On Thu, Oct 31, 2013 at 08:18:08AM +0000, Hiroshi Doyu wrote:

Stephen Warren [off-list ref] wrote @ Wed, 30 Oct 2013 23:44:04 +0100:

quoted

quoted

+	host1x {
+		compatible = "nvidia,tegra30-host1x", "simple-bus";
+		nvidia,memory-clients = <&smmu TEGRA_SWGROUP_HC>;
+		....
+		gr3d {
+			compatible = "nvidia,tegra30-gr3d";
+			nvidia,memory-clients = <&smmu TEGRA_SWGROUP_NV
+						       TEGRA_SWGROUP_NV2>;

Why one cell for the host1x property, and two cells for the gr3d
property; shouldn't they be the same length?

That can vary. Even a single device node in DT can belong to multiple
software groups.

Same with ARM SMMU.

quoted

quoted

diff --git a/drivers/iommu/tegra-smmu.c b/drivers/iommu/tegra-smmu.c

quoted

+static u64 smmu_of_get_memory_client(struct device *dev)

quoted

+	np = of_parse_phandle(dev->of_node, propname, 0);
+	if (np != smmu_handle->dev->of_node)
+		return ~0;
+
+	prop = of_get_property(dev->of_node, propname, &bytes);
+	if (!prop || !bytes)
+		return ~0;

of_parse_phandle_with_fixed_args() might be a good fit here, or perhaps
require a property #smmu-cells in the SMMU node, thus allowing the
non-fixed-length of_parse_phandle_with_args() to be used here.

I once considered of_parse_phandle_with_args() but I couldn't use that
since "#smmu-cells" needed to be fixed in smmu node, not in client
node. In this case, the number of argument(number of swgroup IDs)
varies per client device.

For the ARM SMMU binding, each device has a #stream-id-cells property
describing how many IDs it has, and then the SMMU node has a phandle+args
linkage to each of the devices attached to it, describing their stream IDs.
While this does have some limitations (a device can't be plugged into multiple
SMMUs with a different number of IDs), it seems generally sane.

Thanks,
Mark.