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Voltage Tweaking Comes To R600+ GPUs On Linux

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  • Voltage Tweaking Comes To R600+ GPUs On Linux

    Phoronix: Voltage Tweaking Comes To R600+ GPUs On Linux

    Earlier this month we reported on vastly improved ATI power management support within the open-source Radeon graphics driver stack for Linux that now supports dynamic power management along with different power management profiles. Following that we provided a detailed look at the ATI Linux power management support with plenty of charts showing how the power management is working out with this latest open-source code...

    http://www.phoronix.com/vr.php?view=ODI5NA

  • #2
    It would be awesome to have it merged into Linux 2.6.35, because that's what Ubuntu 10.10 is going to use.

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    • #3
      That an exceeding cool set of patches!

      Were these the last power manager features that were missing, or does the R600/R700/Evergreen have other PM features that would make sense for the OSS drivers?

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      • #4
        Hope to god these end up in 2.6.35 usable oss drivers are so close for me! right now they work great with compiz and I get nice tear free vid playback but my laptop gets REALLY hot REALLY fast.

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        • #5
          Great news. Up to now I was stuck using Catalyst on my notebook, because of dramatic battery drain and heat issues with the OS driver. I am really looking forward testing the new patches soon.

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          • #6
            AWESOME!
            keep up the good work

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            • #7
              Anyone knows if it's available in one of the drm branches?

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              • #8
                From the article:

                Originally posted by article
                Right now these are just patches sitting on the DRI mailing list.
                So I guess they are not in any of the public branches. Shouldn't take long, though. AFAIK, this is the last major building block still missing from the powersaving stuff. It should be mostly optimisation from there.

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                • #9
                  The code is now in drm-radeon-testing, however I'm not very happy with the choice of low power mode switching.

                  While my card runs on 250Mhz on Windows most of the time (maximum clock is 750MHz), the radeon DRM only downclocks to 500MHz when the system is 'idling' (no 3D apps running).

                  Unsatisfied with this (and since I knew that 250Mhz was enough for desktop work) I did this small hack:
                  http://www.math.uni-bielefeld.de/~tj...-profile.patch

                  This just adds a 'minimum' profile which select the 'low'-powerstate and enables the lowest mode inside this state (the same as the one selected when DPMS has the screen turned off).
                  Works for me at least

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                  • #10
                    I think that the priority at this point is getting the code into mainline, tested, and stabilised. The power profiles can easily be tweaked once everything is running smoothly. It's probably just a conservative default for the time being, to avoid strange corner cases, not a final decision set in stone.

                    Am I understanding correctly that this is a drm update, which doesn't need to touch other parts of the stack (like the ddx and Mesa)?

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                    • #11
                      Originally posted by LiquidAcid View Post
                      The code is now in drm-radeon-testing, however I'm not very happy with the choice of low power mode switching.

                      While my card runs on 250Mhz on Windows most of the time (maximum clock is 750MHz), the radeon DRM only downclocks to 500MHz when the system is 'idling' (no 3D apps running).
                      I believe the power states are influenced at least in part by the range of speeds each card/laptop vendor chooses to validate and include in their video BIOS image. In some cases those states are very limited - the GPU and memory may be able to run fine at lower speeds but those speeds are not included in the BIOS power state list.

                      The driver can over-ride those settings but I don't think the devs want to rush into that without a *lot* of testing.

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                      • #12
                        Originally posted by bridgman View Post
                        I believe the power states are influenced at least in part by the range of speeds each card/laptop vendor chooses to validate and include in their video BIOS image. In some cases those states are very limited - the GPU and memory may be able to run fine at lower speeds but those speeds are not included in the BIOS power state list.

                        The driver can over-ride those settings but I don't think the devs want to rush into that without a *lot* of testing.
                        Yeah, but that's not the issue here.

                        The current code never selects the lowest mode inside a powerstate, unless the DPMS state if off - then it _does_ downclock to the lowest mode. That would be 250MHz core clock for me.

                        While a crtc is active the code only reclocks between the medium and high mode of a powerstate, in my case 500MHz and 750MHz.

                        I have verified this by monitoring radeon_pm_info but also by looking at the code. I'm no doubt that Alex did this intentional, probably because on some configurations the lowest mode inside the 'low'-powerstate doesn't provide enough memory bandwidth for scanout.
                        Since memory isn't reclocked on my card (at least I'm not seeing this and I think the ATOM tables all store the same mem clock) it doesn't make a difference for _me_.

                        Again, the diff's just a (dirty) hack, but enough for me to quiet down the card for watching e.g. HD movies on the system.

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                        • #13
                          Some users reported unstable LVDS when the lowest power state was enabled, so I made it DPMS off only for now until we sort out the problem further.

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                          • #14
                            OK, thanks for the confirmation - I'm using an old CRT here, so if there is a problem with LVDS stability then I'm probably not seeing it here

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                            • #15
                              Oh, and anyway - good work on the whole radeon stack Alex! It's really nice to see how everything evolves and how new features are constantly popping up (kms, pm, tiling, gallium, etc.)

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