start.s

RTEMS (Real-Time Executive for Multiprocessor Systems) is a free open source real-time operating sys

/*
 *  start.S :	  RTEMS entry point
 *
 *  Copyright (C) 1999 Eric Valette. [e-mail]
 *
 *  The license and distribution terms for this file may be
 *  found in found in the file LICENSE in this distribution or at
 *  http://www.rtems.com/license/LICENSE.
 *
 *  $Id: start.S,v 1.10.4.4 2005/11/09 03:20:13 strauman Exp $
 *
 */

#include <asm.h>
#include <rtems/score/cpu.h>
#include <libcpu/io.h>
#include <bspopts.h>

#define SYNC \
	sync; \
	isync

#define KERNELBASE	0x0

#define MONITOR_ENTER			\
	mfmsr	r10		;	\
	ori	r10,r10,MSR_IP	;	\
	mtmsr	r10		;	\
	li	r10,0x63	;	\
	sc

	.text
	.globl	__rtems_entry_point
	.type	__rtems_entry_point,@function
__rtems_entry_point:
#ifdef DEBUG_EARLY_START
	MONITOR_ENTER
#endif	
		
/* 
 * PREP
 * This is jumped to on prep systems right after the kernel is relocated
 * to its proper place in memory by the boot loader.  The expected layout
 * of the regs is:	
 *   r3: ptr to residual data
 *   r4: initrd_start or if no initrd then 0
 *   r5: initrd_end - unused if r4 is 0
 *   r6: Start of command line string
 *   r7: End of command line string
 *
 *   The Prep boot loader insure that the MMU is currently off...
 *
 */
	
	mr	r31,r3			/* save parameters */
	mr	r30,r4
	mr	r29,r5
	mr	r28,r6
	mr	r27,r7
	/*
	 * Make sure we have nothing in BATS and TLB
	 */
	bl	clear_bats
	bl	flush_tlbs
/*
 * Use the first pair of BAT registers to map the 1st 256MB
 * of RAM to KERNELBASE. 
 */
	lis	r11,KERNELBASE@h
/* set up BAT registers for 604 */
	ori	r11,r11,0x1ffe		
	li	r8,2			/* R/W access */
	isync
#if defined(mvme2100)
        /* BSP_vme_config() wants to use BAT0, this board will use the
         * available BAT1 to map RAM.
         */
	mtspr	DBAT1L,r8		/* N.B. 6xx (not 601) have valid */
	mtspr	DBAT1U,r11		/* bit in upper BAT register */
	mtspr	IBAT1L,r8
	mtspr	IBAT1U,r11
#else
	mtspr	DBAT0L,r8		/* N.B. 6xx (not 601) have valid */
	mtspr	DBAT0U,r11		/* bit in upper BAT register */
	mtspr	IBAT0L,r8
	mtspr	IBAT0U,r11
#endif
	isync

/*
 * we now have the 1st 256M of ram mapped with the bats. We are still 
 * running on the bootloader stack and cannot switch to an RTEMS allocated 
 * init stack before copying the residual data that may have been set just after
 * rtems_end address. This bug has been experienced on MVME2304. Thank to
 * Till Straumann <[e-mail]> for hunting it and suggesting 
 * the appropriate code.
 */
	
enter_C_code:
	bl	MMUon
	bl      __eabi	/* setup EABI and SYSV environment */
	bl	zero_bss
	/*
	 * restore prep boot params
	 */
	mr	r3,r31
	mr	r4,r30
	mr	r5,r29
	mr	r6,r28
	mr	r7,r27 
	bl	save_boot_params
	/*
	 * stack = &__rtems_end + 4096
	 */
	addis	r9,r0, __rtems_end+(4096-CPU_MINIMUM_STACK_FRAME_SIZE)@ha
        addi	r9,r9, __rtems_end+(4096-CPU_MINIMUM_STACK_FRAME_SIZE)@l
	mr	r1, r9
	/*
	 * We are now in a environment that is totally independent from 
         * bootloader setup.
	 */
        lis	r5,environ@ha
        la	r5,environ@l(r5)	/* environp */
	li	r4, 0			/* argv */
	li	r3, 0			/* argc */
	bl	boot_card
	bl	_return_to_ppcbug

	.globl  MMUon
	.type	MMUon,@function
MMUon:
	mfmsr	r0
	ori	r0,r0, MSR_IP | MSR_RI | MSR_IR | MSR_DR | MSR_EE | MSR_FE0 | MSR_FE1 | MSR_FP
#if (PPC_HAS_FPU == 0)
	xori	r0, r0, MSR_EE | MSR_IP | MSR_FP
#else
	xori	r0, r0, MSR_EE | MSR_IP | MSR_FE0 | MSR_FE1
#endif
	mflr	r11
	mtsrr0	r11
	mtsrr1	r0
	SYNC
	rfi

	.globl  MMUoff
	.type	MMUoff,@function
MMUoff: 
	mfmsr	r0
	ori	r0,r0,MSR_IR| MSR_DR | MSR_IP
	mflr	r11
	xori	r0,r0,MSR_IR|MSR_DR
	mtsrr0	r11
	mtsrr1	r0
	SYNC
	rfi

	.globl	_return_to_ppcbug
	.type	_return_to_ppcbug,@function

	
_return_to_ppcbug:
	mflr	r30
	bl	MMUoff
	MONITOR_ENTER
	bl	MMUon
	mtctr	r30
	bctr	

/* 
 * An undocumented "feature" of 604e requires that the v bit
 * be cleared before changing BAT values.
 *
 * Also, newer IBM firmware does not clear bat3 and 4 so
 * this makes sure it's done.
 *  -- Cort 
 */
clear_bats:
	li	r20,0
	mfspr	r9,PVR
	rlwinm	r9,r9,16,16,31		/* r9 = 1 for 601, 4 for 604 */
	cmpwi	r9, 1
	SYNC
	beq	1f
	mtspr	DBAT0U,r20
	mtspr	DBAT0L,r20	
	mtspr	DBAT1U,r20
	mtspr	DBAT1L,r20
	mtspr	DBAT2U,r20
	mtspr	DBAT2L,r20	
	mtspr	DBAT3U,r20
	mtspr	DBAT3L,r20
1:	
	mtspr	IBAT0U,r20
	mtspr	IBAT0L,r20
	mtspr	IBAT1U,r20
	mtspr	IBAT1L,r20
	mtspr	IBAT2U,r20
	mtspr	IBAT2L,r20
	mtspr	IBAT3U,r20
	mtspr	IBAT3L,r20
	SYNC	
	blr

flush_tlbs:
	lis	r20, 0x1000
1:	addic.	r20, r20, -0x1000
	tlbie	r20
	bgt	1b
	sync
	blr
	

	.comm	environ,4,4