如何在uboot中添加驱动程序

Author：杨正date：2016.9.21

目的

在u-boot中添加驱动程序。

详细举例介绍

在uboot中 *** 作寄存器，实现对gpio及外围设备的控制有两种方法，一种是直接在arch/arm/lib/board.c中添加对寄存器的 *** 作代码，如：

#define muxctrl_reg50x200f0014#define GPIO6_DIR 0x201a0400#define GPIO6_1_DATA0x201a0008 #define GPIO6_1 (1 <<1)#define readl(addr) (*(volatile unsigned int*)(addr))#define writel(val, addr) ((*(volatile unsigned int *) (addr)) = (val)) int clear_irled(void){unsigned int reg_valreg_val = writel(0, muxctrl_reg5)// set gpio modereg_val = readl(GPIO6_DIR) reg_val |= GPIO6_1 writel(reg_val, GPIO6_DIR)reg_val = readl(GPIO6_1_DATA) reg_val &= ~GPIO6_1 writel(reg_val, GPIO6_1_DATA)return 0}void start_armboot (void){init_fnc_t **init_fnc_ptr char *s#ifdef CONFIG_HAS_SLAVEchar *e#endif#if defined(CONFIG_VFD) || defined(CONFIG_LCD)unsigned long addr#endif #ifdef CONFIG_HI3516A // defined in the include/configs/hi3516a.hclear_irled() // clear ir led, add by yangzheng 2016.9.21#endif

来自CODE的代码片

snippet_file_0.txt

另一种方法：

1、在driver/下新建hi_gpio目录，如：

[yangzheng@centos6 hi_gpio]$ ls

hi_gpio.c Makefile

hi_gpio.c内容如下：

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[yangzheng@centos6 hi_gpio]$ cat hi_gpio.c/********************************************************************************** Copyright: (C) 2016 Yang Zheng<Zheng.yang@avatarcontrols.com> * All rights reserved.** Filename: hi_gpio.c*Description: This file* *Version: 1.0.0(09/21/2016~)* Author: Yang Zheng <zheng.yang@avatarcontrols.com>* ChangeLog: 1, Release initial version on "09/21/2016 05:41:41 PM"* ********************************************************************************/#include<common.h>#define readl(addr) (*(volatile unsigned int *) (addr))#define writel(val, addr) (*(volatile unsigned int *) (addr) = (val)) #define muxctrl_reg5 0x200f0014#define GPIO6_DIR 0x201a0400#define GPIO6_1_DATA0x201a0008#define GPIO6_1 1 <<1#define REG_SET 1#define REG_CLR 0 #ifdef DEBUG#define DPRINTF(args...) printf(args)#else#define DPRINTF(args...)#endif int clear_irled(void){unsigned int reg_valreg_val = writel(REG_CLR, muxctrl_reg5)// set gpio modereg_val = readl(GPIO6_DIR) reg_val |= GPIO6_1 writel(reg_val, GPIO6_DIR)writel(REG_CLR, GPIO6_1_DATA) DPRINTF("clear ir led...\n")return 0}

来自CODE的代码片

snippet_file_0.txt

Makefile如下（可以拷贝driver目录下的各模块模板）：

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[yangzheng@centos6 hi_gpio]$ cat Makefile## Copyright 2000-2008# Wolfgang Denk, DENX Software Engineering, wd@denx.de.## See file CREDITS for list of people who contributed to this# project.## This program is free softwareyou can redistribute it and/or# modify it under the terms of the GNU General Public License as# published by the Free Software Foundationeither 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 WARRANTYwithout 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 programif not, write to the Free Software# Foundation, Inc., 59 Temple Place, Suite 330, Boston,# MA 02111-1307 USA# include $(TOPDIR)/config.mk LIB := $(obj)libhi_gpio.a COBJS-$(CONFIG_HI3516A_GPIO)+= hi_gpio.o COBJS := $(COBJS-y)SRCS:= $(COBJS:.o=.c)OBJS:= $(addprefix $(obj),$(COBJS)) all:$(LIB) $(LIB): $(obj).depend $(OBJS)$(AR) $(ARFLAGS) $@ $(OBJS) ######################################################################### # defines $(obj).depend targetinclude $(SRCTREE)/rules.mk sinclude $(obj).depend ########################################################################

