[PATCH 13/17] arm: reimplement startup code in C

[Sascha Hauer <s.hauer@pengutronix.de>]

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Lets translate the startup code to a language we all understand better.
Tested on pcm038 (arm v5) and pcm043 (arm v6).

Signed-off-by: Sascha Hauer <s.hauer@pengutronix.de>
---
 arch/arm/cpu/Makefile              |    6 +-
 arch/arm/cpu/start-arm.S           |  248 ------------------------------------
 arch/arm/cpu/start.c               |  108 ++++++++++++++++
 arch/arm/include/asm/barebox-arm.h |    3 +
 arch/arm/lib/barebox.lds.S         |    2 +-
 5 files changed, 113 insertions(+), 254 deletions(-)
 delete mode 100644 arch/arm/cpu/start-arm.S
 create mode 100644 arch/arm/cpu/start.c

diff --git a/arch/arm/cpu/Makefile b/arch/arm/cpu/Makefile
index ae1f762..036768e 100644
--- a/arch/arm/cpu/Makefile
+++ b/arch/arm/cpu/Makefile
@@ -1,15 +1,11 @@
 obj-y += cpu.o
 obj-y += exceptions.o
 obj-y += interrupts.o
+obj-y += start.o
 
 #
 # Any variants can be called as start-armxyz.S
 #
-obj-$(CONFIG_CPU_ARM920T) += start-arm.o
-obj-$(CONFIG_CPU_ARM926T) += start-arm.o
-obj-$(CONFIG_CPU_V7) += start-arm.o
-obj-$(CONFIG_ARCH_IMX31) += start-arm.o
-obj-$(CONFIG_ARCH_IMX35) += start-arm.o
 obj-$(CONFIG_CMD_ARM_CPUINFO) += cpuinfo.o
 obj-$(CONFIG_MMU) += mmu.o
 obj-$(CONFIG_CPU_32v4T) += cache-armv4.o
diff --git a/arch/arm/cpu/start-arm.S b/arch/arm/cpu/start-arm.S
deleted file mode 100644
index 4d61cee..0000000
--- a/arch/arm/cpu/start-arm.S
+++ /dev/null
@@ -1,248 +0,0 @@
-/*
- *  armboot - Startup Code for ARM CPU-cores
- *
- *  Copyright (c) 2001	Marius Gr���ger <mag@sysgo.de>
- *  Copyright (c) 2002	Alex Z���pke <azu@sysgo.de>
- *  Copyright (c) 2002	Gary Jennejohn <gj@denx.de>
- *
- * See file CREDITS for list of people who contributed to this
- * project.
- *
- * 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
- */
-
-/**
- * @file
- * @brief The very basic beginning of each CPU after reset
- *
- * @note
- * This reset code can be used at least for:
- *  - ARM920T
- *  - i.MX1
- *  - i.MX27
- *  - i.MX31
- *
- */
-	.section ".text_entry","ax"
-
-#include <config.h>
-#include <asm-generic/memory_layout.h>
-
-/*************************************************************************
- * Jump vector table as in table 3.1 in [1]
- *************************************************************************/
-
-.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
-
-	.balignl 16,0xdeadbeef
-
-/*
- *************************************************************************
- *
- * Startup Code (reset vector)
- *
- * do important init only if we don't start from memory!
- * setup Memory and board specific bits prior to relocation.
- * relocate armboot to ram
- * setup stack
- *
- *************************************************************************
- */
-
-/*
- * These are defined in the board-specific linker script.
- */
-.globl _barebox_start
-_barebox_start:
-	.word _start
-
-.globl _bss_start
-_bss_start:
-	.word __bss_start
-
-.globl _bss_end
-_bss_end:
-	.word _end
-
-
-_TEXT_BASE:
-	.word _stext
-
-_MALLOC_BASE:
-	.word MALLOC_BASE
-
-_STACK_START:
-	.word STACK_BASE + STACK_SIZE - 4
-
-#ifdef CONFIG_USE_IRQ
-/* IRQ stack memory */
-IRQ_STACK_START:
-	.word	STACK_BASE + CONFIG_STACKSIZE_IRQ - 4
-
-/* IRQ stack memory */
-FIQ_STACK_START:
-	.word STACK_BASE + CONFIG_STACKSIZE_IRQ + CONFIG_STACKSIZE_FIQ - 4
-#endif
-
-/*************************************************************************
- * the actual reset code
- *************************************************************************/
-reset:
-	/*
-	 * set the cpu to SVC32 mode
-	 */
-	mrs	r0,cpsr
-	bic	r0,r0,#0x1f
-	orr	r0,r0,#0xd3
-	msr	cpsr,r0
-
-#ifdef CONFIG_ARCH_HAS_LOWLEVEL_INIT
-	bl	arch_init_lowlevel
