From b4a11fa3331e163e177e76098fe1d8b12b87cf6b Mon Sep 17 00:00:00 2001 From: Wyes Karny Date: Mon, 29 May 2023 14:25:51 +0000 Subject: cpufreq: Fail driver register if it has adjust_perf without fast_switch If fast_switch_possible flag is set by the scaling driver, the governor is free to select fast_switch function even if adjust_perf is set. Some scaling drivers which use adjust_perf don't set fast_switch thinking that the governor would never fall back to fast_switch. But the governor can fall back to fast_switch even in runtime if frequency invariance is disabled due to some reason. This could crash the kernel if the driver didn't set the fast_switch function pointer. Therefore, fail driver registration if it has adjust_perf without fast_switch. Suggested-by: Rafael J. Wysocki Suggested-by: Viresh Kumar Signed-off-by: Wyes Karny Signed-off-by: Rafael J. Wysocki --- include/linux/cpufreq.h | 5 ++++- 1 file changed, 4 insertions(+), 1 deletion(-) (limited to 'include/linux/cpufreq.h') diff --git a/include/linux/cpufreq.h b/include/linux/cpufreq.h index 26e2eb399484..172ff51c1b2a 100644 --- a/include/linux/cpufreq.h +++ b/include/linux/cpufreq.h @@ -340,7 +340,10 @@ struct cpufreq_driver { /* * ->fast_switch() replacement for drivers that use an internal * representation of performance levels and can pass hints other than - * the target performance level to the hardware. + * the target performance level to the hardware. This can only be set + * if ->fast_switch is set too, because in those cases (under specific + * conditions) scale invariance can be disabled, which causes the + * schedutil governor to fall back to the latter. */ void (*adjust_perf)(unsigned int cpu, unsigned long min_perf, -- cgit v1.2.3