Re: [PATCH 1/1] arm/dts: Tegra30: Add device tree support for SMMU

[Stephen Warren <swarren-3lzwWm7+Weoh9ZMKESR00Q@public.gmane.org>]

On 04/17/2012 11:10 PM, Hiroshi Doyu wrote:
> On Mon, 16 Apr 2012 18:07:06 +0200
> Stephen Warren <swarren-3lzwWm7+Weoh9ZMKESR00Q@public.gmane.org> wrote:
> 
>> On 04/16/2012 04:10 AM, Hiroshi Doyu wrote:
>>> Stephen Warren wrote at Fri, 13 Apr 2012 21:33:47 +0200:
>>>> On 04/13/2012 04:22 AM, Hiroshi Doyu wrote:
>>>>> Add device tree support for Tegra30 IOMMU(SMMU).
>> ...
>>>> But why does the SMMU driver expect to control the AHB arbitration
>>>> registers? They seem unrelated to the SMMU.
>>>
>>> It's necessary to inform AHB that SMMU is ready to use. There's a
>>> dedicated bit for SMMU in this AHB arbitration register.
>>
>> Shouldn't there be a dedicated driver for the AHB arbitration registers
>> that the SMMU driver calls into to achieve this? IIRC, the AHB
>> arbitration registers support much more than the SMMU enable, and if we
>> ever need to touch those other features, going to the SMMU driver to do
>> so probably wouldn't make sense.
> 
> Agree. Sounds like the way to go.
> 
> We haven't upstreamed AHB driver yet. So is it ok to remove AHB entry
> from SMMU dt and add AHB function call when upstreaming AHB driver?
> I'll work on that.

I think that seems reasonable for now, yes. I assume you mean
implementing e.g. arch/arm/mach-tegra/tegra30-ahb.c, similar to how,
say, the fuse APIs work.