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