cpu/arm720t/start.S - filogic/uboot - Gitiles

 /*
  *  armboot - Startup Code for ARM720 CPU-core
  *
  *  Copyright (c) 2001	Marius Gröger <mag@sysgo.de>
  *  Copyright (c) 2002	Alex Züpke <azu@sysgo.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
  */


 #include <config.h>
 #include <version.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 RAM!
  * relocate armboot to ram
  * setup stack
  * jump to second stage
  *
  *************************************************************************
  */

 _TEXT_BASE:
 	.word	TEXT_BASE

 .globl _armboot_start
 _armboot_start:
 	.word _start

 /*
  * These are defined in the board-specific linker script.
  */
 .globl _bss_start
 _bss_start:
 	.word __bss_start

 .globl _bss_end
 _bss_end:
 	.word _end

 #ifdef CONFIG_USE_IRQ
 /* IRQ stack memory (calculated at run-time) */
 .globl IRQ_STACK_START
 IRQ_STACK_START:
 	.word	0x0badc0de

 /* IRQ stack memory (calculated at run-time) */
 .globl FIQ_STACK_START
 FIQ_STACK_START:
 	.word 0x0badc0de
 #endif


 /*
  * the actual reset code
  */

 reset:
 	/*
 	 * set the cpu to SVC32 mode
 	 */
 	mrs	r0,cpsr
 	bic	r0,r0,#0x1f
 	orr	r0,r0,#0x13
 	msr	cpsr,r0

 	/*
 	 * we do sys-critical inits only at reboot,
 	 * not when booting from ram!
 	 */
 #ifdef CONFIG_INIT_CRITICAL
 	bl	cpu_init_crit
 #endif

 relocate:				/* relocate U-Boot 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, _armboot_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, _TEXT_BASE		/* upper 128 KiB: relocated uboot   */
 	sub	r0, r0, #CFG_MALLOC_LEN	/* malloc area                      */
 	sub	r0, r0, #CFG_GBL_DATA_SIZE /* bdinfo                        */
 #ifdef CONFIG_USE_IRQ
 	sub	r0, r0, #(CONFIG_STACKSIZE_IRQ+CONFIG_STACKSIZE_FIQ)
 #endif
 	sub	sp, r0, #12		/* leave 3 words for abort-stack    */

 clear_bss:
 	ldr	r0, _bss_start		/* find start of bss segment        */
 	add	r0, r0, #4		/* start at first byte of bss       */
 	ldr	r1, _bss_end		/* stop here                        */
 	mov 	r2, #0x00000000		/* clear                            */

 clbss_l:str	r2, [r0]		/* clear loop...                    */
 	add	r0, r0, #4
 	cmp	r0, r1
 	bne	clbss_l

 	ldr	pc, _start_armboot

 _start_armboot:	.word start_armboot


 /*
  *************************************************************************
  *
  * CPU_init_critical registers
  *
  * setup important registers
  * setup memory timing
  *
  *************************************************************************
  */


 /* Interupt-Controller base addresses */
 INTMR1:		.word	0x80000280 @ 32 bit size
 INTMR2:		.word	0x80001280 @ 16 bit size
 INTMR3:		.word	0x80002280 @  8 bit size

 /* SYSCONs */
 SYSCON1:	.word	0x80000100
 SYSCON2:	.word	0x80001100
 SYSCON3:	.word	0x80002200

 #define CLKCTL	       0x6  /* mask */
 #define CLKCTL_18      0x0  /* 18.432 MHz */
 #define CLKCTL_36      0x2  /* 36.864 MHz */
 #define CLKCTL_49      0x4  /* 49.152 MHz */
 #define CLKCTL_73      0x6  /* 73.728 MHz */

 cpu_init_crit:
 	/*
 	 * mask all IRQs by clearing all bits in the INTMRs
 	 */
 	mov	r1, #0x00
 	ldr	r0, INTMR1
 	str	r1, [r0]
 	ldr	r0, INTMR2
 	str	r1, [r0]
 	ldr	r0, INTMR3
 	str	r1, [r0]

