linux-stable.git/drivers/cpuidle, branch v4.6.2

cpuidle: Fix cpuidle_state_is_coupled() argument in cpuidle_enter()

2016-06-08T01:23:38+00:00

commit e7387da52028b072489c45efeb7a916c0205ebd2 upstream.

Commit 0b89e9aa2856 (cpuidle: delay enabling interrupts until all
coupled CPUs leave idle) rightfully fixed a regression by letting
the coupled idle state framework to handle local interrupt enabling
when the CPU is exiting an idle state.

The current code checks if the idle state is coupled and, if so, it
will let the coupled code to enable interrupts. This way, it can
decrement the ready-count before handling the interrupt. This
mechanism prevents the other CPUs from waiting for a CPU which is
handling interrupts.

But the check is done against the state index returned by the back
end driver's ->enter functions which could be different from the
initial index passed as parameter to the cpuidle_enter_state()
function.

 entered_state = target_state->enter(dev, drv, index);

 [ ... ]

 if (!cpuidle_state_is_coupled(drv, entered_state))
	local_irq_enable();

 [ ... ]

If the 'index' is referring to a coupled idle state but the
'entered_state' is *not* coupled, then the interrupts are enabled
again. All CPUs blocked on the sync barrier may busy loop longer
if the CPU has interrupts to handle before decrementing the
ready-count. That's consuming more energy than saving.

Fixes: 0b89e9aa2856 (cpuidle: delay enabling interrupts until all coupled CPUs leave idle)
Signed-off-by: Daniel Lezcano 
[ rjw: Subject & changelog ]
Signed-off-by: Rafael J. Wysocki 
Signed-off-by: Greg Kroah-Hartman

cpuidle: Indicate when a device has been unregistered

2016-06-08T01:23:37+00:00

commit c998c07836f985b24361629dc98506ec7893e7a0 upstream.

Currently the 'registered' member of the cpuidle_device struct is set
to 1 during cpuidle_register_device. In this same function there are
checks to see if the device is already registered to prevent duplicate
calls to register the device, but this value is never set to 0 even on
unregister of the device. Because of this, any attempt to call
cpuidle_register_device after a call to cpuidle_unregister_device will
fail which shouldn't be the case.

To prevent this, set registered to 0 when the device is unregistered.

Fixes: c878a52d3c7c (cpuidle: Check if device is already registered)
Signed-off-by: Dave Gerlach 
Acked-by: Daniel Lezcano 
Signed-off-by: Rafael J. Wysocki 
Signed-off-by: Greg Kroah-Hartman

ARM: cpuidle: Pass on arm_cpuidle_suspend()'s return value

2016-04-28T13:15:14+00:00

arm_cpuidle_suspend() may return -EOPNOTSUPP, or any value returned
by the cpu_ops/cpuidle_ops suspend call. arm_enter_idle_state() doesn't
update 'ret' with this value, meaning we always signal success to
cpuidle_enter_state(), causing it to update the usage counters as if we
succeeded.

Fixes: 191de17aa3c1 ("ARM64: cpuidle: Replace cpu_suspend by the common ARM/ARM64 function")
Signed-off-by: James Morse 
Acked-by: Lorenzo Pieralisi 
Acked-by: Daniel Lezcano 
Cc: 4.1+  # 4.1+
Signed-off-by: Rafael J. Wysocki

cpuidle: menu: Fall back to polling if next timer event is near

2016-03-21T14:50:28+00:00

Commit a9ceb78bc75c (cpuidle,menu: use interactivity_req to disable
polling) changed the behavior of the fallback state selection part
of menu_select() so it looks at interactivity_req instead of
data->next_timer_us when it makes its decision.  That effectively
caused polling to be used more often as fallback idle which led to
significant increases of energy consumption in some cases.

Commit e132b9b3bc7f (cpuidle: menu: use high confidence factors
only when considering polling) changed that logic again to be more
predictable, but that didn't help with the increased energy
consumption problem.

For this reason, go back to making decisions on which state to fall
back to based on data->next_timer_us which is the time we know for
sure something will happen rather than a prediction (which may be
inaccurate and turns out to be so often enough to be problematic).
However, take the target residency of the first proper idle state
(C1) into account, so that state is not used as the fallback one
if its target residency is greater than data->next_timer_us.

