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Date: Mon, 6 Oct 2014 10:15:31 +0530 From: Viresh Kumar <viresh.kumar@...aro.org> To: Vince Hsu <vinceh@...dia.com> Cc: "Rafael J. Wysocki" <rjw@...ysocki.net>, "linux-pm@...r.kernel.org" <linux-pm@...r.kernel.org>, Linux Kernel Mailing List <linux-kernel@...r.kernel.org>, Bill Huang <bilhuang@...dia.com>, dgreid@...gle.com, olofj@...omium.org Subject: Re: [PATCH] cpufreq: respect the min/max settings from user space On 2 October 2014 12:25, Vince Hsu <vinceh@...dia.com> 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@...dia.com> > --- > 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? > 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@...aro.org> -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@...r.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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