[PATCH 1/9] PM: Add suspend block api.

From: Arve HjÃnnevÃg
Date: Thu Apr 22 2010 - 21:10:10 EST

Adds /sys/power/policy that selects the behaviour of /sys/power/state.
After setting the policy to opportunistic, writes to /sys/power/state
become non-blocking requests that specify which suspend state to enter
when no suspend blockers are active. A special state, "on", stops the
process by activating the "main" suspend blocker.

Signed-off-by: Arve HjÃnnevÃg <arve@xxxxxxxxxxx>
---
Documentation/power/suspend-blockers.txt | 97 +++++++++++++
include/linux/suspend_blocker.h | 60 ++++++++
kernel/power/Kconfig | 11 ++
kernel/power/Makefile | 1 +
kernel/power/main.c | 84 +++++++++++-
kernel/power/power.h | 5 +
kernel/power/suspend.c | 4 +-
kernel/power/suspend_blocker.c | 219 ++++++++++++++++++++++++++++++
8 files changed, 477 insertions(+), 4 deletions(-)
create mode 100644 Documentation/power/suspend-blockers.txt
create mode 100755 include/linux/suspend_blocker.h
create mode 100644 kernel/power/suspend_blocker.c

diff --git a/Documentation/power/suspend-blockers.txt b/Documentation/power/suspend-blockers.txt
new file mode 100644
index 0000000..1c48514
--- /dev/null
+++ b/Documentation/power/suspend-blockers.txt
@@ -0,0 +1,97 @@
+Suspend blockers
+================
+
+Suspend blockers provide a mechanism for device drivers and user-space processes
+to prevent the system from entering suspend. By default writing to
+/sys/power/state will ignore suspend blockers. Writing "opportunistic" to
+/sys/power/policy will change the behaviour of /sys/power/state to repeatedly
+enter the requested state when no suspend blockers are active. Writing "on" to
+/sys/power/state will cancel the automatic sleep request. Suspend blockers do
+not affect sleep states entered from idle.
+
+To use a suspend blocker, a device driver needs a struct suspend_blocker object
+that has to be initialized with suspend_blocker_init. When no longer needed,
+the suspend blocker must be destroyed with suspend_blocker_destroy.
+
+A suspend blocker is activated using suspend_block, which prevents the system
+from entering suspend until the suspend blocker is deactivated with
+suspend_unblock. Many suspend blockers may be used simultaneously, and the
+system is prevented from entering suspend as long as at least one of them is
+active.
+
+If the suspend operation has already started when calling suspend_block on a
+suspend_blocker, it will abort the suspend operation as long it has not already
+reached called suspend_ops->enter. This means that calling suspend_block from an
+interrupt handler or a freezeable thread always works, but some or all drivers
+may be temporarily suspended.
+
+In cell phones or other embedded systems where powering the screen is a
+significant drain on the battery, suspend blockers can be used to allow
+user-space to decide whether a keystroke received while the system is suspended
+should cause the screen to be turned back on or allow the system to go back into
+suspend. Use set_irq_wake or a platform specific api to make sure the keypad
+interrupt wakes up the cpu. Once the keypad driver has resumed, the sequence of
+events can look like this:
+
+- The Keypad driver gets an interrupt. It then calls suspend_block on the
+ keypad-scan suspend_blocker and starts scanning the keypad matrix.
+- The keypad-scan code detects a key change and reports it to the input-event
+ driver.
+- The input-event driver sees the key change, enqueues an event, and calls
+ suspend_block on the input-event-queue suspend_blocker.
+- The keypad-scan code detects that no keys are held and calls suspend_unblock
+ on the keypad-scan suspend_blocker.
+- The user-space input-event thread returns from select/poll, calls
+ suspend_block on the process-input-events suspend_blocker and then calls read
+ on the input-event device.
+- The input-event driver dequeues the key-event and, since the queue is now
