iommu/of: Handle iommu-map property for PCI

Now that we have a way to pick up the RID translation and target IOMMU,
hook up of_iommu_configure() to bring PCI devices into the of_xlate
mechanism and allow them IOMMU-backed DMA ops without the need for
driver-specific handling.

Reviewed-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>

1 files changed, 41 insertions, 5 deletions

diff --git a/drivers/iommu/of_iommu.c b/drivers/iommu/of_iommu.c
index 57f23eaaa2f9..19e1e8f2f871 100644
--- a/drivers/iommu/of_iommu.c
+++ b/drivers/iommu/of_iommu.c
@@ -22,6 +22,7 @@
 #include <linux/limits.h>
 #include <linux/of.h>
 #include <linux/of_iommu.h>
+#include <linux/of_pci.h>
 #include <linux/slab.h>
 
 static const struct of_device_id __iommu_of_table_sentinel
@@ -134,6 +135,45 @@ const struct iommu_ops *of_iommu_get_ops(struct device_node *np)
         return ops;
 }
 
+static int __get_pci_rid(struct pci_dev *pdev, u16 alias, void *data)
+{
+        struct of_phandle_args *iommu_spec = data;
+
+        iommu_spec->args[0] = alias;
+        return iommu_spec->np == pdev->bus->dev.of_node;
+}
+
+static const struct iommu_ops
+*of_pci_iommu_configure(struct pci_dev *pdev, struct device_node *bridge_np)
+{
+        const struct iommu_ops *ops;
+        struct of_phandle_args iommu_spec;
+
+        /*
+         * Start by tracing the RID alias down the PCI topology as
+         * far as the host bridge whose OF node we have...
+         * (we're not even attempting to handle multi-alias devices yet)
+         */
+        iommu_spec.args_count = 1;
+        iommu_spec.np = bridge_np;
+        pci_for_each_dma_alias(pdev, __get_pci_rid, &iommu_spec);
+        /*
+         * ...then find out what that becomes once it escapes the PCI
+         * bus into the system beyond, and which IOMMU it ends up at.
+         */
+        iommu_spec.np = NULL;
+        if (of_pci_map_rid(bridge_np, iommu_spec.args[0], "iommu-map",
+                           "iommu-map-mask", &iommu_spec.np, iommu_spec.args))
+                return NULL;
+
+        ops = of_iommu_get_ops(iommu_spec.np);
+        if (!ops || !ops->of_xlate || ops->of_xlate(&pdev->dev, &iommu_spec))
+                ops = NULL;
+
+        of_node_put(iommu_spec.np);
+        return ops;
+}
+
 const struct iommu_ops *of_iommu_configure(struct device *dev,
                                            struct device_node *master_np)
 {
@@ -142,12 +182,8 @@ const struct iommu_ops *of_iommu_configure(struct device *dev,
         const struct iommu_ops *ops = NULL;
         int idx = 0;
 
-        /*
-         * We can't do much for PCI devices without knowing how
-         * device IDs are wired up from the PCI bus to the IOMMU.
-         */
         if (dev_is_pci(dev))
-                return NULL;
+                return of_pci_iommu_configure(to_pci_dev(dev), master_np);
 
         /*
          * We don't currently walk up the tree looking for a parent IOMMU.