head.s

底层驱动开发

/* head.S: kernel entry point for FR-V kernel
 *
 * Copyright (C) 2003, 2004 Red Hat, Inc. All Rights Reserved.
 * Written by David Howells ([e-mail])
 *
 * 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/config.h>
#include <linux/threads.h>
#include <linux/linkage.h>
#include <asm/ptrace.h>
#include <asm/page.h>
#include <asm/spr-regs.h>
#include <asm/mb86943a.h>
#include <asm/cache.h>
#include "head.inc"

###############################################################################
#
# void _boot(unsigned long magic, char *command_line) __attribute__((noreturn))
#
# - if magic is 0xdead1eaf, then command_line is assumed to point to the kernel
#   command line string
#
###############################################################################
	.section	.text.head,"ax"
	.balign		4

	.globl		_boot, __head_reference
        .type		_boot,@function
_boot:
__head_reference:
	sethi.p		%hi(LED_ADDR),gr30
	setlo		%lo(LED_ADDR),gr30

	LEDS		0x0000

	# calculate reference address for PC-relative stuff
	call		0f
0:	movsg		lr,gr26
	addi		gr26,#__head_reference-0b,gr26

	# invalidate and disable both of the caches and turn off the memory access checking
	dcef		@(gr0,gr0),1
	bar

	sethi.p		%hi(~(HSR0_ICE|HSR0_DCE|HSR0_CBM|HSR0_EIMMU|HSR0_EDMMU)),gr4
	setlo		%lo(~(HSR0_ICE|HSR0_DCE|HSR0_CBM|HSR0_EIMMU|HSR0_EDMMU)),gr4
	movsg		hsr0,gr5
	and		gr4,gr5,gr5
	movgs		gr5,hsr0
	movsg		hsr0,gr5

	LEDS		0x0001

	icei		@(gr0,gr0),1
	dcei		@(gr0,gr0),1
	bar

	# turn the instruction cache back on
	sethi.p		%hi(HSR0_ICE),gr4
	setlo		%lo(HSR0_ICE),gr4
	movsg		hsr0,gr5
	or		gr4,gr5,gr5
	movgs		gr5,hsr0
	movsg		hsr0,gr5

	bar

	LEDS		0x0002

	# retrieve the parameters (including command line) before we overwrite them
	sethi.p		%hi(0xdead1eaf),gr7
	setlo		%lo(0xdead1eaf),gr7
	subcc		gr7,gr8,gr0,icc0
	bne		icc0,#0,__head_no_parameters

	sethi.p		%hi(redboot_command_line-1),gr6
	setlo		%lo(redboot_command_line-1),gr6
	sethi.p		%hi(__head_reference),gr4
	setlo		%lo(__head_reference),gr4
	sub		gr6,gr4,gr6
	add.p		gr6,gr26,gr6
	subi		gr9,#1,gr9
	setlos.p	#511,gr4
	setlos		#1,gr5

__head_copy_cmdline:
	ldubu.p		@(gr9,gr5),gr16
	subicc		gr4,#1,gr4,icc0
	stbu.p		gr16,@(gr6,gr5)
	subicc		gr16,#0,gr0,icc1
	bls		icc0,#0,__head_end_cmdline
	bne		icc1,#1,__head_copy_cmdline
__head_end_cmdline:
	stbu		gr0,@(gr6,gr5)
__head_no_parameters:

###############################################################################
#
# we need to relocate the SDRAM to 0x00000000 (linux) or 0xC0000000 (uClinux)
# - note that we're going to have to run entirely out of the icache whilst
#   fiddling with the SDRAM controller registers
#
###############################################################################
#ifdef CONFIG_MMU
	call		__head_fr451_describe_sdram

