Messages in this thread | ![/](/images/icornerl.gif) | | Date | Mon, 6 Oct 2014 12:50:24 +0800 | From | Vince Hsu <> | Subject | Re: [PATCH] cpufreq: respect the min/max settings from user space |
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Hi Viresh,
On 10/06/2014 12:45 PM, Viresh Kumar wrote: > On 2 October 2014 12:25, Vince Hsu <vinceh@nvidia.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@nvidia.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? 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@linaro.org>
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