移植Linux内核到norflash

开发板上只有Nor Flash，所以为了实现层次文件系统，需要为Linux2.6.20增加Nor Flash MTD驱动支持。其实工作量并不大，因为已经有现成的程序可供参考。

MTD的驱动程序都集中在drivers/mtd里面。我们需要做的，仅仅是在drivers/mtd/maps下增加自己的分区表。因为有参考的代码，所以比较容易。

（1）构建配置选项

首先，根据edb7312.c构建自己的mtd分区表驱动（根据cfi_flagadm.c这个文件也可以奥，看情况吧！）。

$cd drivers/mtd/maps/

$cp edb7312.c at91rm9200.c

然后，修改drivers/mtd/maps/Kconfig，增加自己的配置选项。

//拷贝过EDB7312稍作修改即可

config MTD_AT91RM9200

tristate "CFI Flash device mapped on AT91RM9200"

depends on ARM &&MTD_CFI

help

This enables access to the CFI Flash on the ATMEL AT91RM9200 DK board.

If you have such a board,say 'Y'here.

最后，修改Makefile，增加编译项目。

obj-$(CONFIG_MTD_EDB7312)+=edb7312.o

obj-$(CONFIG_MTD_AT91RM9200)+=at91rm9200.o

这样，自己建立的MTD分区表驱动就可以编译进内核了。

（2）修改分区表信息

因为第一步的工作中，at91rm9200.c实际上还是edb7312.c的内容，所以需要根据自己的开发板nor flash 的配置做一下修改。

#include

#include

#include

#include

#include

#include

#include

#ifdef CONFIG_MTD_PARTITIONS

#include

#endif

#define WINDOW_ADDR 0x10000000 /* physical properties of flash */

#define WINDOW_SIZE 0x00800000 /* intel 28F640J3A 8MB */

#define BUSWIDTH 2 /* data bus width 16bits */

/* can be "cfi_probe", "jedec_probe", "map_rom", NULL }; */

#define PROBETYPES {"cfi_probe",NULL}

#define MSG_PREFIX "AT91RM9200-NOR:"/* prefix for our printk()'s */

#define MTDID "at91rm9200-%d"/* for mtdparts= partitioning */

static struct mtd_info *mymtd;

struct map_info at91rm9200nor_map ={

.name ="NOR flash on AT91RM9200DK",

.size =WINDOW_SIZE,

.bankwidth =BUSWIDTH,

.phys =WINDOW_ADDR,

};

#ifdef CONFIG_MTD_PARTITIONS

/*

* MTD partitioning stuff

*/

static struct mtd_partition at91rm9200nor_partitions[5]= {

{

// U-boot 128KB

.name ="U-boot",

.size =0x20000,

.offset =0

},

{

// uImage 2MB

.name ="Kernel",

.size =0x200000,

.offset =0x20000

},

{

// RootFS 3MB

.name ="RootFS",

.size =0x300000,

.offset =0x220000

},

{

// UserFS

.name ="Jffs2",

.size =0x2C0000,

.offset =0x520000

},

{

// Parameters

.name ="Parameters",

.size =0x20000,

.offset =0x7E0000

},

};

static const char*probes[]={NULL};

#endif

static int mtd_parts_nb =0;

static struct mtd_partition *mtd_parts =0;

int__init init_at91rm9200nor(void)

{

static const char*rom_probe_types[]=PROBETYPES;

const char**type;

const char*part_type =0;

printk(KERN_NOTICE MSG_PREFIX "0x%08x at 0x%08x\n",

WINDOW_SIZE,WINDOW_ADDR);

at91rm9200nor_map.virt =ioremap(WINDOW_ADDR,WINDOW_SIZE);

if(!at91rm9200nor_map.virt){

printk(MSG_PREFIX "failed to ioremap\n");

return-EIO;

}

simple_map_init(&at91rm9200nor_map);

mymtd =0;

type =rom_probe_types;

for(;!mymtd &&*type;type++){

mymtd =do_map_probe(*type,&at91rm9200nor_map);

