intel_pstate: Correct rounding in busy calculation
authorDoug Smythies <doug.smythies@gmail.com>
Tue, 17 Jun 2014 20:36:10 +0000 (13:36 -0700)
committerRafael J. Wysocki <rafael.j.wysocki@intel.com>
Tue, 17 Jun 2014 20:57:40 +0000 (22:57 +0200)
commit51d211e9c334b9eca3505f4052afa660c3e0606b
treef515484b6eb8f1f5b75bfaa3ec969747a3b41706
parent217886d3f3191f1f052e987740ee2bb32a4fd316
intel_pstate: Correct rounding in busy calculation

There was a mistake in the actual rounding portion this previous patch:
f0fe3cd7e12d (intel_pstate: Correct rounding in busy calculation) such that
the rounding was asymetric and incorrect.

Severity: Not very serious, but can increase target pstate by one extra value.
For real world work flows the issue should self correct (but I have no proof).
It is the equivalent of different PID gains for positive and negative numbers.

Examples:
 -3.000000 used to round to -4, rounds to -3 with this patch.
 -3.503906 used to round to -5, rounds to -4 with this patch.

Fixes: f0fe3cd7e12d (intel_pstate: Correct rounding in busy calculation)
Signed-off-by: Doug Smythies <dsmythies@telus.net>
Cc: 3.14+ <stable@vger.kernel.org> # 3.14+
Signed-off-by: Rafael J. Wysocki <rafael.j.wysocki@intel.com>
drivers/cpufreq/intel_pstate.c