From: Prarit Bhargava <prarit@redhat.com>
To: Viresh Kumar <viresh.kumar@linaro.org>
Cc: linux-kernel@vger.kernel.org,
Srinivas Pandruvada <srinivas.pandruvada@intel.com>,
Len Brown <len.brown@intel.com>,
Alexandra Yates <alexandra.yates@intel.com>,
Kristen Carlson Accardi <kristen@linux.intel.com>,
"Rafael J. Wysocki" <rjw@rjwysocki.net>,
linux-pm@vger.kernel.org
Subject: Re: [PATCH] cpufreq, intel_pstate.c, Fix rounding errors
Date: Thu, 19 Nov 2015 14:07:37 -0500 [thread overview]
Message-ID: <564E1DF9.1020809@redhat.com> (raw)
In-Reply-To: <20151119044639.GD3737@ubuntu>
On 11/18/2015 11:46 PM, Viresh Kumar wrote:
> On 18-11-15, 10:55, Prarit Bhargava wrote:
>> diff --git a/drivers/cpufreq/intel_pstate.c b/drivers/cpufreq/intel_pstate.c
>> index 2e31d09..686f024 100644
>> --- a/drivers/cpufreq/intel_pstate.c
>> +++ b/drivers/cpufreq/intel_pstate.c
>> @@ -1233,6 +1233,8 @@ static int intel_pstate_set_policy(struct cpufreq_policy *policy)
>> struct cpudata *cpu;
>> int i;
>> #endif
>> + int max_policy_calc;
>> +
>> pr_debug("intel_pstate: %s max %u policy->max %u\n", __func__,
>> policy->cpuinfo.max_freq, policy->max);
>> if (!policy->cpuinfo.max_freq)
>> @@ -1249,7 +1251,10 @@ static int intel_pstate_set_policy(struct cpufreq_policy *policy)
>> limits = &powersave_limits;
>> limits->min_policy_pct = (policy->min * 100) / policy->cpuinfo.max_freq;
>> limits->min_policy_pct = clamp_t(int, limits->min_policy_pct, 0 , 100);
>> - limits->max_policy_pct = (policy->max * 100) / policy->cpuinfo.max_freq;
>> +
>> + max_policy_calc = (policy->max * 1000) / policy->cpuinfo.max_freq;
>> + limits->max_policy_pct = DIV_ROUND_UP(max_policy_calc, 10);
>> +
>
> Nice catch, but why can't we do this instead:
>
> limits->max_policy_pct = DIV_ROUND_UP(policy->max * 100, policy->cpuinfo.max_freq);
>
Ah, I got so deep into the code I didn't even think of simplifying the
calculation. Thanks -- I'll do that instead.
>> limits->max_policy_pct = clamp_t(int, limits->max_policy_pct, 0 , 100);
>>
>> /* Normalize user input to [min_policy_pct, max_policy_pct] */
>> @@ -1269,6 +1274,7 @@ static int intel_pstate_set_policy(struct cpufreq_policy *policy)
>> int_tofp(100));
>> limits->max_perf = div_fp(int_tofp(limits->max_perf_pct),
>> int_tofp(100));
>> + limits->max_perf = round_up(limits->max_perf, 8);
>
> Perhaps you should fix this in a separate patch.
>
Okay, I submit these as a 2 part patchset.
P.
prev parent reply other threads:[~2015-11-19 19:07 UTC|newest]
Thread overview: 3+ messages / expand[flat|nested] mbox.gz Atom feed top
2015-11-18 15:55 [PATCH] cpufreq, intel_pstate.c, Fix rounding errors Prarit Bhargava
2015-11-19 4:46 ` Viresh Kumar
2015-11-19 19:07 ` Prarit Bhargava [this message]
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