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. > >> I understand the LCD screen is on pipe B and the VGA screen on pipe A. >> Can I somehow swap current behaviour so that when I monitor IO address >> 0x3DA I can detect vretraces for pipe B instead of for pipe A? That would >> save me the trouble of hacking DRM into this legacy aplication. > > I think the status bit in 0x3da will correspond to the pipe VGA is assigned > to > in VGACNTRL (the headers should have the info you need, if not check out the > docs at http://www.intellinuxgraphics.org). Thanks for the info. Here is what I did. In i830_driver.c I830PreInit() below RestoreHWState() I added this: xf86DrvMsg(pScrn->scrnIndex, X_WARNING, "HACK: setting VGA_PIPE_B_SELECT.\n"); OUTREG(VGACNTRL, pI830->saveVGACNTRL | VGA_PIPE_B_SELECT); Unfortunately the VGA input status register 1 bit 3 still reflects the retraces for the external VGA monitor, instead of the laptop's display panel. So this is problably not correct or I missed something. In Xorg.0.log I read "Output VGA is connected to pipe A" and "Output LVDS is connected to pipe B". Is there a way to swap them, how? And if so would it make a differrence; I mean is it actually possible to have the VGA input status register 1 connected to the LVDS? Theo _______________________________________________ xorg mailing list [email protected] http://lists.freedesktop.org/mailman/listinfo/xorg
