linuxdebug/drivers/firmware/arm_scmi/scmi_power_control.c

363 lines
11 KiB
C

// 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");