[alsa-devel] tea575x-tuner improvements & use in maxiradio

Ondrej Zary linux at rainbow-software.org
Tue Feb 7 23:20:19 CET 2012

On Sunday 05 February 2012 14:17:05 Hans Verkuil wrote:
> These patches improve the tea575x-tuner module to make it up to date with
> the latest V4L2 frameworks.
> The maxiradio driver has also been converted to use the tea575x-tuner and
> I've used that card to test it.
> Unfortunately, this card can't read the data pin, so the new hardware seek
> functionality has been tested only partially (yes, it seeks, but when it
> finds a channel I can't read back the frequency).
> Ondrej, are you able to test these patches for the sound cards that use
> this tea575x tuner?
> Note that these two patches rely on other work that I did and that hasn't
> been merged yet. So it is best to pull from my git tree:
> http://git.linuxtv.org/hverkuil/media_tree.git/shortlog/refs/heads/radio-pc
> You can use the v4l-utils repository (http://git.linuxtv.org/v4l-utils.git)
> to test the drivers: the v4l2-compliance test should succeed and with
> v4l2-ctl you can test the hardware seek:
> To seek down:
> v4l2-ctl -d /dev/radio0 --freq-seek=dir=0
> To seek up:
> v4l2-ctl -d /dev/radio0 --freq-seek=dir=1
> To do the compliance test:
> v4l2-compliance -r /dev/radio0

It seems to work (tested with SF64-PCR - snd_fm801) but the seek is severely 
broken. Reading the frequency immediately after seek does not work, it always 
returns the old value (haven't found a delay that works). Reading it later 
(copied back snd_tea575x_get_freq function) works. The chip seeks randomly up 
or down, ignoring UP/DOWN flag and often stops at wrong place (only noise) or 
even outside the FM range.

So I strongly suggest not to enable this (mis-)feature. The HW seems to be 
completely broken (unless there's some weird bug in the code).

Ondrej Zary

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