> Jordan Crouse schrieb:
> > On 17/01/08 20:53 +0100, Arnd Hannemann wrote:
> >> Andres Salomon schrieb:
> >>> On Thu, 17 Jan 2008 10:54:30 +0100
> >>> Arnd Hannemann <hannemann@i4.informatik.rwth-aachen.de> wrote:
> >>>
> >>>> Andres Salomon schrieb:
> >>>>> On Wed, 16 Jan 2008 16:19:12 -0500
> >>>>> Andres Salomon <dilinger@queued.net> wrote:
> >>>>>
> >>>>>> On Wed, 16 Jan 2008 18:44:07 +0100
> >>>>>> Arnd Hannemann <hannemann@i4.informatik.rwth-aachen.de> wrote:
> >>>>>>
> >>>>>>> Hi,
> >>>>>>>
> >>>>>>> I'm trying to boot 2.6.24-rc8 on a GEODE LX board (ALIX.3),
> >>>>>>> and it hangs during boot:
> >>>>>>>
> >>>>>>> [ 12.689971] NET: Registered protocol family 16
> >>>>>>> [ 12.703329] geode-mfgpt: Registered timer 0
> >>>>>>> [ 12.716149] mfgpt-timer: registering the MFGT timer as a clock event...
> >>>>>>>
> >>>>>> What BIOS are you using? It's possible that our detection code is
> >>>>>> failing to detect in-use timers.
> >>>> I'm using v0.99 (latest available).
> >>>
> >>> v0.99 of what? Jordan seems to think it's an Award BIOS, but I'd like
> >>> to make sure.
> >> Its an ALIX board from PCEngines, they have their own BIOS
> >> implementation (tinyBios).
> >>
http://www.pcengines.ch/alix.htm
> >>
> >>>> Also note when I do enable the mysterios "MFGPT workaround" option in
> >>>> the bios the machine hangs directly after:
> >>>> [ 36.780990] NET: Registered protocol family 16
> >>>
> >>> "MFGPT workaround"? That sounds a bit frightening.
> >>>
> >>> Presumably, the BIOS is using the MFGPTs, but we're not detecting them as
> >>> being in use.
> >> Yes I think so too, for the fun of it I compiled a 2.6.16.29 kernel with
> >> the attached patch from fi4l.
> >
> > Okay - thats an MFPGT patch from pre-OLPC days. I am the guilty and
> > dubious party. We changed the API to work better with the timer tick,
> > and thats the version that ended up in the kernel.
> >
> > I really wish I could take back this patch, because it keeps coming back
> > to torment me. We must, as a people, put it behind us and forgot it. :)
> >
> >> relevant output is this:
> >> [ 31.015425] geode-mfgpt: 7 timers available.
> >> ...
> >> [ 31.245875] geode-mfgpt: Registered timer 0
> >
> >> So the above kernel detects only 7 timers not 8, and it works. But note
> >> that timer 0 is not used as a clock event source but as a watchdog,
> >> which btw actually works fine :-)
> >
> > It detects 7 timers because of a bug in the code - there really are 8
> > timers, which the current code correctly identifies.
> Yes I can confirm this, changed MFGPT_MAX_TIMERS from 7 to 8 in the old
> kernel and it still works.
>
> >> The funny thing is the #define workaround part of this dubious patch and
> >> its interaction with the bios:
> >>
> >> #ifdef WORKAROUND:
> >> I have to turn the "MFPGT workaround" option in the bios ON, to boot
> >> the kernel probably.
> >>
> >> #ifndef WORKAROUND:
> >> I have to turn the "MFPGT workaround" option in the bios OFF, to boot
> >> the kernel probably.
> >
> > So the workaround works around the workaround. Fun. I think that Mitch
> > Bradley verified that if you write the magic MSR when all the clocks are
> > already clear that bad things happen. The workaround probably adds a
> > dummy clock in. Notice that the "magic MSR" no longer is in the vanilla
> > code, and thats the way it should be. If the BIOS doesn't allow use of
> > the clocks, then we have to live with that.
> >
> > So, based on everything you are saying, I think its clear that our
> > problem isn't in the MFGPT, but rather in the timer tick (because, as
> > you said, the watchdog works). We try to use IRQ 7 for the tick, which
> > Andres and I totally plucked out of thin air based on what we had to work
> > with on OLPC. Its totally possible that the TinyBIOS had other ideas.
> > Please try to boot with nomfgpt, and see which interrupts are free, and
> > use mfgpt_irq= to change it to something else if 7 is in use. Based on
> > your findings above, you'll probably need to leave the MFGPT workaround
> > off from now on.
> Great analysis! I think I can confirm this too. I tried the following:
>
> First in mfgpt_timer_setup I commented out "clockevents_register_device"
> result: the system still hangs with "registering the MFGT timer as a
> clock event" !
>
> Then I also commented out "ret = setup_irq(irq, &mfgptirq)".
> result: system boots, voila!
