iommu: Introduce iommu_fwspec

Introduce a common structure to hold the per-device firmware data that
most IOMMU drivers need to keep track of. This enables us to configure
much of that data from common firmware code, and consolidate a lot of
the equivalent implementations, device look-up tables, etc. which are
currently strewn across IOMMU drivers.

This will also be enable us to address the outstanding "multiple IOMMUs
on the platform bus" problem by tweaking IOMMU API calls to prefer
dev->fwspec->ops before falling back to dev->bus->iommu_ops, and thus
gracefully handle those troublesome systems which we currently cannot.

As the first user, hook up the OF IOMMU configuration mechanism. The
driver-defined nature of DT cells means that we still need the drivers
to translate and add the IDs themselves, but future users such as the
much less free-form ACPI IORT will be much simpler and self-contained.

CC: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Suggested-by: Will Deacon <will.deacon@arm.com>
Signed-off-by: Robin Murphy <robin.murphy@arm.com>
Signed-off-by: Will Deacon <will.deacon@arm.com>

drivers/iommu/iommu.c

@@ -31,6 +31,7 @@
 #include <linux/err.h>
 #include <linux/pci.h>
 #include <linux/bitops.h>
+#include <linux/property.h>
 #include <trace/events/iommu.h>
 
 static struct kset *iommu_group_kset;
@@ -1613,3 +1614,60 @@ out:
 
 	return ret;
 }
+
+int iommu_fwspec_init(struct device *dev, struct fwnode_handle *iommu_fwnode,
+		      const struct iommu_ops *ops)
+{
+	struct iommu_fwspec *fwspec = dev->iommu_fwspec;
+
+	if (fwspec)
+		return ops == fwspec->ops ? 0 : -EINVAL;
+
+	fwspec = kzalloc(sizeof(*fwspec), GFP_KERNEL);
+	if (!fwspec)
+		return -ENOMEM;
+
+	of_node_get(to_of_node(iommu_fwnode));
+	fwspec->iommu_fwnode = iommu_fwnode;
+	fwspec->ops = ops;
+	dev->iommu_fwspec = fwspec;
+	return 0;
+}
+EXPORT_SYMBOL_GPL(iommu_fwspec_init);
+
+void iommu_fwspec_free(struct device *dev)
+{
+	struct iommu_fwspec *fwspec = dev->iommu_fwspec;
+
+	if (fwspec) {
+		fwnode_handle_put(fwspec->iommu_fwnode);
+		kfree(fwspec);
+		dev->iommu_fwspec = NULL;
+	}
+}
+EXPORT_SYMBOL_GPL(iommu_fwspec_free);
+
+int iommu_fwspec_add_ids(struct device *dev, u32 *ids, int num_ids)
+{
+	struct iommu_fwspec *fwspec = dev->iommu_fwspec;
+	size_t size;
+	int i;
+
+	if (!fwspec)
+		return -EINVAL;
+
+	size = offsetof(struct iommu_fwspec, ids[fwspec->num_ids + num_ids]);
+	if (size > sizeof(*fwspec)) {
+		fwspec = krealloc(dev->iommu_fwspec, size, GFP_KERNEL);
+		if (!fwspec)
+			return -ENOMEM;
+	}
+
+	for (i = 0; i < num_ids; i++)
+		fwspec->ids[fwspec->num_ids + i] = ids[i];
+
+	fwspec->num_ids += num_ids;
+	dev->iommu_fwspec = fwspec;
+	return 0;
+}
+EXPORT_SYMBOL_GPL(iommu_fwspec_add_ids);

drivers/iommu/of_iommu.c

@@ -167,7 +167,9 @@ static const struct iommu_ops
 		return NULL;
 
 	ops = of_iommu_get_ops(iommu_spec.np);
-	if (!ops || !ops->of_xlate || ops->of_xlate(&pdev->dev, &iommu_spec))
+	if (!ops || !ops->of_xlate ||
+	    iommu_fwspec_init(&pdev->dev, &iommu_spec.np->fwnode, ops) ||
+	    ops->of_xlate(&pdev->dev, &iommu_spec))
 		ops = NULL;
 
 	of_node_put(iommu_spec.np);
@@ -196,7 +198,9 @@ const struct iommu_ops *of_iommu_configure(struct device *dev,
 		np = iommu_spec.np;
 		ops = of_iommu_get_ops(np);
 
-		if (!ops || !ops->of_xlate || ops->of_xlate(dev, &iommu_spec))
+		if (!ops || !ops->of_xlate ||
+		    iommu_fwspec_init(dev, &np->fwnode, ops) ||
+		    ops->of_xlate(dev, &iommu_spec))
 			goto err_put_node;
 
 		of_node_put(np);

include/linux/device.h

@@ -41,6 +41,7 @@ struct device_node;
 struct fwnode_handle;
 struct iommu_ops;
 struct iommu_group;
+struct iommu_fwspec;
 
 struct bus_attribute {
 	struct attribute	attr;
@@ -765,6 +766,7 @@ struct device_dma_parameters {
  * 		gone away. This should be set by the allocator of the
  * 		device (i.e. the bus driver that discovered the device).
  * @iommu_group: IOMMU group the device belongs to.
+ * @iommu_fwspec: IOMMU-specific properties supplied by firmware.
  *
  * @offline_disabled: If set, the device is permanently online.
  * @offline:	Set after successful invocation of bus type's .offline().
@@ -849,6 +851,7 @@ struct device {
 
 	void	(*release)(struct device *dev);
 	struct iommu_group	*iommu_group;
+	struct iommu_fwspec	*iommu_fwspec;
 
 	bool			offline_disabled:1;
 	bool			offline:1;

include/linux/iommu.h

@@ -331,10 +331,32 @@ extern struct iommu_group *pci_device_group(struct device *dev);
 /* Generic device grouping function */
 extern struct iommu_group *generic_device_group(struct device *dev);
 
+/**
+ * struct iommu_fwspec - per-device IOMMU instance data
+ * @ops: ops for this device's IOMMU
+ * @iommu_fwnode: firmware handle for this device's IOMMU
+ * @iommu_priv: IOMMU driver private data for this device
+ * @num_ids: number of associated device IDs
+ * @ids: IDs which this device may present to the IOMMU
+ */
+struct iommu_fwspec {
+	const struct iommu_ops	*ops;
+	struct fwnode_handle	*iommu_fwnode;
+	void			*iommu_priv;
+	unsigned int		num_ids;
+	u32			ids[1];
+};
+
+int iommu_fwspec_init(struct device *dev, struct fwnode_handle *iommu_fwnode,
+		      const struct iommu_ops *ops);
+void iommu_fwspec_free(struct device *dev);
+int iommu_fwspec_add_ids(struct device *dev, u32 *ids, int num_ids);
+
 #else /* CONFIG_IOMMU_API */
 
 struct iommu_ops {};
 struct iommu_group {};
+struct iommu_fwspec {};
 
 static inline bool iommu_present(struct bus_type *bus)
 {
@@ -541,6 +563,23 @@ static inline void iommu_device_unlink(struct device *dev, struct device *link)
 {
 }
 
+static inline int iommu_fwspec_init(struct device *dev,
+				    struct fwnode_handle *iommu_fwnode,
+				    const struct iommu_ops *ops)
+{
+	return -ENODEV;
+}
+
+static inline void iommu_fwspec_free(struct device *dev)
+{
+}
+
+static inline int iommu_fwspec_add_ids(struct device *dev, u32 *ids,
+				       int num_ids)
+{
+	return -ENODEV;
+}
+
 #endif /* CONFIG_IOMMU_API */
 
 #endif /* __LINUX_IOMMU_H */