Re: [PATCH 2/5] powerpc: Generic device tree for all AmigaOne boards

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Datum: Mon, 12 Jan 2009 16:12:18 +1100
Von: Benjamin Herrenschmidt [off-list ref]
An: Gerhard Pircher [off-list ref]
CC: Grant Likely <redacted>, linuxppc-dev@ozlabs.org
Betreff: Re: [PATCH 2/5] powerpc: Generic device tree for all AmigaOne boards

The code in the kernel that retreives the interrupt that way is clearly
marked as a fishy workaround for bogus firmwares :-)

"bogus" applies a little bit to the PCI init code of the A1 firmware. ;-)

But I'm not going to reject things based on that, it will work for
simple board using really only legacy interrupts like yours...

Thanks!

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For the flattened device tree, I think we've settled on the convention
that every node with an IRQ connection should have both the
interrupt-parent and interrupts properties.  (ie. don't rely on the
parent node's interrupt-parent property.)

Even for ISA devices?

I disagree with Grant here. Especially in simple ISA cases like that,
there's really no point in bloating the device-tree.

Okay, so I leave it as it is.

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Can this PCI device be probed?  Typically PCI devices don't get added
to the flattened device tree because PCI is a probeable bus.

Yes, it can be probed. I thought it would be a good idea to include it,
because the IDE controller operates in legacy mode. I planned to specify
the two legacy interrupts in this node (as you can see), but the kernel
didn't like them.

Well, the kernel just didn't make use of them I'd say :-) But that can
probably be fixed with the appropriate hacks. 

I think I throw away the IDE controller node for now, as libata just reads
the PCI register settings (progif) and I guess the IDE subsystem will do
the same in the future.

Gerhard

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I think I throw away the IDE controller node for now, as libata just reads
the PCI register settings (progif) and I guess the IDE subsystem will do
the same in the future.

Well... if all AmigaOne use a 8259, they probably use the same interrupt
routing except for PCI slots. In which case, I would -still- prefer if
you had a proper interrupt tree, and at runtime or boot-wrapper time,
fixed up the PCI host "interrupt-map" property to contain the right
values for a given board.

I'm not going to include the new platform in .29, it's way too late
anyway (it should have been published a couple of weeks before the merge
window at least I'd say) so we have some time til .30 to polish things a
bit.

Another area to look at is to cleanup the non-coherent DMA thingy. The
config option should just enable a set of non-coherent backend ops, but
we should still be able to decide which ones to use (coherent vs.
non-coherent) at runtime.

Cheers,
Ben.