Re: SAA7146 glitch on cold boot

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Hi,

I did some tests and I can reproduce the bug with an Activy GR card...

Andrew de Quincey wrote:
> On Friday 07 July 2006 22:56, Oliver Endriss wrote:
> > Andrew de Quincey wrote:
> > > On Tuesday 04 July 2006 22:04, Oliver Endriss wrote:
> > > > Andrew de Quincey wrote:
> > > > > Sure, I reduced it to:
> > > > >
> > > > > saa7146_write(budget->dev, MC1, MASK_20);	// DMA3 off
> > > > > saa7146_write(budget->dev, MC1, (MASK_04 | MASK_20));	/* DMA3 on */
> >
> > Ok, if we cannot fix it otherwise, your patch should execute exactly
> > these 2 lines. There should be a FIXME comment explaining why the patch
> > has been added. I still hope that we can find the real bug. ;-)
> 
> Yup.
> 
> > > > Hm - this means that DMA3 has either not been started or is stuck.
> > > >
> > > > Does it make a difference if you add both lines at the end of
> > > > start_ts_capture?
> > >
> > > Nope no difference. I'd already tried this by stopping+starting
> > > dvbtraffic before I tuned... it doesn't help (I did try again tho adding
> > > the code to the driver to make sure).
> > >
> > > To recap:
> > >
> > > 1) start dvbtraffic
> > >
> > > 	-- IRQs are received from the saa7146.

Hm - does your frontend deliver garbage data while not tuned?
My card does not generate VPE interrupts here.

> > > 2) tune and lock
> > >
> > > 	-- The IRQs suddenly halt for no reason.

Data transfer does not start here. Strange.

> > > 3) restart dvbtraffic
> > >
> > > 	-- IRQs start again and everything works fine thereafter.

Confirmed.

> > > And all only the very first time DMA is started on cold boot.
> >
> > Very strange. I don't understand why it happens only once.
> >
> > Basically, it looks like an initialization problem. On the other hand,
> > the data transfer was working and stops later.
> >
> > Imho this does not look like a saa7146 bug. A hw bug should show up
> > anytime, not only once after booting.
> >
> > Did you check the budget->feeding stuff? At the first glance it looks
> > strange to me that stop_ts_capture decrements budget->feeding
> > unconditionally, while start_ts_capture checks before incrementing.
> 
> I don't see how that would break only on a cold boot though... I can reboot 
> the machine as many times as I want after that and it works perfectly every 
> time.

There might be a difference:
The frontend might be in a different state (tuned?) during warm boot.

I'll do more testing. Stay tuned.

Oliver

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