1 // SPDX-License-Identifier: GPL-2.0 2 /* 3 * Copyright 2021 Google Inc. 4 * 5 * The DP AUX bus is used for devices that are connected over a DisplayPort 6 * AUX bus. The device on the far side of the bus is referred to as an 7 * endpoint in this code. 8 * 9 * There is only one device connected to the DP AUX bus: an eDP panel. 10 * Though historically panels (even DP panels) have been modeled as simple 11 * platform devices, putting them under the DP AUX bus allows the panel driver 12 * to perform transactions on that bus. 13 */ 14 15 #include <linux/init.h> 16 #include <linux/kernel.h> 17 #include <linux/module.h> 18 #include <linux/of_device.h> 19 #include <linux/pm_domain.h> 20 #include <linux/pm_runtime.h> 21 22 #include <drm/display/drm_dp_aux_bus.h> 23 #include <drm/display/drm_dp_helper.h> 24 25 struct dp_aux_ep_device_with_data { 26 struct dp_aux_ep_device aux_ep; 27 int (*done_probing)(struct drm_dp_aux *aux); 28 }; 29 30 /** 31 * dp_aux_ep_match() - The match function for the dp_aux_bus. 32 * @dev: The device to match. 33 * @drv: The driver to try to match against. 34 * 35 * At the moment, we just match on device tree. 36 * 37 * Return: True if this driver matches this device; false otherwise. 38 */ 39 static int dp_aux_ep_match(struct device *dev, const struct device_driver *drv) 40 { 41 return !!of_match_device(drv->of_match_table, dev); 42 } 43 44 /** 45 * dp_aux_ep_probe() - The probe function for the dp_aux_bus. 46 * @dev: The device to probe. 47 * 48 * Calls through to the endpoint driver probe. 49 * 50 * Return: 0 if no error or negative error code. 51 */ 52 static int dp_aux_ep_probe(struct device *dev) 53 { 54 struct dp_aux_ep_driver *aux_ep_drv = to_dp_aux_ep_drv(dev->driver); 55 struct dp_aux_ep_device *aux_ep = to_dp_aux_ep_dev(dev); 56 struct dp_aux_ep_device_with_data *aux_ep_with_data = 57 container_of(aux_ep, struct dp_aux_ep_device_with_data, aux_ep); 58 int ret; 59 60 ret = dev_pm_domain_attach(dev, true); 61 if (ret) 62 return dev_err_probe(dev, ret, "Failed to attach to PM Domain\n"); 63 64 ret = aux_ep_drv->probe(aux_ep); 65 if (ret) 66 goto err_attached; 67 68 if (aux_ep_with_data->done_probing) { 69 ret = aux_ep_with_data->done_probing(aux_ep->aux); 70 if (ret) { 71 /* 72 * The done_probing() callback should not return 73 * -EPROBE_DEFER to us. If it does, we treat it as an 74 * error. Passing it on as-is would cause the _panel_ 75 * to defer. 76 */ 77 if (ret == -EPROBE_DEFER) { 78 dev_err(dev, 79 "DP AUX done_probing() can't defer\n"); 80 ret = -EINVAL; 81 } 82 goto err_probed; 83 } 84 } 85 86 return 0; 87 err_probed: 88 if (aux_ep_drv->remove) 89 aux_ep_drv->remove(aux_ep); 90 err_attached: 91 dev_pm_domain_detach(dev, true); 92 93 return ret; 94 } 95 96 /** 97 * dp_aux_ep_remove() - The remove function for the dp_aux_bus. 98 * @dev: The device to remove. 99 * 100 * Calls through to the endpoint driver remove. 101 */ 102 static void dp_aux_ep_remove(struct device *dev) 103 { 104 struct dp_aux_ep_driver *aux_ep_drv = to_dp_aux_ep_drv(dev->driver); 105 struct dp_aux_ep_device *aux_ep = to_dp_aux_ep_dev(dev); 106 107 if (aux_ep_drv->remove) 108 aux_ep_drv->remove(aux_ep); 109 dev_pm_domain_detach(dev, true); 110 } 111 112 /** 113 * dp_aux_ep_shutdown() - The shutdown function for the dp_aux_bus. 114 * @dev: The device to shutdown. 115 * 116 * Calls through to the endpoint driver shutdown. 117 */ 118 static void dp_aux_ep_shutdown(struct device *dev) 119 { 120 struct dp_aux_ep_driver *aux_ep_drv; 121 122 if (!dev->driver) 123 return; 124 125 aux_ep_drv = to_dp_aux_ep_drv(dev->driver); 126 if (aux_ep_drv->shutdown) 127 aux_ep_drv->shutdown(to_dp_aux_ep_dev(dev)); 128 } 129 130 static const struct bus_type dp_aux_bus_type = { 131 .name = "dp-aux", 132 .match = dp_aux_ep_match, 133 .probe = dp_aux_ep_probe, 134 .remove = dp_aux_ep_remove, 135 .shutdown = dp_aux_ep_shutdown, 136 }; 137 138 static ssize_t modalias_show(struct device *dev, 139 struct device_attribute *attr, char *buf) 140 { 141 return