2015版uboot的启动过程及网卡驱动结构分析
启动流程和上篇博文介绍的rtems类似
首先是start.s：
在这里选择arm的arm7作为例子分析，代码：/arch/arm/cpu/armv7/start.s
/*
* armboot - Startup Code for OMAP3530/ARM Cortex CPU-core
*
* Copyright (c) 2004 Texas Instruments
*
* Copyright (c) 2001 Marius Gröger
* Copyright (c) 2002 Alex Züpke
* Copyright (c) 2002 Gary Jennejohn
* Copyright (c) 2003 Richard Woodruff
* Copyright (c) 2003 Kshitij
* Copyright (c) 2006-2008 Syed Mohammed Khasim
*
* SPDX-License-Identifier: GPL-2.0+
*/
#include
#include
#include
#include
/*************************************************************************
*
* Startup Code (reset vector) //这是真正的启动代码
*
* 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 reset
.globl save_boot_params_ret
reset:
/* Allow the board to save important registers */
b save_boot_params
save_boot_params_ret:
/*
* disable interrupts (FIQ and IRQ), also set the cpu to SVC32 mode,
* except if in HYP mode already
*/
mrs r0, cpsr
and r1, r0, #0x1f @ mask mode bits
teq r1, #0x1a @ test for HYP mode
bicne r0, r0, #0x1f @ clear all mode bits
orrne r0, r0, #0x13 @ set SVC mode
orr r0, r0, #0xc0 @ disable FIQ and IRQ
msr cpsr,r0
/*
* Setup vector:
* (OMAP4 spl TEXT_BASE is not 32 byte aligned.
* Continue to use ROM code vector only in OMAP4 spl)
*/
#if !(defined(CONFIG_OMAP44XX) && defined(CONFIG_SPL_BUILD))
/* Set V=0 in CP15 SCTLR register - for VBAR to point to vector */
mrc p15, 0, r0, c1, c0, 0 @ Read CP15 SCTLR Register
bic r0, #CR_V @ V = 0
mcr p15, 0, r0, c1, c0, 0 @ Write CP15 SCTLR Register
/* Set vector address in CP15 VBAR register */
ldr r0, =_start
mcr p15, 0, r0, c12, c0, 0 @Set VBAR
#endif
/* the mask ROM code should have PLL and others stable */
#ifndef CONFIG_SKIP_LOWLEVEL_INIT
bl cpu_init_cp15
bl cpu_init_crit
#endif
bl _main
/*------------------------------------------------------------------------------*/
ENTRY(c_runtime_cpu_setup)
/*
* 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
bx lr
ENDPROC(c_runtime_cpu_setup)
/*************************************************************************
*
* void save_boot_params(u32 r0, u32 r1, u32 r2, u32 r3)
* __attribute__((weak));
*
* Stack pointer is not yet initialized at this moment
* Don't save anything to stack even if compiled with -O0
*
*************************************************************************/
ENTRY(save_boot_params)
b save_boot_params_ret @ back to my caller
ENDPROC(save_boot_params)
.weak save_boot_params
/*************************************************************************
*
* cpu_init_cp15
*
* Setup CP15 registers (cache, MMU, TLBs). The I-cache is turned on unless
* CONFIG_SYS_ICACHE_OFF is defined.
