Amit, On Tue, Dec 18, 2012 at 8:17 PM, amit daniel kachhap <amit.dan...@samsung.com> wrote: > On Tue, Dec 18, 2012 at 12:29 AM, Sonny Rao <sonny...@chromium.org> wrote: >> The cpu_thermal generic thermal management code has a bug where once >> max cpu frequency has been lowered in sysfs (scaling_max_freq) it is >> not possible to raise the max back up later. The bug is that the >> notifer gets called by __cpufreq_set_policy() before the user policy >> max is raised, and is incorrectly trying to enforce the max frequency >> policy even when we are trying to change the policy. It is also not >> clear why this driver is looking at the user policy since it is >> primarily supposed to enforce thermal policy, not user set policy. > > Hi Sunny, > > I am not sure if this change is needed.
Do you have a machine that's running with your code? Can you go into sysfs (/sys/devices/system/cpu/cpu0/cpufreq/) and try lowering then raising the max frequency by doing something like this (assumes that you can scale down to 200MHz): cd /sys/devices/system/cpu/cpu0/cpufreq/ OLD_VAL=$(cat scaling_max_freq) cat scaling_min_freq > scaling_max_freq echo ${OLD_VAL} > scaling_max_freq echo "$(cat scaling_max_freq) should be ${OLD_VAL}. Is it?" ...when I run the above without Sonny's patch on my system I see: 200000 should be 1700000. Is it? ...after Sonny's patch then the above works. > There is a check in cpufreq_thermal_notifier function to return 0 if > notify_device == NOTIFY_INVALID. So the user will be always able to > change the max frequency in normal situation. Did you tested this for > some corner cases? > The reason behind putting this check is that I don't want to override > the user constraints. > > Thanks, > Amit Daniel > >> >> Signed-off-by: Sonny Rao <sonny...@chromium.org> >> --- >> drivers/thermal/cpu_cooling.c | 4 ---- >> 1 files changed, 0 insertions(+), 4 deletions(-) >> >> diff --git a/drivers/thermal/cpu_cooling.c b/drivers/thermal/cpu_cooling.c >> index 836828e..63bc708 100644 >> --- a/drivers/thermal/cpu_cooling.c >> +++ b/drivers/thermal/cpu_cooling.c >> @@ -219,10 +219,6 @@ static int cpufreq_thermal_notifier(struct >> notifier_block *nb, >> if (cpumask_test_cpu(policy->cpu, ¬ify_device->allowed_cpus)) >> max_freq = notify_device->cpufreq_val; >> >> - /* Never exceed user_policy.max*/ >> - if (max_freq > policy->user_policy.max) >> - max_freq = policy->user_policy.max; >> - >> if (policy->max != max_freq) >> cpufreq_verify_within_limits(policy, 0, max_freq); >> >> -- >> 1.7.7.3 >> >> -- >> To unsubscribe from this list: send the line "unsubscribe linux-kernel" in >> the body of a message to majord...@vger.kernel.org >> More majordomo info at http://vger.kernel.org/majordomo-info.html >> Please read the FAQ at http://www.tux.org/lkml/ -Doug -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majord...@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/