From c7cd6f04c0dfb6d44337f92b4c32126d20339873 Mon Sep 17 00:00:00 2001 From: Srinivas Pandruvada Date: Tue, 17 Jan 2023 10:22:40 -0800 Subject: [PATCH] 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: Srinivas Pandruvada Acked-by: Daniel Lezcano [ rjw: Changelog edits ] Signed-off-by: Rafael J. Wysocki --- drivers/powercap/idle_inject.c | 6 ++++-- 1 file changed, 4 insertions(+), 2 deletions(-) diff --git a/drivers/powercap/idle_inject.c b/drivers/powercap/idle_inject.c index fe86a09..c03b540 100644 --- a/drivers/powercap/idle_inject.c +++ b/drivers/powercap/idle_inject.c @@ -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", -- 2.7.4