[PATCH v5 2/5] iommu: Implement of_iommu_get_resv_regions()

Thierry Reding
2022-05-12T19:01:13Z

From: Thierry Reding <treding@nvidia.com>

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.

Signed-off-by: Thierry Reding <treding@nvidia.com>
---
Changes in v5:
- update for new "iommu-addresses" device tree bindings

Changes in v4:
- fix build failure on !CONFIG_OF_ADDRESS

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 | 90 ++++++++++++++++++++++++++++++++++++++++
include/linux/of_iommu.h | 8 ++++
2 files changed, 98 insertions(+)

diff --git a/drivers/iommu/of_iommu.c b/drivers/iommu/of_iommu.c
index 5696314ae69e..9e341b5e307f 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

static int of_iommu_xlate(struct device *dev,
@@ -172,3 +175,90 @@ 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)
+{
+#if IS_ENABLED(CONFIG_OF_ADDRESS)
+ struct of_phandle_iterator it;
+ int err;
+
+ of_for_each_phandle(&it, err, dev->of_node, "memory-region", NULL, 0) {
+ struct iommu_resv_region *region;
+ struct resource res;
+ const __be32 *maps;
+ int size;
+
+ memset(&res, 0, sizeof(res));
+
+ /*
+ * The "reg" property is optional and can be omitted by reserved-memory regions
+ * that represent reservations in the IOVA space, which are regions that should
+ * not be mapped.
+ */
+ if (of_find_property(it.node, "reg", NULL)) {
+ 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;
+ }
+ }
+
+ maps = of_get_property(it.node, "iommu-addresses", &size);
+ if (maps) {
+ const __be32 *end = maps + size / sizeof(__be32);
+ struct device_node *np;
+ unsigned int index = 0;
+ u32 phandle;
+ int na, ns;
+
+ while (maps < end) {
+ phys_addr_t start, end;
+ size_t length;
+
+ phandle = be32_to_cpup(maps++);
+ np = of_find_node_by_phandle(phandle);
+ na = of_n_addr_cells(np);
+ ns = of_n_size_cells(np);
+
+ start = of_translate_dma_address(np, maps);
+ length = of_read_number(maps + na, ns);
+ end = start + length - 1;
+
+ if (np == dev->of_node) {
+ int prot = IOMMU_READ | IOMMU_WRITE;
+ enum iommu_resv_type type;
+
+ /*
+ * IOMMU regions without an associated physical region
+ * cannot be mapped and are simply reservations.
+ */
+ if (res.end > res.start)
+ type = IOMMU_RESV_DIRECT_RELAXABLE;
+ else
+ type = IOMMU_RESV_RESERVED;
+
+ region = iommu_alloc_resv_region(start, length, prot, type);
+ if (region)
+ list_add_tail(&region->list, list);
+ }
+
+ maps += na + ns;
+ index++;
+ }
+ }
+ }
+#endif
+}
+EXPORT_SYMBOL(of_iommu_get_resv_regions);
diff --git a/include/linux/of_iommu.h b/include/linux/of_iommu.h
index 55c1eb300a86..9a5e6b410dd2 100644
--- a/include/linux/of_iommu.h
+++ b/include/linux/of_iommu.h
@@ -12,6 +12,9 @@ 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 const struct iommu_ops *of_iommu_configure(struct device *dev,
@@ -21,6 +24,11 @@ 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 */
--
2.36.1