Re: [PATCH] cpufreq: respect the min/max settings from user space

[Vince Hsu]

Hi Viresh,

On 10/06/2014 12:45 PM, Viresh Kumar wrote:
> On 2 October 2014 12:25, Vince Hsu <vinceh@xxxxxxxxxx> wrote:
> > When the user space tries to set scaling_(max|min)_freq through
> > sysfs, the cpufreq_set_policy() asks other driver's opinions
> > for the max/min frequencies. Some device drivers, like Tegra
> > CPU EDP which is not upstreamed yet though, may constrain the
> > CPU maximum frequency dynamically because of board design.
> > So if the user space access happens and some driver is capping
> > the cpu frequency at the same time, the user_policy->(max|min)
> > is overridden by the capped value, and that's not expected by
> > the user space. And if the user space is not invoked again,
> > the CPU will always be capped by the user_policy->(max|min)
> > even no drivers limit the CPU frequency any more.
> >
> > This patch preserves the user specified min/max settings, so that
> > every time the cpufreq policy is updated, the new max/min can
> > be re-evaluated correctly based on the user's expection and
> > the present device drivers' status.
> >
> > Signed-off-by: Vince Hsu <vinceh@xxxxxxxxxx>
> > ---
> > Hi,
> >
> > I'm not sure if any platform that is supported mainlin might have this
> > issue, and this patch is complie tested only.
> Why only compiled tested? Why haven't you tested it on tegra?
I did test with Chrome kernel on Tegra platform. I can't do that with 
mainline kernel because we haven't had the CPU EDP driver upstream yet.

Thanks,
Vince

> >   drivers/cpufreq/cpufreq.c | 6 ++++--
> >   1 file changed, 4 insertions(+), 2 deletions(-)
> >
> > diff --git a/drivers/cpufreq/cpufreq.c b/drivers/cpufreq/cpufreq.c
> > index 24bf76fba141..c007cf2a3d2a 100644
> > --- a/drivers/cpufreq/cpufreq.c
> > +++ b/drivers/cpufreq/cpufreq.c
> > @@ -524,7 +524,7 @@ static int cpufreq_set_policy(struct cpufreq_policy *policy,
> >   static ssize_t store_##file_name                                       \
> >   (struct cpufreq_policy *policy, const char *buf, size_t count)         \
> >   {                                                                      \
> > -       int ret;                                                        \
> > +       int ret, temp;                                          \
> >          struct cpufreq_policy new_policy;                               \
> >                                                                          \
> >          ret = cpufreq_get_policy(&new_policy, policy->cpu);             \
> > @@ -535,8 +535,10 @@ static ssize_t store_##file_name                                   \
> >          if (ret != 1)                                                   \
> >                  return -EINVAL;                                         \
> >                                                                          \
> > +       temp = new_policy.object;                                       \
> >          ret = cpufreq_set_policy(policy, &new_policy);          \
> > -       policy->user_policy.object = policy->object;                    \
> > +       if (!ret)                                                       \
> > +               policy->user_policy.object = temp;                      \
> >                                                                          \
> >          return ret ? ret : count;                                       \
> >   }
> Looks fine otherwise.
>
> Acked-by: Viresh Kumar <viresh.kumar@xxxxxxxxxx>

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