*
*************************************************************************/
ENTRY(cpu_init_cp15)
/*
* 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
#ifdef CONFIG_ARM_ERRATA_716044
mrc p15, 0, r0, c1, c0, 0 @ read system control register
orr r0, r0, #1 << 11 @ set bit #11
mcr p15, 0, r0, c1, c0, 0 @ write system control register
#endif
#if (defined(CONFIG_ARM_ERRATA_742230) || defined(CONFIG_ARM_ERRATA_794072))
mrc p15, 0, r0, c15, c0, 1 @ read diagnostic register
orr r0, r0, #1 << 4 @ set bit #4
mcr p15, 0, r0, c15, c0, 1 @ write diagnostic register
#endif
#ifdef CONFIG_ARM_ERRATA_743622
mrc p15, 0, r0, c15, c0, 1 @ read diagnostic register
orr r0, r0, #1 << 6 @ set bit #6
mcr p15, 0, r0, c15, c0, 1 @ write diagnostic register
#endif
#ifdef CONFIG_ARM_ERRATA_751472
mrc p15, 0, r0, c15, c0, 1 @ read diagnostic register
orr r0, r0, #1 << 11 @ set bit #11
mcr p15, 0, r0, c15, c0, 1 @ write diagnostic register
#endif
#ifdef CONFIG_ARM_ERRATA_761320
mrc p15, 0, r0, c15, c0, 1 @ read diagnostic register
orr r0, r0, #1 << 21 @ set bit #21
mcr p15, 0, r0, c15, c0, 1 @ write diagnostic register
#endif
mov r5, lr @ Store my Caller
mrc p15, 0, r1, c0, c0, 0 @ r1 has Read Main ID Register (MIDR)
mov r3, r1, lsr #20 @ get variant field
and r3, r3, #0xf @ r3 has CPU variant
and r4, r1, #0xf @ r4 has CPU revision
mov r2, r3, lsl #4 @ shift variant field for combined value
orr r2, r4, r2 @ r2 has combined CPU variant + revision
#ifdef CONFIG_ARM_ERRATA_798870
cmp r2, #0x30 @ Applies to lower than R3p0
bge skip_errata_798870 @ skip if not affected rev
cmp r2, #0x20 @ Applies to including and above R2p0
blt skip_errata_798870 @ skip if not affected rev
mrc p15, 1, r0, c15, c0, 0 @ read l2 aux ctrl reg
orr r0, r0, #1 << 7 @ Enable hazard-detect timeout
push {r1-r5} @ Save the cpu info registers
bl v7_arch_cp15_set_l2aux_ctrl
isb @ Recommended ISB after l2actlr update
pop {r1-r5} @ Restore the cpu info - fall through
skip_errata_798870:
#endif
#ifdef CONFIG_ARM_ERRATA_801819
cmp r2, #0x24 @ Applies to lt including R2p4
bgt skip_errata_801819 @ skip if not affected rev
cmp r2, #0x20 @ Applies to including and above R2p0
blt skip_errata_801819 @ skip if not affected rev
mrc p15, 0, r0, c0, c0, 6 @ pick up REVIDR reg
and r0, r0, #1 << 3 @ check REVIDR[3]
cmp r0, #1 << 3
beq skip_errata_801819 @ skip erratum if REVIDR[3] is set
mrc p15, 0, r0, c1, c0, 1 @ read auxilary control register
orr r0, r0, #3 << 27 @ Disables streaming. All write-allocate
@ lines allocate in the L1 or L2 cache.
orr r0, r0, #3 << 25 @ Disables streaming. All write-allocate
@ lines allocate in the L1 cache.
push {r1-r5} @ Save the cpu info registers
bl v7_arch_cp15_set_acr
pop {r1-r5} @ Restore the cpu info - fall through
skip_errata_801819:
#endif
#ifdef CONFIG_ARM_ERRATA_454179
cmp r2, #0x21 @ Only on < r2p1
bge skip_errata_454179
mrc p15, 0, r0, c1, c0, 1 @ Read ACR
orr r0, r0, #(0x3 << 6) @ Set DBSM(BIT7) and IBE(BIT6) bits
push {r1-r5} @ Save the cpu info registers
bl v7_arch_cp15_set_acr
pop {r1-r5} @ Restore the cpu info - fall through
skip_errata_454179:
#endif
#ifdef CONFIG_ARM_ERRATA_430973
cmp r2, #0x21 @ Only on < r2p1
bge skip_errata_430973
mrc p15, 0, r0, c1, c0, 1 @ Read ACR
orr r0, r0, #(0x1 << 6) @ Set IBE bit
push {r1-r5} @ Save the cpu info registers
bl v7_arch_cp15_set_acr
pop {r1-r5} @ Restore the cpu info - fall through
skip_errata_430973:
#endif
#ifdef CONFIG_ARM_ERRATA_621766
cmp r2, #0x21 @ Only on < r2p1
bge skip_errata_621766
mrc p15, 0, r0, c1, c0, 1 @ Read ACR
orr r0, r0, #(0x1 << 5) @ Set L1NEON bit
push {r1-r5} @ Save the cpu info registers
bl v7_arch_cp15_set_acr
pop {r1-r5} @ Restore the cpu info - fall through
skip_errata_621766:
#endif
mov pc, r5 @ back to my caller
ENDPROC(cpu_init_cp15)
#ifndef CONFIG_SKIP_LOWLEVEL_INIT
/*************************************************************************
*
* CPU_init_critical registers
*
* setup important registers
* setup memory timing
*
*************************************************************************/
ENTRY(cpu_init_crit)
/*
* 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.
