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AMD Laptops With Radeon dGPU Graphics Receive Fix For Poor Linux Power Management

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  • AMD Laptops With Radeon dGPU Graphics Receive Fix For Poor Linux Power Management

    Phoronix: AMD Laptops With Radeon dGPU Graphics Receive Fix For Poor Linux Power Management

    The kernel power management changes have been sent in for Linux 5.10 with a few items worth pointing out from faster hibernation to fixing power management handling for AMD laptops with both integrated and discrete graphics...

    http://www.phoronix.com/scan.php?pag...wer-Management

  • #2
    How many of these laptops are there? I know someone who is looking to buy, and I think 5600m would be perfect for them, but I could only find a single laptop with that dgpu.

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    • #3
      It sounds more like it's a workaround for bad ACPI on those laptops, than a bug in kernel code. If the hardware is capable of D3, but the ACPI tables don't have this info, that seems to be the fault of whoever wrote the UEFI.

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      • #4
        Originally posted by doomie View Post
        How many of these laptops are there? I know someone who is looking to buy, and I think 5600m would be perfect for them, but I could only find a single laptop with that dgpu.
        There's the Dell one, and MSI announced they're going to refresh their Alpha line with RX5600M but there was no release date.

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        • #5
          Yes, but still kudos to the indep. dev. Though it should be official devs doing it, but then this likely relies on laptop vendor cooperatin and HW availability to the very devs.
          Stop TCPA, stupid software patents and corrupt politicians!

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          • #6
            Originally posted by sandy8925 View Post
            It sounds more like it's a workaround for bad ACPI on those laptops, than a bug in kernel code. If the hardware is capable of D3, but the ACPI tables don't have this info, that seems to be the fault of whoever wrote the UEFI.
            No it's not : https://lists.freedesktop.org/archiv...er/054426.html

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            • #7
              Originally posted by Azultra View Post
              Yes it is:

              ​​​​​
              However on affected systems, the Root Port is hotplug-capable and pci_bridge_d3_possible() only allows hotplug ports to go to D3 if they
              belong to a Thunderbolt device or if the Root Port possesses a
              "HotPlugSupportInD3" ACPI property. Neither is the case on affected
              laptops.
              And then:

              The reason for whitelisting only specific, known to work hotplug ports for D3 is that there have been reports of SkyLake Xeon-SP
              systems raising Hardware Error NMIs upon suspending their hotplug ports:
              https://lore.kernel.org/linux-pci/[email protected]/
              What you linked to explicitly proves that what I said is true: the ACPI implementation was supposed to say that Hotplug support in D3 is supported. It didn't.

              The workaround they're doing now is to just ignore what ACPI says, and go ahead and assume that it will work out fine if ACPI supports power management for that PCIe port.

              ​​​​​​
              ​​​
              Last edited by sandy8925; 10-14-2020, 09:54 AM.

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              • #8
                Originally posted by sandy8925 View Post
                What you linked to explicitly proves that what I said is true: the ACPI implementation was supposed to say that Hotplug support in D3 is supported. It didn't.

                The workaround they're doing now is to just ignore what ACPI says, and go ahead and assume that it will work out fine if ACPI supports power management for that PCIe port.
                ​​​
                Actually, this bit makes it sound like horse dung Intel and Microsoft cooked up to work around their own hardware peculiarities, and the rest of the world was forced to follow.
                The reason for whitelisting only specific, known to work hotplug ports for D3 is that there have been reports of SkyLake Xeon-SP
                systems raising Hardware Error NMIs upon suspending their hotplug ports:
                https://lore.kernel.org/linux-pci/[email protected]/
                Microsoft defines it at https://docs.microsoft.com/en-us/win...hot-plug-in-d3

                I don't know for certain what happened there, though. I suspect D3cold and hotplug-supported root ports have been around for longer than that property...

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                • #9
                  I find that playing a video, opening chrome and a few other things, wakes my discreet card up which is annoying

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                  • #10
                    "The reason for whitelisting only specific, known to work hotplug ports for D3 is that there have been reports of SkyLake Xeon-SP
                    systems raising Hardware Error NMIs upon suspending their hotplug ports:
                    https://lore.kernel.org/linux-pci/[email protected]/"

                    I did not read the article, but from the quote, it appears this was initially set up for SkyLake Xeon. Interesting.

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