[linux-dvb] Re: Channel switching

[rolf.siebrecht@t-online.de (Rolf Siebrecht)]

Hi!

On Sun, 9 Sep 2001, Klaus Schmidinger wrote:
> So the bottom line from my experiments and other comments on the list seems to be
> that apparently the channel switching problem only occurs on DVB cards of
> rev. 1.3 (2.1 cards don't have this problem), and that for 1.3 cards my driver
> patch leads to a _much_ better channel syncing.
> 
> I don't know if there is a way to dynamically detect the card revision, so that
> the patched behaviour could be performed only for such cards, or if there is a
> totally different way of fixing the underlying problem (maybe in the firmware,
> which I don't have access to).

I would focus on the AFC code in the driver. I loaded tuner.o with debug=1
to view the asserted frequency values. It seems that in those cases of
error the AFC engine lets the frequency drift away instead of driving
against a proper center value. The process of finding only divergent 
figures is finally aborted and the failure event is returned. So I think
the AFC code should get a revision. Perhaps a first attempt may be to make
the AFC feature selectable per module option.

In my tests driver version 0.8.2 doesn't show any tuning failures under
kernel-2.2.19 and 2.4.9. On the other hand 0.9-20010618 under 2.2.19 and
0.9-20010822 under 2.4.9 both have these problems. All with a Rev. 1.3
hardware. Thats a strong hint that the new tuning code of 0.9-x buries the
actual reason for these errors. Whereas the passage where your patch 
applies is contained in both 0.8.x and 0.9-x in a comparable form.


Bye,
     Rolf



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