From: Dr. Tom Blinn, 603-884-0646 [tpb@doctor.zk3.dec.com]
Sent: Tuesday, July 13, 1999 1:51 PM
To: Jim Fitzmaurice
Subject: Re: Some hints on the DEGPA driver kit


> Tom,
> 	That is exactly what I did, several times. Doing a diff between my old and
> new /sys/conf files I see one difference "pseudo-device alt" on the last
> line. That's why I thought the error message I saw, "alt.mod: Cannot
> configure driver" has something to do with it since it came around the time
> I first tried to install the driver software. Does your colleague have any
> other idea's.
> 	FYI. I didn't move it, it's a new install. I only swapped them to test it,
> both cards work in one machine and fail in the other. Both machines are
> 4100's running 4.0D PK3. There is one difference between the two machines. I
> found it running a "psrinfo -v" command. They both have EV5.6 (21164A)
> processors but the cards work on the 4100 running at 599 MHz, but fail on
> the 4100 running at 467 MHz.(Although I seriously doubt this has anything to
> do with the problem.)
> 
> Jim Fitzmaurice
> jpfitz@fnal.gov

That is VERY interesting.  Is one of your 4100 systems SUPPOSED to be 600MHz
and the other one SUPPOSED to be 466MHz?  That is, did you purchase systems
with two different clock speeds?

What firmware revisions are present on the two 4100 systems?  Can you tell at
boot time, or from examing the console firmware output, what PAL revision is
present?

The "alt.mod: Cannot configure driver" would happen (as you surmise) when the
kernel asks the alt driver (for the DEGPA) to configure itself and operate the
hardware.  If something goes wrong in the driver, it may fail to configure,
and you'd get that message.

I have recently heard comments about a possible change in some systems that if
it's what I think it is, might be breaking a routine in the kernel that does a
very short DELAY() on the microsecond level that's used in device drivers a
lot and on many devices, if the DELAY() isn't long enough, the device simply
doesn't work as expected (and if the device doesn't work as expected, then you
get a failed driver or whatever).

This is, in any case, strange behavior, and since it's only showing up on the
4100 (Rawhide) platforms (which I heard were specifically involved with this
other change), I've got to wonder if that's what's happening..  Knowing the
SRM firmware and PALcode revisions might help pin it down.

Tom

 Dr. Thomas P. Blinn + UNIX Software Group + Compaq Computer Corporation
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