[PATCH v5 0/3] SCMI System Power Support

[PATCH v5 0/3] SCMI System Power Support

[Cristian Marussi]

Hi all,

this series wants to add the core SCMI System Power support and related
events' handling logic: the protocol support itself is trivial and boils
down to some bare initializations and supporting one SCMI System Power
notification event meant to carry platform-originated System transition
requests. This is patch [1/3].

On top of this a new SCMI driver has been developed which registers for
such System Power notification and acts accordingly to satisfy such
plaform system-state transition requests that can be of forceful or
graceful kind.

In order to comply with such graceful requests, and co-operate with
userspace entities to drive a clean shutdown/reboot, the logic of the
driver relies on the same orderly_* API methods used by ACPI when handling
ACPI Shutdown bus events.
As an alternative method to tunnel graceful requests to userspace it is
possible to configure, via available module parameters, a specific signal
to be sent to CAD pid. This is patch [2/3].

Patch [3/3] is a mere JUNO example of the minimal DT bindings needed to
enable the protocol at the DT level and is NOT meant to be upstream as of
now.

Based on v5.9-rc1
(which now includes needed SCMI Notifications Core Support)

Thanks

Cristian

----
v4 --> v5
- rebased on v5.9-rc1 

v3 --> v4
- rebased on top of scmi-next/for-next/scmi 5.8-rc3 
- fixed some strict checkpatch issues

V2 --> V3
- changed Kconfig to fix naming and defaulting System Power Control
  driver to n
- fixes related to changes in SCMI Notifications core support V10

V1 --> V2
- use common event enums
- introduced optional alternative signal based comms 2 userspace

Cristian Marussi (3):
  firmware: arm_scmi: Add System Power Protocol support
  firmware: arm_scmi: Add SCMI System Power Control driver
  [DEBUG] arm64: dts: juno: add SCMI SystemPower Protocol support

 arch/arm64/boot/dts/arm/juno-base.dtsi        |   4 +
 drivers/firmware/Kconfig                      |  12 +
 drivers/firmware/arm_scmi/Makefile            |   3 +-
 drivers/firmware/arm_scmi/driver.c            |   1 +
 .../firmware/arm_scmi/scmi_power_control.c    | 389 ++++++++++++++++++
 drivers/firmware/arm_scmi/system.c            | 136 ++++++
 include/linux/scmi_protocol.h                 |  18 +
 7 files changed, 562 insertions(+), 1 deletion(-)
 create mode 100644 drivers/firmware/arm_scmi/scmi_power_control.c
 create mode 100644 drivers/firmware/arm_scmi/system.c

-- 
2.17.1

[PATCH v5 1/3] firmware: arm_scmi: Add System Power Protocol support

[Cristian Marussi]

Add bare protocol support for SCMI SystemPower as needed by an OSPM agent:
basic initialization and SYSTEM_POWER_STATE_NOTIFIER core notification
support.

No event-handling logic is attached to such notification by this commit.

Signed-off-by: Cristian Marussi <cristian.marussi@arm.com>
---
v4 --> v5
- system notifications related fixes needed by v5.9-rc1 rebase
V3 --> V4
- fix alignment issues by checkpatch
V2 --> V3
- fixes related to SCMI Notifications core support V10
V1 --> V2
- use common event enums
---
 drivers/firmware/arm_scmi/Makefile |   2 +-
 drivers/firmware/arm_scmi/system.c | 136 +++++++++++++++++++++++++++++
 include/linux/scmi_protocol.h      |  18 ++++
 3 files changed, 155 insertions(+), 1 deletion(-)
 create mode 100644 drivers/firmware/arm_scmi/system.c

