fit: Add overlay support

This patch adds support to boot FIT image configurations consisting of
a base device tree and one or more overlays. Since extracting the right
compatible string from overlay FDTs is problematic, we'll only support
this for FIT images that have the compatible string pulled out into the
config node.

This patch was adapted from depthcharge's http://crosreview.com/1555293

Change-Id: I0943f9a1869c9e416887c7ff16e33f7d91b74989
Signed-off-by: Julius Werner <jwerner@chromium.org>
Reviewed-on: https://review.coreboot.org/c/coreboot/+/32873
Reviewed-by: Hung-Te Lin <hungte@chromium.org>
Tested-by: build bot (Jenkins) <no-reply@coreboot.org>

src/include/fit.h

@@ -24,8 +24,7 @@
 #include <list.h>
 #include <program_loading.h>
 
-struct fit_image_node
-{
+struct fit_image_node {
 	const char *name;
 	void *data;
 	uint32_t size;
@@ -34,11 +33,11 @@ struct fit_image_node
 	struct list_node list_node;
 };
 
-struct fit_config_node
-{
+struct fit_config_node {
 	const char *name;
 	struct fit_image_node *kernel;
 	struct fit_image_node *fdt;
+	struct list_node overlays;
 	struct fit_image_node *ramdisk;
 	struct fdt_property compat;
 	int compat_rank;
@@ -48,6 +47,11 @@ struct fit_config_node
 	struct list_node list_node;
 };
 
+struct fit_overlay_chain {
+	struct fit_image_node *overlay;
+	struct list_node list_node;
+};
+
 /*
  * Updates the cmdline in the devicetree.
  */

src/lib/fit.c

@@ -96,6 +96,31 @@ static struct fit_image_node *find_image(const char *name)
 	return NULL;
 }
 
+static struct fit_image_node *find_image_with_overlays(const char *name,
+	int bytes, struct list_node *prev)
+{
+	struct fit_image_node *base = find_image(name);
+	if (!base)
+		return NULL;
+
+	int len = strnlen(name, bytes) + 1;
+	bytes -= len;
+	name += len;
+	while (bytes > 0) {
+		struct fit_overlay_chain *next = xzalloc(sizeof(*next));
+		next->overlay = find_image(name);
+		if (!next->overlay)
+			return NULL;
+		list_insert_after(&next->list_node, prev);
+		prev = &next->list_node;
+		len = strnlen(name, bytes) + 1;
+		bytes -= len;
+		name += len;
+	}
+
+	return base;
+}
+
 static void image_node(struct device_tree_node *node)
 {
 	struct fit_image_node *image = xzalloc(sizeof(*image));
@@ -133,7 +158,8 @@ static void config_node(struct device_tree_node *node)
 		if (!strcmp("kernel", prop->prop.name))
 			config->kernel = find_image(prop->prop.data);
 		else if (!strcmp("fdt", prop->prop.name))
-			config->fdt = find_image(prop->prop.data);
+			config->fdt = find_image_with_overlays(prop->prop.data,
+				prop->prop.size, &config->overlays);
 		else if (!strcmp("ramdisk", prop->prop.name))
 			config->ramdisk = find_image(prop->prop.data);
 		else if (!strcmp("compatible", prop->prop.name))
@@ -408,6 +434,14 @@ static int fit_update_compat(struct fit_config_node *config)
 			return -1;
 		}
 
+		// FDT overlays are not supported in legacy FIT images.
+		if (config->overlays.next) {
+			printk(BIOS_ERR,
+			       "ERROR: config %s has overlay but no compat!\n",
+			       config->name);
+			return -1;
+		}
+
 		if (fdt_find_compat(fdt_blob, fdt_offset, &config->compat)) {
 			printk(BIOS_ERR,
 			       "ERROR: Can't find compat string in FDT %s "
@@ -442,6 +476,7 @@ struct fit_config_node *fit_load(void *fit)
 	struct fit_image_node *image;
 	struct fit_config_node *config;
 	struct compat_string_entry *compat_node;
+	struct fit_overlay_chain *overlay_chain;
 
 	printk(BIOS_DEBUG, "FIT: Loading FIT from %p\n", fit);
 
@@ -505,6 +540,8 @@ struct fit_config_node *fit_load(void *fit)
 		}
 		printk(BIOS_DEBUG, ", kernel %s", config->kernel->name);
 		printk(BIOS_DEBUG, ", fdt %s", config->fdt->name);
+		list_for_each(overlay_chain, config->overlays, list_node)
+			printk(BIOS_DEBUG, " %s", overlay_chain->overlay->name);
 		if (config->ramdisk)
 			printk(BIOS_DEBUG, ", ramdisk %s",
 			       config->ramdisk->name);

src/lib/fit_payload.c

@@ -206,6 +206,15 @@ void fit_payload(struct prog *payload)
 		return;
 	}
 
+	struct fit_overlay_chain *chain;
+	list_for_each(chain, config->overlays, list_node) {
+		struct device_tree *overlay = unpack_fdt(chain->overlay);
+		if (!overlay || dt_apply_overlay(dt, overlay)) {
+			printk(BIOS_ERR, "ERROR: Failed to apply overlay %s!\n",
+			       chain->overlay->name);
+		}
+	}
+
 	dt_apply_fixups(dt);
 
 	/* Insert coreboot specific information */