Re: em28xx: msi Digivox ATSC board id [0db0:8810]

["Frank Schäfer" <fschaefer.oss@googlemail.com>]

Am 02.12.2012 15:23, schrieb Antti Palosaari:
> On 12/02/2012 01:44 PM, Frank Schäfer wrote:
>> Am 30.11.2012 02:45, schrieb Matthew Gyurgyik:
>>> On 11/29/2012 02:28 PM, Frank Schäfer wrote:
>>>> Matthew, stay tuned but be patient. ;) Regards, Frank
>>>
>>> Sure thing, just let me know what you need me to do!
>>>
>>
>> Ok, please test the attached experimental patch and post the dmesg
>> output.
>>
>> Open questions:
>> - setting of EM2874 register 0x0f (XCLK): the Windows doesn't touch this
>> register, so the default value seems to be used.
>>    The patch adds 2 debugging lines to find out the default which
>> default
>> value the em2874 uses.
>>    For now, I've set this to 12MHz, because the picture shows a 12MHz
>> oszillator.
>> - meaning of the gpio sequence / gpio lines assignment (see comments in
>> the patch).
>> - remote control support: looking at the product picture on the MSI
>> website,
>>    the remote control could be the same as sues by the Digivox III. But
>> that's just a guess.
>> - LGDT3305 configuration: a few parameters can not be taken form the USB
>> log. Will ask the author of the driver for help.
>>
>> But let's do things step by step and see what happens with the patch.
>>
>> Regards,
>> Frank
>>
>
> Hello
> I looked the patch quickly and here are the findings:
> I2C addresses are in "8-bit" format. Will not work. Example for tuner,
> 0xc0 should be 0x60. Same for the demod. Due to that, no worth to test
> patch. I2C addresses are normally 7-bit, but "unofficial" 8-bit
> notation is also used widely. em28xx uses official notation as almost
> all other media drivers.

Argh, yeah, I didn't check that. The mixed usage of 7 and 8 bit
notations is a mess.

>
> You are using tda18271c2dd tuner driver. I recommended to change to
> the other driver named tda18271. tda18271c2dd is very bad choice in
> that case as it discards all the I2C error without any error logging
> and just silently ignores. I remember case when I used that tuner
> driver for one em28xx + drx-k combination and wasted very many hours
> trying to get it working due to missing error logging :/

Ok, thanks. So we have two drivers for the same chip and tda18271c2dd is
deprecated ? Can both drivers handle both chip models ?
I thought tda18271c2dd is for the c2 model of the chip and tda18271 for
the "normal" model...
I also wonder why tda18271 is in media/tuners while tda18271c2dd is in
media/dvb-frontends ?

>
> Don't care XCLK register, it most likely will just as it is. There is
> many EM2874 boards already supported.
>
> 12MHz clock is correct and it is seen from the hardware. Generally
> 12MHz xtal is used very often for USB (device to device) as it is
> suitable reference clock.

Likely. But XCLK register also controls a few other things (e.g. remote
control settings) and the em28xx driver overwrites the default register
content in any case.
So let's see what dmesg tells us.

>
> According to comments, GPIO7 is used when streaming is started /
> stopped. It is about 99% sure LOCK LED :)
>
> When you look sniffs and see some GPIO is changed for example just
> before and after tuner communication you could make assumption it does
> have something to do with tuner (example tuner hw reset / standby).

That's possible, but on the other hand, there is a delay of 20ms after
GPIO_7. That shouldn't be necessary for a LED.
Any idea what GPIO_0 is ? it is to set to high (50ms delay afterwards)
when the first chunk of data is read from the eeprom and set back to low
afterwards.

>
> You should look used intermediate frequencies from the tuner driver
> and configure demod according to that. OK, 3-4 MHz sounds very
> reasonable low-IF values used with tda18271. tda18271 driver supports
> also get IF callback, but demod driver not. That callback allows
> automatically configure correct IF according to what tuner uses.
> Anyhow, in that case you must ensure those manually from tuner driver
> as demod driver does not support get IF. IF is *critical*, if it is
> wrong then nothing works (because demodulator does not get signal from
> tuner).

Ok, that means the 'qam_if_khz' and 'vsb_if_khz' in struct
lgdt3305_config are mandatory values and must be set manually.
Looking into the tda18271 driver, vsb_if_khz should be set to 3250.
That's what the other em28xx board uses, too.

I will send an updated version of the patch soon. Thanks for your comments.

Regards,
Frank

>
>
> regards
> Antti
>