mvebu: get initial position of register window from image header

A problem when using 2nd stage booting on mvebu is that the first bootloader
already switched the register window location from 0xd0000000 to
0xf1000000 by writing to 0xd0000080. When the second bootloader also
tries to do this switch it writes to the wrong location resulting in an
exception and so a boot failure.

For this reason the base address of the register window is passed in the
barebox header and picked up from there by early code. In a further
patch bootm is taught to put the actual position of the window there for
the second bootloader to finally make second stage booting work.

Signed-off-by: Uwe Kleine-König <u.kleine-koenig@pengutronix.de>

3 files changed, 74 insertions, 3 deletions

diff --git a/arch/arm/mach-mvebu/common.c b/arch/arm/mach-mvebu/common.c
index 7534d8dd01..06bfb72615 100644
--- a/arch/arm/mach-mvebu/common.c
+++ b/arch/arm/mach-mvebu/common.c
@@ -180,14 +180,14 @@ mem_initcall(mvebu_meminit);
  * safely later on, as the remap register itself is within the
  * internal registers.
  */
-#define MVEBU_BOOTUP_INT_REG_BASE	0xd0000000
 #define MVEBU_BRIDGE_REG_BASE		0x20000
 #define DEVICE_INTERNAL_BASE_ADDR	(MVEBU_BRIDGE_REG_BASE + 0x80)
 
 static void mvebu_remap_registers(void)
 {
-	writel(MVEBU_REMAP_INT_REG_BASE,
-	       IOMEM(MVEBU_BOOTUP_INT_REG_BASE) + DEVICE_INTERNAL_BASE_ADDR);
+	void __iomem *base = mvebu_get_initial_int_reg_base();
+
+	writel(MVEBU_REMAP_INT_REG_BASE, base + DEVICE_INTERNAL_BASE_ADDR);
 }
 
 void __naked __noreturn dove_barebox_entry(void *boarddata)
diff --git a/arch/arm/mach-mvebu/include/mach/barebox-arm-head.h b/arch/arm/mach-mvebu/include/mach/barebox-arm-head.h
new file mode 100644
index 0000000000..3035f40ddf
--- /dev/null
+++ b/arch/arm/mach-mvebu/include/mach/barebox-arm-head.h
@@ -0,0 +1,54 @@
+#include <linux/stringify.h>
+#include <mach/common.h>
+
+static inline void __barebox_arm_head(void)
+{
+	__asm__ __volatile__ (
+#ifdef CONFIG_THUMB2_BAREBOX
+		".arm\n"
+		"adr r9, 1f + 1\n"
+		"bx r9\n"
+		".thumb\n"
+		"1:\n"
+		"bl 2f\n"
+		".rept 10\n"
+		"1: b 1b\n"
+		".endr\n"
+#else
+		"b 2f\n"
+		"1: b 1b\n"
+		"1: b 1b\n"
+		"1: b 1b\n"
+		"1: b 1b\n"
+		"1: b 1b\n"
+		"1: b 1b\n"
+		"1: b 1b\n"
+#endif
+		".asciz \"barebox\"\n"
+		".word _text\n"				/* text base. If copied there,
+							 * barebox can skip relocation
+							 */
+		".word _barebox_image_size\n"		/* image size to copy */
+
+		/*
+		 * The following entry (at offset 0x30) is the only intended
+		 * difference to the original arm __barebox_arm_head. This value
+		 * holds the address of the internal register window when the
+		 * image is started. If the window is not at the reset default
+		 * position any more the caller can pass the actual value here.
+		 */
+		".word " __stringify(MVEBU_BOOTUP_INT_REG_BASE) "\n"
+		".rept 7\n"
+		".word 0x55555555\n"
+		".endr\n"
+		"2:\n"
+	);
+}
+
+static inline void barebox_arm_head(void)
+{
+	__barebox_arm_head();
+	__asm__ __volatile__ (
+		"b barebox_arm_reset_vector\n"
+	);
+}
diff --git a/arch/arm/mach-mvebu/include/mach/common.h b/arch/arm/mach-mvebu/include/mach/common.h
index 3cc1bf71c0..529eb61cfd 100644
--- a/arch/arm/mach-mvebu/include/mach/common.h
+++ b/arch/arm/mach-mvebu/include/mach/common.h
@@ -18,6 +18,23 @@
 #ifndef __MACH_COMMON_H__
 #define __MACH_COMMON_H__
 
+#include <asm/sections.h>
+#include <asm/unaligned.h>
+
+#define MVEBU_BOOTUP_INT_REG_BASE	0xd0000000
 #define MVEBU_REMAP_INT_REG_BASE	0xf1000000
 
+/* #including <asm/barebox-arm.h> yields a circle, so we need a forward decl */
+uint32_t get_runtime_offset(void);
+
+static inline void __iomem *mvebu_get_initial_int_reg_base(void)
+{
+#ifdef __PBL__
+	u32 base = __get_unaligned_le32(_text - get_runtime_offset() + 0x30);
+	return (void __force __iomem *)base;
+#else
+	return (void __force __iomem *)MVEBU_REMAP_INT_REG_BASE;
+#endif
+}
+
 #endif