linux-toradex.git/drivers/cpuidle/cpuidle.c, branch v3.11

cpuidle: simplify multiple driver support

2013-06-11T11:42:38+00:00

Commit bf4d1b5 (cpuidle: support multiple drivers) introduced support
for using multiple cpuidle drivers at the same time.  It added a
couple of new APIs to register the driver per CPU, but that led to
some unnecessary code complexity related to the kernel config options
deciding whether or not the multiple driver support is enabled.  The
code has to work as it did before when the multiple driver support is
not enabled and the multiple driver support has to be compatible with
the previously existing API.

Remove the new API, not used by any driver in the tree yet (but
needed for the HMP cpuidle drivers that will be submitted soon), and
add a new cpumask pointer to the cpuidle driver structure that will
point to the mask of CPUs handled by the given driver.  That will
allow the cpuidle_[un]register_driver() API to be used for the
multiple driver support along with the cpuidle_[un]register()
functions added recently.

[rjw: Changelog]
Signed-off-by: Daniel Lezcano 
Signed-off-by: Rafael J. Wysocki

cpuidle: fix comment format

2013-04-23T22:54:51+00:00

Fix comment format for the kernel doc script.

Signed-off-by: Daniel Lezcano 
Signed-off-by: Rafael J. Wysocki

cpuidle: make a single register function for all

2013-04-23T11:45:22+00:00

The usual scheme to initialize a cpuidle driver on a SMP is:

	cpuidle_register_driver(drv);
	for_each_possible_cpu(cpu) {
		device = &per_cpu(cpuidle_dev, cpu);
		cpuidle_register_device(device);
	}

This code is duplicated in each cpuidle driver.

On UP systems, it is done this way:

	cpuidle_register_driver(drv);
	device = &per_cpu(cpuidle_dev, cpu);
	cpuidle_register_device(device);

On UP, the macro 'for_each_cpu' does one iteration:

#define for_each_cpu(cpu, mask)                 \
        for ((cpu) = 0; (cpu) < 1; (cpu)++, (void)mask)

Hence, the initialization loop is the same for UP than SMP.

Beside, we saw different bugs / mis-initialization / return code unchecked in
the different drivers, the code is duplicated including bugs. After fixing all
these ones, it appears the initialization pattern is the same for everyone.

Please note, some drivers are doing dev->state_count = drv->state_count. This is
not necessary because it is done by the cpuidle_enable_device function in the
cpuidle framework. This is true, until you have the same states for all your
devices. Otherwise, the 'low level' API should be used instead with the specific
initialization for the driver.

Let's add a wrapper function doing this initialization with a cpumask parameter
for the coupled idle states and use it for all the drivers.

That will save a lot of LOC, consolidate the code, and the modifications in the
future could be done in a single place. Another benefit is the consolidation of
the cpuidle_device variable which is now in the cpuidle framework and no longer
spread accross the different arch specific drivers.

Signed-off-by: Daniel Lezcano 
Signed-off-by: Rafael J. Wysocki

cpuidle: remove en_core_tk_irqen flag

2013-04-23T11:45:22+00:00

The en_core_tk_irqen flag is set in all the cpuidle driver which
means it is not necessary to specify this flag.

Remove the flag and the code related to it.

Signed-off-by: Daniel Lezcano 
Acked-by: Kevin Hilman   # for mach-omap2/*
Signed-off-by: Rafael J. Wysocki

cpuidle : handle clockevent notify from the cpuidle framework

2013-03-31T23:10:27+00:00

When a cpu enters a deep idle state, the local timers are stopped and
the time framework falls back to the timer device used as a broadcast
timer.

The different cpuidle drivers are calling clockevents_notify ENTER/EXIT
when the idle state stops the local timer.

Add a new flag CPUIDLE_FLAG_TIMER_STOP which can be set by the cpuidle
drivers. If the flag is set, the cpuidle core code takes care of the
notification on behalf of the driver to avoid pointless code duplication.

Signed-off-by: Daniel Lezcano 
Reviewed-by: Thomas Gleixner 
Acked-by: Santosh Shilimkar 
Signed-off-by: Rafael J. Wysocki

PM / tracing: remove deprecated power trace API

2013-01-25T23:39:12+00:00

The text in Documentation said it would be removed in 2.6.41;
the text in the Kconfig said removal in the 3.1 release.  Either
way you look at it, we are well past both, so push it off a cliff.

