Commit c7cd6f04 authored by Srinivas Pandruvada's avatar Srinivas Pandruvada Committed by Rafael J. Wysocki
Browse files

powercap: idle_inject: Support 100% idle injection 



The users of the idle injection framework allow 100% idle injection. For
example: thermal/cpuidle_cooling.c driver. When the ratio is set to
100%, the runtime_duration becomes zero.

However, idle_inject_set_duration() in the idle injection framework
silently ignores run_duration_us == 0 without any error (it is a void
function). The caller will then assume that everything is fine and
100% idle is effective, but in reality the idle duration will not
change.

There are two options:

 - The caller may change their max state to 99% instead of 100% and
   document that 100% is not supported by the idle inject framework.

 - Add 100% idle support to the idle inject framework.

Since there are other protections via RT throttling, this framework can
allow 100% idle. The RT throttling will be activated at 95% idle by
default. The caller disabling RT throttling and injecting 100% idle,
should be aware that CPU can't be used at all.

The idle inject timer is started for (run_duration_us + idle_duration_us)
duration. Hence replace (run_duration_us && idle_duration_us) with
(run_duration_us + idle_duration_us) in the function
idle_inject_set_duration(). Also check for !(run_duration_us +
idle_duration_us) to return -EINVAL in idle_inject_start().

Signed-off-by: default avatarSrinivas Pandruvada <srinivas.pandruvada@linux.intel.com>
Acked-by: default avatarDaniel Lezcano <daniel.lezcano@linaro.org>
[ rjw: Changelog edits ]
Signed-off-by: default avatarRafael J. Wysocki <rafael.j.wysocki@intel.com>
parent 7adc6885

drivers/powercap/idle_inject.c

+4 −2
Original line number Diff line number Diff line
@@ -155,10 +155,12 @@ void idle_inject_set_duration(struct idle_inject_device *ii_dev, 
			      unsigned int run_duration_us,

			      unsigned int idle_duration_us)

{

	if (run_duration_us && idle_duration_us) {

	if (run_duration_us + idle_duration_us) {

		WRITE_ONCE(ii_dev->run_duration_us, run_duration_us);

		WRITE_ONCE(ii_dev->idle_duration_us, idle_duration_us);

	}

	if (!run_duration_us)

		pr_debug("CPU is forced to 100 percent idle\n");

}



/**
@@ -201,7 +203,7 @@ int idle_inject_start(struct idle_inject_device *ii_dev) 
	unsigned int idle_duration_us = READ_ONCE(ii_dev->idle_duration_us);

	unsigned int run_duration_us = READ_ONCE(ii_dev->run_duration_us);



	if (!idle_duration_us || !run_duration_us)

	if (!(idle_duration_us + run_duration_us))

		return -EINVAL;



	pr_debug("Starting injecting idle cycles on CPUs '%*pbl'\n",