Theo Veenker wrote: > Jesse Barnes wrote: > >> On Thursday, September 25, 2008 6:00 am Theo Veenker wrote: >> >>> Hi, >>> >>> I have an application that presents audio-visual stimuli to subjects. To >>> be able to precisely synchronize the audio and graphics the application >>> needs to know when a vsync occurs. My application (from 1994) doesn't yet >>> use libdrm. I'm using a real-time module which (among other things) >>> monitors the vretrace bit in the VGA input status register 1 at 0x3DA and >>> signals the application on each vsync event. It works fine on most graphics >>> hardware. >>> >>> Now I need to make this application work on a laptop with an Intel 945GM. >>> The vretrace bit at IO address 0x3DA doesn't work (under X) unless I >>> connect an external VGA display. Then it works, but it reflects the retrace >>> of the external monitor and not that of the laptop's LCD screen. >>> >>> Since also drmWaitVBlank() didn't work for me on this system, I applied the >>> change hinted in >>> http://lists.freedesktop.org/archives/xorg/2007-June/025166.html to the >>> xf86-video-intel driver (2.4.2). That makes drmWaitVBlank() work (but only >>> after I briefly run a GL application like glxgears first). >>> >> There's some code in the xf86-video-intel driver to disable vblank >> interrupts >> when no 3D client is running (look for want_vblank_interrupts in i830_dri.c, >> you can either remove the code from I830DRISetVBlankInterrupt or make that >> field unconditionally true). Maybe that's what you already did. >> > > Yes that's what I did. With the stock driver drm vblank would only work while > running, for instance, glxgears. After the 'fix' I just need to run glxgears > once and after that it works. I can live with that. >
You do not "fix" it, but mangle a power saving feature not to wake the CPU while vblank is not wanted by any client. -- René Rebe - ExactCODE GmbH - Europe, Germany, Berlin http://exactcode.de | http://t2-project.org | http://rene.rebe.name _______________________________________________ xorg mailing list [email protected] http://lists.freedesktop.org/mailman/listinfo/xorg
