基于devkit8600的2011.04版uboot启动代码Start.s分析
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/* * armboot - Startup Code for OMAP3530/ARM Cortex CPU-core * * Copyright (c) 2004 Texas Instruments <[email protected]> * * Copyright (c) 2001 Marius Gröger <[email protected]> * Copyright (c) 2002 Alex Züpke <[email protected]> * Copyright (c) 2002 Gary Jennejohn <[email protected]> * Copyright (c) 2003 Richard Woodruff <[email protected]> * Copyright (c) 2003 Kshitij <[email protected]> * Copyright (c) 2006-2008 Syed Mohammed Khasim <[email protected]> * * 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 <asm-offsets.h> #include <config.h> #include <version.h> .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 #ifdef CONFIG_SPL_BUILD _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 _pad: .word 0x12345678 /* now 16*4=64 */ #else _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 _pad: .word 0x12345678 /* now 16*4=64 */ #endif /* CONFIG_SPL_BUILD */ .global _end_vect _end_vect: .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 * *************************************************************************/ .globl _TEXT_BASE _TEXT_BASE: .word CONFIG_SYS_TEXT_BASE #ifdef CONFIG_TEGRA2 /* * Tegra2 uses 2 separate CPUs - the AVP (ARM7TDMI) and the CPU (dual A9s). * U-Boot runs on the AVP first, setting things up for the CPU (PLLs, * muxes, clocks, clamps, etc.). Then the AVP halts, and expects the CPU * to pick up its reset vector, which points here. */ .globl _armboot_start _armboot_start: .word _start #endif /* * These are defined in the board-specific linker script. */ .globl _bss_start_ofs _bss_start_ofs: .word __bss_start - _start .global _image_copy_end_ofs _image_copy_end_ofs: .word __image_copy_end - _start .globl _bss_end_ofs _bss_end_ofs: .word __bss_end__ - _start .globl _end_ofs _end_ofs: .word _end - _start #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 /* IRQ stack memory (calculated at run-time) + 8 bytes */ .globl IRQ_STACK_START_IN IRQ_STACK_START_IN: .word 0x0badc0de /* * the actual reset code */ reset: bl save_boot_params
/**************************************************************************/
save_boot_params
在arch/arm/cpu/armv7/cpu.c中定义
在arch/arm/cpu/armv7/ti81xx/lowlevel_init.s中生重定义
/**************************************************************************/
/*
* set the cpu to SVC32 mode
*/
mrs r0, cpsr
bic r0, r0, #0x1f
orr r0, r0, #0xd3
msr cpsr,r0
#if defined(CONFIG_OMAP34XX)
/* Copy vectors to mask ROM indirect addr */
adr r0, _start @ r0 <- current position of code
add r0, r0, #4 @ skip reset vector
mov r2, #64 @ r2 <- size to copy
add r2, r0, r2 @ r2 <- source end address
mov r1, #SRAM_OFFSET0 @ build vect addr
mov r3, #SRAM_OFFSET1
add r1, r1, r3
mov r3, #SRAM_OFFSET2
add r1, r1, r3
next:
ldmia r0!, {r3 - r10} @ copy from source address [r0]
stmia r1!, {r3 - r10} @ copy to target address [r1]
cmp r0, r2 @ until source end address [r2]
bne next @ loop until equal */
#if !defined(CONFIG_SYS_NAND_BOOT) && !defined(CONFIG_SYS_ONENAND_BOOT)
/* No need to copy/exec the clock code - DPLL adjust already done
* in NAND/oneNAND Boot.
