On Friday, September 26, 2008 1:36 am 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. > > >> 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?
I think so, but given that we disable VGA mode during normal operation, it may be that you need to have pipe B selected at some point *while* VGA mode is active. OTOH there may be other bits you need to set as well. You could try searching the docs for the string "VGA" :) But if you just want to poll, there's also a bit in the PIPE*STAT regs that indicates whether vblank is active, iirc. Jesse -- Jesse Barnes, Intel Open Source Technology Center _______________________________________________ xorg mailing list [email protected] http://lists.freedesktop.org/mailman/listinfo/xorg