}

if(mymtd){

mymtd->owner =THIS_MODULE;

#ifdef CONFIG_MTD_PARTITIONS

mtd_parts_nb =parse_mtd_partitions(mymtd,probes,&mt d_parts,0);

if(mtd_parts_nb >0)

part_type ="detected";

if(mtd_parts_nb ==0)

{

mtd_parts =at91rm9200nor_partitions;

mtd_parts_nb =ARRAY_SIZE(at91rm9200nor_ partitions);

part_type ="static";

}

#endif

add_mtd_device(mymtd);

if(mtd_parts_nb ==0)

printk(KERN_NOTICE MSG_PREFIX "no partition info available\n");

else

{

printk(KERN_NOTICE MSG_PREFIX

"using %s partition defin ition\n",part_type);

//mymtd为master mtd_info它不被添加到数组mtd_table[]中，它只用于初始化

//每一个分区的mtd_info。而后将每一个分区对应的mtd_info添加到数组mtd_table[]

//供上层调用。MTD原始设备驱动层的主要工作就是向mtd_table[]中添加mtd_info。

add_mtd_partitions(mymtd,mtd_parts,mtd _parts_nb);

}

return0;

}

iounmap((void*)at91rm9200nor_map.virt);

return-ENXIO;

}

static void__exit cleanup_at91rm9200nor(void)

{

if(mymtd){

del_mtd_device(mymtd);

map_destroy(mymtd);

}

if(at91rm9200nor_map.virt){

iounmap((void*)at91rm9200nor_map.virt);

at91rm9200nor_map.virt =0;

}

}

module_init(init_at91rm9200nor);

module_exit(cleanup_at91rm9200nor);

MODULE_LICENSE("GPL");

MODULE_AUTHOR("Marius Groeger ");

MODULE_DESCRIPTION("Generic configurable MTD map driver");

（3）配置内核

增加MTD，和相应的文件系统的支持。

Devices Drivers --->

Memory Technology Devices (MTD) --->

<*> Memory Technology Device(MTD) support

<*> MTD partitioning support

<*> Direct char device access to MTD devices

<*> Caching block device access to MTD devices

RAM/ROM/Flash chip drivers --->

<*> Detect flash chips by Common Flash Interface(CFI) probe

<*> Support for Intel/Sharp flash chips

Mapping drivers for chip access --->

<*> CFI Flash device mapped on AT91RM9200

File Systems --->

Miscellaneous filesystems --->

<*>Journalling Flash File System v2 (JFFS2) support

<*>Compressed ROM file system support (cramfs)这里选择cramfs或者Jffs2的支持。

（4）编译，然后加载

make Image编译，然后制作成uImage。

这是JFFS2作为根文件系统的信息：

TOPDIR=$($(which pwd))

TMP=$TOPDIR/linux.bin

TARGET=$TOPDIR/uImage

arm-linux-objcopy -O binary -S vmlinux $TMP &&gzip -v9 $TMP &&\

mkimage -n 'RAM disk'-A arm -O linux -T kernel -C gzip \

-a 0x20008000 -e 0x20008000 -d $TMP.gz $TARGET &&\

cp $TARGET /mnt/hgfs/common &&\

rm -f $TMP*

可以看到MTD分区信息。进入shell界面，然后查看/proc/mtd，如下：

AT91RM9200-NOR:0x00800000 at 0x10000000

NOR flash on AT91RM9200DK:Found 1 x16 devices at 0x0 in 16-bit bank Intel/Sharp Extended Query Table at 0x0031

Using buffer write method

cfi_cmdset_0001:Erase suspend on write enabled

AT91RM9200-NOR:using static partition definition

Creating 5 MTD partitions on "NOR flash on AT91RM9200DK":

0x00000000-0x00020000 :"U-boot"

0x00020000-0x00220000 :"Kernel"

0x00220000-0x00520000 :"RootFS"

