shinys000114/linux
1
0
Fork 0
mirror of https://github.com/hardkernel/linux.git synced 2026-06-10 21:07:02 +09:00
Code Issues Packages Projects Releases Wiki Activity

intel_pstate: Correct rounding in busy calculation

Browse Source 
commit 51d211e9c3 upstream.

There was a mistake in the actual rounding portion this previous patch:
f0fe3cd7e1 (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: f0fe3cd7e1 (intel_pstate: Correct rounding in busy calculation)
Signed-off-by: Doug Smythies <dsmythies@telus.net>
Signed-off-by: Rafael J. Wysocki <rafael.j.wysocki@intel.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
This commit is contained in:
Doug Smythies
2014-06-17 13:36:10 -07:00
committed by Greg Kroah-Hartman
parent 3c022c3888
commit 5abec5508d
1 changed files with 1 additions and 4 deletions
Download Patch File Download Diff File Expand all files Collapse all files

5
drivers/cpufreq/intel_pstate.c
View File

@@ -200,10 +200,7 @@ static signed int pid_calc(struct _pid *pid, int32_t busy)
pid->last_err = fp_error;
result = pterm + mul_fp(pid->integral, pid->i_gain) + dterm;
if (result >= 0)
result = result + (1 << (FRAC_BITS-1));
else
result = result - (1 << (FRAC_BITS-1));
result = result + (1 << (FRAC_BITS-1));
return (signed int)fp_toint(result);
}