*/
bl cpy_clk_code @ put dpll adjust code behind vectors
#endif /* NAND Boot */
#endif
/* the mask ROM code should have PLL and others stable */
#ifndef CONFIG_SKIP_LOWLEVEL_INIT
bl cpu_init_crit
/**************************************************************************/
cpu_init_crit在本文件中定义
/**************************************************************************/
#endif /* Set stackpointer in internal RAM to call board_init_f */ call_board_init_f: ldr sp, =(CONFIG_SYS_INIT_SP_ADDR) bic sp, sp, #7 /* 8-byte alignment for ABI compliance */ ldr r0,=0x00000000 bl board_init_f /*------------------------------------------------------------------------------*/
/**************************************************************************/
board_init_f在arch/arm/lib/board.c中定义,
/**************************************************************************/
/* * void relocate_code (addr_sp, gd, addr_moni) * * This "function" does not return, instead it continues in RAM * after relocating the monitor code. * */ .globl relocate_code relocate_code:
/**************************************************************************/
relocate_code由board_init_f返回，它的作用是初始化栈、清零bss段，之后跳到board_init_r，
并将
给gd指针和u-boot代码段地址()作为参数传进去
/**************************************************************************/
mov r4, r0 /* save addr_sp */
mov r5, r1 /* save addr of gd */
mov r6, r2 /* save addr of destination */
/* Set up the stack */
stack_setup:
mov sp, r4
adr r0, _start
cmp r0, r6
moveq r9, #0 /* no relocation. relocation offset(r9) = 0 */
beq clear_bss /* skip relocation */
mov r1, r6 /* r1 <- scratch for copy_loop */
ldr r3, _image_copy_end_ofs
add r2, r0, r3 /* r2 <- source end address */
copy_loop:
ldmia r0!, {r9-r10} /* copy from source address [r0] */
stmia r1!, {r9-r10} /* copy to target address [r1] */
cmp r0, r2 /* until source end address [r2] */
blo copy_loop
#ifndef CONFIG_SPL_BUILD
/*
* fix .rel.dyn relocations
*/
ldr r0, _TEXT_BASE /* r0 <- Text base */
sub r9, r6, r0 /* r9 <- relocation offset */
ldr r10, _dynsym_start_ofs /* r10 <- sym table ofs */
add r10, r10, r0 /* r10 <- sym table in FLASH */
ldr r2, _rel_dyn_start_ofs /* r2 <- rel dyn start ofs */
add r2, r2, r0 /* r2 <- rel dyn start in FLASH */
ldr r3, _rel_dyn_end_ofs /* r3 <- rel dyn end ofs */
add r3, r3, r0 /* r3 <- rel dyn end in FLASH */
fixloop:
ldr r0, [r2] /* r0 <- location to fix up, IN FLASH! */
add r0, r0, r9 /* r0 <- location to fix up in RAM */
ldr r1, [r2, #4]
and r7, r1, #0xff
cmp r7, #23 /* relative fixup? */
beq fixrel
cmp r7, #2 /* absolute fixup? */
beq fixabs
/* ignore unknown type of fixup */
b fixnext
fixabs:
/* absolute fix: set location to (offset) symbol value */
mov r1, r1, LSR #4 /* r1 <- symbol index in .dynsym */
add r1, r10, r1 /* r1 <- address of symbol in table */
ldr r1, [r1, #4] /* r1 <- symbol value */
add r1, r1, r9 /* r1 <- relocated sym addr */
b fixnext
fixrel:
/* relative fix: increase location by offset */
ldr r1, [r0]
add r1, r1, r9
fixnext:
str r1, [r0]
add r2, r2, #8 /* each rel.dyn entry is 8 bytes */
cmp r2, r3
blo fixloop
b clear_bss
_rel_dyn_start_ofs:
.word __rel_dyn_start - _start
_rel_dyn_end_ofs:
.word __rel_dyn_end - _start
_dynsym_start_ofs:
.word __dynsym_start - _start
#endif /* #ifndef CONFIG_SPL_BUILD */
clear_bss:
#ifdef CONFIG_SPL_BUILD
/* No relocation for SPL */
ldr r0, =__bss_start
ldr r1, =__bss_end__
#else
ldr r0, _bss_start_ofs
ldr r1, _bss_end_ofs
mov r4, r6 /* reloc addr */
add r0, r0, r4
add r1, r1, r4
#endif
mov r2, #0x00000000 /* clear */
clbss_l:str r2, [r0] /* clear loop... */
add r0, r0, #4
cmp r0, r1
bne clbss_l
/*
* We are done. Do not return, instead branch to second part of board
* initialization, now running from RAM.
