drift_control - tool for debugging the software PLL routine


drift_control [options]


This program effectively uses a copy of the Xserver patch. It was very helpful for debugging the software PLL routine.

It is important not to use it in active mode when the XV extension is actively used the same time.

Otherwise PLL is confused since accessed by both drift_control and XV extension. Anyway drift_control would show arbitrary measurement values then.


This program needs to be run with root priviledges.

Before starting patched radeon DRM module must be active. Also patched Xserver must be running.


The utility runs in two modes.

  • without args simply monitors drift of frame rate against loop cycle

  • otherwise adjusts frame rate to loop cycle frequency +-0.001441383Hz


  • Sample output without any option.


    tv now: 1218248395.506612 tv vbl: 1218248395.502611 vbls: 303706 trim: 0x00c85501 sync point displacement: -5999 drift speed: 31

  • Sample output in active mode.

    drift_control a

    tv now: 1218248369.513018 tv vbl: 1218248369.503038 vbls: 302406 trim: 0x00c85502 sync point displacement: -20 drift speed: -9 overall compensation: -1 completed o. c. clipped: -1 trim absolute: 1 t. a. clipped: 1 new trim: 0x80c85501


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