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
 25struct 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 */
 39static 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 */
 52static 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;
 87err_probed:
 88	if (aux_ep_drv->remove)
 89		aux_ep_drv->remove(aux_ep);
 90err_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 */
102static 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 */
118static 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
130static 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
138static 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}
143static DEVICE_ATTR_RO(modalias);
144
145static struct attribute *dp_aux_ep_dev_attrs[] = {
146	&dev_attr_modalias.attr,
147	NULL,
148};
149ATTRIBUTE_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 */
155static 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
164static 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
169static 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 */
191static 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 */
216void 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}
220EXPORT_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 */
254int 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
313err_did_set_populated:
314	of_node_clear_flag(np, OF_POPULATED);
315
316err_did_get_np:
317	of_node_put(np);
318
319	return ret;
320}
321EXPORT_SYMBOL_GPL(of_dp_aux_populate_bus);
322
323static 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 */
341int 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}
353EXPORT_SYMBOL_GPL(devm_of_dp_aux_populate_bus);
354
355int __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}
362EXPORT_SYMBOL_GPL(__dp_aux_dp_driver_register);
363
364void dp_aux_dp_driver_unregister(struct dp_aux_ep_driver *drv)
365{
366	driver_unregister(&drv->driver);
367}
368EXPORT_SYMBOL_GPL(dp_aux_dp_driver_unregister);
369
370static 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
381static void __exit dp_aux_bus_exit(void)
382{
383	bus_unregister(&dp_aux_bus_type);
384}
385
386subsys_initcall(dp_aux_bus_init);
387module_exit(dp_aux_bus_exit);
388
389MODULE_AUTHOR("Douglas Anderson <dianders@chromium.org>");
390MODULE_DESCRIPTION("DRM DisplayPort AUX bus");
391MODULE_LICENSE("GPL v2");