1 // SPDX-License-Identifier: GPL-2.0
2 /*
3 * SCMI Generic SystemPower Control driver.
4 *
5 * Copyright (C) 2020-2022 ARM Ltd.
6 */
7 /*
8 * In order to handle platform originated SCMI SystemPower requests (like
9 * shutdowns or cold/warm resets) we register an SCMI Notification notifier
10 * block to react when such SCMI SystemPower events are emitted by platform.
11 *
12 * Once such a notification is received we act accordingly to perform the
13 * required system transition depending on the kind of request.
14 *
15 * Graceful requests are routed to userspace through the same API methods
16 * (orderly_poweroff/reboot()) used by ACPI when handling ACPI Shutdown bus
17 * events.
18 *
19 * Direct forceful requests are not supported since are not meant to be sent
20 * by the SCMI platform to an OSPM like Linux.
21 *
22 * Additionally, graceful request notifications can carry an optional timeout
23 * field stating the maximum amount of time allowed by the platform for
24 * completion after which they are converted to forceful ones: the assumption
25 * here is that even graceful requests can be upper-bound by a maximum final
26 * timeout strictly enforced by the platform itself which can ultimately cut
27 * the power off at will anytime; in order to avoid such extreme scenario, we
28 * track progress of graceful requests through the means of a reboot notifier
29 * converting timed-out graceful requests to forceful ones, so at least we
30 * try to perform a clean sync and shutdown/restart before the power is cut.
31 *
32 * Given the peculiar nature of SCMI SystemPower protocol, that is being in
33 * charge of triggering system wide shutdown/reboot events, there should be
34 * only one SCMI platform actively emitting SystemPower events.
35 * For this reason the SCMI core takes care to enforce the creation of one
36 * single unique device associated to the SCMI System Power protocol; no matter
37 * how many SCMI platforms are defined on the system, only one can be designated
38 * to support System Power: as a consequence this driver will never be probed
39 * more than once.
40 *
41 * For similar reasons as soon as the first valid SystemPower is received by
42 * this driver and the shutdown/reboot is started, any further notification
43 * possibly emitted by the platform will be ignored.
44 */
45
46 #include <linux/math.h>
47 #include <linux/module.h>
48 #include <linux/mutex.h>
49 #include <linux/pm.h>
50 #include <linux/printk.h>
51 #include <linux/reboot.h>
52 #include <linux/scmi_protocol.h>
53 #include <linux/slab.h>
54 #include <linux/suspend.h>
55 #include <linux/time64.h>
56 #include <linux/timer.h>
57 #include <linux/types.h>
58 #include <linux/workqueue.h>
59
60 #ifndef MODULE
61 #include <linux/fs.h>
62 #endif
63
64 enum scmi_syspower_state {
65 SCMI_SYSPOWER_IDLE,
66 SCMI_SYSPOWER_IN_PROGRESS,
67 SCMI_SYSPOWER_REBOOTING
68 };
69
70 /**
71 * struct scmi_syspower_conf - Common configuration
72 *
73 * @dev: A reference device
74 * @state: Current SystemPower state
75 * @state_mtx: @state related mutex
76 * @required_transition: The requested transition as decribed in the received
77 * SCMI SystemPower notification
78 * @userspace_nb: The notifier_block registered against the SCMI SystemPower
79 * notification to start the needed userspace interactions.
80 * @reboot_nb: A notifier_block optionally used to track reboot progress
81 * @forceful_work: A worker used to trigger a forceful transition once a
82 * graceful has timed out.
