Re: [PATCH 3/5] tda18218: fix IF frequency for 7MHz bandwidth channels

[Antti Palosaari <crope@iki.fi>]

On 03.04.2012 03:44, Gianluca Gennari wrote:
> Il 03/04/2012 00:40, Antti Palosaari ha scritto:
>> On 03.04.2012 00:25, Gianluca Gennari wrote:
>>> This is necessary to tune VHF channels with the AVerMedia A835 stick.
>>>
>>> Signed-off-by: Gianluca Gennari<gennarone@gmail.com>
>>> ---
>>>    drivers/media/common/tuners/tda18218.c |    2 +-
>>>    1 files changed, 1 insertions(+), 1 deletions(-)
>>>
>>> diff --git a/drivers/media/common/tuners/tda18218.c
>>> b/drivers/media/common/tuners/tda18218.c
>>> index dfb3a83..b079696 100644
>>> --- a/drivers/media/common/tuners/tda18218.c
>>> +++ b/drivers/media/common/tuners/tda18218.c
>>> @@ -144,7 +144,7 @@ static int tda18218_set_params(struct dvb_frontend
>>> *fe)
>>>            priv->if_frequency = 3000000;
>>>        } else if (bw<= 7000000) {
>>>            LP_Fc = 1;
>>> -        priv->if_frequency = 3500000;
>>> +        priv->if_frequency = 4000000;
>>>        } else {
>>>            LP_Fc = 2;
>>>            priv->if_frequency = 4000000;
>>
>> Kwaak, I will not apply that until I have done background checking. That
>> driver is used only by AF9015 currently. And I did that driver as
>> reverse-engineering and thus there is some things guessed. I have only 8
>> MHz wide signal, thus I never tested 7 and 6 MHz. Have no DVB-T
>> modulator either... Maybe some AF9015 user can confirm? Is there any
>> AF9015&  TDA18218 bug reports seen in discussion forums...
>
> A friend has a AF9015+TDA18218 stick and told me that it works fine with
> the patch (including VHF), but to be safe I will ask him to double check
> with the current media_build tree, with and without the patch. In the
> worst case, we can add a new parameter (or an array of parameters) for
> the IF frequency to struct tda18218_config.

Public short datasheet [1], page 16, says default IFs are BW=8 MHz IF=4 
MHz, BW=7 MHz IF=3.5 MHz, BW=6 MHz IF=3 MHz. I suspect it still locks in 
some cases even IF is off-by 0.5 MHz for BW 7 and 8 but performance is 
reduced. So there is now something wrong, likely bug in the tda18218 driver.

Could someone send me Windows sniff from success tune to 7 MHz BW channel?

[1] http://www.nxp.com/documents/data_sheet/TDA18218HN.pdf
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