Jesse Barnes wrote: > 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" :)
I'm afraid I'm clueless here as I am not comfortable with the internals of the driver. Do you mean I need to be running in VGA mode all the time, or do the VGA_PIPE_B_SELECT while temporarily in VGA mode? How would one achive that? > > But if you just want to poll, there's also a bit in the PIPE*STAT regs that > indicates whether vblank is active, iirc. Thanks. I'm going to check that as well. From kernel space do I need to call mmap or pci_request_regions etc to gain access to these registers, or can I just access them at the MMIO base address + register offset? Theo _______________________________________________ xorg mailing list [email protected] http://lists.freedesktop.org/mailman/listinfo/xorg
