Thomas Schlichter reports the following issue on his Samsung NC20:

"The C-states C1 and C2 to the OS when connected to AC, and additionally
 provides the C3 C-state when disconnected from AC.  However, the number
 of C-states shown in sysfs is fixed to the number of C-states present
 at boot.
   If I boot with AC connected, I always only see the C-states up to C2
   even if I disconnect AC.

   The reason is commit 130a5f692425 (ACPI / cpuidle: remove dev->state_count
   setting).  It removes the update of dev->state_count, but sysfs uses
   exactly this variable to show the C-states.

   The fix is to use drv->state_count in sysfs.  As this is currently the
   last user of dev->state_count, this variable can be completely removed."

Remove dev->state_count as per the above.

Reported-by: Thomas Schlichter <thomas.schlichter@web.de>
Signed-off-by: Bartlomiej Zolnierkiewicz <b.zolnierkie@samsung.com>
Signed-off-by: Kyungmin Park <kyungmin.park@samsung.com>
Acked-by: Daniel Lezcano <daniel.lezcano@linaro.org>
Cc: 3.14+ <stable@vger.kernel.org> # 3.14+
[ rjw: Changelog ]
Signed-off-by: Rafael J. Wysocki <rafael.j.wysocki@intel.com>

Commit 381063133246 (PM / sleep: Re-implement suspend-to-idle handling)
overlooked the fact that entering some sufficiently deep idle states
by CPUs may cause their local timers to stop and in those cases it
is necessary to switch over to a broadcast timer prior to entering
the idle state.  If the cpuidle driver in use does not provide
the new ->enter_freeze callback for any of the idle states, that
problem affects suspend-to-idle too, but it is not taken into account
after the changes made by commit 381063133246.

Fix that by changing the definition of cpuidle_enter_freeze() and
re-arranging of the code in cpuidle_idle_call(), so the former does
not call cpuidle_enter() any more and the fallback case is handled
by cpuidle_idle_call() directly.

Fixes: 381063133246 (PM / sleep: Re-implement suspend-to-idle handling)
Reported-and-tested-by: Lorenzo Pieralisi <lorenzo.pieralisi@arm.com>
Signed-off-by: Rafael J. Wysocki <rafael.j.wysocki@intel.com>
Acked-by: Peter Zijlstra (Intel) <peterz@infradead.org>

The efficiency of suspend-to-idle depends on being able to keep CPUs
in the deepest available idle states for as much time as possible.
Ideally, they should only be brought out of idle by system wakeup
interrupts.

However, timer interrupts occurring periodically prevent that from
happening and it is not practical to chase all of the "misbehaving"
timers in a whack-a-mole fashion.  A much more effective approach is
to suspend the local ticks for all CPUs and the entire timekeeping
along the lines of what is done during full suspend, which also
helps to keep suspend-to-idle and full suspend reasonably similar.

The idea is to suspend the local tick on each CPU executing
cpuidle_enter_freeze() and to make the last of them suspend the
entire timekeeping.  That should prevent timer interrupts from
triggering until an IO interrupt wakes up one of the CPUs.  It
needs to be done with interrupts disabled on all of the CPUs,
though, because otherwise the suspended clocksource might be
accessed by an interrupt handler which might lead to fatal
consequences.

Unfortunately, the existing ->enter callbacks provided by cpuidle
drivers generally cannot be used for implementing that, because some
of them re-enable interrupts temporarily and some idle entry methods
cause interrupts to be re-enabled automatically on exit.  Also some
of these callbacks manipulate local clock event devices of the CPUs
which really shouldn't be done after suspending their ticks.

To overcome that difficulty, introduce a new cpuidle state callback,
->enter_freeze, that will be guaranteed (1) to keep interrupts
disabled all the time (and return with interrupts disabled) and (2)
not to touch the CPU timer devices.  Modify cpuidle_enter_freeze() to
look for the deepest available idle state with ->enter_freeze present
and to make the CPU execute that callback with suspended tick (and the
last of the online CPUs to execute it with suspended timekeeping).

Suggested-by: Thomas Gleixner <tglx@linutronix.de>
Signed-off-by: Rafael J. Wysocki <rafael.j.wysocki@intel.com>
Acked-by: Peter Zijlstra (Intel) <peterz@infradead.org>

In preparation for adding support for quiescing timers in the final
stage of suspend-to-idle transitions, rework the freeze_enter()
function making the system wait on a wakeup event, the freeze_wake()
function terminating the suspend-to-idle loop and the mechanism by
which deep idle states are entered during suspend-to-idle.

First of all, introduce a simple state machine for suspend-to-idle
and make the code in question use it.

Second, prevent freeze_enter() from losing wakeup events due to race
conditions and ensure that the number of online CPUs won't change
while it is being executed.  In addition to that, make it force
all of the CPUs re-enter the idle loop in case they are in idle
states already (so they can enter deeper idle states if possible).

Next, drop cpuidle_use_deepest_state() and replace use_deepest_state
checks in cpuidle_select() and cpuidle_reflect() with a single
suspend-to-idle state check in cpuidle_idle_call().

