On Tue, Jun 26, 2012 at 08:48:18PM -0600, Stephen Warren 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@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.
Wasn't the whole point of using a carveout supposed to be a replacement for the GART? As such I'd think the carveout should rather be a property of the host1x device.
AIUI what we want to do is have a large contiguous region of memory that a central component (host1x) manages as a pool from which clients (DRM, V4L, ...) can allocate buffers as needed. Since all of this memory will be contiguous anyway there isn't much use for the GART anymore.
I have the same understanding. We don't need GART anymore if carveout is enabled. I'm thinking that why we need to define a property and reference to global /memreserve/ in GART or HOST1X node? We can just define a label for /memreserve/, so we can distinguish these memory reservations already in codes.
But maybe I'm misunderstanding.
Thierry
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