fdtdec: Implement carveout support functions

The fdtdec_get_carveout() and fdtdec_set_carveout() function can be used
to read a carveout from a given node or add a carveout to a given node
using the standard device tree bindings (involving reserved-memory nodes
and the memory-region property).

Reviewed-by: Simon Glass <sjg@chromium.org>
Signed-off-by: Thierry Reding <treding@nvidia.com>

include/fdtdec.h

@@ -1069,6 +1069,8 @@ int fdtdec_set_phandle(void *blob, int node, uint32_t phandle);
  * The phandle returned from the function call can be used to reference this
  * reserved memory region from other nodes.
  *
+ * See fdtdec_set_carveout() for a more elaborate example.
+ *
  * @param blob		FDT blob
  * @param basename	base name of the node to create
  * @param carveout	information about the carveout region
@@ -1079,6 +1081,85 @@ int fdtdec_add_reserved_memory(void *blob, const char *basename,
 			       const struct fdt_memory *carveout,
 			       uint32_t *phandlep);
 
+/**
+ * fdtdec_get_carveout() - reads a carveout from an FDT
+ *
+ * Reads information about a carveout region from an FDT. The carveout is a
+ * referenced by its phandle that is read from a given property in a given
+ * node.
+ *
+ * @param blob		FDT blob
+ * @param node		name of a node
+ * @param name		name of the property in the given node that contains
+ *			the phandle for the carveout
+ * @param index		index of the phandle for which to read the carveout
+ * @param carveout	return location for the carveout information
+ * @return 0 on success or a negative error code on failure
+ */
+int fdtdec_get_carveout(const void *blob, const char *node, const char *name,
+			unsigned int index, struct fdt_memory *carveout);
+
+/**
+ * fdtdec_set_carveout() - sets a carveout region for a given node
+ *
+ * Sets a carveout region for a given node. If a reserved-memory node already
+ * exists for the carveout, the phandle for that node will be reused. If no
+ * such node exists, a new one will be created and a phandle to it stored in
+ * a specified property of the given node.
+ *
+ * As an example, consider the following code snippet:
+ *
+ *     const char *node = "/host1x@50000000/dc@54240000";
+ *     struct fdt_memory fb = {
+ *         .start = 0x92cb3000,
+ *         .end = 0x934b2fff,
+ *     };
+ *
+ *     fdtdec_set_carveout(fdt, node, "memory-region", 0, "framebuffer", &fb);
+ *
+ * dc@54200000 is a display controller and was set up by the bootloader to
+ * scan out the framebuffer specified by "fb". This would cause the following
+ * reserved memory region to be added:
+ *
+ *     reserved-memory {
+ *         #address-cells = <0x00000002>;
+ *         #size-cells = <0x00000002>;
+ *         ranges;
+ *
+ *         framebuffer@92cb3000 {
+ *             reg = <0x00000000 0x92cb3000 0x00000000 0x00800000>;
+ *             phandle = <0x0000004d>;
+ *         };
+ *     };
+ *
+ * A "memory-region" property will also be added to the node referenced by the
+ * offset parameter.
+ *
+ *     host1x@50000000 {
+ *         ...
+ *
+ *         dc@54240000 {
+ *             ...
+ *             memory-region = <0x0000004d>;
+ *             ...
+ *         };
+ *
+ *         ...
+ *     };
+ *
+ * @param blob		FDT blob
+ * @param node		name of the node to add the carveout to
+ * @param prop_name	name of the property in which to store the phandle of
+ *			the carveout
+ * @param index		index of the phandle to store
+ * @param name		base name of the reserved-memory node to create
+ * @param carveout	information about the carveout to add
+ * @return 0 on success or a negative error code on failure
+ */
+int fdtdec_set_carveout(void *blob, const char *node, const char *prop_name,
+			unsigned int index, const char *name,
+			const struct fdt_memory *carveout);
+
 /**
  * Set up the device tree ready for use
  */

lib/fdtdec.c

@@ -1399,6 +1399,93 @@ int fdtdec_add_reserved_memory(void *blob, const char *basename,
 	return 0;
 }
 
+int fdtdec_get_carveout(const void *blob, const char *node, const char *name,
+			unsigned int index, struct fdt_memory *carveout)
+{
+	const fdt32_t *prop;
+	uint32_t phandle;
+	int offset, len;
+	fdt_size_t size;
+
+	offset = fdt_path_offset(blob, node);
+	if (offset < 0)
+		return offset;
+
+	prop = fdt_getprop(blob, offset, name, &len);
+	if (!prop) {
+		debug("failed to get %s for %s\n", name, node);
+		return -FDT_ERR_NOTFOUND;
+	}
+
+	if ((len % sizeof(phandle)) != 0) {
+		debug("invalid phandle property\n");
+		return -FDT_ERR_BADPHANDLE;
+	}
+
+	if (len < (sizeof(phandle) * (index + 1))) {
+		debug("invalid phandle index\n");
+		return -FDT_ERR_BADPHANDLE;
+	}
+
+	phandle = fdt32_to_cpu(prop[index]);
+
+	offset = fdt_node_offset_by_phandle(blob, phandle);
+	if (offset < 0) {
+		debug("failed to find node for phandle %u\n", phandle);
+		return offset;
+	}
+
+	carveout->start = fdtdec_get_addr_size_auto_noparent(blob, offset,
+							     "reg", 0, &size,
+							     true);
+	if (carveout->start == FDT_ADDR_T_NONE) {
+		debug("failed to read address/size from \"reg\" property\n");
+		return -FDT_ERR_NOTFOUND;
+	}
+
+	carveout->end = carveout->start + size - 1;
+
+	return 0;
+}
+
+int fdtdec_set_carveout(void *blob, const char *node, const char *prop_name,
+			unsigned int index, const char *name,
+			const struct fdt_memory *carveout)
+{
+	uint32_t phandle;
+	int err, offset;
+	fdt32_t value;
+
+	/* XXX implement support for multiple phandles */
+	if (index > 0) {
+		debug("invalid index %u\n", index);
+		return -FDT_ERR_BADOFFSET;
+	}
+
+	err = fdtdec_add_reserved_memory(blob, name, carveout, &phandle);
+	if (err < 0) {
+		debug("failed to add reserved memory: %d\n", err);
+		return err;
+	}
+
+	offset = fdt_path_offset(blob, node);
+	if (offset < 0) {
+		debug("failed to find offset for node %s: %d\n", node, offset);
+		return offset;
+	}
+
+	value = cpu_to_fdt32(phandle);
+
+	err = fdt_setprop(blob, offset, prop_name, &value, sizeof(value));
+	if (err < 0) {
+		debug("failed to set %s property for node %s: %d\n", prop_name,
+		      node, err);
+		return err;
+	}
+
+	return 0;
+}
+
 int fdtdec_setup(void)
 {
 #if CONFIG_IS_ENABLED(OF_CONTROL)