+ empty, it calls suspend_unblock on the input-event-queue suspend_blocker.
+- The user-space input-event thread returns from read. If it determines that
+ the key should leave the screen off, it calls suspend_unblock on the
+ process_input_events suspend_blocker and then calls select or poll. The
+ system will automatically suspend again, since now no suspend blockers are
+ active.
+
+ Key pressed Key released
+ | |
+keypad-scan ++++++++++++++++++
+input-event-queue +++ +++
+process-input-events +++ +++
+
+
+Driver API
+==========
+
+A driver can use the suspend block api by adding a suspend_blocker variable to
+its state and calling suspend_blocker_init. For instance:
+struct state {
+ struct suspend_blocker suspend_blocker;
+}
+
+init() {
+ suspend_blocker_init(&state->suspend_blocker, "suspend-blocker-name");
+}
+
+Before freeing the memory, suspend_blocker_destroy must be called:
+
+uninit() {
+ suspend_blocker_destroy(&state->suspend_blocker);
+}
+
+When the driver determines that it needs to run (usually in an interrupt
+handler) it calls suspend_block:
+ suspend_block(&state->suspend_blocker);
+
+When it no longer needs to run it calls suspend_unblock:
+ suspend_unblock(&state->suspend_blocker);
+
+Calling suspend_block when the suspend blocker is active or suspend_unblock when
+it is not active has no effect. This allows drivers to update their state and
+call suspend suspend_block or suspend_unblock based on the result.
+For instance:
+
+if (list_empty(&state->pending_work))
+ suspend_unblock(&state->suspend_blocker);
+else
+ suspend_block(&state->suspend_blocker);
+
diff --git a/include/linux/suspend_blocker.h b/include/linux/suspend_blocker.h
new file mode 100755
index 0000000..21689cd
--- /dev/null
+++ b/include/linux/suspend_blocker.h
@@ -0,0 +1,60 @@
+/* include/linux/suspend_blocker.h
+ *
+ * Copyright (C) 2007-2009 Google, Inc.
+ *
+ * This software is licensed under the terms of the GNU General Public
+ * License version 2, as published by the Free Software Foundation, and
+ * may be copied, distributed, and modified under those terms.
+ *
+ * This program is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
+ * GNU General Public License for more details.
+ *
+ */
+
+#ifndef _LINUX_SUSPEND_BLOCKER_H
+#define _LINUX_SUSPEND_BLOCKER_H
+
+/**
+ * struct suspend_blocker - the basic suspend_blocker structure
+ * @flags: Tracks initialized and active state.
+ * @name: Name used for debugging.
+ *
+ * When a suspend_blocker is active it prevents the system from entering
+ * suspend.
+ *
+ * The suspend_blocker structure must be initialized by suspend_blocker_init()
+ */
+
+struct suspend_blocker {
+#ifdef CONFIG_SUSPEND_BLOCKERS
+ atomic_t flags;
+ const char *name;
+#endif
+};
+
+#ifdef CONFIG_SUSPEND_BLOCKERS
+
+void suspend_blocker_init(struct suspend_blocker *blocker, const char *name);
+void suspend_blocker_destroy(struct suspend_blocker *blocker);
+void suspend_block(struct suspend_blocker *blocker);
+void suspend_unblock(struct suspend_blocker *blocker);
+bool suspend_blocker_is_active(struct suspend_blocker *blocker);
+bool suspend_is_blocked(void);
+
+#else
+
+static inline void suspend_blocker_init(struct suspend_blocker *blocker,
+ const char *name) {}
+static inline void suspend_blocker_destroy(struct suspend_blocker *blocker) {}
+static inline void suspend_block(struct suspend_blocker *blocker) {}
+static inline void suspend_unblock(struct suspend_blocker *blocker) {}
+static inline bool suspend_blocker_is_active(struct suspend_blocker *bl)
+ { return 0; }
+static inline bool suspend_is_blocked(void) { return 0; }
+
+#endif
+
+#endif
+
diff --git a/kernel/power/Kconfig b/kernel/power/Kconfig
index 5c36ea9..f8fa246 100644
--- a/kernel/power/Kconfig
+++ b/kernel/power/Kconfig
@@ -130,6 +130,17 @@ config SUSPEND_FREEZER

Turning OFF this setting is NOT recommended! If in doubt, say Y.

