--- /dev/null
+// SPDX-License-Identifier: GPL-2.0
+/*
+ * SCMI Generic SystemPower Control driver.
+ *
+ * Copyright (C) 2020-2022 ARM Ltd.
+ */
+/*
+ * In order to handle platform originated SCMI SystemPower requests (like
+ * shutdowns or cold/warm resets) we register an SCMI Notification notifier
+ * block to react when such SCMI SystemPower events are emitted by platform.
+ *
+ * Once such a notification is received we act accordingly to perform the
+ * required system transition depending on the kind of request.
+ *
+ * Graceful requests are routed to userspace through the same API methods
+ * (orderly_poweroff/reboot()) used by ACPI when handling ACPI Shutdown bus
+ * events.
+ *
+ * Direct forceful requests are not supported since are not meant to be sent
+ * by the SCMI platform to an OSPM like Linux.
+ *
+ * Additionally, graceful request notifications can carry an optional timeout
+ * field stating the maximum amount of time allowed by the platform for
+ * completion after which they are converted to forceful ones: the assumption
+ * here is that even graceful requests can be upper-bound by a maximum final
+ * timeout strictly enforced by the platform itself which can ultimately cut
+ * the power off at will anytime; in order to avoid such extreme scenario, we
+ * track progress of graceful requests through the means of a reboot notifier
+ * converting timed-out graceful requests to forceful ones, so at least we
+ * try to perform a clean sync and shutdown/restart before the power is cut.
+ *
+ * Given the peculiar nature of SCMI SystemPower protocol, that is being in
+ * charge of triggering system wide shutdown/reboot events, there should be
+ * only one SCMI platform actively emitting SystemPower events.
+ * For this reason the SCMI core takes care to enforce the creation of one
+ * single unique device associated to the SCMI System Power protocol; no matter
+ * how many SCMI platforms are defined on the system, only one can be designated
+ * to support System Power: as a consequence this driver will never be probed
+ * more than once.
+ *
+ * For similar reasons as soon as the first valid SystemPower is received by
+ * this driver and the shutdown/reboot is started, any further notification
+ * possibly emitted by the platform will be ignored.
+ */
+
+#include <linux/math.h>
+#include <linux/module.h>
+#include <linux/mutex.h>
+#include <linux/printk.h>
+#include <linux/reboot.h>
+#include <linux/scmi_protocol.h>
+#include <linux/slab.h>
+#include <linux/time64.h>
+#include <linux/timer.h>
+#include <linux/types.h>
+#include <linux/workqueue.h>
+
+#ifndef MODULE
+#include <linux/fs.h>
+#endif
+
+enum scmi_syspower_state {
+ SCMI_SYSPOWER_IDLE,
+ SCMI_SYSPOWER_IN_PROGRESS,
+ SCMI_SYSPOWER_REBOOTING
+};
+
+/**
+ * struct scmi_syspower_conf - Common configuration
+ *
+ * @dev: A reference device
+ * @state: Current SystemPower state
+ * @state_mtx: @state related mutex
+ * @required_transition: The requested transition as decribed in the received
+ * SCMI SystemPower notification
+ * @userspace_nb: The notifier_block registered against the SCMI SystemPower
+ * notification to start the needed userspace interactions.
+ * @reboot_nb: A notifier_block optionally used to track reboot progress
+ * @forceful_work: A worker used to trigger a forceful transition once a
+ * graceful has timed out.
+ */
+struct scmi_syspower_conf {
+ struct device *dev;
+ enum scmi_syspower_state state;
+ /* Protect access to state */
+ struct mutex state_mtx;
+ enum scmi_system_events required_transition;
+
+ struct notifier_block userspace_nb;
+ struct notifier_block reboot_nb;
+
+ struct delayed_work forceful_work;
+};
+
+#define userspace_nb_to_sconf(x) \
+ container_of(x, struct scmi_syspower_conf, userspace_nb)
+
+#define reboot_nb_to_sconf(x) \
+ container_of(x, struct scmi_syspower_conf, reboot_nb)
+
+#define dwork_to_sconf(x) \
+ container_of(x, struct scmi_syspower_conf, forceful_work)
+
+/**
+ * scmi_reboot_notifier - A reboot notifier to catch an ongoing successful
+ * system transition
+ * @nb: Reference to the related notifier block
+ * @reason: The reason for the ongoing reboot
+ * @__unused: The cmd being executed on a restart request (unused)
+ *
+ * When an ongoing system transition is detected, compatible with the one
+ * requested by SCMI, cancel the delayed work.
