cpufreq: intel_pstate: Use HWP capabilities in intel_cpufreq_adjust_perf()

From: Rafael J. Wysocki <[email protected]>

If turbo P-states cannot be used, either due to the configuration of the processor, or because intel_pstate is not allowed to used them, the maximum available P-state with HWP enabled corresponds to the HWP_CAP.GUARANTEED value which is not static.  It can be adjusted by an out-of-band agent or during an Intel Speed Select performance level change, so long as it remains less than or equal to HWP_CAP.MAX.

However, if turbo P-states cannot be used, intel_cpufreq_adjust_perf()
always uses pstate.max_pstate (set during the initialization of the driver only) as the maximum available P-state, so it may miss a change
of the HWP_CAP.GUARANTEED value.

Prevent that from happening by modifyig intel_cpufreq_adjust_perf() to always read the "guaranteed" and "maximum turbo" performance levels from the cached HWP_CAP value.

Signed-off-by Rafael J. Wysocki <[email protected]>

---
 drivers/cpufreq/intel_pstate.c |    5 +++--

 1 file changed, 3 insertions(+), 2 deletions(-)

Index: linux-pm/drivers/cpufreq/intel_pstate.c
===================================================================

drivers/cpufreq/intel_pstate.c +1 -0

@@ -2653,12 +2653,13 @@ static void intel_cpufreq_adjust_perf(un
                                       unsigned long capacity)
  {
         struct cpudata *cpu = all_cpu_data[cpunum];
+       u64 hwp_cap = READ_ONCE(cpu->hwp_cap_cached);
         int old_pstate = cpu->pstate.current_pstate;
         int cap_pstate, min_pstate, max_pstate, target_pstate;

        update_turbo_state();
-       cap_pstate = global.turbo_disabled ? cpu->pstate.max_pstate :
-                                            cpu-

Quoted 1 line

pstate.turbo_pstate;

+       cap_pstate = global.turbo_disabled ? HWP_GUARANTEED_PERF(hwp_cap) :
+
HWP_HIGHEST_PERF(hwp_cap);

        /* Optimization: Avoid unnecessary divisions. */