of_device_modalias(dev, buf, PAGE_SIZE); 142 } 143 static DEVICE_ATTR_RO(modalias); 144 145 static struct attribute *dp_aux_ep_dev_attrs[] = { 146 &dev_attr_modalias.attr, 147 NULL, 148 }; 149 ATTRIBUTE_GROUPS(dp_aux_ep_dev); 150 151 /** 152 * dp_aux_ep_dev_release() - Free memory for the dp_aux_ep device 153 * @dev: The device to free. 154 */ 155 static void dp_aux_ep_dev_release(struct device *dev) 156 { 157 struct dp_aux_ep_device *aux_ep = to_dp_aux_ep_dev(dev); 158 struct dp_aux_ep_device_with_data *aux_ep_with_data = 159 container_of(aux_ep, struct dp_aux_ep_device_with_data, aux_ep); 160 161 kfree(aux_ep_with_data); 162 } 163 164 static int dp_aux_ep_dev_modalias(const struct device *dev, struct kobj_uevent_env *env) 165 { 166 return of_device_uevent_modalias(dev, env); 167 } 168 169 static struct device_type dp_aux_device_type_type = { 170 .groups = dp_aux_ep_dev_groups, 171 .uevent = dp_aux_ep_dev_modalias, 172 .release = dp_aux_ep_dev_release, 173 }; 174 175 /** 176 * of_dp_aux_ep_destroy() - Destroy an DP AUX endpoint device 177 * @dev: The device to destroy. 178 * @data: Not used 179 * 180 * This is just used as a callback by of_dp_aux_depopulate_bus() and 181 * is called for _all_ of the child devices of the device providing the AUX bus. 182 * We'll only act on those that are of type "dp_aux_bus_type". 183 * 184 * This function is effectively an inverse of what's in 185 * of_dp_aux_populate_bus(). NOTE: since we only populate one child 186 * then it's expected that only one device will match all the "if" tests in 187 * this function and get to the device_unregister(). 188 * 189 * Return: 0 if no error or negative error code. 190 */ 191 static int of_dp_aux_ep_destroy(struct device *dev, void *data) 192 { 193 struct device_node *np = dev->of_node; 194 195 if (dev->bus != &dp_aux_bus_type) 196 return 0; 197 198 if (!of_node_check_flag(np, OF_POPULATED)) 199 return 0; 200 201 of_node_clear_flag(np, OF_POPULATED); 202 of_node_put(np); 203 204 device_unregister(dev); 205 206 return 0; 207 } 208 209 /** 210 * of_dp_aux_depopulate_bus() - Undo of_dp_aux_populate_bus 211 * @aux: The AUX channel whose device we want to depopulate 212 * 213 * This will destroy the device that was created 214 * by of_dp_aux_populate_bus(). 215 */ 216 void of_dp_aux_depopulate_bus(struct drm_dp_aux *aux) 217 { 218 device_for_each_child_reverse(aux->dev, NULL, of_dp_aux_ep_destroy); 219 } 220 EXPORT_SYMBOL_GPL(of_dp_aux_depopulate_bus); 221 222 /** 223 * of_dp_aux_populate_bus() - Populate the endpoint device on the DP AUX 224 * @aux: The AUX channel whose device we want to populate. It is required that 225 * drm_dp_aux_init() has already been called for this AUX channel. 226 * @done_probing: Callback functions to call after EP device finishes probing. 227 * Will not be called if there are no EP devices and this 228 * function will return -ENODEV. 229 * 230 * This will populate the device (expected to be an eDP panel) under the 231 * "aux-bus" node of the device providing the AUX channel (AKA aux->dev). 232 * 233 * When this function finishes, it is _possible_ (but not guaranteed) that 234 * our sub-device will have finished probing. It should be noted that if our 235 * sub-device returns -EPROBE_DEFER or is probing asynchronously for some 236 * reason that we will not return any error codes ourselves but our 237 * sub-device will _not_ have actually probed successfully yet. 238 * 239 * In many cases it's important for the caller of this function to be notified 240 * when our sub device finishes probing. Our sub device is expected to be an 241 * eDP panel and the caller is expected to be an eDP controller. The eDP 242 * controller needs to be able to get a reference to the panel when it finishes 243 * probing. For this reason the caller can pass in a function pointer that 244 * will be called when our sub-device finishes probing. 245 * 246 * If this function succeeds you should later make sure you call 247 * of_dp_aux_depopulate_bus() to undo it, or just use the devm version 248 * of this function. 