board: arm: Add support for Broadcom BCM7445
Add support for loading U-Boot on the Broadcom 7445 SoC. This port
assumes Broadcom's BOLT bootloader is acting as the second stage
bootloader, and U-Boot is acting as the third stage bootloader, loaded
as an ELF program by BOLT.
Signed-off-by: Thomas Fitzsimmons <fitzsim@fitzsim.org>
Cc: Stefan Roese <sr@denx.de>
Cc: Tom Rini <trini@konsulko.com>
Cc: Florian Fainelli <f.fainelli@gmail.com>
diff --git a/doc/README.bcm7xxx b/doc/README.bcm7xxx
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+Summary
+=======
+
+This document describes how to use U-Boot on the Broadcom 7445 SoC, as
+a third stage bootloader loaded by Broadcom's BOLT bootloader.
+
+BOLT loads U-Boot as a generic ELF binary. Some U-Boot features such
+as networking are not yet available but other important features are,
+including:
+
+ - ext4 file system traversal
+
+ - support for loading FIT images
+
+ - advanced scripting
+
+ - support for FIT-provided DTBs instead of relying on the
+ BOLT-provided DTB
+
+A customized version of this port has been used in production. The
+same approach may work on other BCM7xxx boards, with some
+configuration adjustments and memory layout experimentation.
+
+Build
+=====
+
+make bcm7445_defconfig
+make
+${CROSS_COMPILE}strip u-boot
+
+Run
+===
+
+Flash the u-boot binary into board storage, then invoke it from BOLT.
+For example:
+
+BOLT> boot -bsu -elf flash0.u-boot1
+
+This port assumes that I-cache and D-cache are already enabled when
+U-Boot is entered.
+
+Flattened Image Tree Support
+============================
+
+What follows is an example FIT image source file. Build it with:
+
+mkimage -f image.its image.itb
+
+Booting the resulting image.itb was tested on BOLT v1.20, with the
+following kernels:
+
+https://github.com/Broadcom/stblinux-3.14
+https://github.com/Broadcom/stblinux-4.1
+https://github.com/Broadcom/stblinux-4.9
+
+and with a generic ARMv7 root file system.
+
+image.its:
+/dts-v1/;
+/ {
+ description = "BCM7445 FIT";
+ images {
+ kernel@1 {
+ description = "Linux kernel";
+ /*
+ * This kernel image output format can be
+ * generated with:
+ *
+ * make vmlinux
+ * ${CROSS_COMPILE}objcopy -O binary -S vmlinux vmlinux.bin
+ * gzip -9 vmlinux.bin
+ *
+ * For stblinux-3.14, the specific Broadcom
+ * board type should be configured in the
+ * kernel, for example CONFIG_BCM7445D0=y.
+ */
+ data = /incbin/("<vmlinux.bin.gz>");
+ type = "kernel";
+ arch = "arm";
+ os = "linux";
+ compression = "gzip";
+ load = <0x8000>;
+ entry = <0x8000>;
+ hash@1 {
+ algo = "sha256";
+ };
+ };
+ ramdisk@1 {
+ description = "Initramfs root file system";
+ data = /incbin/("<initramfs.cpio.gz>");
+ type = "ramdisk";
+ arch = "arm";
+ os = "linux";
+ compression = "gzip";
+ /*
+ * Set the environment variable initrd_high to
+ * 0xffffffff, and set "load" and "entry" here
+ * to 0x0 to keep initramfs in-place and to
+ * accommodate stblinux bmem/CMA reservations.
+ */
+ load = <0x0>;
+ entry = <0x0>;
+ hash@1 {
+ algo = "sha256";
+ };
+ };
+ fdt@1 {
+ description = "Device tree dumped from BOLT";
+ /*
+ * This DTB should be similar to the
+ * BOLT-generated device tree, after BOLT has
+ * done its runtime modifications to it. For
+ * example, it can be dumped from within
+ * U-Boot (at ${fdtcontroladdr}), after BOLT
+ * has loaded U-Boot. The result can be added
+ * to the Linux source tree as a .dts file.
+ *
+ * To support modifications to the device tree
+ * in-place in U-Boot, add to Linux's
+ * arch/arm/boot/dts/Makefile:
+ *
+ * DTC_FLAGS ?= -p 4096
+ *
+ * This will leave some padding in the DTB and
+ * thus reserve room for node additions.
+ *
+ * Also, set the environment variable fdt_high
+ * to 0xffffffff to keep the DTB in-place and
+ * to accommodate stblinux bmem/CMA
+ * reservations.
+ */
+ data = /incbin/("<bolt-<version>.dtb");
+ type = "flat_dt";
+ arch = "arm";
+ compression = "none";
+ hash@1 {
+ algo = "sha256";
+ };
+ };
+ };
+ configurations {
+ default = "conf@bcm7445";
+ conf@bcm7445 {
+ description = "BCM7445 configuration";
+ kernel = "kernel@1";
+ ramdisk = "ramdisk@1";
+ fdt = "fdt@1";
+ };
+ };
+};