Re: m68k: Convert to genirq (WIP)

From: Geert Uytterhoeven
Date: Wed Aug 10 2011 - 05:59:20 EST

On Sun, Jun 5, 2011 at 08:27, Brad Boyer <flar@xxxxxxxxxxxxx> wrote:
> If we could really map all the interrupt controllers, we could probably
> cut down on the largest interrupt number. Most Macs really only have
> 20 or 30 actual interrupt sources. The problem is the two or three
> layers of cascaded mess. None of them have just a single layer. Just
> getting rid of the fixed global mapping could take us down to 64 since
> nothing has both Baboon and PSC, but we have unique numbers for them.
> We have 3 whole blocks of 8 just for PSC, even though that's just in
> two models. We don't even know what most of those do, if anything.

While looking into optimizing interrupts using chain handlers (which cannot
be shared), I noticed several of these cascades are hung on the same interrupt.
Hence we cannot use the optimization of chain handlers for them.

Knowing which are mutually exclusive helps a lot, but my Mac knowledge is
very limited.

I derived from the code this list of cascade handlers and the
interrupts they use:


OSS_IRQLEV_SCSI = IRQ_AUTO_2 conflict: via2_irq
OSS_IRQLEV_SOUND = IRQ_AUTO_5 conflict: psc_irq

OSS_IRQLEV_NUBUS = IRQ_AUTO_3 conflict: psc_irq

IRQ_AUTO_3 conflict: oss_nubus_irq
IRQ_AUTO_5 conflict: oss_irq
IRQ_AUTO_6 conflict: via1_irq

OSS_IRQLEV_VIA1 = IRQ_AUTO_6 (on oss) conflict: psc_irq

IRQ_AUTO_1 conflict: iop_ism_irq
IRQ_AUTO_6 (if via_alt_mapping) conflict: psc_irq

IRQ_AUTO_2 conflict: oss_irq


These are other interrupts using in the Mac core code, which may use the same
interrupts as some of the cascades above:

OSS_IRQLEV_IOPISM = 1 = IRQ_AUTO_1 (on oss) conflict: via1_irq
IRQ_VIA2_0 (on !oss)


timer handler

So baboon and PSC are mutually exclusive? But they don't conflict w.r.t. to
interrupt lines anyway, so they're not an issue.

>From the code, OSS and VIA are also mutually exclusive (except for via1_irq)?

But PSC can coexist with OSS? That's where most of the conflicts are.



Geert Uytterhoeven -- There's lots of Linux beyond ia32 -- geert@xxxxxxxxxxxxxx

In personal conversations with technical people, I call myself a hacker. But
when I'm talking to journalists I just say "programmer" or something like that.
             Â Â -- Linus Torvalds
To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
the body of a message to majordomo@xxxxxxxxxxxxxxx
More majordomo info at
Please read the FAQ at