Re: [PATCH 1/2] cpufreq, intel_pstate, Fix limits->max_policy_pct rounding error

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 1/2] cpufreq, intel_pstate, Fix limits->max_policy_pct rounding error
Date: Fri, 20 Nov 2015 10:43:54 -0500	[thread overview]
Message-ID: <564F3FBA.6030806@redhat.com> (raw)
In-Reply-To: <20151120151944.GE3957@ubuntu>

On 11/20/2015 10:19 AM, Viresh Kumar wrote:
> On 20-11-15, 10:10, Prarit Bhargava wrote:
>>>>  	limits->max_policy_pct = clamp_t(int, limits->max_policy_pct, 0 , 100);
>>>
>>> And put this after the later one ?
>>>
>>>> +	limits->max_policy_pct = DIV_ROUND_UP(policy->max * 100,
>>>> +					      policy->cpuinfo.max_freq);
>>>>  
>>>>  	/* Normalize user input to [min_policy_pct, max_policy_pct] */
>>>>  	limits->min_perf_pct = max(limits->min_policy_pct,
>>>
>>> Sure you tested it  ? :)
>>
>> Oops -- and yeah, tested.  It works because I rewrite the value of
>> max_policy_pct :).  I'll repost shortly.
> 
> But we aren't doing below anymore, doesn't this change the
> calculations at all?
> 
>   	limits->max_policy_pct = clamp_t(int, limits->max_policy_pct, 0 , 100);

The clamp only confines the max_policy between 0 and 100.  AFAIK it doesn't make
any change tothe value of limits->max_policy_pct unless it was outside of that
range.

P.
> 