On 2 October 2014 12:25, Vince Hsu <[email protected]> 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 <[email protected]>
> ---
> 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 <[email protected]>
--
To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
the body of a message to [email protected]
More majordomo info at http://vger.kernel.org/majordomo-info.html
Please read the FAQ at http://www.tux.org/lkml/