#else
	movsg		psr,gr5
	srli		gr5,#28,gr5
	subicc		gr5,#3,gr0,icc0
	beq		icc0,#0,__head_fr551_sdram

	call		__head_fr401_describe_sdram
	bra		__head_do_sdram

__head_fr551_sdram:
	call		__head_fr555_describe_sdram
	LEDS		0x000d

__head_do_sdram:
#endif

	# preload the registers with invalid values in case any DBR/DARS are marked not present
	sethi.p		%hi(0xfe000000),gr17		; unused SDRAM DBR value
	setlo		%lo(0xfe000000),gr17
	or.p		gr17,gr0,gr20
	or		gr17,gr0,gr21
	or.p		gr17,gr0,gr22
	or		gr17,gr0,gr23

	# consult the SDRAM controller CS address registers
	cld		@(gr14,gr0 ),gr20,	cc0,#1	; DBR0 / DARS0
	cld		@(gr14,gr11),gr21,	cc1,#1	; DBR1 / DARS1
	cld		@(gr14,gr12),gr22,	cc2,#1	; DBR2 / DARS2
	cld.p		@(gr14,gr13),gr23,	cc3,#1	; DBR3 / DARS3

	sll		gr20,gr15,gr20			; shift values up for FR551
	sll		gr21,gr15,gr21
	sll		gr22,gr15,gr22
	sll		gr23,gr15,gr23

	LEDS		0x0003

	# assume the lowest valid CS line to be the SDRAM base and get its address
	subcc		gr20,gr17,gr0,icc0
	subcc.p		gr21,gr17,gr0,icc1
	subcc		gr22,gr17,gr0,icc2
	subcc.p		gr23,gr17,gr0,icc3
	ckne		icc0,cc4			; T if DBR0 != 0xfe000000
	ckne		icc1,cc5
	ckne		icc2,cc6
	ckne		icc3,cc7
	cor		gr23,gr0,gr24,		cc7,#1	; GR24 = SDRAM base
	cor		gr22,gr0,gr24,		cc6,#1
	cor		gr21,gr0,gr24,		cc5,#1
	cor		gr20,gr0,gr24,		cc4,#1

	# calculate the displacement required to get the SDRAM into the right place in memory
	sethi.p		%hi(__sdram_base),gr16
	setlo		%lo(__sdram_base),gr16
	sub		gr16,gr24,gr16			; delta = __sdram_base - DBRx

	# calculate the new values to go in the controller regs
	cadd.p		gr20,gr16,gr20,		cc4,#1	; DCS#0 (new) = DCS#0 (old) + delta
	cadd		gr21,gr16,gr21,		cc5,#1
	cadd.p		gr22,gr16,gr22,		cc6,#1
	cadd		gr23,gr16,gr23,		cc7,#1

	srl		gr20,gr15,gr20			; shift values down for FR551
	srl		gr21,gr15,gr21
	srl		gr22,gr15,gr22
	srl		gr23,gr15,gr23

	# work out the address at which the reg updater resides and lock it into icache
	# also work out the address the updater will jump to when finished
	sethi.p		%hi(__head_move_sdram-__head_reference),gr18
	setlo		%lo(__head_move_sdram-__head_reference),gr18
	sethi.p		%hi(__head_sdram_moved-__head_reference),gr19
	setlo		%lo(__head_sdram_moved-__head_reference),gr19
	add.p		gr18,gr26,gr18
	add		gr19,gr26,gr19
	add.p		gr19,gr16,gr19			; moved = addr + (__sdram_base - DBRx)
	add		gr18,gr5,gr4			; two cachelines probably required

	icpl		gr18,gr0,#1			; load and lock the cachelines
	icpl		gr4,gr0,#1
	LEDS		0x0004
	membar
	bar
	jmpl		@(gr18,gr0)