diff --git a/drivers/firmware/arm_scmi/Makefile b/drivers/firmware/arm_scmi/Makefile
index 6f9cbc4aef22..643f2320f976 100644
--- a/drivers/firmware/arm_scmi/Makefile
+++ b/drivers/firmware/arm_scmi/Makefile
@@ -5,5 +5,5 @@ scmi-driver-y = driver.o notify.o
 scmi-transport-y = shmem.o
 scmi-transport-$(CONFIG_MAILBOX) += mailbox.o
 scmi-transport-$(CONFIG_HAVE_ARM_SMCCC_DISCOVERY) += smc.o
-scmi-protocols-y = base.o clock.o perf.o power.o reset.o sensors.o
+scmi-protocols-y = base.o clock.o perf.o power.o reset.o sensors.o system.o
 obj-$(CONFIG_ARM_SCMI_POWER_DOMAIN) += scmi_pm_domain.o
diff --git a/drivers/firmware/arm_scmi/system.c b/drivers/firmware/arm_scmi/system.c
new file mode 100644
index 000000000000..aa1e74f066a0
--- /dev/null
+++ b/drivers/firmware/arm_scmi/system.c
@@ -0,0 +1,136 @@
+// SPDX-License-Identifier: GPL-2.0
+/*
+ * System Control and Management Interface (SCMI) System Power Protocol
+ *
+ * Copyright (C) 2020 ARM Ltd.
+ */
+
+#define pr_fmt(fmt) "SCMI Notifications SYSTEM - " fmt
+
+#include <linux/scmi_protocol.h>
+
+#include "common.h"
+#include "notify.h"
+
+#define SCMI_SYSTEM_NUM_SOURCES		1
+
+enum scmi_system_protocol_cmd {
+	SYSTEM_POWER_STATE_NOTIFY = 0x5,
+};
+
+struct scmi_system_power_state_notify {
+	__le32 notify_enable;
+};
+
+struct scmi_system_power_state_notifier_payld {
+	__le32 agent_id;
+	__le32 flags;
+	__le32 system_state;
+};
+
+struct scmi_system_info {
+	u32 version;
+};
+
+static int scmi_system_request_notify(const struct scmi_handle *handle,
+				      bool enable)
+{
+	int ret;
+	struct scmi_xfer *t;
+	struct scmi_system_power_state_notify *notify;
+
+	ret = scmi_xfer_get_init(handle, SYSTEM_POWER_STATE_NOTIFY,
+				 SCMI_PROTOCOL_SYSTEM, sizeof(*notify), 0, &t);
+	if (ret)
+		return ret;
+
+	notify = t->tx.buf;
+	notify->notify_enable = enable ? cpu_to_le32(BIT(0)) : 0;
+
+	ret = scmi_do_xfer(handle, t);
+
+	scmi_xfer_put(handle, t);
+	return ret;
+}
+
+static int scmi_system_set_notify_enabled(const struct scmi_handle *handle,
+					  u8 evt_id, u32 src_id, bool enable)
+{
+	int ret;
+
+	ret = scmi_system_request_notify(handle, enable);
+	if (ret)
+		pr_debug("FAIL_ENABLE - evt[%X] - ret:%d\n", evt_id, ret);
+
+	return ret;
+}
+
+static void *scmi_system_fill_custom_report(const struct scmi_handle *handle,
+					    u8 evt_id, ktime_t timestamp,
+					    const void *payld, size_t payld_sz,
+					    void *report, u32 *src_id)
+{
+	const struct scmi_system_power_state_notifier_payld *p = payld;
+	struct scmi_system_power_state_notifier_report *r = report;
+
+	if (evt_id != SCMI_EVENT_SYSTEM_POWER_STATE_NOTIFIER ||
+	    sizeof(*p) != payld_sz)
+		return NULL;
+
+	r->timestamp = timestamp;
+	r->agent_id = le32_to_cpu(p->agent_id);
+	r->flags = le32_to_cpu(p->flags);
+	r->system_state = le32_to_cpu(p->system_state);
+	*src_id = 0;
+
+	return r;
+}
+
+static const struct scmi_event system_events[] = {
+	{
+		.id = SCMI_EVENT_SYSTEM_POWER_STATE_NOTIFIER,
+		.max_payld_sz =
+			sizeof(struct scmi_system_power_state_notifier_payld),
+		.max_report_sz =
+			sizeof(struct scmi_system_power_state_notifier_report),
+	},
+};
+
+static const struct scmi_event_ops system_event_ops = {
+	.set_notify_enabled = scmi_system_set_notify_enabled,
+	.fill_custom_report = scmi_system_fill_custom_report,
+};
+
+static int scmi_system_protocol_init(struct scmi_handle *handle)
+{
+	u32 version;
+	struct scmi_system_info *pinfo;
+
+	scmi_version_get(handle, SCMI_PROTOCOL_SYSTEM, &version);
+
+	dev_dbg(handle->dev, "System Power Version %d.%d\n",
+		PROTOCOL_REV_MAJOR(version), PROTOCOL_REV_MINOR(version));
+
+	pinfo = devm_kzalloc(handle->dev, sizeof(*pinfo), GFP_KERNEL);
+	if (!pinfo)
+		return -ENOMEM;
+
+	scmi_register_protocol_events(handle,
+				      SCMI_PROTOCOL_SYSTEM, SCMI_PROTO_QUEUE_SZ,
+				      &system_event_ops,
+				      system_events,
+				      ARRAY_SIZE(system_events),
+				      SCMI_SYSTEM_NUM_SOURCES);
+
+	pinfo->version = version;
+	handle->system_priv = pinfo;
+
+	return 0;
+}
+
+static int __init scmi_system_init(void)
+{
+	return scmi_protocol_register(SCMI_PROTOCOL_SYSTEM,
+				      &scmi_system_protocol_init);
+}
+subsys_initcall(scmi_system_init);
diff --git a/include/linux/scmi_protocol.h b/include/linux/scmi_protocol.h
index 7e5dd7d1e221..76fd0e24f3b6 100644
--- a/include/linux/scmi_protocol.h
+++ b/include/linux/scmi_protocol.h
@@ -292,6 +292,7 @@ struct scmi_handle {
 	void *sensor_priv;
 	void *reset_priv;
 	void *notify_priv;
+	void *system_priv;
 };
 
 enum scmi_std_protocol {
@@ -304,6 +305,15 @@ enum scmi_std_protocol {
 	SCMI_PROTOCOL_RESET = 0x16,
 };
 
