On 12/11/2014 14:08, Arnd Bergmann wrote:
>>> Putting an interrupt in DT is trivial. The hard part is the rest of the
>>> interface, which so far there is no specification for.
>>
>> Have you looked at docs/specs/acpi_{cpu,mem}_hotplug.txt? Writing a DT
>> binding for it is trivial too. Or are we talking about two different
>> things?
>
> Interesting. I agree that doing a DT binding for these will be trivial,
> and the implementation in Linux should also be straightforward, thanks
> for pointing these out.
>
> However, it seems that the implementation that qemu uses is incompatible
> with ARM64, since GPE is not part of the ACPI hardware reduced mode.
That makes it even simpler because you do not have to use SCI.
-M virt currently doesn't have a GPIO controller, but it's easy to add a
PL061 and specify a random GPIO pin in the DT bindings. Then you can
use GPIO-signaled ACPI events in the AML, just move _Lxx methods move
from \_GPE to \_SB.GPIO under the GPIO controller.
Paolo
