Re: [Unichrome-devel] Dragging window in X causes soundcard interrupts to be lost

[Lee Revell <rlrevell@joe-job.com>]

On Sat, 2004-07-31 at 19:37, Alan Cox wrote:
> On Sul, 2004-08-01 at 01:25, Lee Revell wrote:
> > Do you have the original driver source from VIA handy?  This is looking
> > more and more like a hardware bug - 2D acceleration engine activity
> > causes interrupts from the PCI slot to be disabled for long periods. 
> 
> I do. There is no code in the 2D engine that touches interrupt control
> at all. 
> 

Yes, I saw that.  This basically means it has to be a hardware bug,
correct?

> > Maybe it disables interrupts to prevent other processes writing to the
> > shared video/system RAM as it DMAs.  I would like to verify that the
> > problem still occurs with their driver, before I try to convince them
> > there's a hardware issue with the EPIA boards.
> 
> A similar problem occurs with some other chips when you write enough
> data to the chip that the FIFO fills and the PCI bus locks until the
> write can complete. Various vendors implemented this at one point for
> benchmarketing reasons and that would have a similar effect if so.
> 

This was the first thing that occurred to me, but I am not really a
video driver expert, and looking at the code it's just banging bits.  I
have hacked device drivers, just not video, and I don't have the
bandwidth to learn right now.

> The 2D driver source is essentially the same as the source in Xorg CVS
> barring cleanups and the accelerator code has not changed at all. You
> might want to take a look at the fifo management side of things in that
> code.
> 
> > On that note, assuming I verify the bug, does anyone have any
> > recommendations for getting VIA to take me seriously?  The problem is
> > very easy to reproduce.
> 
> I have some contact with VIA however you need to understand that the
> graphics world moves rapidly. I would be suprised if the CLE266 saw any
> more development given the CN400 has been demoed, although I certainly
> can't speak for VIA on this matter.
> 

Yes, I would be happy to just get an acknowledgement of the issue. 
Actually I don't even need that, I just want to know if it's fixed in
the newer ones.  I have a perfectly acceptable workaround.  The 2D
acceleration is pretty shoddy anyway, many things seem to work better
with NoAccel.   I still love the EPIA board.

Maybe you could forward this on to them?  Off the record is fine.

Lee