*/
jump_2_ram:
/*
* If I-cache is enabled invalidate it
*/
#ifndef CONFIG_SYS_ICACHE_OFF
mcr p15, 0, r0, c7, c5, 0 @ invalidate icache
mcr p15, 0, r0, c7, c10, 4 @ DSB
mcr p15, 0, r0, c7, c5, 4 @ ISB
#endif
ldr r0, _board_init_r_ofs
adr r1, _start
add lr, r0, r1
add lr, lr, r9
/* setup parameters for board_init_r */
mov r0, r5 /* gd_t */
mov r1, r6 /* dest_addr */
/* jump to it ... */
mov pc, lr
/**************************************************************************/
跳到board_init_r，它在arch/arm/lib/board.c中定义,其中：
LDR R0，Label 将程序标号地址连续的4个字节（1个字）的数据传送到目的寄存器中
ADR R0, _start把 _start地址读出来，而且这个地址是相对当前pc的，所以和当前程序运行地址相关,r0是代码的当前位置
ldr r0, _board_init_r_ofs //r0=board_init_r - _start(board_init_r偏移地址)
adr r1, _start //r1=_start的运行地址
add lr, r0, r1 //lr=board_init_r的真正运行地址
add lr, lr, r9 //r9保存重定向偏移大小，spl中 r9 = 0
mov r0, r5 //r0 = &gdata
mov r1, r6 //r6=CONFIG_SPL_TEXT_BASE
mov pc, lr //跳转到board_init_r
/**************************************************************************/
_board_init_r_ofs: .word board_init_r - _start #ifndef CONFIG_SKIP_LOWLEVEL_INIT /************************************************************************* * * CPU_init_critical registers * * setup important registers * setup memory timing * *************************************************************************/ cpu_init_crit: /* * Invalidate L1 I/D */ 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 mcr p15, 0, r0, c7, c5, 6 @ invalidate BP array mcr p15, 0, r0, c7, c10, 4 @ DSB mcr p15, 0, r0, c7, c5, 4 @ ISB /* * disable MMU stuff and caches */ mrc p15, 0, r0, c1, c0, 0 bic r0, r0, #0x00002000 @ clear bits 13 (--V-) bic r0, r0, #0x00000007 @ clear bits 2:0 (-CAM) orr r0, r0, #0x00000002 @ set bit 1 (--A-) Align orr r0, r0, #0x00000800 @ set bit 11 (Z---) BTB #ifdef CONFIG_SYS_ICACHE_OFF bic r0, r0, #0x00001000 @ clear bit 12 (I) I-cache #else orr r0, r0, #0x00001000 @ set bit 12 (I) I-cache #endif mcr p15, 0, r0, c1, c0, 0 /* * Jump to board specific initialization... * The Mask ROM will have already initialized * basic memory. Go here to bump up clock rate and handle * wake up conditions. */ mov ip, lr @ persevere link reg across call bl lowlevel_init @ go setup pll,mux,memory
/**************************************************************************/
lowlevel_init在arch/arm/cpu/armv7/ti81xx/lowlevel_init.s中定义
/**************************************************************************/
mov lr, ip @ restore link
mov pc, lr @ back to my caller
#endif
#ifndef CONFIG_SPL_BUILD
/*
*************************************************************************
*
* 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 @ carve out a frame on current
@ user stack
stmia sp, {r0 - r12} @ Save user registers (now in
@ svc mode) r0-r12
ldr r2, IRQ_STACK_START_IN @ set base 2 words into abort
@ stack
ldmia r2, {r2 - r3} @ get values for "aborted" pc
@ and cpsr (into parm regs)
add r0, sp, #S_FRAME_SIZE @ grab pointer to old stack
add r5, sp, #S_SP
mov r1, lr
stmia r5, {r0 - r3} @ save sp_SVC, lr_SVC, pc, cpsr
mov r0, sp @ save current stack into r0
@ (param register)
.endm
.macro irq_save_user_regs
sub sp, sp, #S_FRAME_SIZE
stmia sp, {r0 - r12} @ Calling r0-r12
add r8, sp, #S_PC @ !! R8 NEEDS to be saved !!
