Messages in this thread | | | From | "Rafael J. Wysocki" <> | Date | Thu, 9 Sep 2021 18:12:17 +0200 | Subject | Re: [PATCH] cpufreq: intel_pstate: Override parameters if HWP forced by BIOS |
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On Thu, Sep 9, 2021 at 3:20 PM Doug Smythies <dsmythies@telus.net> wrote: > > On Thu, Sep 9, 2021 at 4:18 AM Rafael J. Wysocki <rafael@kernel.org> wrote: > > > > On Thu, Sep 9, 2021 at 8:52 AM Srinivas Pandruvada > > <srinivas.pandruvada@linux.intel.com> wrote: > > > > > > On Wed, 2021-09-08 at 20:48 -0700, Doug Smythies wrote: > > > > If HWP has been already been enabled by BIOS, it may be > > > > necessary to override some kernel command line parameters. > > > > Once it has been enabled it requires a reset to be disabled. > > > > > > > > Signed-off-by: Doug Smythies <dsmythies@telus.net> > > > > --- > > > > drivers/cpufreq/intel_pstate.c | 22 ++++++++++++++++------ > > > > 1 file changed, 16 insertions(+), 6 deletions(-) > > > > > > > > diff --git a/drivers/cpufreq/intel_pstate.c > > > > b/drivers/cpufreq/intel_pstate.c > > > > index bb4549959b11..073bae5d4498 100644 > > > > --- a/drivers/cpufreq/intel_pstate.c > > > > +++ b/drivers/cpufreq/intel_pstate.c > > > > @@ -3267,7 +3267,7 @@ static int __init intel_pstate_init(void) > > > > */ > > > > if ((!no_hwp && boot_cpu_has(X86_FEATURE_HWP_EPP)) || > > > > intel_pstate_hwp_is_enabled()) { > > > > - hwp_active++; > > > > + hwp_active = 1; > > > Why this change? > > > > I think hwp_active can be changed to bool and then it would make sense > > to update this line. > > > > > > hwp_mode_bdw = id->driver_data; > > > > intel_pstate.attr = hwp_cpufreq_attrs; > > > > intel_cpufreq.attr = hwp_cpufreq_attrs; > > > > @@ -3347,17 +3347,27 @@ device_initcall(intel_pstate_init); > > > > > > > > static int __init intel_pstate_setup(char *str) > > > > { > > > > + /* > > > > + * If BIOS is forcing HWP, then parameter > > > > + * overrides might be needed. Only print > > > > + * the message once, and regardless of > > > > + * any overrides. > > > > + */ > > > > + if(!hwp_active > > > This part of code is from early_param, Is it possible that > > > hwp_active is not 0? > > > > Well, it wouldn't matter even if it were nonzero. This check is just > > pointless anyway. > > > > > > && boot_cpu_has(X86_FEATURE_HWP)) > > > > + if(intel_pstate_hwp_is_enabled()){ > > > > This should be > > > > if (boot_cpu_has(X86_FEATURE_HWP) && intel_pstate_hwp_is_enabled()) { > > Disagree. > This routine gets executed once per intel_pstate related grub command > line entry. The purpose of the "if(!hwp_active" part is to prevent the > printing of the message to the logs multiple times.
Ah OK. Fair enough.
You can do all of the checks in one conditional, though. They will be processed left-to-right anyway.
But then it would be good to avoid calling intel_pstate_hwp_is_enabled() multiple times if it returns false.
And having said all that I'm not sure why you are trying to make no_hwp depend on !hwp_active? I will not be taken into account anyway if intel_pstate_hwp_is_enabled() returns 'true'?
So if no_hwp is covered regardless, you may move the intel_pstate_hwp_is_enabled() inside the no_load conditional.
Alternatively, and I would do that, intel_pstate_hwp_is_enabled() could be evaluated earlier in intel_pstate_init() and if it returned 'true', both no_load and no_hwp would be disregarded.
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