[PATCH][v3] cpufreq: intel_pstate: Get percpu max freq via HWP MSR register if available

[PATCH][v3] cpufreq: intel_pstate: Get percpu max freq via HWP MSR register if available

[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.

Reported-by: Wendy Wang <wendy.wang@intel.com>
Signed-off-by: Chen Yu <yu.c.chen@intel.com>
---
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(-)

diff --git a/drivers/cpufreq/intel_pstate.c b/drivers/cpufreq/intel_pstate.c
index eaf32ef7a030..99e180f644c3 100644
--- a/drivers/cpufreq/intel_pstate.c
+++ b/drivers/cpufreq/intel_pstate.c
@@ -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

Re: [PATCH][v3] cpufreq: intel_pstate: Get percpu max freq via HWP MSR register if available

[Rafael J. Wysocki]

On Tue, Jan 12, 2021 at 6:19 AM Chen Yu <yu.c.chen@intel.com> wrote:
>
> 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 <wendy.wang@intel.com>
> Signed-off-by: Chen Yu <yu.c.chen@intel.com>
> ---
> 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?

> --
>  drivers/cpufreq/intel_pstate.c | 5 +++--
>  1 file changed, 3 insertions(+), 2 deletions(-)
>
> diff --git a/drivers/cpufreq/intel_pstate.c b/drivers/cpufreq/intel_pstate.c
> index eaf32ef7a030..99e180f644c3 100644
> --- a/drivers/cpufreq/intel_pstate.c
> +++ b/drivers/cpufreq/intel_pstate.c
> @@ -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
>

Re: [PATCH][v3] cpufreq: intel_pstate: Get percpu max freq via HWP MSR register if available

[Chen Yu]

On Tue, Jan 12, 2021 at 02:52:50PM +0100, Rafael J. Wysocki wrote:
> On Tue, Jan 12, 2021 at 6:19 AM Chen Yu <yu.c.chen@intel.com> wrote:
> >
> > 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 <wendy.wang@intel.com>
> > Signed-off-by: Chen Yu <yu.c.chen@intel.com>
> > ---
> > 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?
>
Yes, I think so, it should be 
Cc: stable@vger.kernel.org # 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

thanks,
Chenyu

Re: [PATCH][v3] cpufreq: intel_pstate: Get percpu max freq via HWP MSR register if available

[Rafael J. Wysocki]

On Tue, Jan 12, 2021 at 4:00 PM Chen Yu <yu.c.chen@intel.com> wrote:
>
> On Tue, Jan 12, 2021 at 02:52:50PM +0100, Rafael J. Wysocki wrote:
> > On Tue, Jan 12, 2021 at 6:19 AM Chen Yu <yu.c.chen@intel.com> wrote:
> > >
> > > 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 <wendy.wang@intel.com>
> > > Signed-off-by: Chen Yu <yu.c.chen@intel.com>
> > > ---
> > > 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?
> >
> Yes, I think so, it should be
> Cc: stable@vger.kernel.org # 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

OK, applied (with a few minor edits in the subject and changelog) as
5.12 material along with those patches , thanks!