Re: [PATCH v2 7/7] cpufreq: CPPC: add autonomous mode boot parameter support

[Sumit Gupta]

On 24/08/25 05:38, Randy Dunlap wrote:
> On 8/23/25 1:01 PM, Sumit Gupta wrote:
> > Add kernel boot parameter 'cppc_cpufreq.auto_sel_mode' to enable CPPC
> > autonomous performance selection at system startup. When autonomous mode
> > is enabled, the hardware automatically adjusts CPU performance based on
> > workload demands using Energy Performance Preference (EPP) hints from
> > the OS.
> >
> > This parameter allows to configure the autonomous mode on all CPUs
> > without requiring runtime sysfs manipulation if the 'auto_sel' register
> > is present.
> >
> > When auto_sel_mode=1:
> > - All CPUs are configured for autonomous operation during driver init
> > - EPP is set to performance preference (0x0) by default
> > - Min/max performance bounds use defaults
> > - CPU frequency scaling is handled by hardware rather than OS
> >
> > Also ensure that when autonomous mode is active, the set_target callback
> > returns early since hardware controls frequency scaling directly.
> >
> > Signed-off-by: Sumit Gupta <sumitg@xxxxxxxxxx>
>
>
> > ---
> >   .../admin-guide/kernel-parameters.txt         |  12 ++
> >   drivers/cpufreq/cppc_cpufreq.c                | 171 ++++++++++++++++--
> >   2 files changed, 168 insertions(+), 15 deletions(-)
> >
> > diff --git a/Documentation/admin-guide/kernel-parameters.txt b/Documentation/admin-guide/kernel-parameters.txt
> > index 86f395f2933b..ea58deb88c36 100644
> > --- a/Documentation/admin-guide/kernel-parameters.txt
> > +++ b/Documentation/admin-guide/kernel-parameters.txt
> > @@ -911,6 +911,18 @@
> >   			Format:
> >   			<first_slot>,<last_slot>,<port>,<enum_bit>[,<debug>]
> >   
> > +	cppc_cpufreq.auto_sel_mode=
> > +			[CPU_FREQ] Autonomous Performance Level Selection.
> > +			When Autonomous selection is enabled, then the hardware is
> > +			allowed to autonomously select the CPU frequency.
> > +			In Autonomous mode, Energy Performance Preference(EPP)
> > +			provides input to the hardware to favour performance (0x0)
> > +			or energy efficiency (0xff).
> > +			Format: <bool>
> > +			Default: disabled.
> > +			0: force disabled
> > +			1: force enabled
> > +
> >   	cpuidle.off=1	[CPU_IDLE]
> >   			disable the cpuidle sub-system
> >   
> > diff --git a/drivers/cpufreq/cppc_cpufreq.c b/drivers/cpufreq/cppc_cpufreq.c
> > index 5e1bbb5f67b8..bbf654c56ff9 100644
> > --- a/drivers/cpufreq/cppc_cpufreq.c
> > +++ b/drivers/cpufreq/cppc_cpufreq.c
> [snip]
>
> >   
> > +module_param(auto_sel_mode, bool, 0000);
> Hm. Is this changed to readable at some point or
> does it stay invisible?

Yes, it stays invisible. I am not sure about future as of now.

Thank you,
Sumit Gupta
> > +MODULE_PARM_DESC(auto_sel_mode, "Enable Autonomous Performance Level Selection");
> > +
> >   module_exit(cppc_cpufreq_exit);
> >   MODULE_AUTHOR("Ashwin Chaugule");
> >   MODULE_DESCRIPTION("CPUFreq driver based on the ACPI CPPC v5.0+ spec");
> For Documentation/:
> Reviewed-by: Randy Dunlap <rdunlap@xxxxxxxxxxxxx>
>
> Thanks.