On Wed, 27 Jun 2012 16:08:10 +0200
Thierry Reding [off-list ref] wrote:

* PGP Signed by an unknown key

On Wed, Jun 27, 2012 at 03:59:07PM +0300, Hiroshi Doyu wrote:

quoted

On Wed, 27 Jun 2012 07:14:18 +0200
Thierry Reding [off-list ref] wrote:

quoted

quoted

Old Signed by an unknown key

On Tue, Jun 26, 2012 at 08:48:18PM -0600, Stephen Warren wrote:

quoted

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

quoted

quoted

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

quoted

quoted

quoted

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

...

quoted

quoted

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?

Mostly agree. IIUC, we use both carveout/gart allocated buffers in
android/tegra2.

quoted

As such I'd think the carveout should rather be a property
of the host1x device.

Rather than introducing a new property, how about using
"coherent_pool=??M" in the kernel command line if necessary? I think
that this carveout size depends on the system usage/load.

I was hoping that we could get away with using the CMA and perhaps
initialize it based on device tree content. I agree that the carveout
size depends on the use-case, but I still think it makes sense to
specify it on a per-board basis.

DRM driver doesn't know if it uses CMA or not, because DRM only uses
DMA API. I think that "coherent_pool" can be used only when the amount
of contiguous memory is short in your system. Otherwise even unnecessary.

Could you explain a bit more why you want carveout size on per-board basis?