[Soekris] on the IRQ assignment on the net4801

[Igor Sobrado]

Hi again!

I have a question on the IRQ assignment on the net4801.  Looking at the
output of the comBIOS when booting this fine embedded computer:

comBIOS ver. 1.28  20050529  Copyright (C) 2000-2005 Soekris Engineering.

net4801

0256 Mbyte Memory                        CPU Geode 266 Mhz 

Pri Mas  HTS541060G9AT00                 LBA Xlt 1024-255-63  58605 Mbyte
Pri Sla  SILICONSYSTEMS INC 512MB        LBA 1011-16-63  509 Mbyte

Slot   Vend Dev  ClassRev Cmd  Stat CL LT HT  Base1    Base2   Int 
-------------------------------------------------------------------
0:00:0 1078 0001 06000000 0107 0280 00 00 00 00000000 00000000 
0:06:0 100B 0020 02000000 0107 0290 00 3F 00 0000E101 A0000000 10
0:07:0 100B 0020 02000000 0107 0290 00 3F 00 0000E201 A0001000 10
0:08:0 100B 0020 02000000 0107 0290 00 3F 00 0000E301 A0002000 10
0:10:0 104C AC23 06040002 0107 0210 08 3F 01 00000000 00000000 
0:18:2 100B 0502 01018001 0005 0280 00 00 00 00000000 00000000 
0:19:0 0E11 A0F8 0C031008 0117 0280 08 38 00 A0003000 00000000 11
1:00:0 100B 0020 02000000 0107 0290 00 3F 00 0000D001 A4000000 05
1:01:0 100B 0020 02000000 0107 0290 00 3F 00 0000D101 A4001000 11

we can see that there is an IRQ level (10) shared by the MacPhyter
ethernet controllers in the net4801 board, an IRQ level (5) allocated
to the fourth MacPhynter ethernet controller, an IRQ level (11) shared
by the Compaq Computer Corporation ZFMicro Chipset USB and the fifth
ethernet controller (this machine has a lan1621 card on the PCI bus).

It seems that the OS does not change this IRQ allocation:

$ dmesg | grep irq | tail -9  
sis0 at pci0 dev 6 function 0 "NS DP83815 10/100" rev 0x00, DP83816A: irq 10, address 00:00:24:c6:57:90
sis1 at pci0 dev 7 function 0 "NS DP83815 10/100" rev 0x00, DP83816A: irq 10, address 00:00:24:c6:57:91
sis2 at pci0 dev 8 function 0 "NS DP83815 10/100" rev 0x00, DP83816A: irq 10, address 00:00:24:c6:57:92
sis3 at pci1 dev 0 function 0 "NS DP83815 10/100" rev 0x00, DP83816A: irq 5, address 00:00:24:c4:d8:d4
sis4 at pci1 dev 1 function 0 "NS DP83815 10/100" rev 0x00, DP83816A: irq 11, address 00:00:24:c4:d8:d5
ohci0 at pci0 dev 19 function 0 "Compaq USB OpenHost" rev 0x08: irq 11, version 1.0, legacy support
pckbc0: using irq 1 for kbd slot
pccom0 at isa0 port 0x3f8/8 irq 4: ns16550a, 16 byte fifo
pccom1 at isa0 port 0x2f8/8 irq 3: ns16550a, 16 byte fifo

Is it the right IRQ allocation for this device?  Are there plans to do
a better allocation in a firmware upgrade?  I suspect that this IRQ
allocation can be challenging when using, for example, USB devices
(e.g., a net4801 configured as a printer server or as a storage device
with an external HDD attached to it).

Perhaps the fifth ethernet controller should share an IRQ with the
fourth controller (IRQ 5).  Don't know a lot about the architecture
of this machine, but it makes sense to me.

Any feedback on this matter will be highly appreciated.

Cheers,
Igor.