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>

1 files changed, 81 insertions, 0 deletions

diff --git a/include/fdtdec.h b/include/fdtdec.h
index 9bd6a70587..266c58271f 100644
--- a/include/fdtdec.h
+++ b/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
@@ -1080,6 +1082,85 @@ int fdtdec_add_reserved_memory(void *blob, const char *basename,
 			       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
  */
 int fdtdec_setup(void);