DVB tuning fails with HVR-1300 on Linux kernels starting with 2.6.27

[linux@…]

Hi,

after upgrading my Linux kernel on my Debian box running mythTV from 2.6.26 to 2.6.30 DVB tuning would fail with 'could not get signal lock', no matter which channel I tried. I tried different kernels and it seems the problem starts with 2.6.27 and get worse with 2.6.28 and the following.

I tried tuning with kaffeine and it does not find all but most of the channels. tzap can lock all channels.

I have attached the output of the current head revision in trunk for mythtv-setup given a single input channel on both 2.6.26 and 2.6.31-rc7 as well as the tzap output on 2.6.31-rc7 to illustrate the problem.

Please let me know if you need further info.

Thanks and best wishes,

Martin.

[linux@…]

channel tuning output on Linux kernel 2.6.31

[linux@…]

channel tuning output on Linux kernel 2.6.26

[linux@…]

channel tuning output on Linux kernel 2.6.26

[linux@…]

tzap output for same channel on 2.6.31

[janne]

strange, I would say a kernel bug. Please check the frontend status during the scan with femon. if it's is never FE_HAS_LOCK, please attach tzap's channels.conf. I suspect a difference in the parameters. You could also check scanning with more parameters set to auto.

[anonymous]

femon output from MythTV scanning of one multiplex

[anonymous]

channels file made with scan, used as input to tzap tuning

[anonymous]

Output from tzap

[anonymous]

I have a HVR-4000, but the DVB-T part seems to be equal: From mythtv-setup-2.6.31-rc7-edited.log: 2009-09-28 20:58:07.024 DVBChan(4:/dev/dvb/adapter0/frontend0): Using DVB card /dev/dvb/adapter0/frontend0, with frontend 'Conexant CX22702 DVB-T'. From my scan: 2009-10-08 00:37:05.451 DVBChan(1:/dev/dvb/adapter0/frontend1): Using DVB card /dev/dvb/adapter0/frontend1, with frontend 'Conexant CX22702 DVB-T'. So I hope these logs are relevant.

[linux@…]

Replying to janne:

strange, I would say a kernel bug. Please check the frontend status during the scan with femon. if it's is never FE_HAS_LOCK,

A funny thing happened:

• when I start femon and then start the channel scan I get a lock and all channels are found
• However, when I run the channel scan without having femon running at the same time no channel gets found
• If a channel is being scanned and I start femon then, still nothing is found.

Could it be that femon does some initialization on the adapter that is missing in otherwise?

please attach tzap's channels.conf. I suspect a difference in the parameters. You could also check scanning with more parameters set to auto.

I have actually been using the same channels.conf for both mythtv-setup and tzap during my testing so there is no difference.

Thanks for your help and best wishes,

Martin.

[janne]

Replying to linux@martin-kittel.de:

• when I start femon and then start the channel scan I get a lock and all channels are found
• However, when I run the channel scan without having femon running at the same time no channel gets found
• If a channel is being scanned and I start femon then, still nothing is found.

strange

Could it be that femon does some initialization on the adapter that is missing in otherwise?

I don't think so, but I'll look what femon does exactly.

I have actually been using the same channels.conf for both mythtv-setup and tzap during my testing so there is no difference.

could you test the full scan germany?

There is a bug in the kernel for the HVR-1300/4000 which seems to be related

​https://bugs.launchpad.net/mythtv/+bug/439163

it should only affect 2.6.29+ though

[anonymous]

Replying to janne:

could you test the full scan germany?

I tried with 2.6.31 vanilla and again had the same problem: if femon was started before mythtv-setup, the scan was ok, if started femon at a later time, no channels were found.

There is a bug in the kernel for the HVR-1300/4000 which seems to be related

​https://bugs.launchpad.net/mythtv/+bug/439163

I have tried the patch/revert to cx88-dvb.c mentioned in that thread and that seems to do the trick for me as well. I can watch TV again. For now it seems that tuning takes a bit longer than before because I get the channel lock warning which I did not see with earlier kernels. After a few seconds, however, the picture appears. I will keep an eye on this.

BTW, ​http://svn.mythtv.org/trac/ticket/7292 seems to be about the same issue.

it should only affect 2.6.29+ though

Judging from the time the change was made it could have been 2.6.27 as well, but I am no git expert and cannot determine when it actually went into mainline.

What is the correct way to proceed now? Wait for a kernel patch?

In any case, thanks for your help!

[linux@…]

Hi,

I just checked: the problem is fixed in 2.6.32, so this bug can be closed.

Best wishes,

Martin.

[fgunni@…]

The real bug seems to be found. The other solution is now obsolete. Hope this gets into kernel quick.

​http://www.kernellabs.com/blog/?p=1568

How can i prevent that post to fall in the spam filter .... maybe by this line (Did help on the other ticket:) ) This time i need to add some more text it seems.