cpufreq: intel_pstate: Get percpu max freq via HWP MSR register if available

Currently when turbo is disabled(either by BIOS or by the user), the intel_pstate driver reads the max non-turbo frequency from the package-wide MSR_PLATFORM_INFO(0xce) register. However on asymmetric platforms it is possible in theory that small and big core with HWP enabled might have different max non-turbo cpu frequency, because the MSR_HWP_CAPABILITIES is percpu scope according to Intel Software Developer Manual.

The turbo max freq is already percpu basis in current code, thus make similar change to the max non-turbo frequency as well.

Reported-by Wendy Wang <[email protected]>

Signed-off-by Chen Yu <[email protected]>

---
v2: Per Srinivas' suggestion, avoid duplicated assignment of max_pstate.
v3: Per Rafael's suggestion, do not add new argument in intel_pstate_get_hwp_max()
to avoid redundant local vars.
Per Srinivas' suggestion, refined the commit log to reflect the 'non-turbo' max frequency.

--

 drivers/cpufreq/intel_pstate.c | 5 +++--
 1 file changed, 3 insertions(+), 2 deletions(-)

drivers/cpufreq/intel_pstate.c +3 -3

index eaf32ef7a030..99e180f644c3 100644
@@ -1724,11 +1724,9 @@ static void intel_pstate_max_within_limits(struct cpudata *cpu)
 static void intel_pstate_get_cpu_pstates(struct cpudata *cpu)
 {
        cpu->pstate.min_pstate = pstate_funcs.get_min();
-       cpu->pstate.max_pstate = pstate_funcs.get_max();
        cpu->pstate.max_pstate_physical = pstate_funcs.get_max_physical();
        cpu->pstate.turbo_pstate = pstate_funcs.get_turbo();
        cpu->pstate.scaling = pstate_funcs.get_scaling();
-       cpu->pstate.max_freq = cpu->pstate.max_pstate * cpu->pstate.scaling;
 
        if (hwp_active && !hwp_mode_bdw) {
                unsigned int phy_max, current_max;

@@ -1736,9 +1734,12 @@ static void intel_pstate_get_cpu_pstates(struct cpudata *cpu)
                intel_pstate_get_hwp_max(cpu, &phy_max, &current_max);
                cpu->pstate.turbo_freq = phy_max * cpu->pstate.scaling;
                cpu->pstate.turbo_pstate = phy_max;
+               cpu->pstate.max_pstate = HWP_GUARANTEED_PERF(READ_ONCE(cpu->hwp_cap_cached));
        } else {
                cpu->pstate.turbo_freq = cpu->pstate.turbo_pstate * cpu->pstate.scaling;
+               cpu->pstate.max_pstate = pstate_funcs.get_max();
        }
+       cpu->pstate.max_freq = cpu->pstate.max_pstate * cpu->pstate.scaling;
 
        if (pstate_funcs.get_aperf_mperf_shift)
                cpu->aperf_mperf_shift = pstate_funcs.get_aperf_mperf_shift();
--

2.17.1

Quoted 11 lines · Chen Yu

Currently when turbo is disabled(either by BIOS or by the user), the intel_pstate driver reads the max non-turbo frequency from the package-wide MSR_PLATFORM_INFO(0xce) register. However on asymmetric platforms it is possible in theory that small and big core with HWP enabled might have different max non-turbo cpu frequency, because the MSR_HWP_CAPABILITIES is percpu scope according to Intel Software Developer Manual.

The turbo max freq is already percpu basis in current code, thus make similar change to the max non-turbo frequency as well.

Quoted 8 lines

Reported-by Wendy Wang <[email protected]>

Signed-off-by Chen Yu <[email protected]>

---
v2: Per Srinivas' suggestion, avoid duplicated assignment of max_pstate.
v3: Per Rafael's suggestion, do not add new argument in intel_pstate_get_hwp_max()
to avoid redundant local vars.
Per Srinivas' suggestion, refined the commit log to reflect the 'non-turbo' max frequency.

Looks good now, thanks!

Is it needed in -stable and if so, which -stable series should it go into?

Quoted 23 lines · Rafael J. Wysocki

Quoted 11 lines · Chen Yu

Currently when turbo is disabled(either by BIOS or by the user), the intel_pstate driver reads the max non-turbo frequency from the package-wide MSR_PLATFORM_INFO(0xce) register. However on asymmetric platforms it is possible in theory that small and big core with HWP enabled might have different max non-turbo cpu frequency, because the MSR_HWP_CAPABILITIES is percpu scope according to Intel Software Developer Manual.

The turbo max freq is already percpu basis in current code, thus make similar change to the max non-turbo frequency as well.

Quoted 8 lines

Reported-by Wendy Wang <[email protected]>

Signed-off-by Chen Yu <[email protected]>

---
v2: Per Srinivas' suggestion, avoid duplicated assignment of max_pstate.
v3: Per Rafael's suggestion, do not add new argument in intel_pstate_get_hwp_max()
to avoid redundant local vars.
Per Srinivas' suggestion, refined the commit log to reflect the 'non-turbo' max frequency.

Looks good now, thanks!

Quoted 2 lines

Is it needed in -stable and if so, which -stable series should it go into?

Yes, I think so, it should be
Cc: [email protected] # 4.18+
as the HWP reading turbo frequency was firstly introduced in v4.18-rc2 and it was easier to be applied.
BTW, this patch is on top of your previous patch set on intel_pstate clean up:
https://patchwork.kernel.org/project/linux-pm/list/?series=410797