Bug 26736

I am using the 4.3RC4 floppies. 
After inserting the mfsroot.flp and configuring drivers w/Kernel 
config Menu in visual mode, I left (the minimal) following 
Active Drivers:
          Dev---IRQ--Port 
Storage: 
          ata0   14  0x1f0
          ata1   15  0x170
          fdc0   6   0x3f0
Communications:
          ppc0   7
          sio0   4   0x3f8
Input:
         atkbd0  1
         psm0    12
         sc0
Miscellaneous:
         npx0    13   0xf0
Them quit and saved config, and let the kernel autoprobe devices:

--- begin transcript of last lines seen on the screen: 
md0: Preloaded image </mfsroot> 2949120 bytes at 0xc03a0628
md1: Malloc disk
npx0: <math processor> on motherboard
npx0: INT 16 interface
pcbi0: <Intel 82443LX (440 LX) host to PCI bridge> on motherboard
pci0: <PCI bus> on pcib0
pcbi1: <Intel 82443LX (440 LX) PCI-PCI (AGP) bridge> at device 1.0 on pci0
pci1: <PCI bus> on pcib1
pci1: <Cirrus Logic GD5465 SVGA controller> at 0.0 irq 9
isab0: <Intel 82371AB PCI to ISA bridge> at device 4.0 on pci0
isa0: <ISA bus> on isab0
atapci0: <Intel PIIX4 ATA33 controller> port 0xfcd0-0xfcdf at device 4.1 on pci0

ata0: at 0x1f0 irq 14 on atapci0
ata1: at 0x170 irq 15 on atapci0
uhci0: <Intel 82731AB/EB (PIIX4) USB controller> port 0xfce0-0xfcff irq 9 at device 4.2 on pci0
usb0: USB revision 1.0
uhub0: 2 ports with 2 removable, self powered
chip1: <Intel 82371AB Power management controchip1: <Intel 82371AB Power management controller> port 0x8800-0x880f at device 4.3 on pci0
pci0: <Number Nine Imagine 128 graphics accelerator at 12.0 irq 9
--- End of transcript

After which the system completely hangs.
The only way to reboot/turn-off the system is by pulling
the cable from the wall. No keyboard or on/off switch reaction.

--

Notice the IRQ 9 is used by the two graphic cards on this system, and
by the USB, although at different ports.

I then tried disabling IRQ 9 on the  BIOS setup as following:
From the PhoenixBIOS Setup Utility 
-> Advanced -> ISA Resource Exclusion (*)
-> I then changed the value of the IRQ 9 item from "Available" to 
"Reserved" (**). 
All the other IRQ items (3,4,5,7,10,11 and 15) were left "Available".

Trying to boot again after this BIOS setup, does not help: 
The system freezes at the same point with the same messages as above 
except for the following: every instance of 'irq 9' in the text above 
is replaced by 'irq 11'. 

If in addition to disabling the IRQ 9, I also disable the IRQ 11 
and retry, the machine still hangs ('irq 11' is now replaced 
by 'irq 10').

Notes:
(*) For this option, from the 'Item Specific Help' panel in the 
BIOS setup, I read: 
Reserves interrupts for legacy ISA devices to prevent conflict with 
PCI/PnP devices 
(**) The option Available allows to allocate IRQ for PCI or ISA PnP devices.

Fix: 

Workaround: 

    Maybe disabling probing of USB _and_ Power management in GENERIC?

Fix: 

    I do not really know. 

First, notice the system has presently two graphic cards: 
one integrated in the motherboard (AGP Cirrus Logic Laguna GD5465)
and an external one (Number 9 Imagine 128) and both are 
on the PCI bus.
The USB and the two graphic cards presently are reported to 
use the same IRQ, although at different ports. 
Should that happen at all? 

I am also not really sure that this is an IRQ asignement 
problem, as a first look suggests.
It might have to do with the power management controller...

It is worth to mention I had this problem every time I tried
booting from releases floppies in the 4.x branch.
In all those attempts (specifically using 4.0-R,4.1.1-R and 
4.2-R floppies) I had only _one_ graphic card. 
I still observed the same problem, which was reported 
in PR misc/18201.
The USB messages were then slightly different. I guess that is 
due to the work done on the USB code since 4.0-R. 
But still the IRQ 9 was shared by the USB and the single graphic 
card (Cirrus Logic GD5465). In those cases the system stopped 
responding just after printing:

[snip previous lines]
chip1: <Intel 82371AB Power management controller> port 0x8800-0x880f at device 4.3 on pci0
--
After that I had always to pull the chord to reboot.

Puzzle: with 4.3RC4 the system hangs after recognizing the 
2nd graphic card, printed after probing the Power management 
controller. If the 82371AB was the culprit, shouldn't it hang 
before the last line when trying 4.3RC floppies?.

Another failed attempt was as follows:
When playing with the 4.1.1 CD, I managed to install the 
src/sys tree, edited GENERIC, commented out all USB support 
in it (at least I thought so) and finally compiled a 4.x kernel
which I copied to the kernel.flp diskette. No changes to 
mfsroot.flp, though.
I tried in this way to eliminate the sharing of one IRQ by two devices. 
The system still hanged at boot time with these floppies.

----
The box presently runs 3.5-STABLE without no other inconvenience 
than be "forced" to do so.
I am willing to test any floppy pair you send me to overcome 
this problem. Thank you for reading this long post.