249 * 250 * Return: 0 if no error or negative error code; returns -ENODEV if there are 251 * no children. The done_probing() function won't be called in that 252 * case. 253 */ 254 int of_dp_aux_populate_bus(struct drm_dp_aux *aux, 255 int (*done_probing)(struct drm_dp_aux *aux)) 256 { 257 struct device_node *bus = NULL, *np = NULL; 258 struct dp_aux_ep_device *aux_ep; 259 struct dp_aux_ep_device_with_data *aux_ep_with_data; 260 int ret; 261 262 /* drm_dp_aux_init() should have been called already; warn if not */ 263 WARN_ON_ONCE(!aux->ddc.algo); 264 265 if (!aux->dev->of_node) 266 return -ENODEV; 267 bus = of_get_child_by_name(aux->dev->of_node, "aux-bus"); 268 if (!bus) 269 return -ENODEV; 270 271 np = of_get_next_available_child(bus, NULL); 272 of_node_put(bus); 273 if (!np) 274 return -ENODEV; 275 276 if (of_node_test_and_set_flag(np, OF_POPULATED)) { 277 dev_err(aux->dev, "DP AUX EP device already populated\n"); 278 ret = -EINVAL; 279 goto err_did_get_np; 280 } 281 282 aux_ep_with_data = kzalloc(sizeof(*aux_ep_with_data), GFP_KERNEL); 283 if (!aux_ep_with_data) { 284 ret = -ENOMEM; 285 goto err_did_set_populated; 286 } 287 288 aux_ep_with_data->done_probing = done_probing; 289 290 aux_ep = &aux_ep_with_data->aux_ep; 291 aux_ep->aux = aux; 292 aux_ep->dev.parent = aux->dev; 293 aux_ep->dev.bus = &dp_aux_bus_type; 294 aux_ep->dev.type = &dp_aux_device_type_type; 295 aux_ep->dev.of_node = of_node_get(np); 296 dev_set_name(&aux_ep->dev, "aux-%s", dev_name(aux->dev)); 297 298 ret = device_register(&aux_ep->dev); 299 if (ret) { 300 dev_err(aux->dev, "Failed to create AUX EP for %pOF: %d\n", np, ret); 301 302 /* 303 * As per docs of device_register(), call this instead 304 * of kfree() directly for error cases. 305 */ 306 put_device(&aux_ep->dev); 307 308 goto err_did_set_populated; 309 } 310 311 return 0; 312 313 err_did_set_populated: 314 of_node_clear_flag(np, OF_POPULATED); 315 316 err_did_get_np: 317 of_node_put(np); 318 319 return ret; 320 } 321 EXPORT_SYMBOL_GPL(of_dp_aux_populate_bus); 322 323 static void of_dp_aux_depopulate_bus_void(void *data) 324 { 325 of_dp_aux_depopulate_bus(data); 326 } 327 328 /** 329 * devm_of_dp_aux_populate_bus() - devm wrapper for of_dp_aux_populate_bus() 330 * @aux: The AUX channel whose device we want to populate 331 * @done_probing: Callback functions to call after EP device finishes probing. 332 * Will not be called if there are no EP devices and this 333 * function will return -ENODEV. 334 * 335 * Handles freeing w/ devm on the device "aux->dev". 336 * 337 * Return: 0 if no error or negative error code; returns -ENODEV if there are 338 * no children. The done_probing() function won't be called in that 339 * case. 340 */ 341 int devm_of_dp_aux_populate_bus(struct drm_dp_aux *aux, 342 int (*done_probing)(struct drm_dp_aux *aux)) 343 { 344 int ret; 345 346 ret = of_dp_aux_populate_bus(aux, done_probing); 347 if (ret) 348 return ret; 349 350 return devm_add_action_or_reset(aux->dev, 351 of_dp_aux_depopulate_bus_void, aux); 352 } 353 EXPORT_SYMBOL_GPL(devm_of_dp_aux_populate_bus); 354 355 int __dp_aux_dp_driver_register(struct dp_aux_ep_driver *drv, struct module *owner) 356 { 357 drv->driver.owner = owner; 358 drv->driver.bus = &dp_aux_bus_type; 359 360 return driver_register(&drv->driver); 361 } 362 EXPORT_SYMBOL_GPL(__dp_aux_dp_driver_register); 363 364 void dp_aux_dp_driver_unregister(struct dp_aux_ep_driver *drv) 365 { 366 driver_unregister(&drv->driver); 367 } 368 EXPORT_SYMBOL_GPL(dp_aux_dp_driver_unregister); 369 370 static int __init dp_aux_bus_init(void) 371 { 372 int ret; 373 374 ret = bus_register(&dp_aux_bus_type); 375 if (ret) 376 return ret; 377 378 return 0; 379 } 380 381 static void __exit dp_aux_bus_exit(void) 382 { 383 bus_unregister(&dp_aux_bus_type); 384 } 385 386 subsys_initcall(dp_aux_bus_init); 387 module_exit(dp_aux_bus_exit); 388 389 MODULE_AUTHOR("Douglas Anderson <dianders@chromium.org>"); 390 MODULE_DESCRIPTION("DRM DisplayPort AUX bus"); 391 MODULE_LICENSE("GPL v2"); 392