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[directfb-users] Re: WAITFORSYNC sleeps too long
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[directfb-users] Re: WAITFORSYNC sleeps too long



On Thu, Jan 20, 2005 at 07:42:08PM +0100, Jan Gukelberger wrote:
> Hi!
> 
> On Sun, 2005-01-16 at 20:42 +0200, Ville Syrjälä wrote:
> > On Sun, Jan 16, 2005 at 03:59:03PM +0100, Jan Gukelberger wrote:
> [...]
> > > > Secondly make sure the graphics card actually has an irq assigned to it. 
> > > > BIOS usually has an option for it. lspci should tell you if the irq is 
> > > > assigned.
> 
> Yes, it has:
> 0000:01:00.0 VGA compatible controller: Matrox Graphics, Inc. MGA G550 AGP (rev 01) (prog-if 00 [VGA])
>         Subsystem: Matrox Graphics, Inc. Millennium G550 Dual Head DDR 32Mb
>         Flags: bus master, medium devsel, latency 128, IRQ 16
> 
> 
> > You could try pci=noacpi or acpi=off kernel options.
> 
> This didn't seem to help.
> 
> However, there are some new observations and even a fix/workaround:
> 
> Running the DFB app straight after reboot from tty, everything works
> nicely, frame length ~13.3ms. This holds even true if X is running on
> the second graphics card.
> But when the DFB app is started from an xterm running on the second
> card, syslog says "kernel: Disabling IRQ #16.". Though this first run is
> still ok, subsequent runs (from xterm as well as tty) will have a frame
> length of 113ms, i.e. the IRQ has indeed vanished.
> 
> At last, we have found that the bootparam "noirqdebug" will fix this
> problem, so the IRQ is never getting disabled.
> 
> All this seems absolutely weird to me, so does anybody have any clue
> what's going on here?
> How can it make a difference whether the app is launched from xterm or
> tty? And what could actually cause the interrupt to be disabled?

It looks like some other interrupt source besides vsync got enabled on the 
card, or maybe some other device on the same interrupt went nuts and since 
matroxfb doesn't handle the interrupts the kernel disabled it.

As far as the xterm vs. tty thing is concerned, I have no idea why it 
happens.

You could print the status register in matrox_irq() to see if it's the 
matrox card that is generating the unwanted interrupts.

-- 
Ville Syrjälä
syrjala@sci.fi
http://www.sci.fi/~syrjala/




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