powerpc/boot: Add a boot wrapper for Microwatt

This allows microwatt's kernel to be built with an embedded device tree.

Load to arch/powerpc/boot/dtbImage.microwatt to 0x500000:

 mw_debug -b fpga stop load arch/powerpc/boot/dtbImage.microwatt 500000 start

Signed-off-by: Joel Stanley <joel@jms.id.au>
Signed-off-by: Paul Mackerras <paulus@ozlabs.org>
Reviewed-by: Segher Boessenkool <segher@kernel.crashing.org>
Signed-off-by: Michael Ellerman <mpe@ellerman.id.au>
Link: https://lore.kernel.org/r/YMwX19wym3kQ7guu@thinks.paulus.ozlabs.org

1 files changed, 24 insertions, 0 deletions

diff --git a/arch/powerpc/boot/microwatt.c b/arch/powerpc/boot/microwatt.c
new file mode 100644
index 000000000000..ca9d83617fc1
--- /dev/null
+++ b/arch/powerpc/boot/microwatt.c
@@ -0,0 +1,24 @@
+// SPDX-License-Identifier: GPL-2.0-or-later
+
+#include <stddef.h>
+#include "stdio.h"
+#include "types.h"
+#include "io.h"
+#include "ops.h"
+
+BSS_STACK(8192);
+
+void platform_init(unsigned long r3, unsigned long r4, unsigned long r5)
+{
+	unsigned long heapsize = 16*1024*1024 - (unsigned long)_end;
+
+	/*
+	 * Disable interrupts and turn off MSR_RI, since we'll
+	 * shortly be overwriting the interrupt vectors.
+	 */
+	__asm__ volatile("mtmsrd %0,1" : : "r" (0));
+
+	simple_alloc_init(_end, heapsize, 32, 64);
+	fdt_init(_dtb_start);
+	serial_console_init();
+}