On Mon, Dec 05, 2011 at 02:47:29PM -0600, Rob Herring wrote:

On 12/05/2011 02:21 PM, Anton Vorontsov wrote:

quoted

On Mon, Dec 05, 2011 at 01:16:39PM -0600, Rob Herring wrote:
[...]

quoted

At least for DT enabled platforms, we could force "no irq" to be 0 in
the DT irq code. Searching the dts files, I found 2 occurrences of IRQ0.

Please note that there are HW IRQ numbers and "Virtual" IRQ numbers.
dev->irq and thus the thing that we pass into request_irq() is a
virtual IRQ thing, a "cookie".

While in device tree you see real HW IRQ numbers.

Legal VIRQ is always > 0, while HW IRQ could be >= 0.

If this was all true, then there would be no discussion.

This is what we are working towards, but irq_chips all over the arm tree
do not support any translation or have base fixed at compile time. Only
a few have been converted. And some ARM platforms may never get
converted to DT.

quoted

quoted

Prima2 has timer on IRQ0, and VersatileAB has watchdog on IRQ0. Prima2
should be fine currently as it doesn't use the of_irq_* functions to get
the timer irq, but that is an issue as it skips any translation.
VersatileAB should be okay with the VIC irqdomain support.

It shouldn't be an issue to use of_irq_*() functions for these IRQs.
of_irq_*() will remap HW IRQ 0 to some other VIRQ. If it does not do
this currently, then it's a bug and should be fixed.

I think that's what I'm saying. It's either a bug or incomplete DT
conversion for the platform. Either way, those should get fixed first.

Do we expect there to be any platform drivers which are shared between
legacy platforms and newer DT-ised platforms?

Those drivers would be pain points since they would need to understand
both conventions.

So far as I can see, only boards which are not DT-ised, which do not use
DT-ised drivers and which do not use drivers which use interrupts and
are either used by DT-ised boards or by arches with a non-zero NO_IRQ
could safely carry on using a non-zero NO_IRQ.  Tracking down exactly
which boards and drivers this applies to could be hard.  We could have a
CONFIG_NO_IRQ and make them depend on it, but we still have to find that
list of boards and drivers in the first place.


Otherwise, it feels like we might need a strategy for migrating pretty
much everything if we don't want to end up in a mess.

Cheers
---Dave