来自CODE的代码片

snippet_file_0.txt

2、在顶层Makefile添加如下代码：

LIBS += drivers/hi_gpio/libhi_gpio.a

3、在include/configs/hi3516a.h中添加如下代码：

#define CONFIG_HI3516A_GPIO

在include下增加hi_gpio.h文件，内容如下：

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[yangzheng@centos6 u-boot-2010.06]$ cat include/hi_gpio.h/******************************************************************************** * Copyright: (C) 2016 Yang Zheng<Zheng.yang@avatarcontrols.com>* All rights reserved. * * Filename: hi_gpio.h *Description: This head file is control hisi gpio * *Version: 1.0.0(09/21/2016~) * Author: Yang Zheng <zheng.yang@avatarcontrols.com>* ChangeLog: 1, Release initial version on "09/21/2016 06:09:49 PM" * ********************************************************************************/#ifndef __HI_GPIO_H__#define __HI_GPIO_H__ extern int clear_irled(void)#endif

来自CODE的代码片

snippet_file_0.txt

4、在arch/arm/lib/board.c 里面调用即可，如：

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[yangzheng@centos6 u-boot-2010.06]$ vim arch/arm/lib/board.c void start_armboot (void){init_fnc_t **init_fnc_ptr char *s#ifdef CONFIG_HAS_SLAVEchar *e#endif#if defined(CONFIG_VFD) || defined(CONFIG_LCD)unsigned long addr#endif #ifdef CONFIG_HI3516A_GPIO clear_irled() // clear ir led, add by yangzheng 2016.9.21#endif……

来自CODE的代码片

snippet_file_0.txt

重新编译即可，调试uboot的方法：

如果设备有网口，可用tftp服务下载：

sf probe 0

mw.b 82000000 ff 0x80000

tftp 82000000 u-boot.bin

Go 82000000

如果没有网口，可用串口下载：

sf probe 0

mw.b 82000000 ff 0x80000

loady 82000000 u-boot.bin

go 82000000

本人用的android平台用的bootloader用的是uboot，貌似大多数手持设备平台都不用这个，因为功能过于强大用不上，反而显得太复杂了。不知道这个平台开发者是怎么想的。既然用了那就来分析一下，顺便修改一下其中的几个小问题，以符合我们的要求。

uboot等同于其他所有的bootloader程序，从根本上讲是一个稍复杂的裸机程序，是最底层的东西，要分析裸机程序我们要从它的连接文件开始。连 接文件（.lds文件）定义了程序编译之后整个连接过程，这样我们就可以找到这个程序的第一句汇编代码，进而来下一步分析。uboot的链接文件代码在 android\bootable\bootloader\uboot-imx\u-boot.lds

[cpp] view plaincopy

OUTPUT_FORMAT("elf32-littlearm", "elf32-littlearm", "elf32-littlearm") //文件输出格式

OUTPUT_ARCH(arm)

ENTRY(_start) //首地址标示符

SECTIONS

{

. = 0x00000000 //其实地址0

. = ALIGN(4) //4字节对齐

.text ://代码段

{

board/freescale/mx6q_sabresd/flash_header.o (.text.flasheader) //第一个文件是board/freescale/mx6q_sabresd/flash_header.o

cpu/arm_cortexa8/start.o //第二个cpu/arm_cortexa8/start.o

board/freescale/mx6q_sabresd/libmx6q_sabresd.a (.text)

lib_arm/libarm.a (.text)

net/libnet.a (.text)

drivers/mtd/libmtd.a (.text)

drivers/mmc/libmmc.a (.text)

. = DEFINED(env_offset) ? env_offset : .

common/env_embedded.o(.text)

*(.text) //剩余的所有代码

}

. = ALIGN(4)

.rodata : { *(SORT_BY_ALIGNMENT(SORT_BY_NAME(.rodata*))) } //readonly data 段

. = ALIGN(4)

.data : { *(.data) } //所有的readonly data

. = ALIGN(4)

.got : { *(.got) }

. = .