 	/*
 	 * 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 */

 	/*
 	 * disable MMU stuff and caches
 	 */
 	mrc	p15,0,r0,c1,c0
 	bic	r0, r0, #0x00002300	@ clear bits 13, 9:8 (--V- --RS)
 	bic	r0, r0, #0x0000008f	@ clear bits 7, 3:0 (B--- WCAM)
 	orr	r0, r0, #0x00000002	@ set bit 2 (A) Align
 	mcr	p15,0,r0,c1,c0

 #ifdef CONFIG_ARM7_REVD
 	/* set clock speed */
 	/* !!! we run @ 36 MHz due to a hardware flaw in Rev. D processors */
 	/* !!! not doing DRAM refresh properly! */
 	ldr	r0, SYSCON3
 	ldr	r1, [r0]
 	bic	r1, r1, #CLKCTL
 	orr	r1, r1, #CLKCTL_36
 	str	r1, [r0]
 #endif

 	/*
 	 * before relocating, we have to setup RAM timing
 	 * because memory timing is board-dependent, you will
 	 * find a memsetup.S in your board directory.
 	 */
 	mov	ip, lr
 	bl	memsetup
 	mov	lr, ip

 	mov	pc, lr


 /*
  *************************************************************************
  *
  * Interrupt handling
  *
  *************************************************************************
  */

 @
 @ IRQ stack frame.
 @
 #define S_FRAME_SIZE	72

 #define S_OLD_R0	68
 #define S_PSR		64
 #define S_PC		60
 #define S_LR		56
 #define S_SP		52

 #define S_IP		48
 #define S_FP		44
 #define S_R10		40
 #define S_R9		36
 #define S_R8		32
 #define S_R7		28
 #define S_R6		24
 #define S_R5		20
 #define S_R4		16
 #define S_R3		12
 #define S_R2		8
 #define S_R1		4
 #define S_R0		0

 #define MODE_SVC 0x13
 #define I_BIT	 0x80

 /*
  * use bad_save_user_regs for abort/prefetch/undef/swi ...
  * use irq_save_user_regs / irq_restore_user_regs for IRQ/FIQ handling
  */

 	.macro	bad_save_user_regs
 	sub	sp, sp, #S_FRAME_SIZE
 	stmia	sp, {r0 - r12}			@ Calling r0-r12
 	add     r8, sp, #S_PC

 	ldr	r2, _armboot_start
 	sub	r2, r2, #(CONFIG_STACKSIZE+CFG_MALLOC_LEN)
 	sub	r2, r2, #(CFG_GBL_DATA_SIZE+8)  @ set base 2 words into abort stack
 	ldmia	r2, {r2 - r4}                   @ get pc, cpsr, old_r0
 	add	r0, sp, #S_FRAME_SIZE		@ restore sp_SVC

 	add	r5, sp, #S_SP
 	mov	r1, lr
 	stmia	r5, {r0 - r4}                   @ save sp_SVC, lr_SVC, pc, cpsr, old_r
 	mov	r0, sp
 	.endm

 	.macro	irq_save_user_regs
 	sub	sp, sp, #S_FRAME_SIZE
 	stmia	sp, {r0 - r12}			@ Calling r0-r12
 	add     r8, sp, #S_PC
 	stmdb   r8, {sp, lr}^                   @ Calling SP, LR
 	str     lr, [r8, #0]                    @ Save calling PC
 	mrs     r6, spsr
 	str     r6, [r8, #4]                    @ Save CPSR
 	str     r0, [r8, #8]                    @ Save OLD_R0
 	mov	r0, sp
 	.endm

 	.macro	irq_restore_user_regs
 	ldmia	sp, {r0 - lr}^			@ Calling r0 - lr
 	mov	r0, r0
 	ldr	lr, [sp, #S_PC]			@ Get PC
 	add	sp, sp, #S_FRAME_SIZE
 	subs	pc, lr, #4			@ return & move spsr_svc into cpsr
 	.endm