Finally, introduce cpuidle_enter_freeze() that will simply find the
deepest idle state available to the given CPU and enter it using
cpuidle_enter().

Signed-off-by: Rafael J. Wysocki <rafael.j.wysocki@intel.com>
Acked-by: Peter Zijlstra (Intel) <peterz@infradead.org>

CPUIDLE_FLAG_TIME_INVALID is no longer checked
by menu or ladder cpuidle governors, so don't
bother setting or defining it.

It was originally invented to account for the fact that
acpi_safe_halt() enables interrupts to invoke HLT.
That would allow interrupt service routines to be included
in the last_idle duration measurements made in cpuidle_enter_state(),
potentially returning a duration much larger than reality.

But menu and ladder can gracefully handle erroneously large duration
intervals without checking for CPUIDLE_FLAG_TIME_INVALID.
Further, if they don't check CPUIDLE_FLAG_TIME_INVALID, they
can also benefit from the instances when the duration interval
is not erroneously large.

Signed-off-by: Len Brown <len.brown@intel.com>
Acked-by: Daniel Lezcano <daniel.lezcano@linaro.org>
Signed-off-by: Rafael J. Wysocki <rafael.j.wysocki@intel.com>

The only place where the time is invalid is when the ACPI_CSTATE_FFH entry
method is not set. Otherwise for all the drivers, the time can be correctly
measured.

Instead of duplicating the CPUIDLE_FLAG_TIME_VALID flag in all the drivers
for all the states, just invert the logic by replacing it by the flag
CPUIDLE_FLAG_TIME_INVALID, hence we can set this flag only for the acpi idle
driver, remove the former flag from all the drivers and invert the logic with
this flag in the different governor.

Signed-off-by: Daniel Lezcano <daniel.lezcano@linaro.org>
Signed-off-by: Rafael J. Wysocki <rafael.j.wysocki@intel.com>

Pull MIPS updates from Ralf Baechle:
 - three fixes for 3.15 that didn't make it in time
 - limited Octeon 3 support.
 - paravirtualization support
 - improvment to platform support for Netlogix SOCs.
 - add support for powering down the Malta eval board in software
 - add many instructions to the in-kernel microassembler.
 - add support for the BPF JIT.
 - minor cleanups of the BCM47xx code.
 - large cleanup of math emu code resulting in significant code size
   reduction, better readability of the code and more accurate
   emulation.
 - improvments to the MIPS CPS code.
 - support C3 power status for the R4k count/compare clock device.
 - improvments to the GIO support for older SGI workstations.
 - increase number of supported CPUs to 256; this can be reached on
   certain embedded multithreaded ccNUMA configurations.
 - various small cleanups, updates and fixes

* 'upstream' of git://git.linux-mips.org/pub/scm/ralf/upstream-linus: (173 commits)
  MIPS: IP22/IP28: Improve GIO support
  MIPS: Octeon: Add twsi interrupt initialization for OCTEON 3XXX, 5XXX, 63XX
  DEC: Document the R4k MB ASIC mini interrupt controller
  DEC: Add self as the maintainer
  MIPS: Add microMIPS MSA support.
  MIPS: Replace calls to obsolete strict_strto call with kstrto* equivalents.
  MIPS: Replace obsolete strict_strto call with kstrto
  MIPS: BFP: Simplify code slightly.
  MIPS: Call find_vma with the mmap_sem held
  MIPS: Fix 'write_msa_##' inline macro.
  MIPS: Fix MSA toolchain support detection.
  mips: Update the email address of Geert Uytterhoeven
  MIPS: Add minimal defconfig for mips_paravirt
  MIPS: Enable build for new system 'paravirt'
  MIPS: paravirt: Add pci controller for virtio
  MIPS: Add code for new system 'paravirt'
  MIPS: Add functions for hypervisor call
  MIPS: OCTEON: Add OCTEON3 to __get_cpu_type
  MIPS: Add function get_ebase_cpunum
  MIPS: Add minimal support for OCTEON3 to c-r4k.c
  ...

Declaring this allows drivers which need to initialise each struct
cpuidle_device at initialisation time to make use of the structures
already defined in cpuidle.c, rather than having to wastefully define
their own.

Signed-off-by: Paul Burton <paul.burton@imgtec.com>

If freeze_enter() is called, we want to bypass the current cpuidle
governor and always use the deepest available (that is, not disabled)
C-state, because we want to save as much energy as reasonably possible
then and runtime latency constraints don't matter at that point, since
the system is in a sleep state anyway.

Signed-off-by: Rafael J. Wysocki <rafael.j.wysocki@intel.com>
Tested-by: Aubrey Li <aubrey.li@linux.intel.com>

Since both cpuidle_enabled() and cpuidle_select() are only called by
cpuidle_idle_call(), it is not really useful to keep them separate
and combining them will help to avoid complicating cpuidle_idle_call()
even further if governors are changed to return error codes sometimes.

This code modification shouldn't lead to any functional changes.

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