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AMDGPU DC Looks To Have PSR Squared Away - Power-Savings For Newer AMD Laptops

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  • AMDGPU DC Looks To Have PSR Squared Away - Power-Savings For Newer AMD Laptops

    Phoronix: AMDGPU DC Looks To Have PSR Squared Away - Power-Savings For Newer AMD Laptops

    It looks like as soon as Linux 5.5 is where the AMDGPU kernel driver could be ready with Panel Self Refresh (PSR) support for enabling this power-savings feature on newer AMD laptops...

    http://www.phoronix.com/scan.php?pag...-Patches-Ready

  • #2
    Would it be technically possible to support this feature on desktop Freesync displays with DP? Or is it limited to eDP?

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    • #3
      Very interesting better battery time is always welcomed.
      As it is now the battery time doesn't differ much at all even if i lower brightness to 20-30% from 100%.
      Better battery time is needed in Linux but i shouldn't complain the battery time is pretty decent on my ryzen 2500u based laptop.
      I would have liked to see it backported to linux 5.4 that is an longterm kernel.

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      • #4
        Originally posted by ms178 View Post
        Would it be technically possible to support this feature on desktop Freesync displays with DP? Or is it limited to eDP?
        Panel Replay, which is derived from PSR, is an optional part of DisplayPort 2.0.

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        • #5
          Originally posted by Nille_kungen View Post
          Better battery time is needed in Linux but i shouldn't complain the battery time is pretty decent on my ryzen 2500u based laptop.
          What do you get currently? Have you done much yourself to improve power savings at all?

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          • #6
            Originally posted by polarathene View Post

            What do you get currently? Have you done much yourself to improve power savings at all?
            I haven't done much to improve power savings no custom cpufreq or powertop and i haven't installed TLP, or laptop-mode-tools, for me it's more about the default experience but i do lower the brightness since i find it more pleasant.
            I have an Acer A315-41 and i get about 3h with normal work on battery last i checked, i get a some extra time with windows (that i never use) but it's not that much.
            Last edited by Nille_kungen; 10-18-2019, 08:54 AM.

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            • #7
              AFAICT the biggest benefit of PSR is not that you can power down some parts of the GPU, it is that you can put RAM into self-refresh, which saves a lot of power. It also may allow the SoC to go into a deeper sleep state overall.

              It is also possible to batch reads from the framebuffer for display, this is what AMD calls "stutter mode", but it is significantly less effective.
              Last edited by brent; 10-18-2019, 08:41 AM.

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              • #8
                5.5 seems like will be a great kernel for laptops and even better if you have dGPU as it can be finally powered off when not used. Amazing.

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                • #9
                  Is there any easy way (e.g. from a Linux command line or looking at log files) to determine whether the hardware in a laptop supports PSR?
                  I'm not asking about whether the software I'm currently running supports PSR; I'm confident that it doesn't.

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                  • #10
                    Originally posted by brouhaha View Post
                    Is there any easy way (e.g. from a Linux command line or looking at log files) to determine whether the hardware in a laptop supports PSR?
                    I'm not asking about whether the software I'm currently running supports PSR; I'm confident that it doesn't.
                    PSR (Panel Self Refresh) is supported on all eDP (Embedded DisplayPort) screens from version 1.3.
                    eDP V1.13 ublished in February 2011.
                    eDP V1.14 ublished in February 2013.
                    So if your laptop is designed after that and has eDP it is probably supported.
                    An easy way to check if your screen is eDP is with xrandr.
                    You can also check for eDP in /sys/class/drm/ i checked "strings /sys/class/drm/card0-eDP-1/edid" that output "N156HGA-EAB" i could then find more information about that screen.
                    By reading the edid information you should be able to identify your screen.
                    On intel based laptops you can use "cat /sys/kernel/debug/dri/0/i915_edp_psr_status" to see if PSR is supported.
                    I haven't touch on the software support since i haven't tried these patches yet.

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