From mboxrd@z Thu Jan  1 00:00:00 1970
From: bugzilla-daemon@bugzilla.kernel.org
Subject: [Bug 64261] Intel Pstate driver truncates to pstate instead of
 rounding to nearest pstate
Date: Tue, 05 Nov 2013 07:21:34 +0000
Message-ID: <bug-64261-12968-gcPydfVYRn@https.bugzilla.kernel.org/>
References: <bug-64261-12968@https.bugzilla.kernel.org/>
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https://bugzilla.kernel.org/show_bug.cgi?id=64261

--- Comment #7 from Doug Smythies <dsmythies@telus.net> ---
(In reply to Dirk Brandewie from comment #6)
> The percentage
> values to get to a given frequency are SKU dependent.

Yes, of course.

> int(.53 * 34 + 0.5) = 18
> 
> How is it off by a whole P state?

Because it actually goes to 1.7 GHz not 1.8 GHz:
CPU 7 is fully loaded:

doug@s15:~/temp$ cat /sys/devices/system/cpu/intel_pstate/*
53
42
1
doug@s15:~/temp$ cat /sys/devices/system/cpu/cpu7/cpufreq/cpuinfo_cur_freq
1699867

By rounding, we stay away from finite math issues at integer boundaries.

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