armv7: create init.S for early ARMv7 init

The old start.S file did a lot of work and had AP-specific #ifndef's.
The new init.S will eventually contain only bare minimum generic ARM
code for use by the bootblock. Processor-specific stuff and things
that take place later in the boot process should go elsewhere.

Change-Id: I7db0a77ee4bbad1ddecb193ea125d8941a50532b
Signed-off-by: David Hendricks <dhendrix@chromium.org>
Reviewed-on: http://review.coreboot.org/2083
Tested-by: build bot (Jenkins)
Reviewed-by: Ronald G. Minnich <rminnich@gmail.com>

src/arch/armv7/Makefile.inc

@@ -142,9 +142,7 @@ endif
 CFLAGS += -D__KERNEL__
 CFLAGS += -D__LINUX_ARM_ARCH__=7
 
-# FIXME(dhendrix): trying to split start.S apart...
-crt0s = $(src)/arch/armv7/start.S
-#crt0s = $(src)/arch/armv7/romstage.S
+crt0s = $(src)/arch/armv7/init/init.S
 ldscripts =
 ldscripts += $(src)/arch/armv7/romstage.ld
 

src/arch/armv7/init/init.S

@@ -0,0 +1,94 @@
+/*
+ * Early initialization code for ARMv7 architecture.
+ *
+ * This file is based off of the OMAP3530/ARM Cortex start.S file from Das
+ * U-Boot, which itself got the file from armboot.
+ *
+ * Copyright (c) 2004	Texas Instruments <r-woodruff2@ti.com>
+ * Copyright (c) 2001	Marius Gröger <mag@sysgo.de>
+ * Copyright (c) 2002	Alex Züpke <azu@sysgo.de>
+ * Copyright (c) 2002	Gary Jennejohn <garyj@denx.de>
+ * Copyright (c) 2003	Richard Woodruff <r-woodruff2@ti.com>
+ * Copyright (c) 2003	Kshitij <kshitij@ti.com>
+ * Copyright (c) 2006-2008 Syed Mohammed Khasim <x0khasim@ti.com>
+ * Copyright (c) 2013   The Chromium OS Authors
+ *
+ * This program is free software; you can redistribute it and/or
+ * modify it under the terms of the GNU General Public License as
+ * published by the Free Software Foundation; either version 2 of
+ * the License, or (at your option) any later version.
+ *
+ * This program is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.	 See the
+ * GNU General Public License for more details.
+ *
+ * You should have received a copy of the GNU General Public License
+ * along with this program; if not, write to the Free Software
+ * Foundation, Inc., 59 Temple Place, Suite 330, Boston,
+ * MA 02111-1307 USA
+ */
+
+#define __ASSEMBLY__
+#include <system.h>
+
+.globl _start
+_start: b	reset
+	ldr	pc, _undefined_instruction
+	ldr	pc, _software_interrupt
+	ldr	pc, _prefetch_abort
+	ldr	pc, _data_abort
+	ldr	pc, _not_used
+	ldr	pc, _irq
+	ldr	pc, _fiq
+_undefined_instruction: .word _undefined_instruction
+_software_interrupt:	.word _software_interrupt
+_prefetch_abort:	.word _prefetch_abort
+_data_abort:		.word _data_abort
+_not_used:		.word _not_used
+_irq:			.word _irq
+_fiq:			.word _fiq
+_pad:			.word 0x12345678 /* now 16*4=64 */
+
+	.balignl 16,0xdeadbeef
+
+reset:
+	/*
+	 * set the cpu to SVC32 mode
+	 */
+	mrs	r0, cpsr
+	bic	r0, r0, #0x1f
+	orr	r0, r0, #0xd3
+	msr	cpsr,r0
+
+	/*
+	 * From Cortex-A Series Programmer's Guide:
+	 * Only CPU 0 performs initialization. Other CPUs go into WFI
+	 * to do this, first work out which CPU this is
+	 * this code typically is run before any other initialization step
+	 */
+	mrc p15, 0, r1, c0, c0, 5	@ Read Multiprocessor Affinity Register
+	and r1, r1, #0x3 @ Extract CPU ID bits
+	cmp r1, #0
+	bne wait_for_interrupt		@ If this is not core0, wait
+
+	/* Set V=0 in CP15 SCTRL register - for VBAR to point to vector */
+	mrc	p15, 0, r0, c1, c0, 0	@ Read CP15 SCTRL Register
+	bic	r0, #CR_V		@ V = 0
+	mcr	p15, 0, r0, c1, c0, 0	@ Write CP15 SCTRL Register
+
+	/* Set vector address in CP15 VBAR register */
+	ldr	r0, =_start
+	mcr	p15, 0, r0, c12, c0, 0	@Set VBAR
+
+/* Set stackpointer in internal RAM to call board_init_f */
+call_board_init_f:
+	ldr	sp, =(CONFIG_SYS_INIT_SP_ADDR)
+	mov	sp, r0
+	bic	sp, sp, #7 /* 8-byte alignment for ABI compliance */
+	ldr	r0,=0x00000000
+	bl	board_init_f
+
+wait_for_interrupt:
+	wfi
+	mov	pc, lr			@ back to my caller