linux-kernel - Re: [Patch 1/6] cpufreq: use correct unit when verify cur freq

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Message-ID: <05feec0c-c94a-a0e7-3636-1927f6621cb9@nvidia.com>
Date:   Tue, 18 Apr 2023 19:01:44 +0530
From:   Sumit Gupta <sumitg@...dia.com>
To:     "Rafael J. Wysocki" <rafael@...nel.org>
CC:     <viresh.kumar@...aro.org>, <ionela.voinescu@....com>,
        <mark.rutland@....com>, <sudeep.holla@....com>,
        <lpieralisi@...nel.org>, <catalin.marinas@....com>,
        <will@...nel.org>, <linux-pm@...r.kernel.org>,
        <linux-arm-kernel@...ts.infradead.org>,
        <linux-kernel@...r.kernel.org>, <linux-tegra@...r.kernel.org>,
        <treding@...dia.com>, <jonathanh@...dia.com>, <vsethi@...dia.com>,
        <sdonthineni@...dia.com>, <sanjayc@...dia.com>,
        <ksitaraman@...dia.com>, <bbasu@...dia.com>,
        Sumit Gupta <sumitg@...dia.com>
Subject: Re: [Patch 1/6] cpufreq: use correct unit when verify cur freq



On 18/04/23 18:27, Rafael J. Wysocki wrote:
> External email: Use caution opening links or attachments
> 
> 
> On Tue, Apr 18, 2023 at 1:35 PM Sumit Gupta <sumitg@...dia.com> wrote:
>>
>> From: Sanjay Chandrashekara <sanjayc@...dia.com>
>>
>> cpufreq_verify_current_freq checks if the frequency returned by
>> the hardware has a slight delta with the valid frequency value
>> last set and returns "policy->cur" if the delta is within "1 MHz".
>> In the comparison, "policy->cur" is in "kHz" but it's compared
>> against HZ_PER_MHZ. So, the comparison range becomes "1 GHz".
>> Fix this by comparing against KHZ_PER_MHZ instead of HZ_PER_MHZ.
>>
>> Fixes: f55ae08c8987 ("cpufreq: Avoid unnecessary frequency updates due to mismatch")
>> Signed-off-by: Sanjay Chandrashekara <sanjayc@...dia.com>
>> [ sumit gupta: Commit message update ]
>> Signed-off-by: Sumit Gupta <sumitg@...dia.com>
>> ---
>>   drivers/cpufreq/cpufreq.c | 2 +-
>>   1 file changed, 1 insertion(+), 1 deletion(-)
>>
>> diff --git a/drivers/cpufreq/cpufreq.c b/drivers/cpufreq/cpufreq.c
>> index 8b0509f89f1b..6b52ebe5a890 100644
>> --- a/drivers/cpufreq/cpufreq.c
>> +++ b/drivers/cpufreq/cpufreq.c
>> @@ -1732,7 +1732,7 @@ static unsigned int cpufreq_verify_current_freq(struct cpufreq_policy *policy, b
>>                   * MHz. In such cases it is better to avoid getting into
>>                   * unnecessary frequency updates.
>>                   */
>> -               if (abs(policy->cur - new_freq) < HZ_PER_MHZ)
>> +               if (abs(policy->cur - new_freq) < KHZ_PER_MHZ)
>>                          return policy->cur;
>>
>>                  cpufreq_out_of_sync(policy, new_freq);
>> --
> 
> So this is a fix that can be applied separately from the rest of the
> series, isn't it?

Yes.

Thank you,
Sumit Gupta