0x00520000-0x007e0000 :"Jffs2"

0x007e0000-0x00800000 :"Parameters"

可以看到加载是正确的。

内核：linux-2.6.37.3

nor flash芯片：SST39VF6401B

网上有文章说了如何让linux内核支持nor flash。不过那些转载的文章中没有头文件(因为使用了<尖括号>，在一些网页中是不会显示的，详细请参考HTML相关资料)。后来研究了类似的驱动文件，发现它们都是大同小异，只是在一些参数上有改变而已。本文中源代码基于那些转载文章的代码。

MTD设备驱动程序在./driver/mtd下面，分为nor flash和nand flash 两种。在chips中定义了几种访问nor的接口，包括cfi、jedec、map_ram和map_rom，而实际芯片所要添加的“驱动程序”放到maps 目录下(比如本文使用的s3c2440-flash.c文件，详见文章后面)。从map 这个单词来看，它描述的是一些映射信息，当然也包括了芯片信息，如总大小、块总数、访问接口等等。

这个过程其实是在内核代码树中添加自己的驱动的过程，当然是一些“标准”步骤了：在对应的代码树目录下，添加驱动源代码文件、在Makefile添加内容、在Kconfig添加内容，当然，还需要在make menuconfig里配置。

1、./driver/mtd/maps/Makefile

在这个Makefile最后添加：

obj-$(CONFIG_MTD_S3C2440) += s3c2440-flash.o

这个CONFIG_MTD_S3C2440由内核配置所得。

2、./driver/mtd/maps/Kconfig

在这个Kconfig文件最后添加(但在endmenu之前)：

config MTD_S3C2440

tristate “CFI Flash device mapped on S3C2440″

depends on ARM && MTD_CFI

help

This enables access to the CFI Flash on the SMDK2440 board.

If you have such a board, say ‘Y’ here.

这里的MTD_S3C2440就是前面Makefile中的那个，注意，CONFIG_前缀是内核自己添加的。可以在编译内核后生成的autoconf.h文件中查看该宏定义。

3、内核配置

在Device Drivers —> <*> Memory Technology Device (MTD) support —> 下面：

Mapping drivers for chip access —>

<*> CFI Flash device mapped on S3C2440

RAM/ROM/Flash chip drivers —>

<*> Detect flash chips by Common Flash Interface (CFI) probe [*] Flash chip driver advanced configuration options

[*] Specific CFI Flash geometry selection

[*] Support 16-bit buswidth

[*] Support 1-chip flash interleave

4、./driver/mtd/maps/s3c2440-flash.c

代码见文章后面。

这个文件主要是修改前面的几个宏定义。我特地添加一些调试语句。开始时我使用2.6.30.2内核，驱动中使用cfi_probe接口，但是没有显示分区信息，后来我添加多几个接口才发现它是使用map_rom。这个过程花费了一些时间。

在2.6.30.2内核中，启动信息如下：

S3C2440-NOR:0x00800000 at 0x01000000

S3C2440-NOR:func:init_s3c2440nor[120] mymtd:0 type:cfi_prob e

S3C2440-NOR:func:init_s3c2440nor[120] mymtd:0 type:jedec_pr obe

S3C2440-NOR:func:init_s3c2440nor[120] mymtd:c39cb600 type: map_rom

S3C2440-NOR:using static partition definition

Creating 4 MTD partitions on “NOR Flash(SST39VF6401B) on S3C2440″:

0x000000000000-0x000000030000 : “U-Boot”

0x000000030000-0x000000240000 : “Kernel”

0x000000240000-0x0000007f0000 : “RootFS(jffs2)”

0x0000007f0000-0x000000800000 : “Parameter”

可以看到，的确是使用map_rom接口。但是，当我使用2.6.37.2时，发现它使用的是cfi_probe接口，启动信息如下：

S3C2440-NOR:0x00800000 at 0x01000000

NOR Flash(SST39VF6401B) on S3C2440: Found 1 x16 devices at 0x0 in 16-bit bank.