*/
b lowlevel_init @ go setup pll,mux,memory
ENDPROC(cpu_init_crit)
#endif 这部分主要是汇编编写。
然后进入main_loop函数中：
文件：common/main.c
void main_loop(void)
{
const char *s;
bootstage_mark_name(BOOTSTAGE_ID_MAIN_LOOP, "main_loop");
#ifndef CONFIG_SYS_GENERIC_BOARD
puts("Warning: Your board does not use generic board. Please read\n");
puts("doc/README.generic-board and take action. Boards not\n");
puts("upgraded by the late 2014 may break or be removed.\n");
#endif
modem_init();
#ifdef CONFIG_VERSION_VARIABLE
setenv("ver", version_string); /* set version variable */
#endif /* CONFIG_VERSION_VARIABLE */
cli_init();
run_preboot_environment_command();
#if defined(CONFIG_UPDATE_TFTP)
update_tftp(0UL, NULL, NULL);
#endif /* CONFIG_UPDATE_TFTP */
s = bootdelay_process();
if (cli_process_fdt(&s))
cli_secure_boot_cmd(s);
autoboot_command(s);
cli_loop();
}
其中bootdelay_process函数是为了获取各种bootcmd环境变量：
文件：autoboot.c
const char *bootdelay_process(void)
{
char *s;
int bootdelay;
#ifdef CONFIG_BOOTCOUNT_LIMIT
unsigned long bootcount = 0;
unsigned long bootlimit = 0;
#endif /* CONFIG_BOOTCOUNT_LIMIT */
#ifdef CONFIG_BOOTCOUNT_LIMIT
bootcount = bootcount_load();
bootcount++;
bootcount_store(bootcount);
setenv_ulong("bootcount", bootcount);
bootlimit = getenv_ulong("bootlimit", 10, 0);
#endif /* CONFIG_BOOTCOUNT_LIMIT */
s = getenv("bootdelay");
bootdelay = s ? (int)simple_strtol(s, NULL, 10) : CONFIG_BOOTDELAY;
#ifdef CONFIG_OF_CONTROL
bootdelay = fdtdec_get_config_int(gd->fdt_blob, "bootdelay",
bootdelay);
#endif
debug("### main_loop entered: bootdelay=%d\n\n", bootdelay);
#if defined(CONFIG_MENU_SHOW)
bootdelay = menu_show(bootdelay);
#endif
bootretry_init_cmd_timeout();
#ifdef CONFIG_POST
if (gd->flags & GD_FLG_POSTFAIL) {
s = getenv("failbootcmd");
} else
#endif /* CONFIG_POST */
#ifdef CONFIG_BOOTCOUNT_LIMIT
if (bootlimit && (bootcount > bootlimit)) {
printf("Warning: Bootlimit (%u) exceeded. Using altbootcmd.\n",
(unsigned)bootlimit);
s = getenv("altbootcmd");
} else
#endif /* CONFIG_BOOTCOUNT_LIMIT */
s = getenv("bootcmd");
process_fdt_options(gd->fdt_blob);
stored_bootdelay = bootdelay;
return s;
}该函数首先是获取了bootdelay，将其作为按键触发时间限制，这个待会讨论。函数最后，s是获得了bootcmd变量的数据，然后将其返回。
返回到main_loop函数。接下去执行autoboot_command函数：
文件：autoboot.c
void autoboot_command(const char *s)
{
debug("### main_loop: bootcmd=\"%s\"\n", s ? s : "");
if (stored_bootdelay != -1 && s && !abortboot(stored_bootdelay)) {
#if defined(CONFIG_AUTOBOOT_KEYED) && !defined(CONFIG_AUTOBOOT_KEYED_CTRLC)
int prev = disable_ctrlc(1); /* disable Control C checking */
#endif
run_command_list(s, -1, 0);
#if defined(CONFIG_AUTOBOOT_KEYED) && !defined(CONFIG_AUTOBOOT_KEYED_CTRLC)
disable_ctrlc(prev); /* restore Control C checking */
#endif
}
