Linux 6.5 Released With AMD P-State EPP Default, USB4 v2, MIDI 2.0 & More Hardware Bits

[NotMine999]

Just tried to install the new kernel 6.5.0-generic from the Mainline PPA and could not because of unmet dependencies.

libc6 >2.38

????

Been installing and running all of the prior 6.5-rc kernels with no issues.

Currently running Ubuntu 22.04.3 LTS [6.5.0-060500rc7-generic|libc 2.35]

I am fairly certain that 6 is greater than (>) 2.38...even for the smallest values of 6.

On the other hand, I guess "The New Math" has finally landed in the Linux Kernel?

[Keith Myers]

The unmet dependency is in the GLIBC library libc6. Needs versions greater or equal to version 2.38. Ubuntu 22.04 LTS only comes with version 2.35.

That's the problem. Even bigger problem is that that GLIBC library won't ship until the Ubuntu 23.10 version ships in late October.

The kernel seems to have discovered time travel.

[guglovich]

I don't have AMD P-State installed by default.

[Keith Myers]

I don't have AMD P-State installed by default.

What processor does not do that?

What kernel version?

There is a question whether Zen 2 and Zen 3 consumer cpus get automatically installed amd_pstate driver.

We know server cpus don't.

[Ranguvar]

Still acpi-cpufreq on a 5950X with X570 chipset running 6.5.0-arch1-1 from [core-testing].
(CONFIG_X86_AMD_PSTATE_DEFAULT_MODE=3)

I'll try forcing it.
lscpu does not show cppc.
Might be able to fiddle with related UEFI options.
Or, maybe I need `amd_pstate.shared_mem=1` in kernel cmd?

[Keith Myers]

I beleive the main criteria is you have to have CPPC=enabled in your BIOS before you can get amd_pstate.

[Ranguvar]

I did already have CPPC and CPPC Preferred Cores set to Enabled in my Gigabyte UEFI.
I tried changing to Auto but no visible change.

I suspect the Gigabyte ACPI tables are at fault.
I am now testing changing Local APIC Mode to X2APIC and using patch from rene : https://www.youtube.com/watch?v=BTI78pG2V80
If that does not work, I will wait for a newer Gigabyte UEFI to be released.

Update: Can't get cppc feature flag. Disabling/enabling Cool'n'Quiet and X2APIC does nothing.
I'll wait for an updated UEFI from Gigabyte to test more.

amd_pstate is working, though, using
- x2apic (haven't tried without)
- René's x2apic patch (necessary to read frequency once x2apic is enabled)
- amd_pstate=active amd_pstate.shared_mem=1 in kernel cmd
There was a performance warning about this option in the Linux 6.0 docs, but it was removed since.

Frequency behavior appears good to the eye, no benchmarks though. 550MHz lowest clock.
"Appears" to turbo to max instantly.

Seeing further confirmation now that desktop Zen3 at least lacks cppc.
Docs seem to confirm: “Some new Zen3 processors such as Cezanne provide the MSR registers directly”

[guglovich]

What processor does not do that?

What kernel version?

There is a question whether Zen 2 and Zen 3 consumer cpus get automatically installed amd_pstate driver.

We know server cpus don't.

3800X
Kernel 6.5

[Keith Myers]

OK, thanks for the info. I guess Zen 4 is the only candidate cpu that gets the driver automatically installed.

[headkaze]

Question: Do one still has to manually enable the P-State kernel flags, or do they come enabled by default?

amd_pstate.shared_mem=1 amd_prefcore=enable=1 initcall_blacklist=acpi_cpufreq_init

Just a heads up to anyone copy/pasting the above it's meant to be:

amd_prefcore=enable

You can check to see it's enabled by running

cat /sys/devices/system/cpu/amd_pstate/prefcore_state