linux-kernel - Re: [PATCH] cpufreq: CPPC: Avoid overflow when calculating desired

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Date:   Wed, 14 Sep 2016 20:06:45 -0700
From:   Hoan Tran <hotran@....com>
To:     "Rafael J. Wysocki" <rjw@...ysocki.net>
Cc:     Viresh Kumar <viresh.kumar@...aro.org>,
        Prashanth Prakash <pprakash@...eaurora.org>,
        Al Stone <ahs3@...hat.com>, linux-pm@...r.kernel.org,
        lkml <linux-kernel@...r.kernel.org>, Loc Ho <lho@....com>,
        Duc Dang <dhdang@....com>
Subject: Re: [PATCH] cpufreq: CPPC: Avoid overflow when calculating desired_perf

Hi Rafael,

On Wed, Sep 14, 2016 at 5:50 PM, Rafael J. Wysocki <rjw@...ysocki.net> wrote:
> On Wednesday, September 14, 2016 04:08:28 PM Hoan Tran wrote:
>> This patch fixes overflow issue when calculating the desired_perf.
>>
>> Signed-off-by: Hoan Tran <hotran@....com>
>> ---
>>  drivers/cpufreq/cppc_cpufreq.c | 3 ++-
>>  1 file changed, 2 insertions(+), 1 deletion(-)
>>
>> diff --git a/drivers/cpufreq/cppc_cpufreq.c b/drivers/cpufreq/cppc_cpufreq.c
>> index 894e465..3e0961e 100644
>> --- a/drivers/cpufreq/cppc_cpufreq.c
>> +++ b/drivers/cpufreq/cppc_cpufreq.c
>> @@ -84,7 +84,8 @@ static int cppc_cpufreq_set_target(struct cpufreq_policy *policy,
>>
>>       cpu = all_cpu_data[policy->cpu];
>>
>> -     cpu->perf_ctrls.desired_perf = target_freq * policy->max / cppc_dmi_max_khz;
>> +     cpu->perf_ctrls.desired_perf =
>> +             (u64)target_freq * policy->max / cppc_dmi_max_khz;
>>       freqs.old = policy->cur;
>>       freqs.new = target_freq;
>
> That's on top of the CPPC material in linux-next I gather?

Yes, it's on TOP of linux-next.

>
> Which commit does it fix?

This is a fix for ad38677df44b67e0f5b6c4d31e9c2734abde8ed9 (cpufreq:
CPPC: Force reporting values in KHz to fix user space interface)
http://git.kernel.org/cgit/linux/kernel/git/next/linux-next.git/commit/drivers/cpufreq/cppc_cpufreq.c?id=ad38677df44b67e0f5b6c4d31e9c2734abde8ed9

Thanks
Hoan

>
> Thanks,
> Rafael
>