[linux-dvb] Re: Another issue: frontend timeout value and low symbol rates

[Andrew de Quincey <adq_dvb@lidskialf.net>]

On Monday 23 February 2004 17:46, Johannes Stezenbach wrote:
> Andrew de Quincey wrote:
> > Hi, I've finally found the problem (after much fiddling)
> >
> > The linux core drivers already do the seeking-about mechanism you suggest
> > if it can't lock on to the supplied base frequency. And that works fine
> > (seeks about in steps of symbolrate/16000).
> >
> > The problem is that with the frontend driver as it is/was, it retunes the
> > TSA5959 PLL every time. Retuning the PLL every few milliseconds doesn't
> > seem to agree with this module.
> >
> > Also, the PLL resolution is quite low (500kHz). I initially tried
> > increasing the resolution of the PLL but that didn't seem to help. If
> > anything, it seemed to worsen matters.
> >
> > Instead, if the frequency change is quite small (i.e. its obviously
> > seeking about), I program the derotator frequency registers with the
> > offset. I can now reliably lock on to any frequency/symbolrate within a
> > reasonable time (i.e. sub-second).
>
> If you're confident that this is a general improvement (i.e. you didn't
> break anything when fixing tuning on low-SR TPs), please commit.
> Or post patches for others to try, please.

Yup, willdo. I'm just cleaning it up right now.


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