+config SUSPEND_BLOCKERS
+ bool "Suspend blockers"
+ depends on PM
+ select RTC_LIB
+ default n
+ ---help---
+ Suspend blocker support. Write "opportunistic" to /sys/power/policy
+ to enable suspend blockers. Then, when user space requests a sleep
+ state through /sys/power/state, the requested sleep state will be
+ entered when no suspend blockers are active.
+
config HIBERNATION_NVS
bool

diff --git a/kernel/power/Makefile b/kernel/power/Makefile
index 4319181..f570801 100644
--- a/kernel/power/Makefile
+++ b/kernel/power/Makefile
@@ -7,6 +7,7 @@ obj-$(CONFIG_PM) += main.o
obj-$(CONFIG_PM_SLEEP) += console.o
obj-$(CONFIG_FREEZER) += process.o
obj-$(CONFIG_SUSPEND) += suspend.o
+obj-$(CONFIG_SUSPEND_BLOCKERS) += suspend_blocker.o
obj-$(CONFIG_PM_TEST_SUSPEND) += suspend_test.o
obj-$(CONFIG_HIBERNATION) += hibernate.o snapshot.o swap.o user.o
obj-$(CONFIG_HIBERNATION_NVS) += hibernate_nvs.o
diff --git a/kernel/power/main.c b/kernel/power/main.c
index b58800b..9061ea0 100644
--- a/kernel/power/main.c
+++ b/kernel/power/main.c
@@ -12,6 +12,7 @@
#include <linux/string.h>
#include <linux/resume-trace.h>
#include <linux/workqueue.h>
+#include <linux/suspend_blocker.h>

#include "power.h"

@@ -20,6 +21,27 @@ DEFINE_MUTEX(pm_mutex);
unsigned int pm_flags;
EXPORT_SYMBOL(pm_flags);

+struct policy {
+ const char *name;
+ bool (*valid_state)(suspend_state_t state);
+ int (*set_state)(suspend_state_t state);
+};
+static struct policy policies[] = {
+ {
+ .name = "forced",
+ .valid_state = valid_state,
+ .set_state = enter_state,
+ },
+#ifdef CONFIG_SUSPEND_BLOCKERS
+ {
+ .name = "opportunistic",
+ .valid_state = request_suspend_valid_state,
+ .set_state = request_suspend_state,
+ },
+#endif
+};
+static int policy;
+
#ifdef CONFIG_PM_SLEEP

/* Routines for PM-transition notifications */
@@ -146,6 +168,12 @@ struct kobject *power_kobj;
*
* store() accepts one of those strings, translates it into the
* proper enumerated value, and initiates a suspend transition.
+ *
+ * If policy is set to opportunistic, store() does not block until the
+ * system resumes, and it will try to re-enter the state until another
+ * state is requested. Suspend blockers are respected and the requested
+ * state will only be entered when no suspend blockers are active.
+ * Write "on" to cancel.
*/
static ssize_t state_show(struct kobject *kobj, struct kobj_attribute *attr,
char *buf)
@@ -155,7 +183,7 @@ static ssize_t state_show(struct kobject *kobj, struct kobj_attribute *attr,
int i;

for (i = 0; i < PM_SUSPEND_MAX; i++) {
- if (pm_states[i] && valid_state(i))
+ if (pm_states[i] && policies[policy].valid_state(i))
s += sprintf(s,"%s ", pm_states[i]);
}
#endif
@@ -173,7 +201,7 @@ static ssize_t state_store(struct kobject *kobj, struct kobj_attribute *attr,
const char *buf, size_t n)
{
#ifdef CONFIG_SUSPEND
- suspend_state_t state = PM_SUSPEND_STANDBY;
+ suspend_state_t state = PM_SUSPEND_ON;
const char * const *s;
#endif
char *p;
@@ -195,7 +223,7 @@ static ssize_t state_store(struct kobject *kobj, struct kobj_attribute *attr,
break;
}
if (state < PM_SUSPEND_MAX && *s)
- error = enter_state(state);
+ error = policies[policy].set_state(state);
#endif

Exit:
@@ -204,6 +232,55 @@ static ssize_t state_store(struct kobject *kobj, struct kobj_attribute *attr,

power_attr(state);

