/*
* Memory Setup stuff - taken from blob memsetup.S
*
* Copyright (C) 1999 2000 2001 Erik Mouw (J.A.K.Mouw@its.tudelft.nl) and
* Jan-Derk Bakker (J.D.Bakker@its.tudelft.nl)
*
* Modified for the Samsung SMDK2410 by
* (C) Copyright 2002
* David Mueller, ELSOFT AG,
*
* 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
#include
#include
#include "tq210_val.h"
@ 讲start.S的时候已经说过这个TEXT_BASE了
_TEXT_BASE:
.word TEXT_BASE
.globl lowlevel_init
lowlevel_init:
push {lr} @ 将上一个函数的返回地址压入栈中
/* check reset status */
@ 检查复位标志,如果是睡眠唤醒,跳过接下来的初始化
ldr r0, =(ELFIN_CLOCK_POWER_BASE+RST_STAT_OFFSET) @ 跳转到目的地Reset Control Register的地址传送给r0 Address = 0xE010_A000 =0xE010_0000+0xA000
ldr r1, [r0] @ 将存储器地址为 R0(内存储的值) 的字数据读入寄存器 R1
bic r1, r1, #0xfff6ffff @将r1与0xfff6ffff的反码按位进行与运算(既和0xfff6ffff进行与非运算),并写入r1;结合上一步,可知,这一步的作用是16和19bit置一,其他位清零
cmp r1, #0x10000 @ 判断16bit是不是等于1
beq wakeup_reset_pre @ 如果是从睡眠状态唤醒,就跳转到wakeup_reset_pre,既跳过接下来的初始化
cmp r1, #0x80000 @ 判断是不是从深度空闲(Deep-IDLE)状态唤醒
beq wakeup_reset_from_didle @ 如果是,就跳转到wakeup_reset_from_didle
/* IO Retention release */
ldr r0, =(ELFIN_CLOCK_POWER_BASE + OTHERS_OFFSET) @ 将跳转目的地址MISC Register的地址传送给r0 Address = 0xE010_E000 =0xE010_0000+0xE000
ldr r1, [r0] @ 将存储器地址为 R0(内存储的值) 的字数据读入寄存器 R1
ldr r2, =IO_RET_REL @将IO_RET_REL( ((1 << 31) | (1 << 29) | (1 << 28)) )存入r2
orr r1, r1, r2 @ 将r1和r2的值进行或运算,结果存入r1
str r1, [r0] @ 将r1的值写入以r0内的值为地址的内存空间
/* Disable Watchdog */
@ 关闭看门狗
ldr r0, =ELFIN_WATCHDOG_BASE /* 0xE2700000 */
mov r1, #0
str r1, [r0]
/* SRAM(2MB) init for SMDKC110 */
/* GPJ1 SROM_ADDR_16to21 */
@ 配置sram引脚,16位数据宽度,22位地址宽度
ldr r0, =ELFIN_GPIO_BASE
ldr r1, [r0, #GPJ1CON_OFFSET]
bic r1, r1, #0xFFFFFF
ldr r2, =0x444444
orr r1, r1, r2
str r1, [r0, #GPJ1CON_OFFSET]
ldr r1, [r0, #GPJ1PUD_OFFSET]
ldr r2, =0x3ff
bic r1, r1, r2
str r1, [r0, #GPJ1PUD_OFFSET]
/* GPJ4 SROM_ADDR_16to21 */
ldr r1, [r0, #GPJ4CON_OFFSET]
bic r1, r1, #(0xf<<16)
ldr r2, =(0x4<<16)
orr r1, r1, r2
str r1, [r0, #GPJ4CON_OFFSET]
ldr r1, [r0, #GPJ4PUD_OFFSET]
ldr r2, =(0x3<<8)
bic r1, r1, r2
str r1, [r0, #GPJ4PUD_OFFSET]
/* CS0 - 16bit sram, enable nBE, Byte base address */
ldr r0, =ELFIN_SROM_BASE /* 0xE8000000 */
mov r1, #0x1
str r1, [r0]
/* PS_HOLD pin(GPH0_0) set to high */
@ 设置PMIC(Power Management IC)控制引脚,既电源管理ic引脚(基于I2C)
ldr r0, =(ELFIN_CLOCK_POWER_BASE + PS_HOLD_CONTROL_OFFSET)
ldr r1, [r0]
orr r1, r1, #0x300
orr r1, r1, #0x1
str r1, [r0]
/* when we already run in ram, we don't need to relocate U-Boot.
* and actually, memory controller must be configured before U-Boot
* is running in ram.
