Hi Magnus,
On Thu, Oct 27, 2016 at 1:07 PM, Magnus Damm <magnus.damm@xxxxxxxxx> wrote:
> On Thu, Oct 27, 2016 at 7:42 PM, Geert Uytterhoeven
> <geert@xxxxxxxxxxxxxx> wrote:
>> On Thu, Oct 27, 2016 at 12:29 PM, Magnus Damm <magnus.damm@xxxxxxxxx> wrote:
>>> From: Magnus Damm <damm+renesas@xxxxxxxxxxxxx>
>>>
>>> Hook up r8a7795 DMAC nodes to IPMMU-MP1, IPMMU-DS0 and IPMMU-DS1.
>>>
>>> Signed-off-by: Magnus Damm <damm+renesas@xxxxxxxxxxxxx>
>>> ---
>>>
>>> This patch can be merged any time, but it is however not recommended
>>> to enable IPMMU-MP1, IPMMU-DS0 or IPMMU-DS1 until various dependencies
>>> have been resolved:
>>
>> Forgive my ignorance, but how does the driver core treat devices with
>> iommus properties pointing to disabled IOMMU nodes?
>> Is this ignored silently, or does this cause -EPROBEDEFER, like for clocks
>> and power-domains?
>
> Not sure about current state of the driver core to be honest. Earlier
> I needed to add a local workaround in the ->xlate() callback in the
> IPMMU driver but I need to revisit to see if that needs to be updated.
> Any ideas?
>
> I do however know that the IPMMU driver stack included in
> renesas-drivers works both with and without iommus properties and in
> case an iommus property is used then both enabled and disabled are
> known to work.
>
> Looking at mainline, at this point the IPMMU driver changes for
> r8a7795 and r8a7796 are not included yet, so there is no driver code
> that will match with the DT compat string. Once we queue up the IPMMU
> driver code for merge then we need to make sure it still works as
> expected.
Not finding a driver for a compat string and a disabled node should behave
the same (although we had issues in the past where the disabled was ignored).
> I just booted r8a7795 Salvator-X with these patches on top of
> renesas-devel-20161024-v4.9-rc2 (that lacks the IPMMU driver for
> r8a7795) and the DU device that is connected via FCP and VSP operate
> as usual. So all seems fine what I can tell.
Thanks for checking!
Gr{oetje,eeting}s,
Geert
--
Geert Uytterhoeven -- There's lots of Linux beyond ia32 -- geert@xxxxxxxxxxxxxx
In personal conversations with technical people, I call myself a hacker. But
when I'm talking to journalists I just say "programmer" or something like that.
-- Linus Torvalds
