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, 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 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 struct device_type dp_aux_device_type_type = { 165 .groups = dp_aux_ep_dev_groups, 166 .uevent = of_device_uevent_modalias, 167 .release = dp_aux_ep_dev_release, 168 }; 169 170 /** 171 * of_dp_aux_ep_destroy() - Destroy an DP AUX endpoint device 172 * @dev: The device to destroy. 173 * @data: Not used 174 * 175 * This is just used as a callback by of_dp_aux_depopulate_bus() and 176 * is called for _all_ of the child devices of the device providing the AUX bus. 177 * We'll only act on those that are of type "dp_aux_bus_type". 178 * 179 * This function is effectively an inverse of what's in 180 * of_dp_aux_populate_bus(). NOTE: since we only populate one child 181 * then it's expected that only one device will match all the "if" tests in 182 * this function and get to the device_unregister(). 183 * 184 * Return: 0 if no error or negative error code. 185 */ 186 static int of_dp_aux_ep_destroy(struct device *dev, void *data) 187 { 188 struct device_node *np = dev->of_node; 189 190 if (dev->bus != &dp_aux_bus_type) 191 return 0; 192 193 if (!of_node_check_flag(np, OF_POPULATED)) 194 return 0; 195 196 of_node_clear_flag(np, OF_POPULATED); 197 of_node_put(np); 198 199 device_unregister(dev); 200 201 return 0; 202 } 203 204 /** 205 * of_dp_aux_depopulate_bus() - Undo of_dp_aux_populate_bus 206 * @aux: The AUX channel whose device we want to depopulate 207 * 208 * This will destroy the device that was created 209 * by of_dp_aux_populate_bus(). 210 */ 211 void of_dp_aux_depopulate_bus(struct drm_dp_aux *aux) 212 { 213 device_for_each_child_reverse(aux->dev, NULL, of_dp_aux_ep_destroy); 214 } 215 EXPORT_SYMBOL_GPL(of_dp_aux_depopulate_bus); 216 217 /** 218 * of_dp_aux_populate_bus() - Populate the endpoint device on the DP AUX 219 * @aux: The AUX channel whose device we want to populate. It is required that 220 * drm_dp_aux_init() has already been called for this AUX channel. 221 * @done_probing: Callback functions to call after EP device finishes probing. 222 * Will not be called if there are no EP devices and this 223 * function will return -ENODEV. 224 * 225 * This will populate the device (expected to be an eDP panel) under the 226 * "aux-bus" node of the device providing the AUX channel (AKA aux->dev). 227 * 228 * When this function finishes, it is _possible_ (but not guaranteed) that 229 * our sub-device will have finished probing. It should be noted that if our 230 * sub-device returns -EPROBE_DEFER or is probing asynchronously for some 231 * reason that we will not return any error codes ourselves but our 232 * sub-device will _not_ have actually probed successfully yet. 233 * 234 * In many cases it's important for the caller of this function to be notified 235 * when our sub device finishes probing. Our sub device is expected to be an 236 * eDP panel and the caller is expected to be an eDP controller. The eDP 237 * controller needs to be able to get a reference to the panel when it finishes 238 * probing. For this reason the caller can pass in a function pointer that 239 * will be called when our sub-device finishes probing. 240 * 241 * If this function succeeds you should later make sure you call 242 * of_dp_aux_depopulate_bus() to undo it, or just use the devm version 243 * of this function. 