83 * @suspend_work: A worker used to trigger system suspend
84 */
85 struct scmi_syspower_conf {
86 struct device *dev;
87 enum scmi_syspower_state state;
88 /* Protect access to state */
89 struct mutex state_mtx;
90 enum scmi_system_events required_transition;
91
92 struct notifier_block userspace_nb;
93 struct notifier_block reboot_nb;
94
95 struct delayed_work forceful_work;
96 struct work_struct suspend_work;
97 };
98
99 #define userspace_nb_to_sconf(x) \
100 container_of(x, struct scmi_syspower_conf, userspace_nb)
101
102 #define reboot_nb_to_sconf(x) \
103 container_of(x, struct scmi_syspower_conf, reboot_nb)
104
105 #define dwork_to_sconf(x) \
106 container_of(x, struct scmi_syspower_conf, forceful_work)
107
108 /**
109 * scmi_reboot_notifier - A reboot notifier to catch an ongoing successful
110 * system transition
111 * @nb: Reference to the related notifier block
112 * @reason: The reason for the ongoing reboot
113 * @__unused: The cmd being executed on a restart request (unused)
114 *
115 * When an ongoing system transition is detected, compatible with the one
116 * requested by SCMI, cancel the delayed work.
117 *
118 * Return: NOTIFY_OK in any case
119 */
scmi_reboot_notifier(struct notifier_block * nb,unsigned long reason,void * __unused)120 static int scmi_reboot_notifier(struct notifier_block *nb,
121 unsigned long reason, void *__unused)
122 {
123 struct scmi_syspower_conf *sc = reboot_nb_to_sconf(nb);
124
125 mutex_lock(&sc->state_mtx);
126 switch (reason) {
127 case SYS_HALT:
128 case SYS_POWER_OFF:
129 if (sc->required_transition == SCMI_SYSTEM_SHUTDOWN)
130 sc->state = SCMI_SYSPOWER_REBOOTING;
131 break;
132 case SYS_RESTART:
133 if (sc->required_transition == SCMI_SYSTEM_COLDRESET ||
134 sc->required_transition == SCMI_SYSTEM_WARMRESET)
135 sc->state = SCMI_SYSPOWER_REBOOTING;
136 break;
137 default:
138 break;
139 }
140
141 if (sc->state == SCMI_SYSPOWER_REBOOTING) {
142 dev_dbg(sc->dev, "Reboot in progress...cancel delayed work.\n");
143 cancel_delayed_work_sync(&sc->forceful_work);
144 }
145 mutex_unlock(&sc->state_mtx);
146
147 return NOTIFY_OK;
148 }
149
150 /**
151 * scmi_request_forceful_transition - Request forceful SystemPower transition
152 * @sc: A reference to the configuration data
153 *
154 * Initiates the required SystemPower transition without involving userspace:
155 * just trigger the action at the kernel level after issuing an emergency
156 * sync. (if possible at all)
157 */
158 static inline void
scmi_request_forceful_transition(struct scmi_syspower_conf * sc)159 scmi_request_forceful_transition(struct scmi_syspower_conf *sc)
160 {
161 dev_dbg(sc->dev, "Serving forceful request:%d\n",
162 sc->required_transition);
163
164 #ifndef MODULE
165 emergency_sync();
166 #endif
167 switch (sc->required_transition) {
168 case SCMI_SYSTEM_SHUTDOWN:
169 kernel_power_off();
170 break;
171 case SCMI_SYSTEM_COLDRESET:
172 case SCMI_SYSTEM_WARMRESET:
173 kernel_restart(NULL);
174 break;
175 default:
176 break;
177 }
178 }
179
scmi_forceful_work_func(struct work_struct * work)180 static void scmi_forceful_work_func(struct work_struct *work)
181 {
182 struct scmi_syspower_conf *sc;
183 struct delayed_work *dwork;
184
185 if (system_state > SYSTEM_RUNNING)
186 return;
187
188 dwork = to_delayed_work(work);
189 sc = dwork_to_sconf(dwork);
190
191 dev_dbg(sc->dev, "Graceful request timed out...forcing !\n");
192 mutex_lock(&sc->state_mtx);
193 /* avoid deadlock by unregistering reboot notifier first */
194 unregister_reboot_notifier(&sc->reboot_nb);
195 if (sc->state == SCMI_SYSPOWER_IN_PROGRESS)
196 scmi_request_forceful_transition(sc);
197 mutex_unlock(&sc->state_mtx);
198 }
199
200 /**
201 * scmi_request_graceful_transition - Request graceful SystemPower transition
202 * @sc: A reference to the configuration data
203 * @timeout_ms: The desired timeout to wait for the shutdown to complete before
204 * system is forcibly shutdown.