+enum scmi_system_events {
+	SCMI_SYSTEM_SHUTDOWN,
+	SCMI_SYSTEM_COLDRESET,
+	SCMI_SYSTEM_WARMRESET,
+	SCMI_SYSTEM_POWERUP,
+	SCMI_SYSTEM_SUSPEND,
+	SCMI_SYSTEM_MAX
+};
+
 struct scmi_device {
 	u32 id;
 	u8 protocol_id;
@@ -378,6 +388,7 @@ enum scmi_notification_events {
 	SCMI_EVENT_SENSOR_TRIP_POINT_EVENT = 0x0,
 	SCMI_EVENT_RESET_ISSUED = 0x0,
 	SCMI_EVENT_BASE_ERROR_EVENT = 0x0,
+	SCMI_EVENT_SYSTEM_POWER_STATE_NOTIFIER = 0x0,
 };
 
 struct scmi_power_state_changed_report {
@@ -387,6 +398,13 @@ struct scmi_power_state_changed_report {
 	unsigned int	power_state;
 };
 
+struct scmi_system_power_state_notifier_report {
+	ktime_t		timestamp;
+	unsigned int	agent_id;
+	unsigned int	flags;
+	unsigned int	system_state;
+};
+
 struct scmi_perf_limits_report {
 	ktime_t		timestamp;
 	unsigned int	agent_id;
-- 
2.17.1

[PATCH v5 2/3] firmware: arm_scmi: Add SCMI System Power Control driver

[Cristian Marussi]

Add an SCMI System Power control driver to handle platform's requests
carried by SYSTEM_POWER_STATE_NOTIFIER notifications: such platform
requested system power state transitions are handled accordingly,
gracefully or forcefully, depending on the notifications' message flags.

Graceful requests are by default relayed to userspace using the same
Kernel API used to handle ACPI Shutdown bus events: alternatively, instead,
a few available module parameters can be used to tunnel instead such
requests to userspace via signals addressed to CAD pid.

When handling graceful requests, grant userspace processes a maximum
(configurable) time to perform their duties and then revert to a forceful
transition, so avoiding completely timing out platform's maximum grace time
and hitting possible abrupt power-cuts.

Signed-off-by: Cristian Marussi <cristian.marussi@arm.com>
----
V3 --> V4
- fix alignment checkpatch issues
V2 --> V3
- changed Kconfig to fix naming and defaulting to n
V1 --> V2
- use common event enums
- introduced optioanl alternative signal based comms 2 userspace
---
 drivers/firmware/Kconfig                      |  12 +
 drivers/firmware/arm_scmi/Makefile            |   1 +
 drivers/firmware/arm_scmi/driver.c            |   1 +
 .../firmware/arm_scmi/scmi_power_control.c    | 389 ++++++++++++++++++
 4 files changed, 403 insertions(+)
 create mode 100644 drivers/firmware/arm_scmi/scmi_power_control.c

diff --git a/drivers/firmware/Kconfig b/drivers/firmware/Kconfig
index fbd785dd0513..a77545c08040 100644
--- a/drivers/firmware/Kconfig
+++ b/drivers/firmware/Kconfig
@@ -40,6 +40,18 @@ config ARM_SCMI_POWER_DOMAIN
 	  will be called scmi_pm_domain. Note this may needed early in boot
 	  before rootfs may be available.
 
+config ARM_SCMI_POWER_CONTROL
+	bool "SCMI system power control driver"
+	depends on ARM_SCMI_PROTOCOL || (COMPILE_TEST && OF)
+	default n
+	help
+	  This enables System Power control logic which binds system shutdown or
+	  reboot actions to SCMI System Power notifications generated by SCP
+	  firmware.
+
+	  Graceful requests' methods and timeout and can be configured using
+	  a few available module parameters.
+
 config ARM_SCPI_PROTOCOL
 	tristate "ARM System Control and Power Interface (SCPI) Message Protocol"
 	depends on ARM || ARM64 || COMPILE_TEST
diff --git a/drivers/firmware/arm_scmi/Makefile b/drivers/firmware/arm_scmi/Makefile
index 643f2320f976..6a0e24f9e0b1 100644
--- a/drivers/firmware/arm_scmi/Makefile
+++ b/drivers/firmware/arm_scmi/Makefile
@@ -7,3 +7,4 @@ scmi-transport-$(CONFIG_MAILBOX) += mailbox.o
 scmi-transport-$(CONFIG_HAVE_ARM_SMCCC_DISCOVERY) += smc.o
 scmi-protocols-y = base.o clock.o perf.o power.o reset.o sensors.o system.o
 obj-$(CONFIG_ARM_SCMI_POWER_DOMAIN) += scmi_pm_domain.o
+obj-$(CONFIG_ARM_SCMI_POWER_CONTROL) += scmi_power_control.o
diff --git a/drivers/firmware/arm_scmi/driver.c b/drivers/firmware/arm_scmi/driver.c
index f749af6e79fc..484b3f7126b5 100644
--- a/drivers/firmware/arm_scmi/driver.c
+++ b/drivers/firmware/arm_scmi/driver.c
@@ -732,6 +732,7 @@ struct scmi_prot_devnames {
 
