4.0_STABLE soft reboot hangs on PowerEdge 2550

["John D. Baker" <jdbaker%mylinuxisp.com@localhost>]

I've been helping a friend set up a Dell PowerEdge 2550 system.  I first
installed 4.0_RELEASE and then noticed that on the first reboot after
installation it would hang here:

[...]
cd0 at atapibus0 drive 0: <TEAC CD-ROM CD-224E, , 3.7D> cdrom removable
cd0: 32-bit data port
cd0: drive supports PIO mode 4, DMA mode 2, Ultra-DMA mode 2 (Ultra/33)
cd0(rccide0:0:0): using PIO mode 4, DMA mode 2, Ultra-DMA mode 2 (Ultra/33) 
(using DMA)
[hung]

The machine was completely unresponsive and the only remedy was to
power-cycle it.  It then booted fully and worked OK.  See

   http://bobdbob.com/~jdbaker/clamp-dmesg.txt

for the complete dmesg output.

Following several experiments it was clear that rebooting the machine
from software, for any reason (even following BIOS config examination
immediately after power-up) would prevent the kernel from booting,
hanging in the same place every time.  It would always boot completely
from uninterrupted power-on/power-cycle.

Searching the archives, we found the following references that seemed to
describe exactly the same thing we were now seeing with 4.0_RELEASE and
later, 4.0_STABLE.

    http://mail-index.netbsd.org/port-i386/2006/03/14/0003.html
    http://mail-index.netbsd.org/port-i386/2006/03/14/0005.html

and so on.  It seems no conclusion was reached.

Another 2550 running NetBSD 3.1_RELEASE has no problem with soft
reboots.  For 4.0, I found that if I disabled support for IDE disks

    #wd* at atabus?

(it has none, only a CD-ROM drive), it would now boot completely
following a soft reset.  A custom kernel config can be found at:

    http://bobdbob.com/~jdbaker/CLAMP

Now that I have the machine working, it will probably not be available
for any testing, but perhaps this will point to what may be a problem
for others?

Thanks.

--
John D. Baker, KN5UKS                    NetBSD     Darwin/MacOS X
jdbaker(at)mylinuxisp(dot)com                 OpenBSD            FreeBSD
BSD -- It just sits there and _works_!
GPG fingerprint:  D703 4A7E 479F 63F8 D3F4  BD99 9572 8F23 E4AD 1645