205 *
206 * Initiates the required SystemPower transition, requesting userspace
207 * co-operation: it uses the same orderly_ methods used by ACPI Shutdown event
208 * processing.
209 *
210 * Takes care also to register a reboot notifier and to schedule a delayed work
211 * in order to detect if userspace actions are taking too long and in such a
212 * case to trigger a forceful transition.
213 */
scmi_request_graceful_transition(struct scmi_syspower_conf * sc,unsigned int timeout_ms)214 static void scmi_request_graceful_transition(struct scmi_syspower_conf *sc,
215 unsigned int timeout_ms)
216 {
217 unsigned int adj_timeout_ms = 0;
218
219 if (timeout_ms) {
220 int ret;
221
222 sc->reboot_nb.notifier_call = &scmi_reboot_notifier;
223 ret = register_reboot_notifier(&sc->reboot_nb);
224 if (!ret) {
225 /* Wait only up to 75% of the advertised timeout */
226 adj_timeout_ms = mult_frac(timeout_ms, 3, 4);
227 INIT_DELAYED_WORK(&sc->forceful_work,
228 scmi_forceful_work_func);
229 schedule_delayed_work(&sc->forceful_work,
230 msecs_to_jiffies(adj_timeout_ms));
231 } else {
232 /* Carry on best effort even without a reboot notifier */
233 dev_warn(sc->dev,
234 "Cannot register reboot notifier !\n");
235 }
236 }
237
238 dev_dbg(sc->dev,
239 "Serving graceful req:%d (timeout_ms:%u adj_timeout_ms:%u)\n",
240 sc->required_transition, timeout_ms, adj_timeout_ms);
241
242 switch (sc->required_transition) {
243 case SCMI_SYSTEM_SHUTDOWN:
244 /*
245 * When triggered early at boot-time the 'orderly' call will
246 * partially fail due to the lack of userspace itself, but
247 * the force=true argument will start anyway a successful
248 * forced shutdown.
249 */
250 orderly_poweroff(true);
251 break;
252 case SCMI_SYSTEM_COLDRESET:
253 case SCMI_SYSTEM_WARMRESET:
254 orderly_reboot();
255 break;
256 case SCMI_SYSTEM_SUSPEND:
257 schedule_work(&sc->suspend_work);
258 break;
259 default:
260 break;
261 }
262 }
263
264 /**
265 * scmi_userspace_notifier - Notifier callback to act on SystemPower
266 * Notifications
267 * @nb: Reference to the related notifier block
268 * @event: The SystemPower notification event id
269 * @data: The SystemPower event report
270 *
271 * This callback is in charge of decoding the received SystemPower report
272 * and act accordingly triggering a graceful or forceful system transition.
273 *
274 * Note that once a valid SCMI SystemPower event starts being served, any
275 * other following SystemPower notification received from the same SCMI
276 * instance (handle) will be ignored.
277 *
278 * Return: NOTIFY_OK once a valid SystemPower event has been successfully
279 * processed.
280 */
scmi_userspace_notifier(struct notifier_block * nb,unsigned long event,void * data)281 static int scmi_userspace_notifier(struct notifier_block *nb,
282 unsigned long event, void *data)
283 {
284 struct scmi_system_power_state_notifier_report *er = data;
285 struct scmi_syspower_conf *sc = userspace_nb_to_sconf(nb);
286
287 if (er->system_state >= SCMI_SYSTEM_MAX ||
288 er->system_state == SCMI_SYSTEM_POWERUP) {
289 dev_err(sc->dev, "Ignoring unsupported system_state: 0x%X\n",
290 er->system_state);
291 return NOTIFY_DONE;
292 }
293
294 if (!SCMI_SYSPOWER_IS_REQUEST_GRACEFUL(er->flags)) {
295 dev_err(sc->dev, "Ignoring forceful notification.\n");
296 return NOTIFY_DONE;
297 }
298
299 /*
300 * Bail out if system is already shutting down or an SCMI SystemPower
301 * requested is already being served.
