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cpufreq: intel_pstate: ITMT support for overclocked system 

On systems with overclocking enabled, CPPC Highest Performance can be
hard coded to 0xff. In this case even if we have cores with different
highest performance, ITMT can't be enabled as the current implementation
depends on CPPC Highest Performance.

On such systems we can use MSR_HWP_CAPABILITIES maximum performance field
when CPPC.Highest Performance is 0xff.

Due to legacy reasons, we can't solely depend on MSR_HWP_CAPABILITIES as
in some older systems CPPC Highest Performance is the only way to identify
different performing cores.

Reported-by: Michael Larabel <Michael@MichaelLarabel.com>
Signed-off-by: Srinivas Pandruvada <srinivas.pandruvada@linux.intel.com>
Tested-by: Michael Larabel <Michael@MichaelLarabel.com>
Signed-off-by: Rafael J. Wysocki <rafael.j.wysocki@intel.com>
This commit is contained in:
Srinivas Pandruvada 2021-11-18 21:18:01 -08:00 committed by Rafael J. Wysocki
parent ed38eb49d1
commit 03c83982a0
1 changed files with 10 additions and 0 deletions
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10
drivers/cpufreq/intel_pstate.c
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@ -338,6 +338,8 @@ static void intel_pstste_sched_itmt_work_fn(struct work_struct *work)
static DECLARE_WORK(sched_itmt_work, intel_pstste_sched_itmt_work_fn);
#define CPPC_MAX_PERF U8_MAX
static void intel_pstate_set_itmt_prio(int cpu)
{
struct cppc_perf_caps cppc_perf;
@ -348,6 +350,14 @@ static void intel_pstate_set_itmt_prio(int cpu)
if (ret)
return;
/*
* On some systems with overclocking enabled, CPPC.highest_perf is hardcoded to 0xff.
* In this case we can't use CPPC.highest_perf to enable ITMT.
* In this case we can look at MSR_HWP_CAPABILITIES bits [8:0] to decide.
*/
if (cppc_perf.highest_perf == CPPC_MAX_PERF)
cppc_perf.highest_perf = HWP_HIGHEST_PERF(READ_ONCE(all_cpu_data[cpu]->hwp_cap_cached));
/*
* The priorities can be set regardless of whether or not
* sched_set_itmt_support(true) has been called and it is valid to