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From: Michael Olbrich <m.olbrich@pengutronix.de>
Date: Sat, 10 Sep 2016 17:40:56 +0200
Subject: [PATCH] vexpress: use device tree provided by QEMU if available

Signed-off-by: Michael Olbrich <m.olbrich@pengutronix.de>
---
 arch/arm/boards/vexpress/lowlevel.c | 20 ++++++++++++++++++--
 1 file changed, 18 insertions(+), 2 deletions(-)

diff --git a/arch/arm/boards/vexpress/lowlevel.c b/arch/arm/boards/vexpress/lowlevel.c
index 0a226b295c2a..9fe7c836b7b6 100644
--- a/arch/arm/boards/vexpress/lowlevel.c
+++ b/arch/arm/boards/vexpress/lowlevel.c
@@ -9,18 +9,34 @@
 #include <asm/barebox-arm-head.h>
 #include <asm/barebox-arm.h>
 #include <asm/system_info.h>
+#include <asm/unaligned.h>
 #include <linux/amba/sp804.h>
 
 static inline void start_vexpress_common(void *internal_dt)
 {
 	void *fdt = internal_dt - get_runtime_offset();
+	unsigned long membase, memsize = SZ_512M;
 
 	arm_cpu_lowlevel_init();
 
 	if (amba_is_arm_sp804(IOMEM(0x10011000)))
-		barebox_arm_entry(0x60000000, SZ_512M, fdt);
+		membase = 0x60000000;
 	else
-		barebox_arm_entry(0x80000000, SZ_512M, fdt);
+		membase = 0x80000000;
+
+	/* QEMU may put a DTB at the start of RAM */
+	if (IS_ENABLED(CONFIG_OFDEVICE) &&
+	    get_unaligned_be32((void*)membase) == FDT_MAGIC) {
+		fdt = (void*)membase;
+		/*
+		 * Need to move membase a bit as the PBL wants to relocate
+		 * to the start of RAM, which would overwrite the DTB.
+		 */
+		membase += SZ_4M;
+		memsize -= SZ_4M;
+	}
+
+	barebox_arm_entry(membase, memsize, fdt);
 }
 
 extern char __dtb_vexpress_v2p_ca9_start[];