 	.macro get_bad_stack
 	ldr	r13, _armboot_start		@ setup our mode stack
 	sub	r13, r13, #(CONFIG_STACKSIZE+CFG_MALLOC_LEN)
 	sub	r13, r13, #(CFG_GBL_DATA_SIZE+8) @ reserved a couple spots in abort stack

 	str	lr, [r13]			@ save caller lr / spsr
 	mrs	lr, spsr
 	str     lr, [r13, #4]

 	mov	r13, #MODE_SVC			@ prepare SVC-Mode
 	msr	spsr_c, r13
 	mov	lr, pc
 	movs	pc, lr
 	.endm

 	.macro get_irq_stack			@ setup IRQ stack
 	ldr	sp, IRQ_STACK_START
 	.endm

 	.macro get_fiq_stack			@ setup FIQ stack
 	ldr	sp, FIQ_STACK_START
 	.endm

 /*
  * exception handlers
  */
 	.align  5
 undefined_instruction:
 	get_bad_stack
 	bad_save_user_regs
 	bl 	do_undefined_instruction

 	.align	5
 software_interrupt:
 	get_bad_stack
 	bad_save_user_regs
 	bl 	do_software_interrupt

 	.align	5
 prefetch_abort:
 	get_bad_stack
 	bad_save_user_regs
 	bl 	do_prefetch_abort

 	.align	5
 data_abort:
 	get_bad_stack
 	bad_save_user_regs
 	bl 	do_data_abort

 	.align	5
 not_used:
 	get_bad_stack
 	bad_save_user_regs
 	bl 	do_not_used

 #ifdef CONFIG_USE_IRQ

 	.align	5
 irq:
 	get_irq_stack
 	irq_save_user_regs
 	bl 	do_irq
 	irq_restore_user_regs

 	.align	5
 fiq:
 	get_fiq_stack
 	/* someone ought to write a more effiction fiq_save_user_regs */
 	irq_save_user_regs
 	bl 	do_fiq
 	irq_restore_user_regs

 #else

 	.align	5
 irq:
 	get_bad_stack
 	bad_save_user_regs
 	bl 	do_irq

 	.align	5
 fiq:
 	get_bad_stack
 	bad_save_user_regs
 	bl 	do_fiq

 #endif

 	.align	5
 .globl reset_cpu
 reset_cpu:
 	mov     ip, #0
 	mcr     p15, 0, ip, c7, c7, 0           @ invalidate cache
 	mcr     p15, 0, ip, c8, c7, 0           @ flush TLB (v4)
 	mrc     p15, 0, ip, c1, c0, 0           @ get ctrl register
 	bic     ip, ip, #0x000f                 @ ............wcam
 	bic     ip, ip, #0x2100                 @ ..v....s........
 	mcr     p15, 0, ip, c1, c0, 0           @ ctrl register
 	mov     pc, r0
	/*
	* armboot - Startup Code for ARM720 CPU-core
	*
	* Copyright (c) 2001 Marius Gröger <mag@sysgo.de>
	* Copyright (c) 2002 Alex Züpke <azu@sysgo.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
	*/


	#include <config.h>
	#include <version.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 RAM!
	* relocate armboot to ram
	* setup stack
	* jump to second stage
	*
	*************************************************************************
	*/

	_TEXT_BASE:
	.word TEXT_BASE

	.globl _armboot_start
	_armboot_start:
	.word _start

	/*
	* These are defined in the board-specific linker script.
	*/
	.globl _bss_start
	_bss_start:
	.word __bss_start

	.globl _bss_end
	_bss_end:
	.word _end

	#ifdef CONFIG_USE_IRQ
	/* IRQ stack memory (calculated at run-time) */
	.globl IRQ_STACK_START
	IRQ_STACK_START:
	.word 0x0badc0de

	/* IRQ stack memory (calculated at run-time) */
	.globl FIQ_STACK_START
	FIQ_STACK_START:
	.word 0x0badc0de
	#endif


	/*
	* the actual reset code
	*/

	reset:
	/*
	* set the cpu to SVC32 mode
	*/
	mrs r0,cpsr
	bic r0,r0,#0x1f
	orr r0,r0,#0x13
	msr cpsr,r0

