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    SubjectRe: [PATCH] [RFC] cpufreq: can't raise max frequency with cpu_thermal
    On Wed, Dec 26, 2012 at 11:32 AM, amit daniel kachhap
    <amit.daniel@samsung.com> wrote:
    >
    > On Tue, Dec 18, 2012 at 9:45 PM, Doug Anderson <dianders@chromium.org> wrote:
    > > Amit,
    > >
    > > On Tue, Dec 18, 2012 at 8:17 PM, amit daniel kachhap
    > > <amit.daniel@samsung.com> wrote:
    > >> On Tue, Dec 18, 2012 at 12:29 AM, Sonny Rao <sonnyrao@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.
    > Hi Doug,
    >
    > I tested the above steps on exynos origen board with all cpufreq
    > cooling configs enabled in kernel version 3.8-rc1.
    > In my tests I am able to vary scaling_max_freq to all values. Also I
    > am in normal temperature threshold. So basically I am not able to
    > reproduce the error reported,
    >
    > Thanks,
    > Amit Daniel


    Hi, thanks for checking it out. I'm a bit surprised that you couldn't
    reproduce it, but it might just be that it will only manifest on a
    platform which is using that driver - like Exynos 5? We'll try it out
    on a 3.8-rc on an Exynos and let you know if we see it or not.

    Thanks again,
    Sonny


    >
    > >
    > >> 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 <sonnyrao@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, &notify_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 majordomo@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 majordomo@vger.kernel.org
    > > More majordomo info at http://vger.kernel.org/majordomo-info.html
    > > Please read the FAQ at http://www.tux.org/lkml/


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