On Sun, 31 Mar 2002, Egbert Eich wrote:
> Mark Vojkovich writes:
> >
> > Looking at the code for the siliconmotion driver in the tree, I'm
> > not surprised. It looks like the driver is polling until the retrace
> > everytime it has to put a frame. I would expect that to eat up more
> > CPU than just doing all the video in software. You should probably
> > try it without Xv, if that's being used now. Or somebody should fix
> > the drivers.
> >
>
> OK, I will look into this next week.
>
> I guess this retrace waiting was done to prevent shearing.
> Only very few chipsets support some kind of double buffering
> with automatic buffer switching on retrace. On all others
> we need to poll the chip to detect a retrace.
Well, I know that ATI chipsets did this at least since Rage Pro. Also,
AFAIK, mga does it too and I would be surprised if nvidia does not do it.
The way it is implemented in ATI chips is that registers that describe a
buffer in ram are buffered with new values taking effect after retrace.
I do not think this takes any significant amount of chip real estate.
So there should not be any reason not to implement this.
Vladimir Dergachev
>
> Mark, do you have any new idea how to solve this problem?
> I guess a solution would be to have some limited kernel
> support to handle interrupts.
>
> Regards,
> Egbert.
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