 static struct scmi_prot_devnames devnames[] = {
 	{ SCMI_PROTOCOL_POWER,  { "genpd" },},
+	{ SCMI_PROTOCOL_SYSTEM, {"syspower" },},
 	{ SCMI_PROTOCOL_PERF,   { "cpufreq" },},
 	{ SCMI_PROTOCOL_CLOCK,  { "clocks" },},
 	{ SCMI_PROTOCOL_SENSOR, { "hwmon" },},
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..17de66e9ba96
--- /dev/null
+++ b/drivers/firmware/arm_scmi/scmi_power_control.c
@@ -0,0 +1,389 @@
+// SPDX-License-Identifier: GPL-2.0
+/*
+ * SCMI Generic System Power support.
+ *
+ * Copyright (C) 2020 ARM Ltd.
+ */
+/**
+ * DOC: Theory of operation
+ *
+ * In order to handle platform originated SCMI System Power requests (like
+ * shutdowns or cold/warm resets) we register an SCMI Notification notifier
+ * block to react when such SCMI System Power events are emitted.
+ *
+ * Once such a notification is received we act accordingly to perform the
+ * required system transition depending on the kind of request.
+ *
+ * By default graceful requests are routed to userspace through the same
+ * API methods (orderly_poweroff/reboot()) used by ACPI when handling ACPI
+ * Shutdown bus events: alternatively, by properly setting a couple of module
+ * parameters, it is possible to choose to use signals to CAD pid as a mean
+ * to communicate such graceful requests.
+ *
+ * Forceful requests instead simply cause and immediate emergency_sync() and
+ * subsequent Kernel-only shutdown/reboot.
+ *
+ * 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
+ * finally cuts the power off at will: in such a scenario, which we want to
+ * avoid, we track the graceful requests progress through the means of a
+ * reboot_notifier and promptly convert a timed-out graceful request to a
+ * forceful one when userspace is late, in order to at least perform a clean
+ * sync and shutdown/restart.
+ *
+ * Given that such platform hard-timeout, when present, is anyway highly
+ * platform/event specific and not exposed at run-time, we make it configurable
+ * via the Kernel module param @scmi_graceful_request_tmo_ms.
+ */
+
+#include <linux/atomic.h>
+#include <linux/bitfield.h>
+#include <linux/err.h>
+#include <linux/fs.h>
+#include <linux/module.h>
+#include <linux/reboot.h>
+#include <linux/sched/signal.h>
+#include <linux/scmi_protocol.h>
+#include <linux/slab.h>
+#include <linux/timer.h>
+#include <linux/types.h>
+#include <linux/workqueue.h>
+
+#define DEFAULT_GRACE_TMO_MS	5000
+static unsigned int scmi_graceful_request_tmo_ms = DEFAULT_GRACE_TMO_MS;
+static unsigned int scmi_graceful_poweroff_signum;
+static unsigned int scmi_graceful_reboot_signum;
+
+enum scmi_system_request_status {
+	SCMI_SYSPOWER_IDLE,
+	SCMI_SYSPOWER_SERVED,
+	SCMI_SYSPOWER_INPROGRESS,
+	SCMI_SYSPOWER_FORCING,
+};
+
+struct scmi_syspower_config {
+	struct device *dev;
+
+	atomic_t status;
+
+	u32 required_state;
+
+	void (*request_graceful_transition)(struct scmi_syspower_config *conf);
+	void (*request_forceful_transition)(struct scmi_syspower_config *conf);
+
+	struct notifier_block userspace_nb;
+	struct notifier_block reboot_nb;
+
+	struct timer_list request_timer;
+	struct work_struct forceful_work;
+};
+
+static void scmi_forceful_work_func(struct work_struct *work)
+{
+	struct scmi_syspower_config *conf =
+		container_of(work, struct scmi_syspower_config, forceful_work);
+
+	conf->request_forceful_transition(conf);
+}
+
+/**
+ * scmi_request_timeout  - On timeout trigger a forceful transition
+ * @t: The timer reference
+ *
+ * Actual work is deferred out of the timer IRQ context since shutdown/reboot
+ * code do not play well when !in_task().
+ */
+static void scmi_request_timeout(struct timer_list *t)
+{
+	struct scmi_syspower_config *conf = from_timer(conf, t, request_timer);
+
+	dev_warn(conf->dev,
+		 "SCMI Graceful System Transition request timed out !\n");
+	atomic_set(&conf->status, SCMI_SYSPOWER_FORCING);
