linux-toradex.git/drivers/cpuidle/cpuidle.c, branch v5.4-rc1

cpuidle: add poll_limit_ns to cpuidle_device structure

2019-07-30T15:27:37+00:00

Add a poll_limit_ns variable to cpuidle_device structure.

Calculate and configure it in the new cpuidle_poll_time
function, in case its zero.

Individual governors are allowed to override this value.

Signed-off-by: Marcelo Tosatti 
Signed-off-by: Rafael J. Wysocki

cpuidle: Export the next timer expiration for CPUs

2019-04-09T22:32:34+00:00

To be able to predict the sleep duration for a CPU entering idle, it
is essential to know the expiration time of the next timer.  Both the
teo and the menu cpuidle governors already use this information for
CPU idle state selection.

Moving forward, a similar prediction needs to be made for a group of
idle CPUs rather than for a single one and the following changes
implement a new genpd governor for that purpose.

In order to support that feature, add a new function called
tick_nohz_get_next_hrtimer() that will return the next hrtimer
expiration time of a given CPU to be invoked after deciding
whether or not to stop the scheduler tick on that CPU.

Make the cpuidle core call tick_nohz_get_next_hrtimer() right
before invoking the ->enter() callback provided by the cpuidle
driver for the given state and store its return value in the
per-CPU struct cpuidle_device, so as to make it available to code
outside of cpuidle.

Note that at the point when cpuidle calls tick_nohz_get_next_hrtimer(),
the governor's ->select() callback has already returned and indicated
whether or not the tick should be stopped, so in fact the value
returned by tick_nohz_get_next_hrtimer() always is the next hrtimer
expiration time for the given CPU, possibly including the tick (if
it hasn't been stopped).

Co-developed-by: Lina Iyer 
Co-developed-by: Daniel Lezcano 
Acked-by: Daniel Lezcano 
Signed-off-by: Ulf Hansson 
[ rjw: Subject & changelog ]
Signed-off-by: Rafael J. Wysocki

cpuidle: Add 'above' and 'below' idle state metrics

2018-12-12T22:22:18+00:00

Add two new metrics for CPU idle states, "above" and "below", to count
the number of times the given state had been asked for (or entered
from the kernel's perspective), but the observed idle duration turned
out to be too short or too long for it (respectively).

These metrics help to estimate the quality of the CPU idle governor
in use.

Signed-off-by: Rafael J. Wysocki

cpuidle: Add cpuidle.governor= command line parameter

2018-12-11T11:08:44+00:00

Add cpuidle.governor= command line parameter to allow the default
cpuidle governor to be replaced.

That is useful, for example, if someone running a tickful kernel
wants to use the menu governor on it.

Signed-off-by: Rafael J. Wysocki

cpuidle: enter_state: Don't needlessly calculate diff time

2018-09-18T07:32:56+00:00

Currently, ktime_us_delta() is invoked unconditionally to compute the
idle residency of the CPU, but it only makes sense to do that if a
valid idle state has been entered, so move the ktime_us_delta()
invocation after the entered_state >= 0 check.

While at it, merge two comment blocks in there into one and drop
a space between type casting of diff.

This patch has no functional changes.

Signed-off-by: Fieah Lim 
[ rjw: Changelog cleanup, comment format fix ]
Signed-off-by: Rafael J. Wysocki

cpuidle: Return nohz hint from cpuidle_select()

2018-04-06T07:29:34+00:00

Add a new pointer argument to cpuidle_select() and to the ->select
cpuidle governor callback to allow a boolean value indicating
whether or not the tick should be stopped before entering the
selected state to be returned from there.

Make the ladder governor ignore that pointer (to preserve its
current behavior) and make the menu governor return 'false" through
it if:
 (1) the idle exit latency is constrained at 0, or
 (2) the selected state is a polling one, or
 (3) the expected idle period duration is within the tick period
     range.

In addition to that, the correction factor computations in the menu
governor need to take the possibility that the tick may not be
stopped into account to avoid artificially small correction factor
values.  To that end, add a mechanism to record tick wakeups, as
suggested by Peter Zijlstra, and use it to modify the menu_update()
behavior when tick wakeup occurs.  Namely, if the CPU is woken up by
the tick and the return value of tick_nohz_get_sleep_length() is not
within the tick boundary, the predicted idle duration is likely too
short, so make menu_update() try to compensate for that by updating
the governor statistics as though the CPU was idle for a long time.

Since the value returned through the new argument pointer of
cpuidle_select() is not used by its caller yet, this change by
itself is not expected to alter the functionality of the code.

Signed-off-by: Rafael J. Wysocki 
Acked-by: Peter Zijlstra (Intel)

PM: cpuidle/suspend: Add s2idle usage and time state attributes

2018-03-29T11:06:08+00:00

Add a new attribute group called "s2idle" under the sysfs directory
of each cpuidle state that supports the ->enter_s2idle callback
and put two new attributes, "usage" and "time", into that group to
represent the number of times the given state was requested for
suspend-to-idle and the total time spent in suspend-to-idle after
requesting that state, respectively.

That will allow diagnostic information related to suspend-to-idle
to be collected without enabling advanced debug features and
analyzing dmesg output.

Signed-off-by: Rafael J. Wysocki

cpuidle: Avoid assignment in if () argument

2017-11-08T22:15:30+00:00

Clean up cpuidle_enable_device() to avoid doing an assignment
in an expression evaluated as an argument of if (), which also
makes the code in question more readable.

Signed-off-by: Gaurav Jindal 
[ rjw: Subject & changelog ]
Signed-off-by: Rafael J. Wysocki

cpuidle: Clean up cpuidle_enable_device() error handling a bit

2017-11-08T22:09:52+00:00

Do not fetch per CPU drv if cpuidle_curr_governor is NULL
to avoid useless per CPU processing.

Signed-off-by: Gaurav Jindal 
[ rjw: Subject & changelog ]
Signed-off-by: Rafael J. Wysocki

cpuidle: fix broadcast control when broadcast can not be entered

2017-09-28T00:18:07+00:00

When failing to enter broadcast timer mode for an idle state that
requires it, a new state is selected that does not require broadcast,
but the broadcast variable remains set. This causes
tick_broadcast_exit to be called despite not having entered broadcast
mode.

This causes the WARN_ON_ONCE(!irqs_disabled()) to trigger in some
cases. It does not appear to cause problems for code today, but seems
to violate the interface so should be fixed.

Signed-off-by: Nicholas Piggin 
Reviewed-by: Thomas Gleixner 
Signed-off-by: Rafael J. Wysocki