#ifdef CONFIG_MENUKEY
if (menukey == CONFIG_MENUKEY) {
s = getenv("menucmd");
if (s)
run_command_list(s, -1, 0);
}
#endif /* CONFIG_MENUKEY */
} 该函数首先判断bootdelay，利用一个判断式：if (stored_bootdelay != -1 && s && !abortboot(stored_bootdelay))
该判断式中调用了abortboot函数：
static int abortboot(int bootdelay)
{
#ifdef CONFIG_AUTOBOOT_KEYED
return abortboot_keyed(bootdelay);
#else
return abortboot_normal(bootdelay);
#endif
}
这里没有定义CONFIG_AUTOBOOT_KEYED，这个宏定义的意思是定义了指定按键，我们是按任意键停止boot，所以没有定义，执行abortboot_normal函数。
abortboot_normal：
static int abortboot_normal(int bootdelay)
{
int abort = 0;
unsigned long ts;
#ifdef CONFIG_MENUPROMPT
printf(CONFIG_MENUPROMPT);
#else
if (bootdelay >= 0)
printf("Hit any key to stop autoboot: %2d ", bootdelay);
#endif
#if defined CONFIG_ZERO_BOOTDELAY_CHECK
/*
* Check if key already pressed
* Don't check if bootdelay < 0
*/
if (bootdelay >= 0) {
if (tstc()) { /* we got a key press */
(void) getc(); /* consume input */
puts("\b\b\b 0");
abort = 1; /* don't auto boot */
}
}
#endif
while ((bootdelay > 0) && (!abort)) {
--bootdelay;
/* delay 1000 ms */
ts = get_timer(0);
do {
if (tstc()) { /* we got a key press */
abort = 1; /* don't auto boot */
bootdelay = 0; /* no more delay */
# ifdef CONFIG_MENUKEY
menukey = getc();
# else
(void) getc(); /* consume input */
# endif
break;
}
udelay(10000);
} while (!abort && get_timer(ts) < 1000);
printf("\b\b\b%2d ", bootdelay);
}
putc('\n');
#ifdef CONFIG_SILENT_CONSOLE
if (abort)
gd->flags &= ~GD_FLG_SILENT;
#endif
return abort;
}这里判断如果bootdelay是大于0的，也就是定义了bootdelay时间，那么打印Hit any key to stop autoboot:，提示敲击任意键即可终止，然后函数开始检测有无按键按下：
if (tstc()) { /* we got a key press */ 如果有按键按下
abort = 1; /* don't auto boot */ 将abort置为1
bootdelay = 0; //将bootdelay设置为0最后函数返回abort。
然后回到autoboot_command函数的判断式中，如果按键没有按下，也就是abort函数返回0，判断式条件成立，将禁用ctrl+c按键，并调用run_command_list函数，该函数执行从环境变量读取的bootcmd的值，也就是s。
该函数在cli.c文件中：
int run_command_list(const char *cmd, int len, int flag)
{
int need_buff = 1;
char *buff = (char *)cmd; /* cast away const */
int rcode = 0;
if (len == -1) {
len = strlen(cmd);
#ifdef CONFIG_SYS_HUSH_PARSER
/* hush will never change our string */
need_buff = 0;
#else
/* the built-in parser will change our string if it sees \n */
need_buff = strchr(cmd, '\n') != NULL;
#endif
}
if (need_buff) {
buff = malloc(len + 1);
if (!buff)
return 1;
memcpy(buff, cmd, len);
buff[len] = '\0';
}
#ifdef CONFIG_SYS_HUSH_PARSER
rcode = parse_string_outer(buff, FLAG_PARSE_SEMICOLON);
#else
/*
* This function will overwrite any \n it sees with a \0, which
* is why it can't work with a const char *. Here we are making
* using of internal knowledge of this function, to avoid always
* doing a malloc() which is actually required only in a case that
* is pretty rare.
