[Intel-gfx] [PATCH] Don't touch the pipestat regs for detecting FIFO underrun. The kernel owns them.

[Eric Anholt]

On Mon, 2009-01-05 at 11:25 -0800, Jesse Barnes wrote:
> On Friday, January 2, 2009 6:43 pm Eric Anholt wrote:
> > On Mon, 2008-12-29 at 14:07 -0800, Jesse Barnes wrote:
> > > On Monday, December 29, 2008 1:45 pm Eric Anholt wrote:
> > > > Since we don't perform any synchronization with the kernel on these
> > > > regs, we could race with the kernel to write stale values and end up
> > > > not having vblank interrupts enabled when somebody was waiting on one.
> > > > ---
> > > >  src/i830_display.c |    4 ----
> > > >  src/i830_driver.c  |   26 --------------------------
> > > >  2 files changed, 0 insertions(+), 30 deletions(-)
> > >
> > > If we do this (patch seems fine) we should check for it in the kernel
> > > instead, maybe by enabling the corresponding error interrupt.
> >
> > There's preliminary stuff for it in the error-recovery branch of my
> > tree, but it got backed out because it caused hangs that killed ssh and
> > I didn't have time to debug.
> 
> How hard would it be to just extract the underrun reporting?  It's already 
> helped us find quite a few bugs, so just getting the info would be a big help 
> even if we don't recover very well from it...

I want to make sure that we tie it in with modesetting next time,
though.  The false positives from the harmless report after a mode
switch were nasty.

I don't think there was much to do in getting error-recovery fixed to
just report and not try to recover as much.  But it'll take debugging
what that startup failure was.

-- 
Eric Anholt
eric at anholt.net                         eric.anholt at intel.com


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