	.balign		L1_CACHE_BYTES
__head_move_sdram:
	cst		gr20,@(gr14,gr0 ),	cc4,#1
	cst		gr21,@(gr14,gr11),	cc5,#1
	cst		gr22,@(gr14,gr12),	cc6,#1
	cst		gr23,@(gr14,gr13),	cc7,#1
	cld		@(gr14,gr0 ),gr20,	cc4,#1
	cld		@(gr14,gr11),gr21,	cc5,#1
	cld		@(gr14,gr12),gr22,	cc4,#1
	cld		@(gr14,gr13),gr23,	cc7,#1
	bar
	membar
	jmpl		@(gr19,gr0)

	.balign		L1_CACHE_BYTES
__head_sdram_moved:
	icul		gr18
	add		gr18,gr5,gr4
	icul		gr4
	icei		@(gr0,gr0),1
	dcei		@(gr0,gr0),1

	LEDS		0x0005

	# recalculate reference address
	call		0f
0:	movsg		lr,gr26
	addi		gr26,#__head_reference-0b,gr26


###############################################################################
#
# move the kernel image down to the bottom of the SDRAM
#
###############################################################################
	sethi.p		%hi(__kernel_image_size_no_bss+15),gr4
	setlo		%lo(__kernel_image_size_no_bss+15),gr4
	srli.p		gr4,#4,gr4			; count
	or		gr26,gr26,gr16			; source

	sethi.p		%hi(__sdram_base),gr17		; destination
	setlo		%lo(__sdram_base),gr17

	setlos		#8,gr5
	sub.p		gr16,gr5,gr16			; adjust src for LDDU
	sub		gr17,gr5,gr17			; adjust dst for LDDU

	sethi.p		%hi(__head_move_kernel-__head_reference),gr18
	setlo		%lo(__head_move_kernel-__head_reference),gr18
	sethi.p		%hi(__head_kernel_moved-__head_reference+__sdram_base),gr19
	setlo		%lo(__head_kernel_moved-__head_reference+__sdram_base),gr19
	add		gr18,gr26,gr18
	icpl		gr18,gr0,#1
	jmpl		@(gr18,gr0)

	.balign		32
__head_move_kernel:
	lddu		@(gr16,gr5),gr10
	lddu		@(gr16,gr5),gr12
	stdu.p		gr10,@(gr17,gr5)
	subicc		gr4,#1,gr4,icc0
	stdu.p		gr12,@(gr17,gr5)
	bhi		icc0,#0,__head_move_kernel
	jmpl		@(gr19,gr0)

	.balign		32
__head_kernel_moved:
	icul		gr18
	icei		@(gr0,gr0),1
	dcei		@(gr0,gr0),1

	LEDS		0x0006

	# recalculate reference address
	call		0f
0:	movsg		lr,gr26
	addi		gr26,#__head_reference-0b,gr26


###############################################################################
#
# rearrange the iomem map and set the protection registers
#
###############################################################################

#ifdef CONFIG_MMU
	LEDS		0x3301
	call		__head_fr451_set_busctl
	LEDS		0x3303
	call		__head_fr451_survey_sdram
	LEDS		0x3305
	call		__head_fr451_set_protection

#else
	movsg		psr,gr5
	srli		gr5,#PSR_IMPLE_SHIFT,gr5
	subicc		gr5,#PSR_IMPLE_FR551,gr0,icc0
	beq		icc0,#0,__head_fr555_memmap
	subicc		gr5,#PSR_IMPLE_FR451,gr0,icc0
	beq		icc0,#0,__head_fr451_memmap

	LEDS		0x3101
	call		__head_fr401_set_busctl
	LEDS		0x3103
	call		__head_fr401_survey_sdram
	LEDS		0x3105
	call		__head_fr401_set_protection
	bra		__head_done_memmap

__head_fr451_memmap:
	LEDS		0x3301
	call		__head_fr401_set_busctl
	LEDS		0x3303
	call		__head_fr401_survey_sdram
	LEDS		0x3305
	call		__head_fr451_set_protection
	bra		__head_done_memmap

__head_fr555_memmap:
	LEDS		0x3501
	call		__head_fr555_set_busctl
	LEDS		0x3503
	call		__head_fr555_survey_sdram