ATI Drivers report bogus dot_clock to xvidtune

[Greg Stark]

"Alex Deucher" <alexdeucher at gmail.com> writes:

> On 3/28/06, Roland Scheidegger <rscheidegger_lists at hispeed.ch> wrote:
>
> I also don't see how the dotclock would be of any use for vblank, but
> I suspect you are seeing a limitation of mergedfb.  Mergedfb is
> basically a hack to treat 2 crtcs as a single screen.  since you have
> two crtcs with different timings there's no way to know which dotclock
> or refresh rate, etc. is relevant (since they both are). Hence you end
> up with some weirdness for certain fields.  Disable mergedfb if you
> want relevant numbers for those fields.

Yes I expect it's caused by mergedfb. I suspect what's happening is that it's
calculating the dot clock based on the refresh rate and the combined desktop
size. And it's overflowing somewhere. Though I'm stumped where since it ought
not be overflowing a 32-bit integer. Perhaps it's doing some of the math in
16-bit integers?

> > This looks like a driver bug. I have no idea though what driver you're
> > talking about, there is no such thing as a ati driver (well there is
> > technically, a driver wrapper which is called ati, but it doesn't do
> > anyhting itself). So is this mach64? rage128? radeon? fglrx (take it to
> > ati in that case)?
> > If that's radeon are you using mergedfb? It works just fine for me
> > without mergedfb.
> > That said, I don't know why mythtv would need the pixel clock to sync to
> > vblank, I'd think it's a pretty useless number for that.

It's radeon. The card is a radeon 9600 (RV350). And yes I'm using mergedfb. 

I would actually rather not be using mergedfb but I haven't figured out how to
configure it not to.

It calculates the refresh rate and then I guess it tries to lock the output
frame rate to the refresh rate. Ie, there's no need to output frames faster
than the refresh rate.

-- 
greg