3 files changed, 66 insertions, 0 deletions
diff --git a/board/raspberrypi/rpi/Makefile b/board/raspberrypi/rpi/Makefile
index 4ce2c98..dcb25ac 100644
--- a/board/raspberrypi/rpi/Makefile
+++ b/board/raspberrypi/rpi/Makefile
@@ -5,3 +5,4 @@
 #
 
 obj-y	:= rpi.o
+obj-y	+= lowlevel_init.o
diff --git a/board/raspberrypi/rpi/lowlevel_init.S b/board/raspberrypi/rpi/lowlevel_init.S
new file mode 100644
index 0000000..cdbd8e1
--- /dev/null
+++ b/board/raspberrypi/rpi/lowlevel_init.S
@@ -0,0 +1,36 @@
+/*
+ * (C) Copyright 2016
+ * Cédric Schieli <cschieli@gmail.com>
+ *
+ * SPDX-License-Identifier:	GPL-2.0+
+ */
+
+#include <config.h>
+
+.align 8
+.global fw_dtb_pointer
+fw_dtb_pointer:
+#ifdef CONFIG_ARM64
+	.dword 0x0
+#else
+	.word 0x0
+#endif
+
+/*
+ * Routine: save_boot_params (called after reset from start.S)
+ * Description: save ATAG/FDT address provided by the firmware at boot time
+ */
+
+.global save_boot_params
+save_boot_params:
+
+	/* The firmware provided ATAG/FDT address can be found in r2/x0 */
+#ifdef CONFIG_ARM64
+	adr	x8, fw_dtb_pointer
+	str	x0, [x8]
+#else
+	str	r2, fw_dtb_pointer
+#endif
+
+	/* Returns */
+	b	save_boot_params_ret
diff --git a/board/raspberrypi/rpi/rpi.c b/board/raspberrypi/rpi/rpi.c
index 6245b36..ffd6d31 100644
--- a/board/raspberrypi/rpi/rpi.c
+++ b/board/raspberrypi/rpi/rpi.c
@@ -25,6 +25,9 @@
 
 DECLARE_GLOBAL_DATA_PTR;
 
+/* From lowlevel_init.S */
+extern unsigned long fw_dtb_pointer;
+
 static const struct bcm2835_gpio_platdata gpio_platdata = {
 	.base = BCM2835_GPIO_BASE,
 };
@@ -285,6 +288,31 @@ static void set_fdtfile(void)
 	setenv("fdtfile", fdtfile);
 }
 
+/*
+ * If the firmware provided a valid FDT at boot time, let's expose it in
+ * ${fdt_addr} so it may be passed unmodified to the kernel.
+ */
+static void set_fdt_addr(void)
+{
+	if (getenv("fdt_addr"))
+		return;
+
+	if (fdt_magic(fw_dtb_pointer) != FDT_MAGIC)
+		return;
+
+	setenv_hex("fdt_addr", fw_dtb_pointer);
+}
+
+/*
+ * Prevent relocation from stomping on a firmware provided FDT blob.
+ */
+unsigned long board_get_usable_ram_top(unsigned long total_size)
+{
+	if ((gd->ram_top - fw_dtb_pointer) > SZ_64M)
+		return gd->ram_top;
+	return fw_dtb_pointer & ~0xffff;
+}
+
 static void set_usbethaddr(void)
 {
 	ALLOC_CACHE_ALIGN_BUFFER(struct msg_get_mac_address, msg, 1);
@@ -356,6 +384,7 @@ static void set_serial_number(void)
 
 int misc_init_r(void)
 {
+	set_fdt_addr();
 	set_fdtfile();
 	set_usbethaddr();
 #ifdef CONFIG_ENV_VARS_UBOOT_RUNTIME_CONFIG