Note that the POWER_CSTATE and the POWER_PSTATE are part of the
legacy tracing API.  Remove all tracepoints which use these flags.
As can be seen from context, most already have a trace entry via
trace_cpu_idle anyways.

Also, the cpufreq/cpufreq.c PSTATE one is actually unpaired, as
compared to the CSTATE ones which all have a clear start/stop.
As part of this, the trace_power_frequency also becomes orphaned,
so it too is deleted.

Signed-off-by: Paul Gortmaker 
Acked-by: Steven Rostedt 
Signed-off-by: Rafael J. Wysocki

cpuidle: remove the power_specified field in the driver

2013-01-15T13:18:04+00:00

We realized that the power usage field is never filled and when it
is filled for tegra, the power_specified flag is not set causing all
of these values to be reset when the driver is initialized with
set_power_state().

However, the power_specified flag can be simply removed under the
assumption that the states are always backward sorted, which is the
case with the current code.

This change allows the menu governor select function and the
cpuidle_play_dead() to be simplified.  Moreover, the
set_power_states() function can removed as it does not make sense
any more.

Drop the power_specified flag from struct cpuidle_driver and make
the related changes as described above.

As a consequence, this also fixes the bug where on the dynamic
C-states system, the power fields are not initialized.

[rjw: Changelog]
References: https://bugzilla.kernel.org/show_bug.cgi?id=42870
References: https://bugzilla.kernel.org/show_bug.cgi?id=43349
References: https://lkml.org/lkml/2012/10/16/518
Signed-off-by: Daniel Lezcano 
Signed-off-by: Rafael J. Wysocki

cpuidle: Fix finding state with min power_usage

2013-01-03T12:11:05+00:00

Since cpuidle_state.power_usage is a signed value, use INT_MAX (instead
of -1) to init the local copies so that functions that tries to find
cpuidle states with minimum power usage works correctly even if they use
non-negative values.

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

cpuidle: Measure idle state durations with monotonic clock

2012-11-27T13:17:58+00:00

Many cpuidle drivers measure their time spent in an idle state by
reading the wallclock time before and after idling and calculating the
difference. This leads to erroneous results when the wallclock time gets
updated by another processor in the meantime, adding that clock
adjustment to the idle state's time counter.

If the clock adjustment was negative, the result is even worse due to an
erroneous cast from int to unsigned long long of the last_residency
variable. The negative 32 bit integer will zero-extend and result in a
forward time jump of roughly four billion milliseconds or 1.3 hours on
the idle state residency counter.

This patch changes all affected cpuidle drivers to either use the
monotonic clock for their measurements or make use of the generic time
measurement wrapper in cpuidle.c, which was already working correctly.
Some superfluous CLIs/STIs in the ACPI code are removed (interrupts
should always already be disabled before entering the idle function, and
not get reenabled until the generic wrapper has performed its second
measurement). It also removes the erroneous cast, making sure that
negative residency values are applied correctly even though they should
not appear anymore.

Signed-off-by: Julius Werner 
Reviewed-by: Preeti U Murthy 
Tested-by: Daniel Lezcano 
Acked-by: Daniel Lezcano 
Acked-by: Len Brown 
Signed-off-by: Rafael J. Wysocki

cpuidle: support multiple drivers

2012-11-14T23:34:23+00:00

With the tegra3 and the big.LITTLE [1] new architectures, several cpus
with different characteristics (latencies and states) can co-exists on the
system.

The cpuidle framework has the limitation of handling only identical cpus.

This patch removes this limitation by introducing the multiple driver support
for cpuidle.

This option is configurable at compile time and should be enabled for the
architectures mentioned above. So there is no impact for the other platforms
if the option is disabled. The option defaults to 'n'. Note the multiple drivers
support is also compatible with the existing drivers, even if just one driver is
needed, all the cpu will be tied to this driver using an extra small chunk of
processor memory.

The multiple driver support use a per-cpu driver pointer instead of a global
variable and the accessor to this variable are done from a cpu context.

In order to keep the compatibility with the existing drivers, the function
'cpuidle_register_driver' and 'cpuidle_unregister_driver' will register
the specified driver for all the cpus.

The semantic for the output of /sys/devices/system/cpu/cpuidle/current_driver
remains the same except the driver name will be related to the current cpu.

The /sys/devices/system/cpu/cpu[0-9]/cpuidle/driver/name files are added
allowing to read the per cpu driver name.

[1] http://lwn.net/Articles/481055/

Signed-off-by: Daniel Lezcano 
Acked-by: Peter De Schrijver 
Signed-off-by: Rafael J. Wysocki