tree b2dfd6fe3afcc74a880a594ed5f819f27411c1d2
parent 5ad7346b4ae2d59cfee106ec8e40ee2561476d47
author Srinivas Pandruvada <srinivas.pandruvada@linux.intel.com> 1529351265 -0700
committer Rafael J. Wysocki <rafael.j.wysocki@intel.com> 1529397629 +0200

cpufreq: intel_pstate: Fix scaling max/min limits with Turbo 3.0

When scaling max/min settings are changed, internally they are converted
to a ratio using the max turbo 1 core turbo frequency. This works fine
when 1 core max is same irrespective of the core. But under Turbo 3.0,
this will not be the case. For example:
Core 0: max turbo pstate: 43 (4.3GHz)
Core 1: max turbo pstate: 45 (4.5GHz)
In this case 1 core turbo ratio will be maximum of all, so it will be
45 (4.5GHz). Suppose scaling max is set to 4GHz (ratio 40) for all cores
,then on core one it will be
 = max_state * policy->max / max_freq;
 = 43 * (4000000/4500000) = 38 (3.8GHz)
 = 38
which is 200MHz less than the desired.
On core2, it will be correctly set to ratio 40 (4GHz). Same holds true
for scaling min frequency limit. So this requires usage of correct turbo
max frequency for core one, which in this case is 4.3GHz. So we need to
adjust per CPU cpu->pstate.turbo_freq using the maximum HWP ratio of that
core.

This change uses the HWP capability of a core to adjust max turbo
frequency. But since Broadwell HWP doesn't use ratios in the HWP
capabilities, we have to use legacy max 1 core turbo ratio. This is not
a problem as the HWP capabilities don't differ among cores in Broadwell.
We need to check for non Broadwell CPU model for applying this change,
though.

Signed-off-by: Srinivas Pandruvada <srinivas.pandruvada@linux.intel.com>
Cc: 4.6+ <stable@vger.kernel.org> # 4.6+
Signed-off-by: Rafael J. Wysocki <rafael.j.wysocki@intel.com>