From mboxrd@z Thu Jan 1 00:00:00 1970 From: Vince Hsu Subject: Re: [PATCH] cpufreq: respect the min/max settings from user space Date: Mon, 6 Oct 2014 12:50:24 +0800 Message-ID: <54321F90.2010103@nvidia.com> References: <1412232900-11238-1-git-send-email-vinceh@nvidia.com> Mime-Version: 1.0 Content-Type: text/plain; charset="utf-8"; format=flowed Content-Transfer-Encoding: 7bit Return-path: Received: from hqemgate14.nvidia.com ([216.228.121.143]:19314 "EHLO hqemgate14.nvidia.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751264AbaJFEuy (ORCPT ); Mon, 6 Oct 2014 00:50:54 -0400 In-Reply-To: Sender: linux-pm-owner@vger.kernel.org List-Id: linux-pm@vger.kernel.org To: Viresh Kumar Cc: "Rafael J. Wysocki" , "linux-pm@vger.kernel.org" , Linux Kernel Mailing List , Bill Huang , dgreid@google.com, olofj@chromium.org Hi Viresh, On 10/06/2014 12:45 PM, Viresh Kumar wrote: > On 2 October 2014 12:25, Vince Hsu 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 >> --- >> 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