Problem: This flag does not get cleared currently in the suspend or
resume path in the following cases:

 * In case some driver's suspend routine returns an error.
 * Successful s2idle case
 * etc?

Why is this a problem: What happens is that the next suspend attempt
could fail even though the user did not enable the flag by writing to
/sys/power/wakeup_count. This is 1 use case how the issue can be seen
(but similar use case with driver suspend failure can be thought of):

 1. Read /sys/power/wakeup_count
 2. echo count > /sys/power/wakeup_count
 3. echo freeze > /sys/power/wakeup_count
 4. Let the system suspend, and wakeup the system using some wake source
    that calls pm_wakeup_event() e.g. power button or something.
 5. Note that the combined wakeup count would be incremented due
    to the pm_wakeup_event() in the resume path.
 6. After resuming the events_check_enabled flag is still set.

At this point if the user attempts to freeze again (without writing to
/sys/power/wakeup_count), the suspend would fail even though there has
been no wake event since the past resume.

Address that by clearing the flag just before a resume is completed,
so that it is always cleared for the corner cases mentioned above.

Signed-off-by: Rajat Jain <rajatja@google.com>
Acked-by: Pavel Machek <pavel@ucw.cz>
Signed-off-by: Rafael J. Wysocki <rafael.j.wysocki@intel.com>

The role of the ->wake() platform callback for suspend-to-idle is to
deal with possible spurious wakeups, among other things.  The ACPI
implementation of it, acpi_s2idle_wake(), additionally checks the
conditions for entering the Low Power S0 Idle state by the platform
and reports the ones that have not been met.

However, the ->wake() platform callback is invoked after calling
dpm_noirq_resume_devices(), which means that the power states of some
devices may have changed since s2idle_enter() returned, so some unmet
Low Power S0 Idle conditions may be reported incorrectly as a result
of that.

To avoid these false positives, reorder the invocations of the
dpm_noirq_resume_devices() routine and the ->wake() platform callback
in s2idle_loop().

Fixes: 726fb6b4f2a8 (ACPI / PM: Check low power idle constraints for debug only)
Tested-by: Srinivas Pandruvada <srinivas.pandruvada@linux.intel.com>
Signed-off-by: Rafael J. Wysocki <rafael.j.wysocki@intel.com>

Rename struct platform_freeze_ops to platform_s2idle_ops to make it
clear that the callbacks in it are used during suspend-to-idle
suspend/resume transitions and rename the related functions,
variables and so on accordingly.

Signed-off-by: Rafael J. Wysocki <rafael.j.wysocki@intel.com>

Rename the freeze_state enum representing the suspend-to-idle state
machine states to s2idle_states and rename the related variables and
functions accordingly.

Signed-off-by: Rafael J. Wysocki <rafael.j.wysocki@intel.com>

To make it clear that the symbol in question refers to
suspend-to-idle, rename it from PM_SUSPEND_FREEZE to
PM_SUSPEND_TO_IDLE.

Signed-off-by: Rafael J. Wysocki <rafael.j.wysocki@intel.com>

Modify the ACPI system sleep support setup code to select
suspend-to-idle as the default system sleep state if
(1) the ACPI_FADT_LOW_POWER_S0 flag is set in the FADT and
(2) the Low Power Idle S0 _DSM interface has been discovered and
(3) the default sleep state was not selected from the kernel command
line.

The main motivation for this change is that systems where the (1) and
(2) conditions are met typically ship with OSes that don't exercise
the S3 path in the platform firmware which remains untested and turns
out to be non-functional at least in some cases.

Signed-off-by: Rafael J. Wysocki <rafael.j.wysocki@intel.com>
Tested-by: Mario Limonciello <mario.limonciello@dell.com>

Define a common prefix ("PM:") for messages printed by the
code in kernel/power/suspend.c.

Signed-off-by: Rafael J. Wysocki <rafael.j.wysocki@intel.com>
Reviewed-by: Andy Shevchenko <andy.shevchenko@gmail.com>

Some messages in suspend.c currently print state names from
pm_states[], but that may be confusing if the mem_sleep sysfs
attribute is changed to anything different from "mem", because
in those cases the messages will say either "freeze" or "standby"
after writing "mem" to /sys/power/state.

To avoid the confusion, use mem_sleep_labels[] strings in those
messages instead.

Signed-off-by: Rafael J. Wysocki <rafael.j.wysocki@intel.com>
Reviewed-by: Andy Shevchenko <andy.shevchenko@gmail.com>

Restore the pm_wakeup_pending() check in __device_suspend_noirq()
removed by commit eed4d47efe95 (ACPI / sleep: Ignore spurious SCI
wakeups from suspend-to-idle) as that allows the function to return
earlier if there's a wakeup event pending already (so that it may
spend less time on carrying out operations that will be reversed
shortly anyway) and rework the main suspend-to-idle loop to take
that optimization into account.

Signed-off-by: Rafael J. Wysocki <rafael.j.wysocki@intel.com>

As a preparation for subsequent changes, rearrange the core
suspend-to-idle code by moving the initial invocation of
dpm_suspend_noirq() into s2idle_loop().

This also causes debug messages from that code to appear in
a less confusing order.

Signed-off-by: Rafael J. Wysocki <rafael.j.wysocki@intel.com>