+/**
+ * policy - set policy for state
+ */
+
+static ssize_t policy_show(struct kobject *kobj,
+ struct kobj_attribute *attr, char *buf)
+{
+ char *s = buf;
+ int i;
+
+ for (i = 0; i < ARRAY_SIZE(policies); i++) {
+ if (i == policy)
+ s += sprintf(s, "[%s] ", policies[i].name);
+ else
+ s += sprintf(s, "%s ", policies[i].name);
+ }
+ if (s != buf)
+ /* convert the last space to a newline */
+ *(s-1) = '\n';
+ return (s - buf);
+}
+
+static ssize_t policy_store(struct kobject *kobj,
+ struct kobj_attribute *attr,
+ const char *buf, size_t n)
+{
+ const char *s;
+ char *p;
+ int len;
+ int i;
+
+ p = memchr(buf, '\n', n);
+ len = p ? p - buf : n;
+
+ for (i = 0; i < ARRAY_SIZE(policies); i++) {
+ s = policies[i].name;
+ if (s && len == strlen(s) && !strncmp(buf, s, len)) {
+ mutex_lock(&pm_mutex);
+ policies[policy].set_state(PM_SUSPEND_ON);
+ policy = i;
+ mutex_unlock(&pm_mutex);
+ return n;
+ }
+ }
+ return -EINVAL;
+}
+
+power_attr(policy);
+
#ifdef CONFIG_PM_TRACE
int pm_trace_enabled;

@@ -231,6 +308,7 @@ power_attr(pm_trace);

static struct attribute * g[] = {
&state_attr.attr,
+ &policy_attr.attr,
#ifdef CONFIG_PM_TRACE
&pm_trace_attr.attr,
#endif
diff --git a/kernel/power/power.h b/kernel/power/power.h
index 46c5a26..9b468d7 100644
--- a/kernel/power/power.h
+++ b/kernel/power/power.h
@@ -236,3 +236,8 @@ static inline void suspend_thaw_processes(void)
{
}
#endif
+
+/* kernel/power/suspend_block.c */
+extern int request_suspend_state(suspend_state_t state);
+extern bool request_suspend_valid_state(suspend_state_t state);
+
diff --git a/kernel/power/suspend.c b/kernel/power/suspend.c
index 56e7dbb..dc42006 100644
--- a/kernel/power/suspend.c
+++ b/kernel/power/suspend.c
@@ -16,10 +16,12 @@
#include <linux/cpu.h>
#include <linux/syscalls.h>
#include <linux/gfp.h>
+#include <linux/suspend_blocker.h>

#include "power.h"

const char *const pm_states[PM_SUSPEND_MAX] = {
+ [PM_SUSPEND_ON] = "on",
[PM_SUSPEND_STANDBY] = "standby",
[PM_SUSPEND_MEM] = "mem",
};
@@ -157,7 +159,7 @@ static int suspend_enter(suspend_state_t state)