-#endif
-
-#ifdef CONFIG_CPU_V7
-	/*
-	 * Invalidate v7 I/D caches
-	 */
-	mov	r0, #0			/* set up for MCR */
-	mcr	p15, 0, r0, c8, c7, 0	/* invalidate TLBs */
-	mcr	p15, 0, r0, c7, c5, 0	/* invalidate icache */
-	/* Invalidate all Dcaches */
-#ifndef CONFIG_CPU_V7_DCACHE_SKIP
-	/* If Arch specific ROM code SMI handling does not exist */
-	mrc	p15, 1, r0, c0, c0, 1	/* read clidr */
-	ands	r3, r0, #0x7000000	/* extract loc from clidr */
-	mov	r3, r3, lsr #23		/* left align loc bit field */
-	beq	finished_inval		/* if loc is 0, then no need to clean */
-	mov	r10, #0			/* start clean at cache level 0 */
-inval_loop1:
-	add	r2, r10, r10, lsr #1	/* work out 3x current cache level */
-	mov	r1, r0, lsr r2		/* extract cache type bits from clidr */
-	and	r1, r1, #	7	/* mask of the bits for current cache only */
-	cmp	r1, #2			/* see what cache we have at this level */
-	blt	skip_inval		/* skip if no cache, or just i-cache */
-	mcr	p15, 2, r10, c0, c0, 0	/* select current cache level in cssr */
-	isb				/* isb to sych the new cssr&csidr */
-	mrc	p15, 1, r1, c0, c0, 0	/* read the new csidr */
-	and	r2, r1, #7		/* extract the length of the cache lines */
-	add	r2, r2, #4		/* add 4 (line length offset) */
-	ldr	r4, =0x3ff
-	ands	r4, r4, r1, lsr #3	/* find maximum number on the way size*/
-	clz	r5, r4			/* find bit position of way size increment */
-	ldr	r7, =0x7fff
-	ands	r7, r7, r1, lsr #13	/* extract max number of the index size */
-inval_loop2:
-	mov	r9, r4			/* create working copy of max way size */
-inval_loop3:
-	orr	r11, r10, r9, lsl r5	/* factor way and cache number into r11*/
-	orr	r11, r11, r7, lsl r2	/* factor index number into r11 */
-	mcr	p15, 0, r11, c7, c6, 2	/* invalidate by set/way */
-	subs	r9, r9, #1		/* decrement the way */
-	bge	inval_loop3
-	subs	r7, r7, #1		/* decrement the index */
-	bge	inval_loop2
-skip_inval:
-	add	r10, r10, #2		/* increment cache number */
-	cmp	r3, r10
-	bgt	inval_loop1
-finished_inval:
-	mov	r10, #0			/* swith back to cache level 0 */
-	mcr	p15, 2, r10, c0, c0, 0	/* select current cache level in cssr */
-	isb
-#endif /* CONFIG_CPU_V7_DCACHE_SKIP */
-
-#else
-	/*
-	 * flush v4 I/D caches
-	 */
-	mov	r0, #0
-	mcr	p15, 0, r0, c7, c7, 0	/* flush v3/v4 cache */
-	mcr	p15, 0, r0, c8, c7, 0	/* flush v4 TLB */
-#endif
-
-	/*
-	 * disable MMU stuff and caches
-	 */
-	mrc	p15, 0, r0, c1, c0, 0
-	bic	r0, r0, #0x00002300	/* clear bits 13, 9:8 (--V- --RS) */
-	bic	r0, r0, #0x00000087	/* clear bits 7, 2:0 (B--- -CAM) */
-	orr	r0, r0, #0x00000002	/* set bit 2 (A) Align */
-	orr	r0, r0, #0x00001000	/* set bit 12 (I) I-Cache */
-	mcr	p15, 0, r0, c1, c0, 0
-
-	/*
-	 * before relocating, we have to setup RAM timing
-	 * because memory timing is board-dependend, you will
-	 * find a lowlevel_init.S in your board directory.
-	 */
-#ifdef CONFIG_MACH_DO_LOWLEVEL_INIT
-	bl	board_init_lowlevel
-#endif
-
-relocate:				/* relocate barebox to RAM	    */
-	adr	r0, _start		/* r0 <- current position of code   */
-	ldr	r1, _TEXT_BASE		/* test if we run from flash or RAM */
-	cmp	r0, r1			/* don't reloc during debug         */
-	beq	stack_setup
-
-	ldr	r2, _barebox_start
-	ldr	r3, _bss_start
-	sub	r2, r3, r2		/* r2 <- size of armboot            */
-	add	r2, r0, r2		/* r2 <- source end address         */
-
-copy_loop:
-	ldmia	r0!, {r3-r10}		/* copy from source address [r0]    */
-	stmia	r1!, {r3-r10}		/* copy to   target address [r1]    */
-	cmp	r0, r2			/* until source end addreee [r2]    */
-	ble	copy_loop
-
-	/* Set up the stack						    */
-stack_setup:
-	ldr	r0, _STACK_START
-	sub	sp, r0, #12		/* leave 3 words for abort-stack    */
-
-clear_bss:
-	ldr	r0, _bss_start		/* find start of bss segment        */
-	ldr	r1, _bss_end		/* stop here                        */