	/*
	* we do sys-critical inits only at reboot,
	* not when booting from ram!
	*/
	#ifdef CONFIG_INIT_CRITICAL
	bl cpu_init_crit
	#endif

	relocate: /* relocate U-Boot 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, _armboot_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, _TEXT_BASE /* upper 128 KiB: relocated uboot */
	sub r0, r0, #CFG_MALLOC_LEN /* malloc area */
	sub r0, r0, #CFG_GBL_DATA_SIZE /* bdinfo */
	#ifdef CONFIG_USE_IRQ
	sub r0, r0, #(CONFIG_STACKSIZE_IRQ+CONFIG_STACKSIZE_FIQ)
	#endif
	sub sp, r0, #12 /* leave 3 words for abort-stack */

	clear_bss:
	ldr r0, _bss_start /* find start of bss segment */
	add r0, r0, #4 /* start at first byte of bss */
	ldr r1, _bss_end /* stop here */
	mov r2, #0x00000000 /* clear */

	clbss_l:str r2, [r0] /* clear loop... */
	add r0, r0, #4
	cmp r0, r1
	bne clbss_l

	ldr pc, _start_armboot

	_start_armboot: .word start_armboot


	/*
	*************************************************************************
	*
	* CPU_init_critical registers
	*
	* setup important registers
	* setup memory timing
	*
	*************************************************************************
	*/


	/* Interupt-Controller base addresses */
	INTMR1: .word 0x80000280 @ 32 bit size
	INTMR2: .word 0x80001280 @ 16 bit size
	INTMR3: .word 0x80002280 @ 8 bit size

	/* SYSCONs */
	SYSCON1: .word 0x80000100
	SYSCON2: .word 0x80001100
	SYSCON3: .word 0x80002200

	#define CLKCTL 0x6 /* mask */
	#define CLKCTL_18 0x0 /* 18.432 MHz */
	#define CLKCTL_36 0x2 /* 36.864 MHz */
	#define CLKCTL_49 0x4 /* 49.152 MHz */
	#define CLKCTL_73 0x6 /* 73.728 MHz */

	cpu_init_crit:
	/*
	* mask all IRQs by clearing all bits in the INTMRs
	*/
	mov r1, #0x00
	ldr r0, INTMR1
	str r1, [r0]
	ldr r0, INTMR2
	str r1, [r0]
	ldr r0, INTMR3
	str r1, [r0]

	/*
	* 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 */

	/*
	* disable MMU stuff and caches
	*/
	mrc p15,0,r0,c1,c0
	bic r0, r0, #0x00002300 @ clear bits 13, 9:8 (--V- --RS)
	bic r0, r0, #0x0000008f @ clear bits 7, 3:0 (B--- WCAM)
	orr r0, r0, #0x00000002 @ set bit 2 (A) Align
	mcr p15,0,r0,c1,c0

	#ifdef CONFIG_ARM7_REVD
	/* set clock speed */
	/* !!! we run @ 36 MHz due to a hardware flaw in Rev. D processors */
	/* !!! not doing DRAM refresh properly! */
	ldr r0, SYSCON3
	ldr r1, [r0]
	bic r1, r1, #CLKCTL
	orr r1, r1, #CLKCTL_36
	str r1, [r0]
	#endif

	/*
	* before relocating, we have to setup RAM timing
	* because memory timing is board-dependent, you will
	* find a memsetup.S in your board directory.
	*/
	mov ip, lr
	bl memsetup
	mov lr, ip

	mov pc, lr


	/*
	*************************************************************************
	*
	* Interrupt handling
	*
	*************************************************************************
	*/

	@
	@ IRQ stack frame.
	@
	#define S_FRAME_SIZE 72

	#define S_OLD_R0 68
	#define S_PSR 64
	#define S_PC 60
	#define S_LR 56
	#define S_SP 52

	#define S_IP 48
	#define S_FP 44
	#define S_R10 40
	#define S_R9 36
	#define S_R8 32
	#define S_R7 28
	#define S_R6 24
	#define S_R5 20
	#define S_R4 16
	#define S_R3 12
	#define S_R2 8
	#define S_R1 4
	#define S_R0 0

	#define MODE_SVC 0x13
	#define I_BIT 0x80

	/*
	* use bad_save_user_regs for abort/prefetch/undef/swi ...
	* use irq_save_user_regs / irq_restore_user_regs for IRQ/FIQ handling
	*/