302 */
303 if (system_state > SYSTEM_RUNNING)
304 return NOTIFY_DONE;
305 mutex_lock(&sc->state_mtx);
306 if (sc->state != SCMI_SYSPOWER_IDLE) {
307 dev_dbg(sc->dev,
308 "Transition already in progress...ignore.\n");
309 mutex_unlock(&sc->state_mtx);
310 return NOTIFY_DONE;
311 }
312 sc->state = SCMI_SYSPOWER_IN_PROGRESS;
313 mutex_unlock(&sc->state_mtx);
314
315 sc->required_transition = er->system_state;
316
317 /* Leaving a trace in logs of who triggered the shutdown/reboot. */
318 dev_info(sc->dev, "Serving shutdown/reboot request: %d\n",
319 sc->required_transition);
320
321 scmi_request_graceful_transition(sc, er->timeout);
322
323 return NOTIFY_OK;
324 }
325
scmi_suspend_work_func(struct work_struct * work)326 static void scmi_suspend_work_func(struct work_struct *work)
327 {
328 pm_suspend(PM_SUSPEND_MEM);
329 }
330
scmi_syspower_probe(struct scmi_device * sdev)331 static int scmi_syspower_probe(struct scmi_device *sdev)
332 {
333 int ret;
334 struct scmi_syspower_conf *sc;
335 struct scmi_handle *handle = sdev->handle;
336
337 if (!handle)
338 return -ENODEV;
339
340 ret = handle->devm_protocol_acquire(sdev, SCMI_PROTOCOL_SYSTEM);
341 if (ret)
342 return ret;
343
344 sc = devm_kzalloc(&sdev->dev, sizeof(*sc), GFP_KERNEL);
345 if (!sc)
346 return -ENOMEM;
347
348 sc->state = SCMI_SYSPOWER_IDLE;
349 mutex_init(&sc->state_mtx);
350 sc->required_transition = SCMI_SYSTEM_MAX;
351 sc->userspace_nb.notifier_call = &scmi_userspace_notifier;
352 sc->dev = &sdev->dev;
353 dev_set_drvdata(&sdev->dev, sc);
354
355 INIT_WORK(&sc->suspend_work, scmi_suspend_work_func);
356
357 return handle->notify_ops->devm_event_notifier_register(sdev,
358 SCMI_PROTOCOL_SYSTEM,
359 SCMI_EVENT_SYSTEM_POWER_STATE_NOTIFIER,
360 NULL, &sc->userspace_nb);
361 }
362
scmi_system_power_resume(struct device * dev)363 static int scmi_system_power_resume(struct device *dev)
364 {
365 struct scmi_syspower_conf *sc = dev_get_drvdata(dev);
366
367 sc->state = SCMI_SYSPOWER_IDLE;
368 return 0;
369 }
370
371 static const struct dev_pm_ops scmi_system_power_pmops = {
372 SYSTEM_SLEEP_PM_OPS(NULL, scmi_system_power_resume)
373 };
374
375 static const struct scmi_device_id scmi_id_table[] = {
376 { SCMI_PROTOCOL_SYSTEM, "syspower" },
377 { },
378 };
379 MODULE_DEVICE_TABLE(scmi, scmi_id_table);
380
381 static struct scmi_driver scmi_system_power_driver = {
382 .driver = {
383 .pm = pm_sleep_ptr(&scmi_system_power_pmops),
384 },
385 .name = "scmi-system-power",
386 .probe = scmi_syspower_probe,
387 .id_table = scmi_id_table,
388 };
389 module_scmi_driver(scmi_system_power_driver);
390
391 MODULE_AUTHOR("Cristian Marussi <cristian.marussi@arm.com>");
392 MODULE_DESCRIPTION("ARM SCMI SystemPower Control driver");
393 MODULE_LICENSE("GPL");
394