On Wed, 27 Jun 2012 04:48:18 +0200
Stephen Warren [off-list ref] wrote:

On 06/26/2012 08:32 PM, Mark Zhang wrote:

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On 06/26/2012 07:46 PM, Mark Zhang wrote:

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On Tue, 26 Jun 2012 12:55:13 +0200
Thierry Reding [off-list ref] wrote:

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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.