Re: [PATCH v5 11/11] cpufreq: CPPC: add autonomous mode boot parameter support

[Sumit Gupta]

On 26/12/25 13:33, zhenglifeng (A) wrote:
> External email: Use caution opening links or attachments
>
>
> On 2025/12/23 20:13, Sumit Gupta wrote:
> > Add kernel boot parameter 'cppc_cpufreq.auto_sel_mode' to enable CPPC
> > autonomous performance selection on all CPUs at system startup without
> > requiring runtime sysfs manipulation. When autonomous mode is enabled,
> > the hardware automatically adjusts CPU performance based on workload
> > demands using Energy Performance Preference (EPP) hints.
> >
> > When auto_sel_mode=1:
> > - All CPUs are configured for autonomous operation during init
> > - EPP is set to performance preference (0x0) by default
> > - Min/max performance bounds use defaults or already set values
> > - CPU frequency scaling is handled by hardware instead of OS governor
> >
> > The boot parameter is applied only during first policy initialization.
> > User's runtime sysfs configuration is preserved across hotplug.
> >
> > For Documentation/:
> > Reviewed-by: Randy Dunlap <rdunlap@xxxxxxxxxxxxx>
> > Signed-off-by: Sumit Gupta <sumitg@xxxxxxxxxx>
> > ---
> >   .../admin-guide/kernel-parameters.txt         | 13 +++
> >   drivers/cpufreq/cppc_cpufreq.c                | 85 +++++++++++++++++--
> >   2 files changed, 90 insertions(+), 8 deletions(-)
> >
> > diff --git a/Documentation/admin-guide/kernel-parameters.txt b/Documentation/admin-guide/kernel-parameters.txt
> > index aab72efa1acd..450f0b0225dc 100644
> > --- a/Documentation/admin-guide/kernel-parameters.txt
> > +++ b/Documentation/admin-guide/kernel-parameters.txt
> > @@ -1035,6 +1035,19 @@ Kernel parameters
> >                        Format:
> >                        <first_slot>,<last_slot>,<port>,<enum_bit>[,<debug>]
> >
> > +     cppc_cpufreq.auto_sel_mode=
> > +                     [CPU_FREQ] Enable ACPI CPPC autonomous performance
> > +                     selection. When enabled, hardware automatically adjusts
> > +                     CPU frequency on all CPUs based on workload demands.
> > +                     In Autonomous mode, Energy Performance Preference (EPP)
> > +                     hints guide hardware toward performance (0x0) or energy
> > +                     efficiency (0xff).
> > +                     Requires ACPI CPPC autonomous selection register support.
> > +                     Format: <bool>
> > +                     Default: 0 (disabled)
> > +                     0: use cpufreq governors
> > +                     1: enable if supported by hardware
> > +
> >        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 b3da263c18b0..8c6869e68504 100644
> > --- a/drivers/cpufreq/cppc_cpufreq.c
> > +++ b/drivers/cpufreq/cppc_cpufreq.c
> > @@ -30,6 +30,9 @@ static struct cpufreq_driver cppc_cpufreq_driver;
> >
> >   static DEFINE_MUTEX(cppc_cpufreq_update_autosel_config_lock);
> >
> > +/* Autonomous Selection boot parameter */
> > +static bool auto_sel_mode;
> > +
> >   #ifdef CONFIG_ACPI_CPPC_CPUFREQ_FIE
> >   static enum {
> >        FIE_UNSET = -1,
> > @@ -643,11 +646,16 @@ static int cppc_cpufreq_set_mperf_limit(struct cpufreq_policy *policy, u64 val,
> >    * cppc_cpufreq_update_autosel_config - Update autonomous selection config
> >    * @policy: cpufreq policy
> >    * @is_auto_sel: enable/disable autonomous selection
> > + * @epp_val: EPP value (used only if update_epp true)
> > + * @update_epp: whether to update EPP register
> > + * @update_policy: whether to update policy constraints
> >    *
> >    * Return: 0 on success, negative error code on failure
> >    */
> >   static int cppc_cpufreq_update_autosel_config(struct cpufreq_policy *policy,
> > -                                           bool is_auto_sel)
> > +                                           bool is_auto_sel, u32 epp_val,
> > +                                           bool update_epp,
> > +                                           bool update_policy)
> cppc_cpufreq_set_mperf_limit() and cppc_cpufreq_update_autosel_config()
> have too much bool input param. Just break them down into several separate
> functions and call them only when needed. These two functions are now too
> hard to read.

Sure, will break them and open code in v6.

Thank you,
Sumit Gupta

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