[PATCH 4/6] iommu/arm-smmu: implement generic DT bindings

Will Deacon [off-list ref] writes:

[adding Rob, Mark, Arnd, Thierry and Hiroshi]

On Wed, Aug 13, 2014 at 01:51:37AM +0100, Mitchel Humpherys wrote:

quoted

Generic IOMMU device tree bindings were recently added in
["devicetree: Add generic IOMMU device tree bindings"]. Implement the
bindings in the ARM SMMU driver.

See Documentation/devicetree/bindings/iommu/iommu.txt for the bindings
themselves.

Could you look at moving the parsing code into a separate file please (maybe
under lib/ ?). That way, other IOMMUs can use the same binding without the
boilerplate having to be rewritten each time.

quoted

diff --git a/drivers/iommu/arm-smmu.c b/drivers/iommu/arm-smmu.c
index 63c6707fad..22e25f3172 100644
--- a/drivers/iommu/arm-smmu.c
+++ b/drivers/iommu/arm-smmu.c

@@ -538,25 +538,32 @@ static int insert_smmu_master(struct arm_smmu_device *smmu,
 	return 0;
 }
 
+struct iommus_entry {
+	struct list_head list;
+	struct device_node *node;
+	u16 streamids[MAX_MASTER_STREAMIDS];
+	int num_sids;
+};
+
 static int register_smmu_master(struct arm_smmu_device *smmu,
-				struct device *dev,
-				struct of_phandle_args *masterspec)
+				struct iommus_entry *entry)
 {
 	int i;
 	struct arm_smmu_master *master;
+	struct device *dev = smmu->dev;
 
-	master = find_smmu_master(smmu, masterspec->np);
+	master = find_smmu_master(smmu, entry->node);
 	if (master) {
 		dev_err(dev,
 			"rejecting multiple registrations for master device %s\n",
-			masterspec->np->name);
+			entry->node->name);
 		return -EBUSY;
 	}
 
-	if (masterspec->args_count > MAX_MASTER_STREAMIDS) {
+	if (entry->num_sids > MAX_MASTER_STREAMIDS) {
 		dev_err(dev,
 			"reached maximum number (%d) of stream IDs for master device %s\n",
-			MAX_MASTER_STREAMIDS, masterspec->np->name);
+			MAX_MASTER_STREAMIDS, entry->node->name);
 		return -ENOSPC;
 	}
 

@@ -564,15 +571,58 @@ static int register_smmu_master(struct arm_smmu_device *smmu,
 	if (!master)
 		return -ENOMEM;
 
-	master->of_node			= masterspec->np;
-	master->cfg.num_streamids	= masterspec->args_count;
+	master->of_node			= entry->node;
+	master->cfg.num_streamids	= entry->num_sids;
 
 	for (i = 0; i < master->cfg.num_streamids; ++i)
-		master->cfg.streamids[i] = masterspec->args[i];
+		master->cfg.streamids[i] = entry->streamids[i];
 
 	return insert_smmu_master(smmu, master);
 }
 
+static int arm_smmu_parse_iommus_properties(struct arm_smmu_device *smmu,
+					int *num_masters)
+{
+	struct of_phandle_args iommuspec;
+	struct device_node *dn;
+
+	for_each_node_with_property(dn, "iommus") {
+		int arg_ind = 0;
+		struct iommus_entry *entry, *n;
+		LIST_HEAD(iommus);

You may want to use the macro, "of_property_for_each_phandle_with_args()"
to parse "iommus=".

  https://patchwork.ozlabs.org/patch/354073/

quoted

+
+		while (!of_parse_phandle_with_args(dn, "iommus", "#iommu-cells",
+							arg_ind, &iommuspec)) {

We need to check that the phandle does indeed point at one of our SMMUs
here, in case we have a system with multiple IOMMU types, all using the
generic binding.

quoted

+			int i;
+
+			list_for_each_entry(entry, &iommus, list)
+				if (entry->node == dn)
+					break;

Oh, yuck, this is really nasty to parse...

quoted

+			if (&entry->list == &iommus) {

Where is entry initialised the first time around?

quoted

+				entry = devm_kzalloc(smmu->dev, sizeof(*entry),
+						GFP_KERNEL);
+				if (!entry)
+					return -ENOMEM;

You need to of_node_put the guys you've got back from the phandle parsing
code.

quoted

+				entry->node = dn;
+				list_add(&entry->list, &iommus);
+			}
+			entry->num_sids = iommuspec.args_count;
+			for (i = 0; i < entry->num_sids; ++i)
+				entry->streamids[i] = iommuspec.args[i];
+			arg_ind++;

Isn't this defined by #iommu-cells?

quoted

+		}
+
+		list_for_each_entry_safe(entry, n, &iommus, list) {

Why the _safe variant? This is a local list, right?

Will