SPL: FIT: allow loading multiple images

So far we were not using the FIT image format to its full potential:
The SPL FIT loader was just loading the first image from the /images
node plus one of the listed DTBs.
Now with the refactored loader code it's easy to load an arbitrary
number of images in addition to the two mentioned above.
As described in the FIT image source file format description, iterate
over all images listed at the "loadables" property in the configuration
node and load every image at its desired location.
This allows to load any kind of images:
- firmware images to execute before U-Boot proper (for instance
  ARM Trusted Firmware (ATF))
- firmware images for management processors (SCP, arisc, ...)
- firmware images for devices like WiFi controllers
- bit files for FPGAs
- additional configuration data
- kernels and/or ramdisks
The actual usage of this feature would be platform and/or board specific.

Also update the FIT documentation to mention the new SPL feature and
provide an example .its file to demonstrate its features.

Signed-off-by: Andre Przywara <andre.przywara@arm.com>
Reviewed-by: Lokesh Vutla <lokeshvuta@ti.com>
Reviewed-by: Simon Glass <sjg@chromium.org>
Tested-by: Heiko Stuebner <heiko@sntech.de>
Reviewed-by: Kever Yang <kever.yang@rock-chips.com>
Tested-by: Kever Yang <kever.yang@rock-chips.com>
Tested-by: Jagan Teki <jagan@openedev.com>
Reviewed-by: Jagan Teki <jagan@openedev.com>

common/spl/spl_fit.c

@@ -234,6 +234,7 @@ int spl_load_simple_fit(struct spl_image_info *spl_image,
 	struct spl_image_info image_info;
 	int node, images, ret;
 	int base_offset, align_len = ARCH_DMA_MINALIGN - 1;
+	int index = 0;
 
 	/*
 	 * Figure out where the external images start. This is the base for the
@@ -278,6 +279,11 @@ int spl_load_simple_fit(struct spl_image_info *spl_image,
 	if (node < 0) {
 		debug("could not find firmware image, trying loadables...\n");
 		node = spl_fit_get_image_node(fit, images, "loadables", 0);
+		/*
+		 * If we pick the U-Boot image from "loadables", start at
+		 * the second image when later loading additional images.
+		 */
+		index = 1;
 	}
 	if (node < 0) {
 		debug("%s: Cannot find u-boot image node: %d\n",
@@ -305,6 +311,38 @@ int spl_load_simple_fit(struct spl_image_info *spl_image,
 	 * Align the destination address to ARCH_DMA_MINALIGN.
 	 */
 	image_info.load_addr = spl_image->load_addr + spl_image->size;
-	return spl_load_fit_image(info, sector, fit, base_offset, node,
-				  &image_info);
+	ret = spl_load_fit_image(info, sector, fit, base_offset, node,
+				 &image_info);
+	if (ret < 0)
+		return ret;
+
+	/* Now check if there are more images for us to load */
+	for (; ; index++) {
+		node = spl_fit_get_image_node(fit, images, "loadables", index);
+		if (node < 0)
+			break;
+
+		ret = spl_load_fit_image(info, sector, fit, base_offset, node,
+					 &image_info);
+		if (ret < 0)
+			continue;
+
+		/*
+		 * If the "firmware" image did not provide an entry point,
+		 * use the first valid entry point from the loadables.
+		 */
+		if (spl_image->entry_point == FDT_ERROR &&
+		    image_info.entry_point != FDT_ERROR)
+			spl_image->entry_point = image_info.entry_point;
+	}
+
+	/*
+	 * If a platform does not provide CONFIG_SYS_UBOOT_START, U-Boot's
+	 * Makefile will set it to 0 and it will end up as the entry point
+	 * here. What it actually means is: use the load address.
+	 */
+	if (spl_image->entry_point == FDT_ERROR || spl_image->entry_point == 0)
+		spl_image->entry_point = spl_image->load_addr;
+
+	return 0;
 }

doc/uImage.FIT/howto.txt

@@ -44,6 +44,27 @@ image source file     mkimage + dtc		  transfer to target
 	+	     ---------------> image file --------------------> bootm
 image data file(s)
 
+SPL usage
+---------
+
+The SPL can make use of the new image format as well, this traditionally
+is used to ship multiple device tree files within one image. Code in the SPL
+will choose the one matching the current board and append this to the
+U-Boot proper binary to be automatically used up by it.
+Aside from U-Boot proper and one device tree blob the SPL can load multiple,
+arbitrary image files as well. These binaries should be specified in their
+own subnode under the /images node, which should then be referenced from one or
+multiple /configurations subnodes. The required images must be enumerated in
+the "loadables" property as a list of strings.
+
+If a platform specific image source file (.its) is shipped with the U-Boot
+source, it can be specified using the CONFIG_SPL_FIT_SOURCE Kconfig symbol.
+In this case it will be automatically used by U-Boot's Makefile to generate
+the image.
+If a static source file is not flexible enough, CONFIG_SPL_FIT_GENERATOR
+can point to a script which generates this image source file during
+the build process. It gets passed a list of device tree files (taken from the
+CONFIG_OF_LIST symbol).
 
 Example 1 -- old-style (non-FDT) kernel booting
 -----------------------------------------------

doc/uImage.FIT/multi_spl.its

@@ -0,0 +1,89 @@
+/dts-v1/;
+
+/*
+ * (Bogus) example FIT image description file demonstrating the usage
+ * of multiple images loaded by the SPL.
+ * Several binaries will be loaded at their respective load addresses.
+ * Finally the one image specifying an entry point will be entered by the SPL.
+ */
+
+/ {
+	description = "multiple firmware blobs and U-Boot, loaded by SPL";
+	#address-cells = <0x1>;
+
+	images {
+
+		uboot {
+			description = "U-Boot (64-bit)";
+			type = "standalone";
+			arch = "arm64";
+			compression = "none";
+			load = <0x4a000000>;
+		};
+
+		atf {
+			description = "ARM Trusted Firmware";
+			type = "firmware";
+			arch = "arm64";
+			compression = "none";
+			load = <0x18000>;
+			entry = <0x18000>;
+		};
+
+		mgmt-firmware {
+			description = "arisc management processor firmware";
+			type = "firmware";
+			arch = "or1k";
+			compression = "none";
+			load = <0x40000>;
+		};
+
+		fdt@1 {
+			description = "Pine64+ DT";
+			type = "flat_dt";
+			compression = "none";
+			load = <0x4fa00000>;
+			arch = "arm64";
+		};
+
+		fdt@2 {
+			description = "Pine64 DT";
+			type = "flat_dt";
+			compression = "none";
+			load = <0x4fa00000>;
+			arch = "arm64";
+		};
+
+		kernel {
+			description = "4.7-rc5 kernel";
+			type = "kernel";
+			compression = "none";
+			load = <0x40080000>;
+			arch = "arm64";
+		};
+
+		initrd {
+			description = "Debian installer initrd";
+			type = "ramdisk";
+			compression = "none";
+			load = <0x4fe00000>;
+			arch = "arm64";
+		};
+	};
+
+	configurations {
+		default = "config@1";
+
+		config@1 {
+			description = "sun50i-a64-pine64-plus";
+			loadables = "uboot", "atf", "kernel", "initrd";
+			fdt = "fdt@1";
+		};
+
+		config@2 {
+			description = "sun50i-a64-pine64";
+			loadables = "uboot", "atf", "mgmt-firmware";
+			fdt = "fdt@2";
+		};
+	};
+};