__u_boot_cmd_start = . //u_boot_cmd段，里面是所有uboot命令的一个列表

.u_boot_cmd : { *(.u_boot_cmd) }

__u_boot_cmd_end = .

. = ALIGN(4)

_end_of_copy = .

__bss_start = . //bss段 就是内存数据段

.bss : { *(.bss) }

_end = .

}

从上面的代码可以看出我们编译生成的二进制应用程序组成是：代码段->rodata段->uboot命令列表->bss段。我们启动这个应用程序时候是从，0地址开始的，因此我们来看

board/freescale/mx6q_sabresd/flash_header.s这个文件。

这个文件中除了分配内存和宏定义的伪汇编指令以外，真正执行的命令有一条

[cpp] view plaincopy

.section ".text.flasheader", "x"

b _start

.orgCONFIG_FLASH_HEADER_OFFSET

也就是说，这个文件一执行就直接跳到_start 位置处。_start 在android\bootable\bootloader\uboot-imx\cpu\arm_cortexa8\ start.S中，因此我们来看这个文件代码

[cpp] view plaincopy

.globl _start

_start: b reset

这里直接跳转的reset中接下来看

[csharp] view plaincopy

reset:

/*

* set the cpu to SVC32 modecpu设置成32位管理模式

*/

mrs r0, cpsr

bic r0, r0, #0x1f

orr r0, r0, #0xd3

msr cpsr,r0

#if (CONFIG_OMAP34XX) //因为我们的cpu不是ompa的 所以这段不会编译

.............................

#endif

/* the mask ROM code should have PLL and others stable */

#ifndef CONFIG_SKIP_LOWLEVEL_INIT

bl cpu_init_crit

#endif

这里接下来执行cpu_init_crit

[csharp] view plaincopy

/*************************************************************************

*

* 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

/*

* disable MMU stuff and caches //关闭mmu

*/

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 12 (Z---) BTB

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//执行lowlevel_init这个函数代码在

@\bootloader\uboot-imx\board\freescale\mx6q_sabresd\lowlevel_init.S中

@主要对时钟,外部ram，rom等进行了初始化代码不贴了。

mov lr, ip @ restore link

mov pc, lr @ back to my caller

初始化完成后，接下来执行

[csharp] view plaincopy

#ifndef CONFIG_SKIP_RELOCATE_UBOOT

relocate: @ relocate U-Boot to RAM将uboot重新定位到内存中

adr r0, _start @ r0 <- current position of code

ldr r1, _TEXT_BASE @ test if we run from flash or RAM

cmp r0, r1 @ don't reloc during debug测试当前代码是否已经在内存中

beq stack_setup @如果在的话就直接跳转到stack_setup

ldr r2, _armboot_start @如果不在的话，加载_armboot_start地址到r2中。_armboot_start是uboot执行的主体c函数。

ldr r3, _bss_start

sub r2, r3, r2 @ r2 <- size of armboot计算bss_start-armboot_start 保存到R2中，也就是uboot的总大小

add r2, r0, r2 @ r2 <- source end address 计算出uboot代码和rodata地址

copy_loop: @ copy 32 bytes at a time //开始拷贝

ldmia r0!, {r3 - r10} @ copy from source address [r0]

stmia r1!, {r3 - r10} @ copy to target address [r1]

cmp r0, r2 @ until source end addreee [r2]

ble copy_loop

#endif /* CONFIG_SKIP_RELOCATE_UBOOT */

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