Re: 83xx GPIO/EXT int in arch/powerpc/

In addition, linux always reserve numbers 0...15. 0 is
always illegal and 1..15 can only be mapped to a 8259 type legacy ISA
controller. This is to avoid problem with stupid drivers from the x86
world.

Of course, it doesn't help if you have an i8259 but have
non-legacy-PC devices on it.  Oh the horror!

Now, there is no automagic way of setting up GPIOs. You have to 
manually
(from your firmware that is, or maybe from your platform code),
configure the appropriate GPIO to the appropriate HW irq source on the
IPIC that matches what you put in your DTS.

It *really* shouldn't be Linux platform code, if you can
avoid it at all.  It's just more trouble than it's worth.

 - You can create a device-node for the PCI device. PCI devices
normally, in linux, don't need to have device-nodes in the DTS, at 
least
it's not mandatory, but you -can- do it. If your node has the correct
"reg" property,

What is "correct" in this case?  We probably should describe
what properties are required in a (non-phb) pci node for
platforms that don't use the device tree for probing PCI.
In this specific case, do you only need the configuration
address in the "reg"?

it should be matches by the linux parser, and thus you
have the ability to put an interrupts property in there. It would
normally be a PCI interrupt specification, but you can specify
explicitely an interrupt parent that points to the IPIC and thus have 
an
interrupt pointing directly there. That's the example that, I think,
Andy gave you

Yeah.

 - You can do it in your interrupt-map. That's probably the cleanest 
way
to do it.

Not really.  If the device interrupt is physically connected
directly to a GPIO or a PIC or whatever, if it doesn't go
through the PCI bus; then it shouldn't be represented in
the device tree as if it did.  The higher-up bridge has
nothing whatsoever to do with this device's interrupt.

It's a simple hack of course, it can be useful sometimes.
It's not "clean" at all however.

Just make sure you have
an entry there for your device pin A dev/fn whose specification points
to the IPIC with the appropriate IRQ number and that should work fine.

Depending on the rest of the tree, this would often mean
you have to do a much bigger interrupt-map-mask than
without this hack, and the corresponding explosion in
interrupt-map size.

Now, that's assuming GPIOs, when used as external interrupts, are
directly routed to the IPIC. I don't know the 83xx so I just assumed
it :-)

Almost always that's how it works yeah.  And the "GPIO"
stage isn't normally represented in the device tree, GPIO
settings are considered a part of the PCB layout ;-) (one
more reason why Linux shouldn't have to touch it).

If that's not the case, you may need some intermediary cascaded
interrupt controller or something around those lines.

Yeah, but that's just the more general case of the
general case :-)


Segher