244 * 245 * Return: 0 if no error or negative error code; returns -ENODEV if there are 246 * no children. The done_probing() function won't be called in that 247 * case. 248 */ 249 int of_dp_aux_populate_bus(struct drm_dp_aux *aux, 250 int (*done_probing)(struct drm_dp_aux *aux)) 251 { 252 struct device_node *bus = NULL, *np = NULL; 253 struct dp_aux_ep_device *aux_ep; 254 struct dp_aux_ep_device_with_data *aux_ep_with_data; 255 int ret; 256 257 /* drm_dp_aux_init() should have been called already; warn if not */ 258 WARN_ON_ONCE(!aux->ddc.algo); 259 260 if (!aux->dev->of_node) 261 return -ENODEV; 262 bus = of_get_child_by_name(aux->dev->of_node, "aux-bus"); 263 if (!bus) 264 return -ENODEV; 265 266 np = of_get_next_available_child(bus, NULL); 267 of_node_put(bus); 268 if (!np) 269 return -ENODEV; 270 271 if (of_node_test_and_set_flag(np, OF_POPULATED)) { 272 dev_err(aux->dev, "DP AUX EP device already populated\n"); 273 ret = -EINVAL; 274 goto err_did_get_np; 275 } 276 277 aux_ep_with_data = kzalloc(sizeof(*aux_ep_with_data), GFP_KERNEL); 278 if (!aux_ep_with_data) { 279 ret = -ENOMEM; 280 goto err_did_set_populated; 281 } 282 283 aux_ep_with_data->done_probing = done_probing; 284 285 aux_ep = &aux_ep_with_data->aux_ep; 286 aux_ep->aux = aux; 287 aux_ep->dev.parent = aux->dev; 288 aux_ep->dev.bus = &dp_aux_bus_type; 289 aux_ep->dev.type = &dp_aux_device_type_type; 290 aux_ep->dev.of_node = of_node_get(np); 291 dev_set_name(&aux_ep->dev, "aux-%s", dev_name(aux->dev)); 292 293 ret = device_register(&aux_ep->dev); 294 if (ret) { 295 dev_err(aux->dev, "Failed to create AUX EP for %pOF: %d\n", np, ret); 296 297 /* 298 * As per docs of device_register(), call this instead 299 * of kfree() directly for error cases. 300 */ 301 put_device(&aux_ep->dev); 302 303 goto err_did_set_populated; 304 } 305 306 return 0; 307 308 err_did_set_populated: 309 of_node_clear_flag(np, OF_POPULATED); 310 311 err_did_get_np: 312 of_node_put(np); 313 314 return ret; 315 } 316 EXPORT_SYMBOL_GPL(of_dp_aux_populate_bus); 317 318 static void of_dp_aux_depopulate_bus_void(void *data) 319 { 320 of_dp_aux_depopulate_bus(data); 321 } 322 323 /** 324 * devm_of_dp_aux_populate_bus() - devm wrapper for of_dp_aux_populate_bus() 325 * @aux: The AUX channel whose device we want to populate 326 * @done_probing: Callback functions to call after EP device finishes probing. 327 * Will not be called if there are no EP devices and this 328 * function will return -ENODEV. 329 * 330 * Handles freeing w/ devm on the device "aux->dev". 331 * 332 * Return: 0 if no error or negative error code; returns -ENODEV if there are 333 * no children. The done_probing() function won't be called in that 334 * case. 335 */ 336 int devm_of_dp_aux_populate_bus(struct drm_dp_aux *aux, 337 int (*done_probing)(struct drm_dp_aux *aux)) 338 { 339 int ret; 340 341 ret = of_dp_aux_populate_bus(aux, done_probing); 342 if (ret) 343 return ret; 344 345 return devm_add_action_or_reset(aux->dev, 346 of_dp_aux_depopulate_bus_void, aux); 347 } 348 EXPORT_SYMBOL_GPL(devm_of_dp_aux_populate_bus); 349 350 int __dp_aux_dp_driver_register(struct dp_aux_ep_driver *drv, struct module *owner) 351 { 352 drv->driver.owner = owner; 353 drv->driver.bus = &dp_aux_bus_type; 354 355 return driver_register(&drv->driver); 356 } 357 EXPORT_SYMBOL_GPL(__dp_aux_dp_driver_register); 358 359 void dp_aux_dp_driver_unregister(struct dp_aux_ep_driver *drv) 360 { 361 driver_unregister(&drv->driver); 362 } 363 EXPORT_SYMBOL_GPL(dp_aux_dp_driver_unregister); 364 365 static int __init dp_aux_bus_init(void) 366 { 367 int ret; 368 369 ret = bus_register(&dp_aux_bus_type); 370 if (ret) 371 return ret; 372 373 return 0; 374 } 375 376 static void __exit dp_aux_bus_exit(void) 377 { 378 bus_unregister(&dp_aux_bus_type); 379 } 380 381 subsys_initcall(dp_aux_bus_init); 382 module_exit(dp_aux_bus_exit); 383 384 MODULE_AUTHOR("Douglas Anderson <dianders@chromium.org>"); 385 MODULE_DESCRIPTION("DRM DisplayPort AUX bus"); 386 MODULE_LICENSE("GPL v2"); 387