diff options
| author | Wyes Karny <wyes.karny@amd.com> | 2023-05-29 14:25:51 +0000 |
|---|---|---|
| committer | Rafael J. Wysocki <rafael.j.wysocki@intel.com> | 2023-06-15 18:15:25 +0200 |
| commit | b4a11fa3331e163e177e76098fe1d8b12b87cf6b (patch) | |
| tree | 0bde84560ef3272e9bfc4ad1e3866f1a625a2da7 /include/linux/cpufreq.h | |
| parent | 858fd168a95c5b9669aac8db6c14a9aeab446375 (diff) | |
| download | lwn-b4a11fa3331e163e177e76098fe1d8b12b87cf6b.tar.gz lwn-b4a11fa3331e163e177e76098fe1d8b12b87cf6b.zip | |
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 <rafael@kernel.org>
Suggested-by: Viresh Kumar <viresh.kumar@linaro.org>
Signed-off-by: Wyes Karny <wyes.karny@amd.com>
Signed-off-by: Rafael J. Wysocki <rafael.j.wysocki@intel.com>
Diffstat (limited to 'include/linux/cpufreq.h')
| -rw-r--r-- | include/linux/cpufreq.h | 5 |
1 files changed, 4 insertions, 1 deletions
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, |