error = sysdev_suspend(PMSG_SUSPEND);
if (!error) {
- if (!suspend_test(TEST_CORE))
+ if (!suspend_is_blocked() && !suspend_test(TEST_CORE))
error = suspend_ops->enter(state);
sysdev_resume();
}
diff --git a/kernel/power/suspend_blocker.c b/kernel/power/suspend_blocker.c
new file mode 100644
index 0000000..1b345d1
--- /dev/null
+++ b/kernel/power/suspend_blocker.c
@@ -0,0 +1,219 @@
+/* kernel/power/suspend_blocker.c
+ *
+ * Copyright (C) 2005-2010 Google, Inc.
+ *
+ * This software is licensed under the terms of the GNU General Public
+ * License version 2, as published by the Free Software Foundation, and
+ * may be copied, distributed, and modified under those terms.
+ *
+ * This program is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
+ * GNU General Public License for more details.
+ *
+ */
+
+#include <linux/module.h>
+#include <linux/rtc.h>
+#include <linux/suspend.h>
+#include <linux/suspend_blocker.h>
+#include "power.h"
+
+enum {
+ DEBUG_EXIT_SUSPEND = 1U << 0,
+ DEBUG_WAKEUP = 1U << 1,
+ DEBUG_USER_STATE = 1U << 2,
+ DEBUG_SUSPEND = 1U << 3,
+ DEBUG_SUSPEND_BLOCKER = 1U << 4,
+};
+static int debug_mask = DEBUG_EXIT_SUSPEND | DEBUG_WAKEUP | DEBUG_USER_STATE;
+module_param_named(debug_mask, debug_mask, int, S_IRUGO | S_IWUSR | S_IWGRP);
+
+#define SB_INITIALIZED (1U << 8)
+#define SB_ACTIVE (1U << 9)
+
+static DEFINE_SPINLOCK(state_lock);
+static atomic_t suspend_block_count;
+static atomic_t current_event_num;
+struct workqueue_struct *suspend_work_queue;
+struct suspend_blocker main_suspend_blocker;
+static suspend_state_t requested_suspend_state = PM_SUSPEND_MEM;
+static bool enable_suspend_blockers;
+
+#define pr_info_time(fmt, args...) \
+ do { \
+ struct timespec ts; \
+ struct rtc_time tm; \
+ getnstimeofday(&ts); \
+ rtc_time_to_tm(ts.tv_sec, &tm); \
+ pr_info(fmt "(%d-%02d-%02d %02d:%02d:%02d.%09lu UTC)\n" , \
+ args, \
+ tm.tm_year + 1900, tm.tm_mon + 1, tm.tm_mday, \
+ tm.tm_hour, tm.tm_min, tm.tm_sec, ts.tv_nsec); \
+ } while (0);
+
+/**
+ * suspend_is_blocked() - Check if suspend should be blocked
+ *
+ * suspend_is_blocked can be used by generic power management code to abort
+ * suspend.
+ *
+ * To preserve backward compatibility suspend_is_blocked returns 0 unless it
+ * is called during suspend initiated from the suspend_block code.
+ */
+bool suspend_is_blocked(void)
+{
+ if (!enable_suspend_blockers)
+ return 0;
+ return !!atomic_read(&suspend_block_count);
+}
+
+static void suspend_worker(struct work_struct *work)
+{
+ int ret;
+ int entry_event_num;
+
+ enable_suspend_blockers = true;
+ while (!suspend_is_blocked()) {
+ entry_event_num = atomic_read(&current_event_num);
+ if (debug_mask & DEBUG_SUSPEND)
+ pr_info("suspend: enter suspend\n");
+ ret = pm_suspend(requested_suspend_state);
+ if (debug_mask & DEBUG_EXIT_SUSPEND)
+ pr_info_time("suspend: exit suspend, ret = %d ", ret);
+ if (atomic_read(&current_event_num) == entry_event_num)
+ pr_info("suspend: pm_suspend returned with no event\n");
+ }
+ enable_suspend_blockers = false;
+}
+static DECLARE_WORK(suspend_work, suspend_worker);
+
+/**
+ * suspend_blocker_init() - Initialize a suspend blocker
+ * @blocker: The suspend blocker to initialize.
+ * @name: The name of the suspend blocker to show in debug messages.
+ *
+ * The suspend blocker struct and name must not be freed before calling
+ * suspend_blocker_destroy.
+ */
+void suspend_blocker_init(struct suspend_blocker *blocker, const char *name)
+{
+ WARN_ON(!name);
+
+ if (debug_mask & DEBUG_SUSPEND_BLOCKER)