+	/* Ensure atomic values are updated */
+	smp_mb__after_atomic();
+	schedule_work(&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 requested
+ * one, cancel the timer work.
+ *
+ * Return: NOTIFY_OK in any case
+ */
+static int scmi_reboot_notifier(struct notifier_block *nb,
+				unsigned long reason, void *__unused)
+{
+	struct scmi_syspower_config *conf;
+
+	conf = container_of(nb, struct scmi_syspower_config, reboot_nb);
+
+	/* Ensure atomic values are updated */
+	smp_mb__before_atomic();
+	if (unlikely(atomic_read(&conf->status) == SCMI_SYSPOWER_FORCING))
+		return NOTIFY_OK;
+
+	switch (reason) {
+	case SYS_HALT:
+	case SYS_POWER_OFF:
+		if (conf->required_state == SCMI_SYSTEM_SHUTDOWN)
+			atomic_set(&conf->status, SCMI_SYSPOWER_INPROGRESS);
+		break;
+	case SYS_RESTART:
+		if (conf->required_state == SCMI_SYSTEM_COLDRESET ||
+		    conf->required_state == SCMI_SYSTEM_WARMRESET)
+			atomic_set(&conf->status, SCMI_SYSPOWER_INPROGRESS);
+		break;
+	default:
+		break;
+	}
+
+	/* Ensure atomic values are updated */
+	smp_mb__after_atomic();
+	if (atomic_read(&conf->status) == SCMI_SYSPOWER_INPROGRESS) {
+		dev_info(conf->dev,
+			 "SCMI System State request in progress...\n");
+		del_timer_sync(&conf->request_timer);
+	}
+
+	return NOTIFY_OK;
+}
+
+static inline void scmi_send_cad_signal(struct device *dev, unsigned int sig)
+{
+	dev_info(dev, "SCMI Sending signal %d to CAD pid\n", sig);
+
+	kill_cad_pid(sig, 1);
+}
+
+/**
+ * scmi_request_graceful_transition  - Request graceful SystemPower transition
+ * @conf: The current SystemPower configuration descriptor
+ *
+ * Initiates the required SystemPower transition, requesting userspace
+ * co-operation using the same orderly_ methods used by ACPI Shutdown event
+ * processing.
+ *
+ * This takes care also to register a reboot notifier and a timer callback in
+ * order to detect if userspace actions are taking too long; in such a case
+ * the timeout callback will finally perform a forceful transition, ignoring
+ * lagging userspace: the aim here is to at least perform an emergency_sync()
+ * and a clean shutdown or reboot transition when userspace is late, avoiding
+ * the brutal final power-cut from platform.
+ */
+static void scmi_request_graceful_transition(struct scmi_syspower_config *conf)
+{
+	int ret;
+	u32 status;
+
+	if (conf->required_state >= SCMI_SYSTEM_POWERUP) {
+		dev_warn(conf->dev,
+			 "Received unexpected SYSTEM POWER request: %d\n",
+			 conf->required_state);
+		return;
+	}
+
+	status = atomic_cmpxchg(&conf->status, SCMI_SYSPOWER_IDLE,
+				SCMI_SYSPOWER_SERVED);
+	if (status != SCMI_SYSPOWER_IDLE)
+		return;
+
+	ret = devm_register_reboot_notifier(conf->dev, &conf->reboot_nb);
+	if (ret)
+		dev_warn(conf->dev, "Cannot register reboot notifier !\n");
+
+	INIT_WORK(&conf->forceful_work, scmi_forceful_work_func);
+	conf->request_timer.expires = jiffies +
+				msecs_to_jiffies(scmi_graceful_request_tmo_ms);
+	timer_setup(&conf->request_timer, scmi_request_timeout, 0);
+	add_timer(&conf->request_timer);
+
+	dev_info(conf->dev,
+		 "Serving SCMI Graceful request: %d (timeout_ms:%d)\n",
+		 conf->required_state, scmi_graceful_request_tmo_ms);
+
+	switch (conf->required_state) {
+	case SCMI_SYSTEM_SHUTDOWN:
+		/*
+		 * When received early at boot-time the 'orderly' part will
+		 * fail due to the lack of userspace itself, but the force=true
+		 * argument will anyway be able trigger a successful forced
+		 * shutdown.
+		 */
+		if (!scmi_graceful_poweroff_signum)
+			orderly_poweroff(true);
+		else
+			scmi_send_cad_signal(conf->dev,
+					     scmi_graceful_poweroff_signum);
+		break;
+	case SCMI_SYSTEM_COLDRESET:
+	case SCMI_SYSTEM_WARMRESET:
+		if (!scmi_graceful_reboot_signum)
+			orderly_reboot();
+		else
+			scmi_send_cad_signal(conf->dev,
+					     scmi_graceful_reboot_signum);
+		break;
+	default:
+		break;
+	}
+}
+
