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Updated AMD P-State Driver Posted For Improving Linux Power Efficiency

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  • Updated AMD P-State Driver Posted For Improving Linux Power Efficiency

    Phoronix: Updated AMD P-State Driver Posted For Improving Linux Power Efficiency

    A fourth iteration of the AMD P-State CPU frequency scaling driver patches for Linux have been sent out for review and testing...

    https://www.phoronix.com/scan.php?pa...AMD-P-State-v4

  • #2
    Great. Is this patch still zen3-only or is the zen2 support turned on already?

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    • #3
      Originally posted by bezirg View Post
      Great. Is this patch still zen3-only or is the zen2 support turned on already?
      there's nothing inherently zen3 specific about it. bios must provide "sane" cppc tables, and either have a cpu which has the amd cppc capability bit set (4000G for example) or the pcc mechanism.
      It works for me on 4750g out of the box; on the 5950x it needs to be force enabled with "amd_pstate.shared_mem=1"

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      • #4
        Originally posted by mlau View Post

        there's nothing inherently zen3 specific about it. bios must provide "sane" cppc tables, and either have a cpu which has the amd cppc capability bit set (4000G for example) or the pcc mechanism.
        It works for me on 4750g out of the box; on the 5950x it needs to be force enabled with "amd_pstate.shared_mem=1"
        I have the 4700u, is there a way to check if this is activated?
        And if not, is it just a kernel parameter to pass?
        Or do I also need to tell my system somehow to drop cpufreq governors and use this instead?

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        • #5
          if you have "amd_cppc" in /proc/cpuinfo after applying this patchset, the driver should work out of the box on 4700u (which is also renoir, so my guess is yes).
          Also file "/sys/devices/system/cpu/cpufreq/policy0/scaling_driver" should contain "amd-pstate" if your bios is also fine.
          On an idle system you should see a lot of cores at around 500MHz instead of 2000MHz as is with acpi-cpufreq.

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          • #6
            Very cool. Valve found the way to work around AMD's inability to manage software teams: hold their hand through everything. :+ )

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            • #7
              amdgpu + dc is still ~entirely maintained by AMD only, and I think very successfully (though Valve surely will provide feedback or perhaps even MRs for the Steam Deck). CPU clock governors is a different domain, situation is just sucky on Linux in general and I can imagine that collaboration with AMD could be better than it would be with Intel. Some company needs to tell Intel that intel_pstate=powersave is atrocious garbage...

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              • #8
                Build as module, I get
                Code:
                ERROR: could not insert 'amd_pstate': No such device
                when trying to load it.

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                • #9
                  Originally posted by PuckPoltergeist View Post
                  Build as module, I get
                  Code:
                  ERROR: could not insert 'amd_pstate': No such device
                  when trying to load it.
                  either your bios has buggy cppc tables, or you need to modprobe it as "modrobe amd-pstate shared_mem=1"

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                  • #10
                    Originally posted by mlau View Post
                    if you have "amd_cppc" in /proc/cpuinfo after applying this patchset, the driver should work out of the box on 4700u (which is also renoir, so my guess is yes).
                    Also file "/sys/devices/system/cpu/cpufreq/policy0/scaling_driver" should contain "amd-pstate" if your bios is also fine.
                    On an idle system you should see a lot of cores at around 500MHz instead of 2000MHz as is with acpi-cpufreq.
                    True:


                    Setting amd_pstate.shared_mem=1 wasn't necessary here, but that could be because of xanmod's kernel.
                    Last edited by reba; 19 November 2021, 01:10 PM.

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