Tegra DRM device tree bindings

[Hiroshi Doyu]

On Wed, 27 Jun 2012 04:48:18 +0200
Stephen Warren <swarren at nvidia.com> wrote:

> On 06/26/2012 08:32 PM, Mark Zhang wrote:
> >> On 06/26/2012 07:46 PM, Mark Zhang wrote:
> >>>>> On Tue, 26 Jun 2012 12:55:13 +0200
> >>>>> Thierry Reding <thierry.reding at avionic-design.de> wrote:
> >> ...
> >>>> I'm not sure I understand how information about the carveout would be
> >>>> obtained from the IOMMU API, though.
> >>>
> >>> I think that can be similar with current gart implementation. Define carveout as:
> >>>
> >>> carveout {
> >>>         compatible = "nvidia,tegra20-carveout";
> >>>         size = <0x10000000>;
> >>> };
> >>>
> >>> Then create a file such like "tegra-carveout.c" to get these definitions and
> >> register itself as platform device's iommu instance.
> >>
> >> The carveout isn't a HW object, so it doesn't seem appropriate to define a DT
> >> node to represent it.
> > 
> > Yes. But I think it's better to export the size of carveout as a configurable item.
> > So we need to define this somewhere. How about define carveout as a property of gart?
> 
> There already exists a way of preventing Linux from using certain chunks
> of memory; the /memreserve/ syntax. From a brief look at the dtc source,
> it looks like /memreserve/ entries can have labels, which implies that a
> property in the GART node could refer to the /memreserve/ entry by
> phandle in order to know what memory regions to use.

I think that we don't need the starting address for carveout but we
need its size. carveout memory is just anonymous physically
continguous buffer.