+static void scmi_request_forceful_transition(struct scmi_syspower_config *conf)
+{
+	/* Ensure atomic values are updated */
+	smp_mb__before_atomic();
+	if (unlikely(atomic_read(&conf->status) == SCMI_SYSPOWER_INPROGRESS))
+		return;
+
+	dev_info(conf->dev, "Serving SCMI FORCEFUL SystemPower request:%d\n",
+		 conf->required_state);
+
+	emergency_sync();
+	switch (conf->required_state) {
+	case SCMI_SYSTEM_SHUTDOWN:
+		kernel_power_off();
+		break;
+	case SCMI_SYSTEM_COLDRESET:
+	case SCMI_SYSTEM_WARMRESET:
+		kernel_restart(NULL);
+		break;
+	default:
+		break;
+	}
+}
+
+#define SCMI_IS_REQUEST_GRACEFUL(flags)		((flags) & BIT(0))
+
+/**
+ * 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.
+ *
+ * Return: NOTIFY_OK in any case
+ */
+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_config *conf;
+
+	if (unlikely(system_state > SYSTEM_RUNNING))
+		return NOTIFY_OK;
+
+	conf = container_of(nb, struct scmi_syspower_config, userspace_nb);
+	conf->required_state = er->system_state;
+
+	if (conf->required_state >= SCMI_SYSTEM_MAX)
+		return NOTIFY_OK;
+
+	if (SCMI_IS_REQUEST_GRACEFUL(er->flags))
+		conf->request_graceful_transition(conf);
+	else
+		conf->request_forceful_transition(conf);
+
+	return NOTIFY_OK;
+}
+
+/**
+ * scmi_syspower_configure  - General SystemPower configuration init
+ * @dev: The associated struct device
+ *
+ * Return: SystemPower configuration descriptor on Success, NULL otherwise
+ */
+static void *scmi_syspower_configure(struct device *dev)
+{
+	struct scmi_syspower_config *conf;
+
+	conf = devm_kzalloc(dev, sizeof(*conf), GFP_KERNEL);
+	if (!conf)
+		return NULL;
+
+	conf->dev = dev;
+	conf->required_state = SCMI_SYSTEM_MAX;
+	conf->request_graceful_transition = &scmi_request_graceful_transition;
+	conf->request_forceful_transition = &scmi_request_forceful_transition;
+	conf->userspace_nb.notifier_call = &scmi_userspace_notifier;
+	conf->reboot_nb.notifier_call = &scmi_reboot_notifier;
+	atomic_set(&conf->status, SCMI_SYSPOWER_IDLE);
+	/* Ensure atomic values are updated */
+	smp_mb__after_atomic();
+
+	return conf;
+}
+
+static int scmi_syspower_probe(struct scmi_device *sdev)
+{
+	int ret;
+	struct scmi_handle *handle = sdev->handle;
+	struct scmi_syspower_config *syspower_conf;
+
+	if (!handle)
+		return -ENODEV;
+
+	syspower_conf = scmi_syspower_configure(&sdev->dev);
+	if (!syspower_conf)
+		return -ENOMEM;
+
+	dev_set_drvdata(&sdev->dev, syspower_conf);
+	ret = handle->notify_ops->register_event_notifier(handle,
+						SCMI_PROTOCOL_SYSTEM,
+					SCMI_EVENT_SYSTEM_POWER_STATE_NOTIFIER,
+					NULL, &syspower_conf->userspace_nb);
+
+	return 0;
+}
+
+static void scmi_syspower_remove(struct scmi_device *sdev)
+{
+	int ret;
+	const struct scmi_handle *handle = sdev->handle;
+	struct scmi_syspower_config *syspower_conf;
+
+	syspower_conf = dev_get_drvdata(&sdev->dev);
+	ret = handle->notify_ops->unregister_event_notifier(handle,
+						SCMI_PROTOCOL_SYSTEM,
+					SCMI_EVENT_SYSTEM_POWER_STATE_NOTIFIER,
+					NULL, &syspower_conf->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,
+	.remove = scmi_syspower_remove,
+	.id_table = scmi_id_table,
+};
+module_scmi_driver(scmi_system_power_driver);
+
+module_param(scmi_graceful_request_tmo_ms, uint, 0644);
+MODULE_PARM_DESC(scmi_graceful_request_tmo_ms,
+		 "Maximum time(ms) allowed to userspace for complying to the request.");
+
+module_param(scmi_graceful_poweroff_signum, uint, 0644);
+MODULE_PARM_DESC(scmi_graceful_poweroff_signum,
+		 "Signal to request graceful poweroff to CAD process. Ignored if zero.");
+
+module_param(scmi_graceful_reboot_signum, uint, 0644);
+MODULE_PARM_DESC(scmi_graceful_reboot_signum,
+		 "Signal to request graceful reboot to CAD process. Ignored if zero.");
+
+MODULE_AUTHOR("Cristian Marussi <cristian.marussi@arm.com>");
+MODULE_DESCRIPTION("ARM SCMI System Power driver");
+MODULE_LICENSE("GPL v2");
-- 
2.17.1

