 unlock: 376 mutex_unlock(&aux->cec.lock); 377 } 378 EXPORT_SYMBOL(drm_dp_cec_set_edid); 379 380 /* 381 * The EDID disappeared (likely because of the HPD going down). 382 */ 383 void drm_dp_cec_unset_edid(struct drm_dp_aux *aux) 384 { 385 /* No transfer function was set, so not a DP connector */ 386 if (!aux->transfer) 387 return; 388 389 cancel_delayed_work_sync(&aux->cec.unregister_work); 390 391 mutex_lock(&aux->cec.lock); 392 if (!aux->cec.adap) 393 goto unlock; 394 395 cec_phys_addr_invalidate(aux->cec.adap); 396 /* 397 * We're done if we want to keep the CEC device 398 * (drm_dp_cec_unregister_delay is >= NEVER_UNREG_DELAY) or if the 399 * DPCD still indicates the CEC capability (expected for an integrated 400 * HDMI branch device). 401 */ 402 if (drm_dp_cec_unregister_delay < NEVER_UNREG_DELAY && 403 !drm_dp_cec_cap(aux, NULL)) { 404 /* 405 * Unregister the CEC adapter after drm_dp_cec_unregister_delay 406 * seconds. This to debounce short HPD off-and-on cycles from 407 * displays. 408 */ 409 schedule_delayed_work(&aux->cec.unregister_work, 410 drm_dp_cec_unregister_delay * HZ); 411 } 412 unlock: 413 mutex_unlock(&aux->cec.lock); 414 } 415 EXPORT_SYMBOL(drm_dp_cec_unset_edid); 416 417 /** 418 * drm_dp_cec_register_connector() - register a new connector 419 * @aux: DisplayPort AUX channel 420 * @connector: drm connector 421 * 422 * A new connector was registered with associated CEC adapter name and 423 * CEC adapter parent device. After registering the name and parent 424 * drm_dp_cec_set_edid() is called to check if the connector supports 425 * CEC and to register a CEC adapter if that is the case. 426 */ 427 void drm_dp_cec_register_connector(struct drm_dp_aux *aux, 428 struct drm_connector *connector) 429 { 430 WARN_ON(aux->cec.adap); 431 if (WARN_ON(!aux->transfer)) 432 return; 433 aux->cec.connector = connector; 434 INIT_DELAYED_WORK(&aux->cec.unregister_work, 435 drm_dp_cec_unregister_work); 436 } 437 EXPORT_SYMBOL(drm_dp_cec_register_connector); 438 439 /** 440 * drm_dp_cec_unregister_connector() - unregister the CEC adapter, if any 441 * @aux: DisplayPort AUX channel 442 */ 443 void drm_dp_cec_unregister_connector(struct drm_dp_aux *aux) 444 { 445 if (!aux->cec.adap) 446 return; 447 cancel_delayed_work_sync(&aux->cec.unregister_work); 448 cec_unregister_adapter(aux->cec.adap); 449 aux->cec.adap = NULL; 450 } 451 EXPORT_SYMBOL(drm_dp_cec_unregister_connector); 452