Re: [PATCHv2] ath9k_hw: Handle AR_INTR_SYNC_HOST1_FATAL on AR9003

[Simon Wunderlich <simon.wunderlich@s2003.tu-chemnitz.de>]

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Hey Adrian,

On Tue, Oct 02, 2012 at 06:13:37AM -0700, Adrian Chadd wrote:
> .. well, the rule here is "You shouldn't get PERR/FATAL interrupts."
> 
> Haven't I posted a summary of what those errors are?
> 
> Ok. So they're signals from the PCIe core (named host1_fatal and
> host1_perr. Helpfully.) Those errors occured during a DMA transfer.
> 
> So the question is why you're seeing PERR interrupts when creating an
> adhoc interface. That hints to me that something odd is going on..

thanks for the explanation!

> 
> I've seen these issues creep up when the NIC is in some way behaving
> very, very badly (lots of timeouts and sync errors with little to no
> traffic at all), which resulted in all kinds of odd and weird,
> unstable behaviour. After replacing the NIC with another NIC (in my
> case, an AR9280 -> AR9280 NIC :-) the errors went away and things
> continued swimmingly.

Sounds like a good solution, but I'm afraid it won't work for us. We
are using AR9330 SoCs (Hornet), and as long as we don't have a very sharp knife
we won't be able to replace the NIC ... And cutting a few thousand of
them will also not be funny.

I'm starting to lose a little bit of confidence in these insects ... :/

> 
> I'd have to go digging through the PCIe core source to figure out
> exactly what host1_peer and host1_fatal mean. I can if you'd like,
> it'll just take some time as I'm not familiar at all with the PCIe
> host interface.

It would at least be interesting if we are supposed to handle the interrupt
somehow, instead of resetting the chip.

Thanks,
	Simon
> 
> Thanks,
> 
> 
> 
> Adrian
> 
> On 2 October 2012 03:33, Sven Eckelmann <sven@narfation.org> wrote:
> > Interrupts with the sync_cause AR_INTR_SYNC_HOST1_FATAL has to be handled
> > using a chip reset. Otherwise a interrupt storm with unhandled interrupts
> > will cause a hang or crash of the machine.
> >
> > Signed-off-by: Sven Eckelmann <sven@narfation.org>
> > ---
> > I was informed that AR_INTR_SYNC_HOST1_PERR should not be handled this way
> > because it can create system freezes after an adhoc interface was created.
> >
> > I really need some Atheros developer who can check the documentation to
> > verify the interpretation of these flags. Otherwise this is just guessing
> > and may lead to even bigger problems.
> >
> >  drivers/net/wireless/ath/ath9k/ar9003_mac.c |    5 +++++
> >  1 file changed, 5 insertions(+)
> >
> > diff --git a/drivers/net/wireless/ath/ath9k/ar9003_mac.c b/drivers/net/wireless/ath/ath9k/ar9003_mac.c
> > index d5b2e0e..6031bdf 100644
> > --- a/drivers/net/wireless/ath/ath9k/ar9003_mac.c
> > +++ b/drivers/net/wireless/ath/ath9k/ar9003_mac.c
> > @@ -311,6 +311,11 @@ static bool ar9003_hw_get_isr(struct ath_hw *ah, enum ath9k_int *masked)
> >         if (sync_cause) {
> >                 ath9k_debug_sync_cause(common, sync_cause);
> >
> > +               if (sync_cause & AR_INTR_SYNC_HOST1_FATAL) {
> > +                       ath_dbg(common, ANY, "received PCI FATAL interrupt\n");
> > +                       *masked |= ATH9K_INT_FATAL;
> > +               }
> > +
> >                 if (sync_cause & AR_INTR_SYNC_RADM_CPL_TIMEOUT) {
> >                         REG_WRITE(ah, AR_RC, AR_RC_HOSTIF);
> >                         REG_WRITE(ah, AR_RC, 0);
> > --
> > 1.7.10.4
> >
> > --
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