*/
rcode = cli_simple_run_command_list(buff, flag);
if (need_buff)
free(buff);
#endif
return rcode;
}该函数通过parse_string_outer函数调用了bush_shell的命令解释器parse_stream_outer函数来解释bootcmd的命令，而环境变量bootcmd的启动命令用来设置linux必要的启动环境，然后加载和启动内核。
回到上面，如果有按键进行干预，那么判读式不成立，跳出执行menucmd命令：
#ifdef CONFIG_MENUKEY
if (menukey == CONFIG_MENUKEY) {
s = getenv("menucmd");
if (s)
run_command_list(s, -1, 0);
}s = getenv("menucmd");是用来获取在uboot命令行下输入的命令，menucmd就是存储命令的环境变量。然后同样运行run_command_list进行命令解释，然后跳回到main_loop函数，执行最后的cli_loop函数，也就是进入了uboot命令行模式。
以上就是uboot的启动过程的分析。
接下来简单说说uboot对于网卡驱动的结构：
首先是最底层的驱动文件，在这里选择cpsw.c驱动文件进行分析，这是ti公司处理器所独创的一种驱动方式：
文件：driver/net/cpsw.c
这里面包含了cpsw的发送，接受，初始化，注册等。
int cpsw_register(struct cpsw_platform_data *data)
{
struct cpsw_priv *priv;
struct cpsw_slave *slave;
void *regs = (void *)data->cpsw_base;
struct eth_device *dev;
dev = calloc(sizeof(*dev), 1);
if (!dev)
return -ENOMEM;
priv = calloc(sizeof(*priv), 1);
if (!priv) {
free(dev);
return -ENOMEM;
}
priv->data = *data;
priv->dev = dev;
priv->slaves = malloc(sizeof(struct cpsw_slave) * data->slaves);
if (!priv->slaves) {
free(dev);
free(priv);
return -ENOMEM;
}
priv->host_port = data->host_port_num;
priv->regs = regs;
priv->host_port_regs = regs + data->host_port_reg_ofs;
priv->dma_regs = regs + data->cpdma_reg_ofs;
priv->ale_regs = regs + data->ale_reg_ofs;
priv->descs = (void *)regs + data->bd_ram_ofs;
int idx = 0;
for_each_slave(slave, priv) {
cpsw_slave_setup(slave, idx, priv);
idx = idx + 1;
}
strcpy(dev->name, "cpsw");
dev->iobase = 0;
dev->init = cpsw_init;
dev->halt = cpsw_halt;
dev->send = cpsw_send;
dev->recv = cpsw_recv;
dev->priv = priv;
eth_register(dev);
cpsw_mdio_init(dev->name, data->mdio_base, data->mdio_div);
priv->bus = miiphy_get_dev_by_name(dev->name);
for_active_slave(slave, priv)
cpsw_phy_init(dev, slave);
return 1;
}然后是smsc的一个注册函数，注册具体的以太网芯片，这里选择lan8710：
文件：net/phy/smsc.c
static struct phy_driver lan8710_driver = {
.name = "SMSC LAN8710/LAN8720",
.uid = 0x0007c0f0,
.mask = 0xffff0,
.features = PHY_BASIC_FEATURES,
.config = &genphy_config_aneg,
.startup = &genphy_startup,
.shutdown = &genphy_shutdown,
};
int phy_smsc_init(void)
{
phy_register(&lan8710_driver);
phy_register(&lan911x_driver);
phy_register(&lan8700_driver);
return 0;
}phy_smsc_init函数包含在phy_init()函数中，然后phy_init()函数包含在miiphy_init函数中，位于miiphyinit.c，然后该函数包含在eth_common_init函数中，位于eth.c文件中，然后该函数包含在eth_initialize函数中，位于eth.c中。然后该函数包含在board_eth_init函数中，位于board.c文件中，然后在uboot初始化时，调用board_eth_init函数从而完成网络驱动的注册和初始化。