[RFC] Add support for Xen ARM guest on FreeBSD

[Julien Grall]

On 01/17/2014 03:04 AM, Nathan Whitehorn wrote:
> On 01/16/14 18:36, Julien Grall wrote:
>
> The specification is actually a little unclear on this point, but
> FreeBSD follows the same rules as Linux in any case. Most, if not all,
> FreeBSD code should check any ancestor at this point as well. In
> particular fdt_intr_to_rl does this. What it *doesn't* do is allow
> #interrupt-cells to be larger than 2. I'll fix this this weekend.

Thanks, for working on this part.

Another things to take into account: the first cell doesn't always 
contain the interrupt.
With the Linux binding (#interrupt-cells == 3)
   - cell 1: 1 or 0 (PPI vs SPI)
   - cell 2: relative IRQ number to the start of PPI/SPI
   - cell 3: cpu mask + interrupt flags (edge/level...)

>>> On the subject of simple-bus, they usually aren't necessary. For
>>> example, all hypervisor devices on IBM hardware live under /vdevice,
>>> which is attached to the device tree root. They don't use MMIO, so
>>> simple-bus doesn't really make sense. How does Xen communicate with the
>>> OS in these devices?
>>> -Nathan
>>
>> As I understand, only the simple bus code (see simplebus_attach) is
>> translating the interrupts in the device on a resource.
>> So if you have a node directly attached to the root node with
>> interrupts and MMIO, the driver won't be able to retrieve and
>> translate the interrupts via bus_alloc_resources.
>
> Why not? nexus on ARM, MIPS, PowerPC, and sparc64 can do this.

I have noticed at least one issue (which is not related to my problem):
   - When the OFW nexus translate IRQ (with #interrupt-cells > 1), the 
rid will be equal to 0, 0 + #interrupt-cells, ... So the number will be 
discontinued. Rather than on simple-bus for the same device, the rid 
will be 0, 1, 2...

For my issue, I will look at it again this week-end.

BTW when I look to the FDT (sys/dev/fdt_common.c) and the ofw 
(sys/dev/ofw_nexus.c) code, I have notice that lots of code are duplicated.

It would be nice to have common helper to avoid duplicate code and issue 
for the future :).

-- 
Julien Grall