+ *
+ * Return: NOTIFY_OK in any case
+ */
+static int scmi_reboot_notifier(struct notifier_block *nb,
+ unsigned long reason, void *__unused)
+{
+ struct scmi_syspower_conf *sc = reboot_nb_to_sconf(nb);
+
+ mutex_lock(&sc->state_mtx);
+ switch (reason) {
+ case SYS_HALT:
+ case SYS_POWER_OFF:
+ if (sc->required_transition == SCMI_SYSTEM_SHUTDOWN)
+ sc->state = SCMI_SYSPOWER_REBOOTING;
+ break;
+ case SYS_RESTART:
+ if (sc->required_transition == SCMI_SYSTEM_COLDRESET ||
+ sc->required_transition == SCMI_SYSTEM_WARMRESET)
+ sc->state = SCMI_SYSPOWER_REBOOTING;
+ break;
+ default:
+ break;
+ }
+
+ if (sc->state == SCMI_SYSPOWER_REBOOTING) {
+ dev_dbg(sc->dev, "Reboot in progress...cancel delayed work.\n");
+ cancel_delayed_work_sync(&sc->forceful_work);
+ }
+ mutex_unlock(&sc->state_mtx);
+
+ return NOTIFY_OK;
+}
+
+/**
+ * scmi_request_forceful_transition - Request forceful SystemPower transition
+ * @sc: A reference to the configuration data
+ *
+ * Initiates the required SystemPower transition without involving userspace:
+ * just trigger the action at the kernel level after issuing an emergency
+ * sync. (if possible at all)
+ */
+static inline void
+scmi_request_forceful_transition(struct scmi_syspower_conf *sc)
+{
+ dev_dbg(sc->dev, "Serving forceful request:%d\n",
+ sc->required_transition);
+
+#ifndef MODULE
+ emergency_sync();
+#endif
+ switch (sc->required_transition) {
+ case SCMI_SYSTEM_SHUTDOWN:
+ kernel_power_off();
+ break;
+ case SCMI_SYSTEM_COLDRESET:
+ case SCMI_SYSTEM_WARMRESET:
+ kernel_restart(NULL);
+ break;
+ default:
+ break;
+ }
+}
+
+static void scmi_forceful_work_func(struct work_struct *work)
+{
+ struct scmi_syspower_conf *sc;
+ struct delayed_work *dwork;
+
+ if (system_state > SYSTEM_RUNNING)
+ return;
+
+ dwork = to_delayed_work(work);
+ sc = dwork_to_sconf(dwork);
+
+ dev_dbg(sc->dev, "Graceful request timed out...forcing !\n");
+ mutex_lock(&sc->state_mtx);
+ /* avoid deadlock by unregistering reboot notifier first */
+ unregister_reboot_notifier(&sc->reboot_nb);
+ if (sc->state == SCMI_SYSPOWER_IN_PROGRESS)
+ scmi_request_forceful_transition(sc);
+ mutex_unlock(&sc->state_mtx);
+}
+
+/**
+ * scmi_request_graceful_transition - Request graceful SystemPower transition
+ * @sc: A reference to the configuration data
+ * @timeout_ms: The desired timeout to wait for the shutdown to complete before
+ * system is forcibly shutdown.
+ *
+ * Initiates the required SystemPower transition, requesting userspace
+ * co-operation: it uses the same orderly_ methods used by ACPI Shutdown event
+ * processing.
+ *
+ * Takes care also to register a reboot notifier and to schedule a delayed work
+ * in order to detect if userspace actions are taking too long and in such a
+ * case to trigger a forceful transition.
+ */
+static void scmi_request_graceful_transition(struct scmi_syspower_conf *sc,
+ unsigned int timeout_ms)
+{
+ unsigned int adj_timeout_ms = 0;
+
+ if (timeout_ms) {
+ int ret;
+
+ sc->reboot_nb.notifier_call = &scmi_reboot_notifier;
+ ret = register_reboot_notifier(&sc->reboot_nb);
+ if (!ret) {
+ /* Wait only up to 75% of the advertised timeout */
+ adj_timeout_ms = mult_frac(timeout_ms, 3, 4);
+ INIT_DELAYED_WORK(&sc->forceful_work,
+ scmi_forceful_work_func);
+ schedule_delayed_work(&sc->forceful_work,
+ msecs_to_jiffies(adj_timeout_ms));
+ } else {
+ /* Carry on best effort even without a reboot notifier */
+ dev_warn(sc->dev,
+ "Cannot register reboot notifier !\n");
+ }
+ }
+
+ dev_dbg(sc->dev,
+ "Serving graceful req:%d (timeout_ms:%u adj_timeout_ms:%u)\n",
+ sc->required_transition, timeout_ms, adj_timeout_ms);
+
+ switch (sc->required_transition) {
+ case SCMI_SYSTEM_SHUTDOWN:
+ /*
+ * When triggered early at boot-time the 'orderly' call will
+ * partially fail due to the lack of userspace itself, but
+ * the force=true argument will start anyway a successful
+ * forced shutdown.
