Re: [PATCH 2/2] cpufreq: intel_pstate: Fix set_policy interface for no_turbo
flat view
From: "Rafael J. Wysocki" <rafael@kernel.org>
Date: 2016-06-08 01:06:04
On Wed, Jun 8, 2016 at 2:38 AM, Srinivas Pandruvada [off-list ref] wrote:
quoted hunk ↗ jump to hunk
When turbo is disabled, the set_policy interface is broken. For example, when turbo is disabled and cpuinfo.max = 2900000 (full max turbo frequency) Setting the limits results in frequency less than settings: Set 1000000 KHz results in 0700000 KHz Set 1500000 KHz results in 1100000 KHz Set 2000000 KHz results in 1500000 KHz This is because limits->max_perf fraction is calculated using max turbo frequency as the reference, but when the max P-State is capped in the function intel_pstate_get_min_max, the reference is not the max turbo P-State. This results in reducing max P-State. One option is to always use max turbo as reference for calculating limits. But this will not be correct. By definition the intel_pstate sysfs limits, shows percentage of available performance. So when BIOS has disabled turbo, the available performance is max non turbo. So the max_perf_pct should still show 100%. Signed-off-by: Srinivas Pandruvada <srinivas.pandruvada@linux.intel.com> --- drivers/cpufreq/intel_pstate.c | 10 ++++++++-- 1 file changed, 8 insertions(+), 2 deletions(-)diff --git a/drivers/cpufreq/intel_pstate.c b/drivers/cpufreq/intel_pstate.c index 724b905..2116666 100644 --- a/drivers/cpufreq/intel_pstate.c +++ b/drivers/cpufreq/intel_pstate.c@@ -1561,8 +1561,14 @@ static int intel_pstate_cpu_init(struct cpufreq_policy *policy) /* cpuinfo and default policy values */ policy->cpuinfo.min_freq = cpu->pstate.min_pstate * cpu->pstate.scaling; - policy->cpuinfo.max_freq = - cpu->pstate.turbo_pstate * cpu->pstate.scaling; + update_turbo_state(); + if (limits->turbo_disabled) + policy->cpuinfo.max_freq = + cpu->pstate.max_pstate * cpu->pstate.scaling; + else + policy->cpuinfo.max_freq = + cpu->pstate.turbo_pstate * cpu->pstate.scaling; + intel_pstate_init_acpi_perf_limits(policy); policy->cpuinfo.transition_latency = CPUFREQ_ETERNAL; cpumask_set_cpu(policy->cpu, policy->cpus); --
BTW, I would write this slightly differently. What about: policy->cpuinfo.max_freq = limits->turbo_disabled ? cpu->pstate.max_pstate : cpu->pstate.turbo_pstate; policy->cpuinfo.max_freq *= cpu->pstate.scaling;