diff options
Diffstat (limited to 'drivers/firmware/arm_scmi/scmi_power_control.c')
| -rw-r--r-- | drivers/firmware/arm_scmi/scmi_power_control.c | 362 |
1 files changed, 362 insertions, 0 deletions
diff --git a/drivers/firmware/arm_scmi/scmi_power_control.c b/drivers/firmware/arm_scmi/scmi_power_control.c new file mode 100644 index 000000000000..6eb7d2a4b6b1 --- /dev/null +++ b/drivers/firmware/arm_scmi/scmi_power_control.c @@ -0,0 +1,362 @@ +// 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"); |