[PATCH v5 3/3] [DEBUG] arm64: dts: juno: add SCMI SystemPower Protocol support

[Cristian Marussi]

arm64: dts: juno: add SCMI SystemPower Protocol support

Signed-off-by: Cristian Marussi <cristian.marussi@arm.com>
---
 arch/arm64/boot/dts/arm/juno-base.dtsi | 4 ++++
 1 file changed, 4 insertions(+)

diff --git a/arch/arm64/boot/dts/arm/juno-base.dtsi b/arch/arm64/boot/dts/arm/juno-base.dtsi
index dd20a5242c45..41e602ce71e2 100644
--- a/arch/arm64/boot/dts/arm/juno-base.dtsi
+++ b/arch/arm64/boot/dts/arm/juno-base.dtsi
@@ -581,6 +581,10 @@
 				#power-domain-cells = <1>;
 			};
 
+			scmi_system: protocol@12 {
+				reg = <0x12>;
+			};
+
 			scmi_dvfs: protocol@13 {
 				reg = <0x13>;
 				#clock-cells = <1>;
-- 
2.17.1

Re: [PATCH v5 2/3] firmware: arm_scmi: Add SCMI System Power Control driver

[Sudeep Holla]

On Wed, Aug 19, 2020 at 05:10:01PM +0100, Cristian Marussi wrote:
> Add an SCMI System Power control driver to handle platform's requests
> carried by SYSTEM_POWER_STATE_NOTIFIER notifications: such platform
> requested system power state transitions are handled accordingly,
> gracefully or forcefully, depending on the notifications' message flags.
> 
> Graceful requests are by default relayed to userspace using the same
> Kernel API used to handle ACPI Shutdown bus events: alternatively, instead,
> a few available module parameters can be used to tunnel instead such
> requests to userspace via signals addressed to CAD pid.
> 
> When handling graceful requests, grant userspace processes a maximum
> (configurable) time to perform their duties and then revert to a forceful
> transition, so avoiding completely timing out platform's maximum grace time
> and hitting possible abrupt power-cuts.
> 
> Signed-off-by: Cristian Marussi <cristian.marussi@arm.com>
> ----
> V3 --> V4
> - fix alignment checkpatch issues
> V2 --> V3
> - changed Kconfig to fix naming and defaulting to n
> V1 --> V2
> - use common event enums
> - introduced optioanl alternative signal based comms 2 userspace
> ---
>  drivers/firmware/Kconfig                      |  12 +
>  drivers/firmware/arm_scmi/Makefile            |   1 +
>  drivers/firmware/arm_scmi/driver.c            |   1 +
>  .../firmware/arm_scmi/scmi_power_control.c    | 389 ++++++++++++++++++
>  4 files changed, 403 insertions(+)
>  create mode 100644 drivers/firmware/arm_scmi/scmi_power_control.c
> 
> diff --git a/drivers/firmware/Kconfig b/drivers/firmware/Kconfig
> index fbd785dd0513..a77545c08040 100644
> --- a/drivers/firmware/Kconfig
> +++ b/drivers/firmware/Kconfig
> @@ -40,6 +40,18 @@ config ARM_SCMI_POWER_DOMAIN
>  	  will be called scmi_pm_domain. Note this may needed early in boot
>  	  before rootfs may be available.
>  
> +config ARM_SCMI_POWER_CONTROL
> +	bool "SCMI system power control driver"
> +	depends on ARM_SCMI_PROTOCOL || (COMPILE_TEST && OF)
> +	default n
> +	help
> +	  This enables System Power control logic which binds system shutdown or
> +	  reboot actions to SCMI System Power notifications generated by SCP
> +	  firmware.
> +
> +	  Graceful requests' methods and timeout and can be configured using
> +	  a few available module parameters.
> +
>  config ARM_SCPI_PROTOCOL
>  	tristate "ARM System Control and Power Interface (SCPI) Message Protocol"
>  	depends on ARM || ARM64 || COMPILE_TEST
> diff --git a/drivers/firmware/arm_scmi/Makefile b/drivers/firmware/arm_scmi/Makefile
> index 643f2320f976..6a0e24f9e0b1 100644
> --- a/drivers/firmware/arm_scmi/Makefile
> +++ b/drivers/firmware/arm_scmi/Makefile
> @@ -7,3 +7,4 @@ scmi-transport-$(CONFIG_MAILBOX) += mailbox.o
>  scmi-transport-$(CONFIG_HAVE_ARM_SMCCC_DISCOVERY) += smc.o
>  scmi-protocols-y = base.o clock.o perf.o power.o reset.o sensors.o system.o
>  obj-$(CONFIG_ARM_SCMI_POWER_DOMAIN) += scmi_pm_domain.o
> +obj-$(CONFIG_ARM_SCMI_POWER_CONTROL) += scmi_power_control.o
> diff --git a/drivers/firmware/arm_scmi/driver.c b/drivers/firmware/arm_scmi/driver.c
> index f749af6e79fc..484b3f7126b5 100644
> --- a/drivers/firmware/arm_scmi/driver.c
> +++ b/drivers/firmware/arm_scmi/driver.c
> @@ -732,6 +732,7 @@ struct scmi_prot_devnames {
>  
>  static struct scmi_prot_devnames devnames[] = {
>  	{ SCMI_PROTOCOL_POWER,  { "genpd" },},
> +	{ SCMI_PROTOCOL_SYSTEM, {"syspower" },},

				^ missing space

Split the above into separate patch as it doesn't depend on new config
and can be added without it. I plan to merge the scmi system protocol
part for v5.10 and the above addition of device. We need to wait for more
feedback on the driver front especially user notification part.

