more multiple dec21140 on ppc

Valette Eric eric.valette at
Fri Feb 28 09:42:34 UTC 2003

Till Straumann wrote:

> a) I do nothing, boot -> dec driver reports it is using interrupt 10
>    which in fact is the ISA interrupt.
> b) Knowing (from the manual) that the ethernet chip is also hooked
>    to OpenPIC IRQ2, I use PPCbug (knowing that the on-board dec is
>    in slot 0xe) to manually fix the PCI_INTERRUPT_LINE config register:
>    CSAW 0 e 0 3c 12 ; B
>    NBO
>    I.e. I use PPCBug to write the INTERRUPT_LINE register.
>    I added the BSP_PCI_INTERRRUPT_LOWEST_OFFSET because the driver
>    currently does not do so. Note that PPCBug takes hex arguments,
>    i.e. the 12 value corresponds to decimal 18 which is picked up
>    by the driver/BSP and used 1:1 as the 'irq name'.
>    After booting up (the _identical_ application binary), the driver
>    reports it's now using IRQ 18 and it works fine.
>    If I provide the CSAW command with anything else than
>    0xa (isa irq) or 0x12 (OpenPIC IRQ) the driver does not get
>    any interrupts, as expected.

So the status is not so bad :
	1) This means that someone could just do a kind of "pci init" to change 
the irq value because the firmware does not make it. Look at linux 
prep-pci.c to see what I mean...
	2) Of course the openpic code management should be enhanced as you 
proposed to reduce latency,

-- eric

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