	.macro bad_save_user_regs
	sub sp, sp, #S_FRAME_SIZE
	stmia sp, {r0 - r12} @ Calling r0-r12
	add r8, sp, #S_PC

	ldr r2, _armboot_start
	sub r2, r2, #(CONFIG_STACKSIZE+CFG_MALLOC_LEN)
	sub r2, r2, #(CFG_GBL_DATA_SIZE+8) @ set base 2 words into abort stack
	ldmia r2, {r2 - r4} @ get pc, cpsr, old_r0
	add r0, sp, #S_FRAME_SIZE @ restore sp_SVC

	add r5, sp, #S_SP
	mov r1, lr
	stmia r5, {r0 - r4} @ save sp_SVC, lr_SVC, pc, cpsr, old_r
	mov r0, sp
	.endm

	.macro irq_save_user_regs
	sub sp, sp, #S_FRAME_SIZE
	stmia sp, {r0 - r12} @ Calling r0-r12
	add r8, sp, #S_PC
	stmdb r8, {sp, lr}^ @ Calling SP, LR
	str lr, [r8, #0] @ Save calling PC
	mrs r6, spsr
	str r6, [r8, #4] @ Save CPSR
	str r0, [r8, #8] @ Save OLD_R0
	mov r0, sp
	.endm

	.macro irq_restore_user_regs
	ldmia sp, {r0 - lr}^ @ Calling r0 - lr
	mov r0, r0
	ldr lr, [sp, #S_PC] @ Get PC
	add sp, sp, #S_FRAME_SIZE
	subs pc, lr, #4 @ return & move spsr_svc into cpsr
	.endm

	.macro get_bad_stack
	ldr r13, _armboot_start @ setup our mode stack
	sub r13, r13, #(CONFIG_STACKSIZE+CFG_MALLOC_LEN)
	sub r13, r13, #(CFG_GBL_DATA_SIZE+8) @ reserved a couple spots in abort stack

	str lr, [r13] @ save caller lr / spsr
	mrs lr, spsr
	str lr, [r13, #4]

	mov r13, #MODE_SVC @ prepare SVC-Mode
	msr spsr_c, r13
	mov lr, pc
	movs pc, lr
	.endm

	.macro get_irq_stack @ setup IRQ stack
	ldr sp, IRQ_STACK_START
	.endm

	.macro get_fiq_stack @ setup FIQ stack
	ldr sp, FIQ_STACK_START
	.endm

	/*
	* exception handlers
	*/
	.align 5
	undefined_instruction:
	get_bad_stack
	bad_save_user_regs
	bl do_undefined_instruction

	.align 5
	software_interrupt:
	get_bad_stack
	bad_save_user_regs
	bl do_software_interrupt

	.align 5
	prefetch_abort:
	get_bad_stack
	bad_save_user_regs
	bl do_prefetch_abort

	.align 5
	data_abort:
	get_bad_stack
	bad_save_user_regs
	bl do_data_abort

	.align 5
	not_used:
	get_bad_stack
	bad_save_user_regs
	bl do_not_used

	#ifdef CONFIG_USE_IRQ

	.align 5
	irq:
	get_irq_stack
	irq_save_user_regs
	bl do_irq
	irq_restore_user_regs

	.align 5
	fiq:
	get_fiq_stack
	/* someone ought to write a more effiction fiq_save_user_regs */
	irq_save_user_regs
	bl do_fiq
	irq_restore_user_regs

	#else

	.align 5
	irq:
	get_bad_stack
	bad_save_user_regs
	bl do_irq

	.align 5
	fiq:
	get_bad_stack
	bad_save_user_regs
	bl do_fiq

	#endif

	.align 5
	.globl reset_cpu
	reset_cpu:
	mov ip, #0
	mcr p15, 0, ip, c7, c7, 0 @ invalidate cache
	mcr p15, 0, ip, c8, c7, 0 @ flush TLB (v4)
	mrc p15, 0, ip, c1, c0, 0 @ get ctrl register
	bic ip, ip, #0x000f @ ............wcam
	bic ip, ip, #0x2100 @ ..v....s........
	mcr p15, 0, ip, c1, c0, 0 @ ctrl register
	mov pc, r0