path: root/arch/powerpc/kernel/head_44x.S

/*
 * Kernel execution entry point code.
 *
 *    Copyright (c) 1995-1996 Gary Thomas <gdt@linuxppc.org>
 *      Initial PowerPC version.
 *    Copyright (c) 1996 Cort Dougan <cort@cs.nmt.edu>
 *      Rewritten for PReP
 *    Copyright (c) 1996 Paul Mackerras <paulus@cs.anu.edu.au>
 *      Low-level exception handers, MMU support, and rewrite.
 *    Copyright (c) 1997 Dan Malek <dmalek@jlc.net>
 *      PowerPC 8xx modifications.
 *    Copyright (c) 1998-1999 TiVo, Inc.
 *      PowerPC 403GCX modifications.
 *    Copyright (c) 1999 Grant Erickson <grant@lcse.umn.edu>
 *      PowerPC 403GCX/405GP modifications.
 *    Copyright 2000 MontaVista Software Inc.
 *	PPC405 modifications
 *      PowerPC 403GCX/405GP modifications.
 * 	Author: MontaVista Software, Inc.
 *         	frank_rowand@mvista.com or source@mvista.com
 * 	   	debbie_chu@mvista.com
 *    Copyright 2002-2005 MontaVista Software, Inc.
 *      PowerPC 44x support, Matt Porter <mporter@kernel.crashing.org>
 *
 * 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.
 */

#include <linux/init.h>
#include <asm/processor.h>
#include <asm/page.h>
#include <asm/mmu.h>
#include <asm/pgtable.h>
#include <asm/cputable.h>
#include <asm/thread_info.h>
#include <asm/ppc_asm.h>
#include <asm/asm-offsets.h>
#include <asm/ptrace.h>
#include <asm/synch.h>
#include "head_booke.h"


/* As with the other PowerPC ports, it is expected that when code
 * execution begins here, the following registers contain valid, yet
 * optional, information:
 *
 *   r3 - Board info structure pointer (DRAM, frequency, MAC address, etc.)
 *   r4 - Starting address of the init RAM disk
 *   r5 - Ending address of the init RAM disk
 *   r6 - Start of kernel command line string (e.g. "mem=128")
 *   r7 - End of kernel command line string
 *
 */
	__HEAD
_ENTRY(_stext);
_ENTRY(_start);
	/*
	 * Reserve a word at a fixed location to store the address
	 * of abatron_pteptrs
	 */
	nop
	mr	r31,r3		/* save device tree ptr */
	li	r24,0		/* CPU number */

#ifdef CONFIG_RELOCATABLE
/*
 * Relocate ourselves to the current runtime address.
 * This is called only by the Boot CPU.
 * "relocate" is called with our current runtime virutal
 * address.
 * r21 will be loaded with the physical runtime address of _stext
 */
	bl	0f				/* Get our runtime address */
0:	mflr	r21				/* Make it accessible */
	addis	r21,r21,(_stext - 0b)@ha
	addi	r21,r21,(_stext - 0b)@l 	/* Get our current runtime base */

	/*
	 * We have the runtime (virutal) address of our base.
	 * We calculate our shift of offset from a 256M page.
	 * We could map the 256M page we belong to at PAGE_OFFSET and
	 * get going from there.
	 */
	lis	r4,KERNELBASE@h
	ori	r4,r4,KERNELBASE@l
	rlwinm	r6,r21,0,4,31			/* r6 = PHYS_START % 256M */
	rlwinm	r5,r4,0,4,31			/* r5 = KERNELBASE % 256M */
	subf	r3,r5,r6			/* r3 = r6 - r5 */
	add	r3,r4,r3			/* Required Virutal Address */

	bl	relocate
#endif

	bl	init_cpu_state

	/*
	 * This is where the main kernel code starts.
	 */

	/* ptr to current */
	lis	r2,init_task@h
	ori	r2,r2,init_task@l

	/* ptr to current thread */
	addi	r4,r2,THREAD	/* init task's THREAD */
	mtspr	SPRN_SPRG_THREAD,r4

	/* stack */
	lis	r1,init_thread_union@h
	ori	r1,r1,init_thread_union@l
	li	r0,0
	stwu	r0,THREAD_SIZE-STACK_FRAME_OVERHEAD(r1)

	bl	early_init

#ifdef CONFIG_RELOCATABLE
	/*
	 * Relocatable kernel support based on processing of dynamic
	 * relocation entries.
	 *
	 * r25 will contain RPN/ERPN for the start address of memory
	 * r21 will contain the current offset of _stext
	 */
	lis	r3,kernstart_addr@ha
	la	r3,kernstart_addr@l(r3)

	/*
	 * Compute the kernstart_addr.
	 * kernstart_addr => (r6,r8)
	 * kernstart_addr & ~0xfffffff => (r6,r7)
	 */
	rlwinm	r6,r25,0,28,31	/* ERPN. Bits 32-35 of Address */
	rlwinm	r7,r25,0,0,3	/* RPN - assuming 256 MB page size */
	rlwinm	r8,r21,0,4,31	/* r8 = (_stext & 0xfffffff) */
	or	r8,r7,r8	/* Compute the lower 32bit of kernstart_addr */

	/* Store kernstart_addr */
	stw	r6,0(r3)	/* higher 32bit */
	stw	r8,4(r3)	/* lower 32bit  */

	/*
	 * Compute the virt_phys_offset :
	 * virt_phys_offset = stext.run - kernstart_addr
	 *
	 * stext.run = (KERNELBASE & ~0xfffffff) + (kernstart_addr & 0xfffffff)
	 * When we relocate, we have :
	 *
	 *	(kernstart_addr & 0xfffffff) = (stext.run & 0xfffffff)
	 *
	 * hence:
	 *  virt_phys_offset = (KERNELBASE & ~0xfffffff) - (kernstart_addr & ~0xfffffff)
	 *
	 */

	/* KERNELBASE&~0xfffffff => (r4,r5) */
	li	r4, 0		/* higer 32bit */
	lis	r5,KERNELBASE@h
	rlwinm	r5,r5,0,0,3	/* Align to 256M, lower 32bit */

	/*
	 * 64bit subtraction.
	 */
	subfc	r5,r7,r5
	subfe	r4,r6,r4

	/* Store virt_phys_offset */
	lis	r3,virt_phys_offset@ha
	la	r3,virt_phys_offset@l(r3)

	stw	r4,0(r3)
	stw	r5,4(r3)

#elif defined(CONFIG_DYNAMIC_MEMSTART)
	/*
	 * Mapping based, page aligned dynamic kernel loading.
	 *
	 * r25 will contain RPN/ERPN for the start address of memory
	 *
	 * Add the difference between KERNELBASE and PAGE_OFFSET to the
	 * start of physical memory to get kernstart_addr.
	 */
	lis	r3,kernstart_addr@ha
	la	r3,kernstart_addr@l(r3)

	lis	r4,KERNELBASE@h
	ori	r4,r4,KERNELBASE@l
	lis	r5,PAGE_OFFSET@h
	ori	r5,r5,PAGE_OFFSET@l