Re: [PATCHv3 14/19] iommu/tegra: smmu: Get "nvidia,memory-clients" from DT

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

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.

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.