+ pr_info("suspend_blocker_init name=%s\n", name);
+
+ blocker->name = name;
+ atomic_set(&blocker->flags, SB_INITIALIZED);
+}
+EXPORT_SYMBOL(suspend_blocker_init);
+
+/**
+ * suspend_blocker_destroy() - Destroy a suspend blocker
+ * @blocker: The suspend blocker to destroy.
+ */
+void suspend_blocker_destroy(struct suspend_blocker *blocker)
+{
+ int flags;
+ if (debug_mask & DEBUG_SUSPEND_BLOCKER)
+ pr_info("suspend_blocker_destroy name=%s\n", blocker->name);
+ flags = atomic_xchg(&blocker->flags, 0);
+ WARN(!(flags & SB_INITIALIZED), "suspend_blocker_destroy called on "
+ "uninitialized suspend_blocker\n");
+ if (flags == (SB_INITIALIZED | SB_ACTIVE))
+ if (atomic_dec_and_test(&suspend_block_count))
+ queue_work(suspend_work_queue, &suspend_work);
+}
+EXPORT_SYMBOL(suspend_blocker_destroy);
+
+/**
+ * suspend_block() - Block suspend
+ * @blocker: The suspend blocker to use
+ */
+void suspend_block(struct suspend_blocker *blocker)
+{
+ WARN_ON(!(atomic_read(&blocker->flags) & SB_INITIALIZED));
+
+ if (debug_mask & DEBUG_SUSPEND_BLOCKER)
+ pr_info("suspend_block: %s\n", blocker->name);
+ if (atomic_cmpxchg(&blocker->flags, SB_INITIALIZED,
+ SB_INITIALIZED | SB_ACTIVE) == SB_INITIALIZED)
+ atomic_inc(&suspend_block_count);
+
+ atomic_inc(&current_event_num);
+}
+EXPORT_SYMBOL(suspend_block);
+
+/**
+ * suspend_unblock() - Unblock suspend
+ * @blocker: The suspend blocker to unblock.
+ *
+ * If no other suspend blockers block suspend, the system will suspend.
+ */
+void suspend_unblock(struct suspend_blocker *blocker)
+{
+ WARN_ON(!(atomic_read(&blocker->flags) & SB_INITIALIZED));
+
+ if (debug_mask & DEBUG_SUSPEND_BLOCKER)
+ pr_info("suspend_unblock: %s\n", blocker->name);
+
+ if (atomic_cmpxchg(&blocker->flags, SB_INITIALIZED | SB_ACTIVE,
+ SB_INITIALIZED) == (SB_INITIALIZED | SB_ACTIVE))
+ if (atomic_dec_and_test(&suspend_block_count))
+ queue_work(suspend_work_queue, &suspend_work);
+}
+EXPORT_SYMBOL(suspend_unblock);
+
+/**
+ * suspend_blocker_is_active() - Test if a suspend blocker is blocking suspend
+ * @blocker: The suspend blocker to check.
+ *
+ * Returns true if the suspend_blocker is currently active.
+ */
+bool suspend_blocker_is_active(struct suspend_blocker *blocker)
+{
+ WARN_ON(!(atomic_read(&blocker->flags) & SB_INITIALIZED));
+
+ return !!(atomic_read(&blocker->flags) & SB_ACTIVE);
+}
+EXPORT_SYMBOL(suspend_blocker_is_active);
+
+bool request_suspend_valid_state(suspend_state_t state)
+{
+ return (state == PM_SUSPEND_ON) || valid_state(state);
+}
+
+int request_suspend_state(suspend_state_t state)
+{
+ unsigned long irqflags;
+
+ if (!request_suspend_valid_state(state))
+ return -ENODEV;
+
+ spin_lock_irqsave(&state_lock, irqflags);
+ if (debug_mask & DEBUG_USER_STATE)
+ pr_info_time("request_suspend_state: %s (%d->%d) at %lld ",
+ state != PM_SUSPEND_ON ? "sleep" : "wakeup",
+ requested_suspend_state, state,
+ ktime_to_ns(ktime_get()));
+ requested_suspend_state = state;
+ if (state == PM_SUSPEND_ON)
+ suspend_block(&main_suspend_blocker);
+ else
+ suspend_unblock(&main_suspend_blocker);
+ spin_unlock_irqrestore(&state_lock, irqflags);
+ return 0;
+}
+
+static int __init suspend_block_init(void)
+{
+ suspend_work_queue = create_singlethread_workqueue("suspend");
+ if (!suspend_work_queue)
+ return -ENOMEM;
+
+ suspend_blocker_init(&main_suspend_blocker, "main");
+ suspend_block(&main_suspend_blocker);
+ return 0;
+}
+
+core_initcall(suspend_block_init);
--
1.6.5.1

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