From: Thierry Reding <treding@xxxxxxxxxx>
This is an implementation that IOMMU drivers can use to obtain reserved
memory regions from a device tree node. It uses the reserved-memory DT
bindings to find the regions associated with a given device. If these
regions are marked accordingly, identity mappings will be created for
them in the IOMMU domain that the devices will be attached to.
Cc: Frank Rowand <frowand.list@xxxxxxxxx>
Cc: devicetree@xxxxxxxxxxxxxxx
Reviewed-by: Rob Herring <robh@xxxxxxxxxx>
Signed-off-by: Thierry Reding <treding@xxxxxxxxxx>
---
Changes in v3:
- change "active" property to identity mapping flag that is part of the
memory region specifier (as defined by #memory-region-cells) to allow
per-reference flags to be used
Changes in v2:
- use "active" property to determine whether direct mappings are needed
---
drivers/iommu/of_iommu.c | 54 ++++++++++++++++++++++++++++++++++++++++
include/linux/of_iommu.h | 8 ++++++
2 files changed, 62 insertions(+)
diff --git a/drivers/iommu/of_iommu.c b/drivers/iommu/of_iommu.c
index a9d2df001149..321ebd5fdaba 100644
--- a/drivers/iommu/of_iommu.c
+++ b/drivers/iommu/of_iommu.c
@@ -11,12 +11,15 @@
#include <linux/module.h>
#include <linux/msi.h>
#include <linux/of.h>
+#include <linux/of_address.h>
#include <linux/of_iommu.h>
#include <linux/of_pci.h>
#include <linux/pci.h>
#include <linux/slab.h>
#include <linux/fsl/mc.h>
+#include <dt-bindings/reserved-memory.h>
+
#define NO_IOMMU 1
/**
@@ -240,3 +243,54 @@ const struct iommu_ops *of_iommu_configure(struct device *dev,
return ops;
}
+
+/**
+ * of_iommu_get_resv_regions - reserved region driver helper for device tree
+ * @dev: device for which to get reserved regions
+ * @list: reserved region list
+ *
+ * IOMMU drivers can use this to implement their .get_resv_regions() callback
+ * for memory regions attached to a device tree node. See the reserved-memory
+ * device tree bindings on how to use these:
+ *
+ * Documentation/devicetree/bindings/reserved-memory/reserved-memory.txt
+ */
+void of_iommu_get_resv_regions(struct device *dev, struct list_head *list)
+{
+ struct of_phandle_iterator it;
+ int err;
+
+ of_for_each_phandle(&it, err, dev->of_node, "memory-region", "#memory-region-cells", 0) {
+ struct iommu_resv_region *region;
+ struct of_phandle_args args;
+ struct resource res;
+
+ args.args_count = of_phandle_iterator_args(&it, args.args, MAX_PHANDLE_ARGS);
+
+ err = of_address_to_resource(it.node, 0, &res);
+ if (err < 0) {
+ dev_err(dev, "failed to parse memory region %pOF: %d\n",
+ it.node, err);
+ continue;
+ }
+
+ if (args.args_count > 0) {
+ /*
+ * Active memory regions are expected to be accessed by hardware during
+ * boot and must therefore have an identity mapping created prior to the
+ * driver taking control of the hardware. This ensures that non-quiescent
+ * hardware doesn't cause IOMMU faults during boot.
+ */
+ if (args.args[0] & MEMORY_REGION_IDENTITY_MAPPING) {
+ region = iommu_alloc_resv_region(res.start, resource_size(&res),
+ IOMMU_READ | IOMMU_WRITE,
+ IOMMU_RESV_DIRECT_RELAXABLE);
+ if (!region)
+ continue;
+
+ list_add_tail(®ion->list, list);
+ }
+ }
+ }
+}
+EXPORT_SYMBOL(of_iommu_get_resv_regions);
diff --git a/include/linux/of_iommu.h b/include/linux/of_iommu.h
index 16f4b3e87f20..8412437acaac 100644
--- a/include/linux/of_iommu.h
+++ b/include/linux/of_iommu.h
@@ -16,6 +16,9 @@ extern const struct iommu_ops *of_iommu_configure(struct device *dev,
struct device_node *master_np,
const u32 *id);
+extern void of_iommu_get_resv_regions(struct device *dev,
+ struct list_head *list);
+
#else
static inline int of_get_dma_window(struct device_node *dn, const char *prefix,
@@ -32,6 +35,11 @@ static inline const struct iommu_ops *of_iommu_configure(struct device *dev,
return NULL;
}
+static inline void of_iommu_get_resv_regions(struct device *dev,
+ struct list_head *list)
+{
+}
+
#endif /* CONFIG_OF_IOMMU */
#endif /* __OF_IOMMU_H */
--
2.30.2