-- 
Regards,
Sudeep

Re: [PATCH v5 2/3] firmware: arm_scmi: Add SCMI System Power Control driver

[Cristian Marussi]

Hi Sudeep

thanks for the review.

On Mon, Sep 07, 2020 at 05:43:51PM +0100, Sudeep Holla wrote:
> On Wed, Aug 19, 2020 at 05:10:01PM +0100, Cristian Marussi wrote:
> > Add an SCMI System Power control driver to handle platform's requests
> > carried by SYSTEM_POWER_STATE_NOTIFIER notifications: such platform
> > requested system power state transitions are handled accordingly,
> > gracefully or forcefully, depending on the notifications' message flags.
> > 
> > Graceful requests are by default relayed to userspace using the same
> > Kernel API used to handle ACPI Shutdown bus events: alternatively, instead,
> > a few available module parameters can be used to tunnel instead such
> > requests to userspace via signals addressed to CAD pid.
> > 
> > When handling graceful requests, grant userspace processes a maximum
> > (configurable) time to perform their duties and then revert to a forceful
> > transition, so avoiding completely timing out platform's maximum grace time
> > and hitting possible abrupt power-cuts.
> > 
> > Signed-off-by: Cristian Marussi <cristian.marussi@arm.com>
> > ----
> > V3 --> V4
> > - fix alignment checkpatch issues
> > V2 --> V3
> > - changed Kconfig to fix naming and defaulting to n
> > V1 --> V2
> > - use common event enums
> > - introduced optioanl alternative signal based comms 2 userspace
> > ---
> >  drivers/firmware/Kconfig                      |  12 +
> >  drivers/firmware/arm_scmi/Makefile            |   1 +
> >  drivers/firmware/arm_scmi/driver.c            |   1 +
> >  .../firmware/arm_scmi/scmi_power_control.c    | 389 ++++++++++++++++++
> >  4 files changed, 403 insertions(+)
> >  create mode 100644 drivers/firmware/arm_scmi/scmi_power_control.c
> > 
> > diff --git a/drivers/firmware/Kconfig b/drivers/firmware/Kconfig
> > index fbd785dd0513..a77545c08040 100644
> > --- a/drivers/firmware/Kconfig
> > +++ b/drivers/firmware/Kconfig
> > @@ -40,6 +40,18 @@ config ARM_SCMI_POWER_DOMAIN
> >  	  will be called scmi_pm_domain. Note this may needed early in boot
> >  	  before rootfs may be available.
> >  
> > +config ARM_SCMI_POWER_CONTROL
> > +	bool "SCMI system power control driver"
> > +	depends on ARM_SCMI_PROTOCOL || (COMPILE_TEST && OF)
> > +	default n
> > +	help
> > +	  This enables System Power control logic which binds system shutdown or
> > +	  reboot actions to SCMI System Power notifications generated by SCP
> > +	  firmware.
> > +
> > +	  Graceful requests' methods and timeout and can be configured using
> > +	  a few available module parameters.
> > +
> >  config ARM_SCPI_PROTOCOL
> >  	tristate "ARM System Control and Power Interface (SCPI) Message Protocol"
> >  	depends on ARM || ARM64 || COMPILE_TEST
> > diff --git a/drivers/firmware/arm_scmi/Makefile b/drivers/firmware/arm_scmi/Makefile
> > index 643f2320f976..6a0e24f9e0b1 100644
> > --- a/drivers/firmware/arm_scmi/Makefile
> > +++ b/drivers/firmware/arm_scmi/Makefile
> > @@ -7,3 +7,4 @@ scmi-transport-$(CONFIG_MAILBOX) += mailbox.o
> >  scmi-transport-$(CONFIG_HAVE_ARM_SMCCC_DISCOVERY) += smc.o
> >  scmi-protocols-y = base.o clock.o perf.o power.o reset.o sensors.o system.o
> >  obj-$(CONFIG_ARM_SCMI_POWER_DOMAIN) += scmi_pm_domain.o
> > +obj-$(CONFIG_ARM_SCMI_POWER_CONTROL) += scmi_power_control.o
> > diff --git a/drivers/firmware/arm_scmi/driver.c b/drivers/firmware/arm_scmi/driver.c
> > index f749af6e79fc..484b3f7126b5 100644
> > --- a/drivers/firmware/arm_scmi/driver.c
> > +++ b/drivers/firmware/arm_scmi/driver.c
> > @@ -732,6 +732,7 @@ struct scmi_prot_devnames {
> >  
> >  static struct scmi_prot_devnames devnames[] = {
> >  	{ SCMI_PROTOCOL_POWER,  { "genpd" },},
> > +	{ SCMI_PROTOCOL_SYSTEM, {"syspower" },},
> 
> 				^ missing space
> 
> Split the above into separate patch as it doesn't depend on new config
> and can be added without it. I plan to merge the scmi system protocol
> part for v5.10 and the above addition of device. We need to wait for more
> feedback on the driver front especially user notification part.
> 

I'll do in v6.

Cristian

> -- 
> Regards,
> Sudeep