-	mov 	r2, #0x00000000		/* clear                            */
-
-clbss_l:
-	str	r2, [r0]		/* clear loop...                    */
-	add	r0, r0, #4
-	cmp	r0, r1
-	ble	clbss_l
-
-	ldr	pc, _start_armboot
-
-_start_armboot:
-	.word start_barebox
diff --git a/arch/arm/cpu/start.c b/arch/arm/cpu/start.c
new file mode 100644
index 0000000..67d54a6
--- /dev/null
+++ b/arch/arm/cpu/start.c
@@ -0,0 +1,108 @@
+/*
+ * start-arm.c
+ *
+ * Copyright (c) 2010 Sascha Hauer <s.hauer@pengutronix.de>, Pengutronix
+ *
+ * See file CREDITS for list of people who contributed to this
+ * project.
+ *
+ * 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.
+ *
+ * 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
+ */
+
+#include <common.h>
+#include <init.h>
+#include <asm/barebox-arm.h>
+#include <asm/system.h>
+#include <asm-generic/memory_layout.h>
+
+void __naked __section(.text_entry) exception_vectors(void)
+{
+	__asm__ __volatile__ (
+		"b reset\n"				/* reset */
+		"ldr pc, =undefined_instruction\n"	/* undefined instruction */
+		"ldr pc, =software_interrupt\n"		/* software interrupt (SWI) */
+		"ldr pc, =prefetch_abort\n"		/* prefetch abort */
+		"ldr pc, =data_abort\n"			/* data abort */
+		"ldr pc, =not_used\n"			/* (reserved) */
+		"ldr pc, =irq\n"			/* irq (interrupt) */
+		"ldr pc, =fiq\n"			/* fiq (fast interrupt) */
+	);
+}
+
+extern char __bss_start, _end;
+
+/*
+ * The actual reset vector. This code is position independent and usually
+ * does not run at the address it's linked at.
+ */
+void __naked __bare_init reset(void)
+{
+	uint32_t r;
+
+	/* set the cpu to SVC32 mode */
+	__asm__ __volatile__("mrs %0, cpsr":"=r"(r));
+	r &= ~0x1f;
+	r |= 0xd3;
+	__asm__ __volatile__("msr cpsr, %0" : : "r"(r));
+
+	__asm__ __volatile__ (
+		"bl __mmu_cache_flush;"
+		:
+		:
+		: "r0", "r1", "r2", "r3", "r6", "r10", "r12", "cc", "memory"
+	);
+
+	/* disable MMU stuff and caches */
+	r = get_cr();
+	r &= ~(CR_M | CR_C | CR_B | CR_S | CR_R | CR_V);
+	r |= CR_A | CR_I;
+	set_cr(r);
+
+#ifdef CONFIG_MACH_DO_LOWLEVEL_INIT
+	board_init_lowlevel();
+#endif
+	board_init_lowlevel_return();
+}
+
+/*
+ * Board code can jump here by either returning from board_init_lowlevel
+ * or by calling this funtion directly.
+ */
+void __naked __bare_init board_init_lowlevel_return(void)
+{
+	uint32_t r;
+
+	/* Setup the stack */
+	r = STACK_BASE + STACK_SIZE - 16;
+	__asm__ __volatile__("mov sp, %0" : : "r"(r));
+
+	/* Get runtime address of this function */
+	__asm__ __volatile__("adr %0, 0":"=r"(r));
+
+	/* Get start of binary image */
+	r -= (uint32_t)&board_init_lowlevel_return - TEXT_BASE;
+
+	/* relocate to link address if necessary */
+	if (r != TEXT_BASE)
+		memcpy((void *)TEXT_BASE, (void *)r,
+				(unsigned int)&__bss_start - TEXT_BASE);
+
+	/* clear bss */
+	memset(&__bss_start, 0, &_end - &__bss_start);
+
+	/* call start_barebox with its absolute address */
+	r = (unsigned int)&start_barebox;
+	__asm__ __volatile__("mov pc, %0" : : "r"(r));
+}
+
diff --git a/arch/arm/include/asm/barebox-arm.h b/arch/arm/include/asm/barebox-arm.h
index ff3a60d..54561c3 100644
--- a/arch/arm/include/asm/barebox-arm.h
+++ b/arch/arm/include/asm/barebox-arm.h
@@ -36,4 +36,7 @@ int	cleanup_before_linux(void);
 int	board_init(void);
 int	dram_init (void);
 
+void board_init_lowlevel(void);
+void board_init_lowlevel_return(void);
+
 #endif	/* _BAREBOX_ARM_H_ */
diff --git a/arch/arm/lib/barebox.lds.S b/arch/arm/lib/barebox.lds.S
index a5eaefa..5bee0a1 100644
--- a/arch/arm/lib/barebox.lds.S
+++ b/arch/arm/lib/barebox.lds.S
@@ -26,7 +26,7 @@
 
 OUTPUT_FORMAT("elf32-littlearm", "elf32-littlearm", "elf32-littlearm")
 OUTPUT_ARCH(arm)
-ENTRY(_start)
+ENTRY(exception_vectors)
 SECTIONS
 {
 	. = TEXT_BASE;
-- 
1.7.0



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