[Bug 217931] amd-pstate lacks crucial features: CPU frequency and boost control

[bugzilla-daemon@kernel.org]

https://bugzilla.kernel.org/show_bug.cgi?id=217931

--- Comment #62 from Mario Limonciello (AMD) (mario.limonciello@amd.com) ---
> 1. * /sys/devices/system/cpu/cpufreq/policyX/scaling_available_governors
>   performance powersave
> 2. How is it related to 
> /sys/devices/system/cpu/cpufreq/policy0/energy_performance_preference which
> can > be of 
> default performance balance_performance balance_power power?

When using EPP then the frequency selection is done by the firmware not the
kernel.  The kernel will set upper and lower performance targets and a bias
between performance and efficiency is configured using the EPP value.

> 1. I can enable/disable boost (not possible under amd-pstate on 6.9.4)

Boost support in EPP mode is not yet merged.  Perry shared some patches for
this, but they will need to spin again.  We're aiming for 6.11 to get this
merged.

> 3. And what's the "default" state?

As per kernel documentation [1]:

"default represents the epp value is set by platform firmware"

> energy_performance_preference doesn't accept "default":

Thanks for mentioning.  I've sent a patch for discussion on that [2].

[1] https://www.kernel.org/doc/html/latest/admin-guide/pm/amd-pstate.html
[2]
https://lore.kernel.org/linux-pm/20240612145737.1618-1-mario.limonciello@amd.com/T/#u

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