Re: [PATCH v3 10/11] cpufreq: amd-pstate: Add documentation for `amd_pstate_hw_prefcore`

[Mario Limonciello]

On 9/10/2024 05:19, Russell Haley wrote:
> On 9/5/24 11:30 AM, Mario Limonciello wrote:
> > From: Mario Limonciello <mario.limonciello@xxxxxxx>
> >
> > Explain that the sysfs file represents both preferred core being
> > enabled by the user and supported by the hardware.
> >
> > Reviewed-by: Gautham R. Shenoy <gautham.shenoy@xxxxxxx>
> > Signed-off-by: Mario Limonciello <mario.limonciello@xxxxxxx>
> > ---
> > v2->v3:
> >   * Add tag
> > ---
> >   Documentation/admin-guide/pm/amd-pstate.rst | 5 +++++
> >   1 file changed, 5 insertions(+)
> >
> > diff --git a/Documentation/admin-guide/pm/amd-pstate.rst b/Documentation/admin-guide/pm/amd-pstate.rst
> > index e13915c540648..d5c050ea390dc 100644
> > --- a/Documentation/admin-guide/pm/amd-pstate.rst
> > +++ b/Documentation/admin-guide/pm/amd-pstate.rst
> > @@ -263,6 +263,11 @@ lowest non-linear performance in `AMD CPPC Performance Capability
> >   <perf_cap_>`_.)
> >   This attribute is read-only.
> >   
> > +``amd_pstate_hw_prefcore``
> > +
> > +Whether the platform supports the preferred core feature and it has been
> > +enabled. This attribute is read-only.
> > +
> >   ``energy_performance_available_preferences``
> >   
> >   A list of all the supported EPP preferences that could be used for
>
> I notice I am confused. If the attribute is read only, how can it be
> enabled by the user?

It is enabled by default.  It can be disabled by the user via the kernel 
command line:

amd_prefcore=disable

This is documented separately in kernel-parameters.txt.