+ */
+ orderly_poweroff(true);
+ break;
+ case SCMI_SYSTEM_COLDRESET:
+ case SCMI_SYSTEM_WARMRESET:
+ orderly_reboot();
+ break;
+ default:
+ break;
+ }
+}
+
+/**
+ * scmi_userspace_notifier - Notifier callback to act on SystemPower
+ * Notifications
+ * @nb: Reference to the related notifier block
+ * @event: The SystemPower notification event id
+ * @data: The SystemPower event report
+ *
+ * This callback is in charge of decoding the received SystemPower report
+ * and act accordingly triggering a graceful or forceful system transition.
+ *
+ * Note that once a valid SCMI SystemPower event starts being served, any
+ * other following SystemPower notification received from the same SCMI
+ * instance (handle) will be ignored.
+ *
+ * Return: NOTIFY_OK once a valid SystemPower event has been successfully
+ * processed.
+ */
+static int scmi_userspace_notifier(struct notifier_block *nb,
+ unsigned long event, void *data)
+{
+ struct scmi_system_power_state_notifier_report *er = data;
+ struct scmi_syspower_conf *sc = userspace_nb_to_sconf(nb);
+
+ if (er->system_state >= SCMI_SYSTEM_POWERUP) {
+ dev_err(sc->dev, "Ignoring unsupported system_state: 0x%X\n",
+ er->system_state);
+ return NOTIFY_DONE;
+ }
+
+ if (!SCMI_SYSPOWER_IS_REQUEST_GRACEFUL(er->flags)) {
+ dev_err(sc->dev, "Ignoring forceful notification.\n");
+ return NOTIFY_DONE;
+ }
+
+ /*
+ * Bail out if system is already shutting down or an SCMI SystemPower
+ * requested is already being served.
+ */
+ if (system_state > SYSTEM_RUNNING)
+ return NOTIFY_DONE;
+ mutex_lock(&sc->state_mtx);
+ if (sc->state != SCMI_SYSPOWER_IDLE) {
+ dev_dbg(sc->dev,
+ "Transition already in progress...ignore.\n");
+ mutex_unlock(&sc->state_mtx);
+ return NOTIFY_DONE;
+ }
+ sc->state = SCMI_SYSPOWER_IN_PROGRESS;
+ mutex_unlock(&sc->state_mtx);
+
+ sc->required_transition = er->system_state;
+
+ /* Leaving a trace in logs of who triggered the shutdown/reboot. */
+ dev_info(sc->dev, "Serving shutdown/reboot request: %d\n",
+ sc->required_transition);
+
+ scmi_request_graceful_transition(sc, er->timeout);
+
+ return NOTIFY_OK;
+}
+
+static int scmi_syspower_probe(struct scmi_device *sdev)
+{
+ int ret;
+ struct scmi_syspower_conf *sc;
+ struct scmi_handle *handle = sdev->handle;
+
+ if (!handle)
+ return -ENODEV;
+
+ ret = handle->devm_protocol_acquire(sdev, SCMI_PROTOCOL_SYSTEM);
+ if (ret)
+ return ret;
+
+ sc = devm_kzalloc(&sdev->dev, sizeof(*sc), GFP_KERNEL);
+ if (!sc)
+ return -ENOMEM;
+
+ sc->state = SCMI_SYSPOWER_IDLE;
+ mutex_init(&sc->state_mtx);
+ sc->required_transition = SCMI_SYSTEM_MAX;
+ sc->userspace_nb.notifier_call = &scmi_userspace_notifier;
+ sc->dev = &sdev->dev;
+
+ return handle->notify_ops->devm_event_notifier_register(sdev,
+ SCMI_PROTOCOL_SYSTEM,
+ SCMI_EVENT_SYSTEM_POWER_STATE_NOTIFIER,
+ NULL, &sc->userspace_nb);
+}
+
+static const struct scmi_device_id scmi_id_table[] = {
+ { SCMI_PROTOCOL_SYSTEM, "syspower" },
+ { },
+};
+MODULE_DEVICE_TABLE(scmi, scmi_id_table);
+
+static struct scmi_driver scmi_system_power_driver = {
+ .name = "scmi-system-power",
+ .probe = scmi_syspower_probe,
+ .id_table = scmi_id_table,
+};
+module_scmi_driver(scmi_system_power_driver);
+
+MODULE_AUTHOR("Cristian Marussi <cristian.marussi@arm.com>");
+MODULE_DESCRIPTION("ARM SCMI SystemPower Control driver");
+MODULE_LICENSE("GPL");
projects / platform / kernel / linux-starfive.git / commitdiff