@ a reserved stack spot would
@ be good.
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, IRQ_STACK_START_IN @ setup our mode stack (enter
@ in banked mode)
str lr, [r13] @ save caller lr in position 0
@ of saved stack
mrs lr, spsr @ get the spsr
str lr, [r13, #4] @ save spsr in position 1 of
@ saved stack
mov r13, #MODE_SVC @ prepare SVC-Mode
@ msr spsr_c, r13
msr spsr, r13 @ switch modes, make sure
@ moves will execute
mov lr, pc @ capture return pc
movs pc, lr @ jump to next instruction &
@ switch modes.
.endm
.macro get_bad_stack_swi
sub r13, r13, #4 @ space on current stack for
@ scratch reg.
str r0, [r13] @ save R0‘s value.
ldr r0, IRQ_STACK_START_IN @ get data regions start
@ spots for abort stack
str lr, [r0] @ save caller lr in position 0
@ of saved stack
mrs r0, spsr @ get the spsr
str lr, [r0, #4] @ save spsr in position 1 of
@ saved stack
ldr r0, [r13] @ restore r0
add r13, r13, #4 @ pop stack entry
.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_swi
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 effective 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 /* CONFIG_USE_IRQ */
#endif /* CONFIG_SPL_BUILD */
/***************************************************************************** * lowlevel_init: - Platform low level init. * Corrupted Register : r0, r1, r2, r3, r4, r5, r6 ****************************************************************************/ .globl lowlevel_init lowlevel_init: /* The link register is saved in ip by start.S */ mov r6, ip /* check if we are already running from RAM */ ldr r2, _lowlevel_init ldr r3, _TEXT_BASE sub r4, r2, r3 sub r0, pc, r4 /* require dummy instr or subtract pc by 4 instead i‘m doing stack init */ ldr sp, SRAM_STACK mark1: ldr r5, _mark1 sub r5, r5, r2 /* bytes between mark1 and lowlevel_init */ sub r0, r0, r5 /* r0 <- _start w.r.t current place of execution */ mov r10, #0x0 /* r10 has in_ddr used by s_init() */ #ifdef CONFIG_NOR_BOOT cmp r0, #0x08000000 /* check for running from NOR */ beq ocmc_init_start /* if == then running from NOR */ ands r0, r0, #0xC0000000 /* MSB 2 bits <> 0 then we are in ocmc or DDR */ cmp r0, #0x40000000 /* if running from ocmc */ beq nor_init_start /* if == skip ocmc init and jump to nor init */ mov r10, #0x01 /* if <> we are running from DDR hence skip ddr init */ /* by setting in_ddr to 1 */ b s_init_start /* and jump to s_init */
/**************************************************************************/
s_init_start在本源代最后部分定义
/**************************************************************************/
#else ands r0, r0, #0xC0000000 /* MSB 2 bits <> 0 then we are in ocmc or DDR */ cmp r0, #0x80000000 bne s_init_start mov r10, #0x01 b s_init_start #endif #ifdef CONFIG_NOR_BOOT ocmc_init_start: /**** enable ocmc 0 ****/ /* CLKSTCTRL */ ldr r5, cm_alwon_ocmc_0_clkstctrl_addr mov r2, #0x2 str r2, [r5] /* wait for gpmc enable to settle */ ocmc0_wait0: ldr r2, [r5] #ifdef CONFIG_AM335X ands r2, r2, #0x00000100 cmp r2, #0x00000100 #else ands r2, r2, #0x00000010 cmp r2, #0x00000010 #endif bne ocmc0_wait0 /* CLKCTRL */ ldr r5, cm_alwon_ocmc_0_clkctrl_addr mov r2, #0x2 str r2, [r5] /* wait for gpmc enable to settle */ ocmc0_wait1: ldr r2, [r5] ands r2, r2, #0x00030000 cmp r2, #0 bne ocmc0_wait1 #ifndef CONFIG_AM335X /**** enable ocmc 1 ****/ /* CLKSTCTRL */ ldr r5, cm_alwon_ocmc_1_clkstctrl_addr mov r2, #0x2 str r2, [r5] /* wait for gpmc enable to settle */ ocmc1_wait0: ldr r2, [r5] ands r2, r2, #0x00000100 cmp r2, #0x00000100 bne ocmc1_wait0 /* CLKCTRL */ ldr r5, cm_alwon_ocmc_1_clkctrl_addr mov r2, #0x2 str r2, [r5] /* wait for gpmc enable to settle */ ocmc1_wait1: ldr r2, [r5] ands r2, r2, #0x00030000 cmp r2, #0 bne ocmc1_wait1 #endif nor_init_start: /* gpmc init */ bl cpy_nor_gpmc_code /* copy nor gpmc init code to sram */ mov r0, pc add r0, r0, #12 /* 12 is for next three instructions */ mov lr, r0 /* gpmc init code in sram should return to s_init_start */ ldr r0, sram_pc_start mov pc, r0 /* transfer ctrl to nor_gpmc_init() in sram */ #endif s_init_start: mov r0, r10 /* passing in_ddr in r0 */ bl s_init
/**************************************************************************/
s_init在board/embest/devkit8600/evm.c中定义,
/**************************************************************************/
/* back to arch calling code */ mov pc, r6 /* the literal pools origin */ .ltorg #ifdef CONFIG_NOR_BOOT cm_alwon_ocmc_0_clkstctrl_addr: .word CM_ALWON_OCMC_0_CLKSTCTRL cm_alwon_ocmc_0_clkctrl_addr: .word CM_ALWON_OCMC_0_CLKCTRL #ifndef CONFIG_AM335X cm_alwon_ocmc_1_clkstctrl_addr: .word CM_ALWON_OCMC_1_CLKSTCTRL cm_alwon_ocmc_1_clkctrl_addr: .word CM_ALWON_OCMC_1_CLKCTRL #endif #endif SRAM_STACK: .word LOW_LEVEL_SRAM_STACK _mark1: .word mark1 _lowlevel_init: .word lowlevel_init _s_init_start: .word s_init_start
/*
* early system init of muxing and clocks.
*/
void s_init(void)
{
/* Can be removed as A8 comes up with L2 enabled */
l2_cache_enable();
/* WDT1 is already running when the bootloader gets control
* Disable it to avoid "random" resets
*/
__raw_writel(0xAAAA, WDT_WSPR);
while(__raw_readl(WDT_WWPS) != 0x0);
__raw_writel(0x5555, WDT_WSPR);
while(__raw_readl(WDT_WWPS) != 0x0);
#ifdef CONFIG_SPL_BUILD
/* Setup the PLLs and the clocks for the peripherals */
pll_init();
/* UART softreset */
u32 regVal;
u32 uart_base = DEFAULT_UART_BASE;
enable_uart0_pin_mux();
/* IA Motor Control Board has default console on UART3*/
/* XXX: This is before we‘ve probed / set board_id */
if (board_id == IA_BOARD) {
uart_base = UART3_BASE;
}
regVal = __raw_readl(uart_base + UART_SYSCFG_OFFSET);
regVal |= UART_RESET;
__raw_writel(regVal, (uart_base + UART_SYSCFG_OFFSET) );
while ((__raw_readl(uart_base + UART_SYSSTS_OFFSET) &
UART_CLK_RUNNING_MASK) != UART_CLK_RUNNING_MASK);
/* Disable smart idle */
regVal = __raw_readl((uart_base + UART_SYSCFG_OFFSET));
regVal |= UART_SMART_IDLE_EN;
__raw_writel(regVal, (uart_base + UART_SYSCFG_OFFSET));
/* Initialize the Timer */
init_timer();
preloader_console_init();
config_am335x_ddr();
#endif
}
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