Fixes: a9ceb78bc75c (cpuidle,menu: use interactivity_req to disable polling)
Signed-off-by: Rafael J. Wysocki 
Reported-and-tested-by: Doug Smythies

cpuidle: menu: use high confidence factors only when considering polling

2016-03-17T01:40:32+00:00

The menu governor uses five different factors to pick the
idle state:
 - the user configured latency_req
 - the time until the next timer (next_timer_us)
 - the typical sleep interval, as measured recently
 - an estimate of sleep time by dividing next_timer_us by an observed factor
 - a load corrected version of the above, divided again by load

Only the first three items are known with enough confidence that
we can use them to consider polling, instead of an actual CPU
idle state, because the cost of being wrong about polling can be
excessive power use.

The latter two are used in the menu governor's main selection
loop, and can result in choosing a shallower idle state when
the system is expected to be busy again soon.

This pushes a busy system in the "performance" direction of
the performance<>power tradeoff, when choosing between idle
states, but stays more strictly on the "power" state when
deciding between polling and C1.

Signed-off-by: Rik van Riel 
Signed-off-by: Rafael J. Wysocki

cpuidle: menu: help gcc generate slightly better code

2016-02-16T23:28:15+00:00

We know that the avg variable actually ends up holding a 32 bit
quantity, since it's an average of such numbers. It is only a u64
because it is temporarily used to hold the sum. Making it an actual
u32 allows gcc to generate slightly better code, e.g. when computing
the square, it can do a 32x32->64 multiply.

Signed-off-by: Rasmus Villemoes 
Signed-off-by: Rafael J. Wysocki

cpuidle: menu: avoid expensive square root computation

2016-02-16T23:27:16+00:00

Computing the integer square root is a rather expensive operation, at
least compared to doing a 64x64 -> 64 multiply (avg*avg) and, on 64
bit platforms, doing an extra comparison to a constant (variance <=
U64_MAX/36).

On 64 bit platforms, this does mean that we add a restriction on the
range of the variance where we end up using the estimate (since
previously the stddev <= ULONG_MAX was a tautology), but on the other
hand, we extend the range quite substantially on 32 bit platforms - in
both cases, we now allow standard deviations up to 715 seconds, which
is for example guaranteed if all observations are less than 1430
seconds.

Signed-off-by: Rasmus Villemoes 
Signed-off-by: Rafael J. Wysocki

Merge branches 'pm-cpuidle', 'pm-cpufreq', 'pm-domains' and 'pm-sleep'

2016-01-29T20:45:17+00:00

* pm-cpuidle:
  cpuidle: coupled: remove unused define cpuidle_coupled_lock
  cpuidle: fix fallback mechanism for suspend to idle in absence of enter_freeze

* pm-cpufreq:
  cpufreq: cpufreq-dt: avoid uninitialized variable warnings:
  cpufreq: pxa2xx: fix pxa_cpufreq_change_voltage prototype
  cpufreq: Use list_is_last() to check last entry of the policy list
  cpufreq: Fix NULL reference crash while accessing policy->governor_data

* pm-domains:
  PM / Domains: Fix typo in comment
  PM / Domains: Fix potential deadlock while adding/removing subdomains
  PM / domains: fix lockdep issue for all subdomains

* pm-sleep:
  PM: APM_EMULATION does not depend on PM

cpuidle: coupled: remove unused define cpuidle_coupled_lock

2016-01-27T22:08:46+00:00

This was found with the -RT patch enabled, but the fix should apply to
non-RT also.

Used multi_v7_defconfig+PREEMPT_RT_FULL=y and this caused a compilation
warning without this fix:
../drivers/cpuidle/coupled.c:122:21: warning: 'cpuidle_coupled_lock'
defined but not used [-Wunused-variable]

Signed-off-by: Anders Roxell 
Signed-off-by: Rafael J. Wysocki

cpuidle: fix fallback mechanism for suspend to idle in absence of enter_freeze

2016-01-22T01:35:49+00:00

Commit 51164251f5c3 "sched / idle: Drop default_idle_call() fallback
from call_cpuidle()" made find_deepest_state() return non-negative
value and check all the states with index > 0.  Also as a result,
find_deepest_state() returns 0 even when enter_freeze callbacks are not
implemented and enter_freeze_proper() is called which ends up crashing
the kernel.

This patch updates the check for index > 0 in cpuidle_enter_freeze and
cpuidle_idle_call(when idle_should_freeze is true) to restore the
suspend-to-idle functionality in absence of enter_freeze callback.

Fixes: 51164251f5c3 "sched / idle: Drop default_idle_call() fallback from call_cpuidle()"
Signed-off-by: Sudeep Holla 
Signed-off-by: Rafael J. Wysocki