*/
/*下面的代码事实上只是判断pc和_TEXT_BASE(0X23e00000)的最高两位是否相同*/
/* 根据s5pv210的数据手册可知,首先,系统会运行固化在irom的BL0,紧接着会从外部nand
* 或sdcard等设备读取前16K的BL1代码到IRAM中的0xD0020000处。然后从0xD0020010处运行(因为前16byte是校验和的值)
* BL1的作用是初始化DRAM,拷贝BL2到DRAM中_TEXT_BASE(0X23e00000)处,然后跳到DRAM中运行
* 因此可以通过最高两位来判断代码是在哪里运行
* 同时可知,当代码已经就在DRAM中运行时,就必须跳过DRAM的初始化
*/
ldr r0, =0xff000fff
bic r1, pc, r0 /* r0
ldr r2, _TEXT_BASE /* r1
bic r2, r2, r0 /* r0
cmp r1, r2 /* compare r0, r1 */
beq 1f /* r0 == r1 then skip sdram init */
/* init PMIC chip */
#ifdef CONFIG_TQ210_IIC_PM_CHIP
bl PMIC_InitIp
#endif
/* init system clock */
@ 时钟初始化 PLL初始化,要想看懂此汇编,请查看datsheet中,clk control章节
bl system_clock_init
/* Memory initialize */
@ 内存初始化
bl mem_ctrl_asm_init
1:
/* for UART */
@ 串口初始化,要看懂此汇编, 请查看datsheet中, 请查看串口章节
bl uart_asm_init
bl tzpc_init
@ 这段不执行
#if defined(CONFIG_ONENAND)
bl onenandcon_init
#endif
@ nand初始化
#if defined(CONFIG_NAND)
/* simple init for NAND */
bl nand_asm_init
#endif
/* check reset status */
ldr r0, =(ELFIN_CLOCK_POWER_BASE+RST_STAT_OFFSET)
ldr r1, [r0]
bic r1, r1, #0xfffeffff
cmp r1, #0x10000
beq wakeup_reset_pre
/* ABB disable */
ldr r0, =0xE010C300
orr r1, r1, #(0x1<<23)
str r1, [r0]
/* Print 'K' */
ldr r0, =ELFIN_UART_CONSOLE_BASE
ldr r1, =0x4b4b4b4b
str r1, [r0, #UTXH_OFFSET]
pop {pc} @ 返回到start.S
wakeup_reset_from_didle: @ 从深度睡眠中唤醒
/* Wait when APLL is locked */
ldr r0, =ELFIN_CLOCK_POWER_BASE
lockloop:
ldr r1, [r0, #APLL_CON0_OFFSET]
and r1, r1, #(1<<29)
cmp r1, #(1<<29)
bne lockloop @ 这里使用循环
beq exit_wakeup
wakeup_reset_pre:
mrc p15, 0, r1, c1, c0, 1 @Read CP15 Auxiliary control register
and r1, r1, #0x80000000 @Check L2RD is disable or not
cmp r1, #0x80000000
bne wakeup_reset @if L2RD is not disable jump to wakeup_reset
bl disable_l2cache
bl v7_flush_dcache_all
/* L2 cache enable at sleep.S of kernel
* bl enable_l2cache
*/
#ifdef CONFIG_TQ210
bl enable_l2cache
#endif
wakeup_reset:
/* init system clock */
bl system_clock_init
bl mem_ctrl_asm_init
bl tzpc_init
#if defined(CONFIG_ONENAND)
bl onenandcon_init
#endif
#if defined(CONFIG_NAND)
bl nand_asm_init
#endif
exit_wakeup:
/*Load return address and jump to kernel*/
ldr r0, =(INF_REG_BASE+INF_REG0_OFFSET)
ldr r1, [r0] /* r1 = physical address of s5pc110_cpu_resume function*/
mov pc, r1 /*Jump to kernel */
nop
nop
/*
* system_clock_init: Initialize core clock and bus clock.
* void system_clock_init(void)
*/
system_clock_init:
/* 这一段的作用是将Clock Source Control Registers值清空
* 具体的作用是将VPLL_SEL、EPLL_SEL、MPLL_SEL和APLL_SEL的时钟源设置为FINVPLL,将MUX_MSYS_SEL、MUX_DSYS_SEL和MUX_PSYS_SEL时钟源设置为SCLKMPLL
* 将ONENAND_SEL时钟源设置为HCLK_PSYS
* 为什么这样设置,因为未设置 PLL 和各种分频系数之前,我们不能使用 PLL,为了保险起见,暂时直接使用频率较低
* 的外接的 24MHz 晶振,待设置好 PLL 和分频系数后再重新设置各种时钟开关
*/
ldr r0, =ELFIN_CLOCK_POWER_BASE @0xe0100000
/* Set Mux to FIN */
ldr r1, =0x0
str r1, [r0, #CLK_SRC0_OFFSET]
ldr r1, =APLL_LOCKTIME_VAL @将APLL_LOCKTIME_VAL(0x2cf)装入r1
str r1, [r0, #APLL_LOCK_OFFSET] @将r1内的值装入地址为(r0内的值+CLK_SRC0_OFFSET = 0xe0100000)的内存,即设置APLL的锁定周期
/*
* A PLL requires locking period when input frequency is changed or frequency division (multiplication) values are
* changed.PLL_LOCK register specifies this locking period, which is based on PLL’s source clock. During this
* period, output will be low state
*/
/* Disable PLL */
#if defined(CONFIG_CHECK_MPLL_LOCK)
retryloop:
#endif
ldr r1, =0x0
str r1, [r0, #APLL_CON0_OFFSET] @ 将APLL控制寄存器的值清空,这个寄存器的第31位置零关闭APLL 25-16bit配置MDIV的分频
@ 13-8bit配置PDIV的分频 2-0bit配置SDIV的分频
ldr r1, =0x0
str r1, [r0, #MPLL_CON_OFFSET] @ 配置MPLL
ldr r1, =0x0
str r1, [r0, #MPLL_CON_OFFSET] @ 重复配置MPLL,确保MPLL配置成功
ldr r1, [r0, #CLK_DIV0_OFFSET] @ Clock Divider Control Register(0xe0100300)
ldr r2, =CLK_DIV0_MASK @ CLK_DIV0_MASK(0x7fffffff)
bic r1, r1, r2 @ 首先清零
ldr r2, =
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