metag: Boot

Add boot code for metag. Due to the multi-threaded nature of Meta it is
not uncommon for an RTOS or bare metal application to be started on
other hardware threads by the bootloader. Since there is a single MMU
switch which affects all threads, the MMU is traditionally configured by
the bootloader prior to starting Linux. The bootloader passes a
structure to Linux which among other things contains information about
memory regions which have been mapped. Linux then assumes control of the
local heap memory region.

A kernel arguments string pointer or a flattened device tree pointer can
be provided in the third argument.
Signed-off-by: James Hogan <james.hogan@imgtec.com>

arch/metag/boot/.gitignore

+vmlinux*
+uImage*
+ramdisk.*
+*.dtb

arch/metag/include/asm/mach/arch.h

+/*
+ * arch/metag/include/asm/mach/arch.h
+ *
+ * Copyright (C) 2012 Imagination Technologies Ltd.
+ *
+ * based on the ARM version:
+ *  Copyright (C) 2000 Russell King
+ *
+ * This program is free software; you can redistribute it and/or modify
+ * it under the terms of the GNU General Public License version 2 as
+ * published by the Free Software Foundation.
+ */
+
+#ifndef _METAG_MACH_ARCH_H_
+#define _METAG_MACH_ARCH_H_
+
+#include <linux/stddef.h>
+
+/**
+ * struct machine_desc - Describes a board controlled by a Meta.
+ * @name:		Board/SoC name.
+ * @dt_compat:		Array of device tree 'compatible' strings.
+ *
+ * @nr_irqs:		Maximum number of IRQs.
+ *			If 0, defaults to NR_IRQS in asm-generic/irq.h.
+ *
+ * @init_early:		Early init callback.
+ * @init_irq:		IRQ init callback for setting up IRQ controllers.
+ * @init_machine:	Arch init callback for setting up devices.
+ * @init_late:		Late init callback.
+ *
+ * This structure is provided by each board which can be controlled by a Meta.
+ * It is chosen by matching the compatible strings in the device tree provided
+ * by the bootloader with the strings in @dt_compat, and sets up any aspects of
+ * the machine that aren't configured with device tree (yet).
+ */
+struct machine_desc {
+	const char		*name;
+	const char		**dt_compat;
+
+	unsigned int		nr_irqs;
+
+	void			(*init_early)(void);
+	void			(*init_irq)(void);
+	void			(*init_machine)(void);
+	void			(*init_late)(void);
+};
+
+/*
+ * Current machine - only accessible during boot.
+ */
+extern struct machine_desc *machine_desc;
+
+/*
+ * Machine type table - also only accessible during boot
+ */
+extern struct machine_desc __arch_info_begin[], __arch_info_end[];
+#define for_each_machine_desc(p)			\
+	for (p = __arch_info_begin; p < __arch_info_end; p++)
+
+static inline struct machine_desc *default_machine_desc(void)
+{
+	/* the default machine is the last one linked in */
+	if (__arch_info_end - 1 < __arch_info_begin)
+		return NULL;
+	return __arch_info_end - 1;
+}
+
+/*
+ * Set of macros to define architecture features.  This is built into
+ * a table by the linker.
+ */
+#define MACHINE_START(_type, _name)			\
+static const struct machine_desc __mach_desc_##_type	\
+__used							\
+__attribute__((__section__(".arch.info.init"))) = {	\
+	.name		= _name,
+
+#define MACHINE_END				\
+};
+
+#endif /* _METAG_MACH_ARCH_H_ */

arch/metag/include/asm/setup.h

+#ifndef _ASM_METAG_SETUP_H
+#define _ASM_METAG_SETUP_H
+
+#include <uapi/asm/setup.h>
+
+void per_cpu_trap_init(unsigned long);
+extern void __init dump_machine_table(void);
+#endif /* _ASM_METAG_SETUP_H */

arch/metag/kernel/head.S

+	! Copyright 2005,2006,2007,2009 Imagination Technologies
+
+#include <linux/init.h>
+#include <generated/asm-offsets.h>
+#undef __exit
+
+	__HEAD
+	! Setup the stack and get going into _metag_start_kernel
+	.global	__start
+	.type   __start,function
+__start:
+	! D1Ar1 contains pTBI (ISTAT)
+	! D0Ar2 contains pTBI
+	! D1Ar3 contains __pTBISegs
+	! D0Ar4 contains kernel arglist pointer
+
+	MOVT    D0Re0,#HI(___pTBIs)
+	ADD     D0Re0,D0Re0,#LO(___pTBIs)
+	SETL    [D0Re0],D0Ar2,D1Ar1
+	MOVT    D0Re0,#HI(___pTBISegs)
+	ADD     D0Re0,D0Re0,#LO(___pTBISegs)
+	SETD    [D0Re0],D1Ar3
+	MOV	A0FrP,#0
+	MOV	D0Re0,#0
+	MOV	D1Re0,#0
+	MOV	D1Ar3,#0
+	MOV	D1Ar1,D0Ar4			!Store kernel boot params
+	MOV	D1Ar5,#0
+	MOV	D0Ar6,#0
+#ifdef CONFIG_METAG_DSP
+	MOV	D0.8,#0
+#endif
+	MOVT    A0StP,#HI(_init_thread_union)
+	ADD	A0StP,A0StP,#LO(_init_thread_union)
+	ADD     A0StP,A0StP,#THREAD_INFO_SIZE
+	MOVT	D1RtP,#HI(_metag_start_kernel)
+	CALL	D1RtP,#LO(_metag_start_kernel)
+	.size	__start,.-__start
+
+	!! Needed by TBX
+	.global	__exit
+	.type   __exit,function
+__exit:
+	XOR     TXENABLE,D0Re0,D0Re0
+	.size	__exit,.-__exit

arch/metag/kernel/machines.c

+/*
+ *  arch/metag/kernel/machines.c
+ *
+ *  Copyright (C) 2012 Imagination Technologies Ltd.
+ *
+ *  Generic Meta Boards.
+ */
+
+#include <linux/init.h>
+#include <asm/irq.h>
+#include <asm/mach/arch.h>
+
+static const char *meta_boards_compat[] __initdata = {
+	"img,meta",
+	NULL,
+};
+
+MACHINE_START(META, "Generic Meta")
+	.dt_compat	= meta_boards_compat,
+MACHINE_END