Re: Hangs with 100baseTX, RedHat 7.1, kernel 2.4.x and AlphaPC 164

[Jay Estabrook <Jay Estabrook compaq com>]

On Thu, Oct 04, 2001 at 09:21:46PM +0200, Mads Peter Bach wrote:
>
> > Yes, well, the 2.2. kernels dealt with a PC164 "anomaly" much better,
> > and even 2.4.10 deals with it, but ONLY if you've booted from MILO.
> 
> Ahhh:-) Palcode fixes?

Actually, no.

History
-------

The PC164 mobos were shipping before it was detected that the IRQ
masking hardware chips were broken. The problem was never fixed in
hardware, correct functioning depends on a software workaround.

Kernel 2.0 and 2.2 IRQ processing didn't require, or could easily be
prevented from, working IRQ masking hardware.

Kernel 2.4 originally did require working IRQ masking hardware because it
wants to:

1. MASK off the current interrupt
2. lower IPL to allow any other interrupts (ie any priority) to come
   through

Patches were introduced specifically for PC164 that worked around the
problem by not lowering IPL below the current interrupt.

However, they worked only for PC164 running with MILO, because MILO
correctly sets up the HWRPB to indicate EB164 family and PC164
variation, while SRM console indicates EB164 family and (erroneously)
EB164 variation. I don't know how it ever worked even as well as it
did (from SRM).

So, the new patches correctly identify the PC164 variation and
correctly activate the above workaround.

> Colour me impressed! That was quick. The patch seems to work great.

Well, I'd actually worked it out last week from some other reports of
the same problem... ;-}

> Is there a patch for the clock detection problem among the ones that
> have been submitted to Linus? (I currently have to use the cycle
> kernel parameter, to get sane BogoMIPS and timer ticks - even though
> I was quite impressed with 2900 BogoMIPS from a 366 MHz EV56)

Maybe; I solved a problem with a machine which was hanging hard in
the new code that attempts to use the programmable interval timer
to calculate the correct cycle frequency, but I'm not sure it's the
same problem.

I think maybe Ivan has some patches that do a better job in that area,
and I know he's going to submit them soon. Maybe he'll post them here
for some additional testing... :-) :-)

--Jay++

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Jay A Estabrook                            Alpha Engineering - LINUX Project
Compaq Computer Corp. - MRO1-2/K20         (508) 467-2080
200 Forest Street, Marlboro MA 01752       Jay.Estabrook@compaq.com
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