Manufacturer ID 0x0000bf Chip ID 0x00236d

number of CFI chips: 1

## LL debug S3C2440-NOR:func:init_s3c2440nor[121] mymtd:c3 a19200 type:cfi_probe

mtd: Giving out device 0 to NOR Flash(SST39VF6401B) on S3C2 440

S3C2440-NOR:using static partition definition

Creating 4 MTD partitions on “NOR Flash(SST39VF6401B) on

S3C2440″:

0x000000000000-0x000000030000 : “U-Boot”

mtd: Giving out device 1 to U-Boot

0x000000030000-0x000000240000 : “Kernel”

mtd: Giving out device 2 to Kernel

0x000000240000-0x0000007f0000 : “Rootfs(jffs2)”

mtd: Giving out device 3 to Rootfs(jffs2)

0x0000007f0000-0x000000800000 : “Parameter”

mtd: Giving out device 4 to Parameter

与前面不同的是，它打印了芯片的信息，如厂商ID、芯片ID等等。这是我想不通的地方，也是我采用新内核的原因。

不过，在这片nor flash上使用jffs2文件系统却不成功，出现了大量的警告信息，提示说制作根文件系统时的erase block有问题。

s3c2440-flash.c源代码：

/*

* $Id: s3c2410.c,v 1.00 2006/12/05 10:18:14 gleixner Exp $

*

* Handle mapping of the NOR flash on Cogent S3C2410 boards *

* Copyright 2002 SYSGO Real-Time Solutions GmbH

*

*

This program is free software; you can redistribute it and/or mo dify

*

it under the terms of the GNU General Public License version 2 as

* published by the Free Software Foundation.

*/

/*

* Late Lee

*

This file is modified and the file name has changed to ‘s3c244 0-flash.c’.

*

The SMDK2440 board has only one flash bank which is a 64Mbit (4Mx16) SST SST39VF6401B;

* 128 x 64 KiB blocks.

*

* This code is GPLed.

*/

#include

#include

#include

#include

#include

#include

#include

#include

#ifdef CONFIG_MTD_PARTITIONS

#include

#endif

#define WINDOW_ADDR 0x01000000 /* physical properties of flash */

#define WINDOW_SIZE 0x800000 /* 8MB */

#define BUSWIDTH 2 /* 2*8 = 16 */

#define FLASH_BLOCKSIZE_MAIN 0x10000 /* 64KB(0x1000 0) 128 blocks */

#define FLASH_NUMBLOCKS_MAIN 128

/* can be “cfi_probe”, “jedec_probe”, “map_rom”, NULL }; */ #define PROBETYPES { “cfi_probe”, “jedec_probe”, “map_r om”, NULL }

#define MSG_PREFIX “S3C2440-NOR:” /* prefix for our print k()’s */

#define MTDID “s3c2440-nor” /* for mtdparts= partitio ning */

#define DEBUG_FLASH

#ifdef DEBUG_FLASH

#define flash_debug(fmt, args…) printk(KERN_NOTICE “## LL debug “ MSG_PREFIX fmt, ##args)

#else

#define flash_debug(fmt, args…)

#endif

static struct mtd_info *mymtd;

struct map_info s3c2440nor_map = {

.name = “NOR Flash(SST39VF6401B) on S3C2440″,

.size = WINDOW_SIZE,

.bankwidth = BUSWIDTH,

.phys = WINDOW_ADDR,

};

#ifdef CONFIG_MTD_PARTITIONS

/*

* MTD partitioning stuff

*/

static struct mtd_partition static_partitions[] = {

/*0: U-Boot: 0-0x30000 0x30000=192KB*/

{

.name = “U-Boot”,

.size = 0x030000,

.offset = 0x0,

},

/*1: Kernel: 0x30000-0x240000 0x210000=2112KB=2.0625MB*/ {

.name = “Kernel”,

.size = 0x210000,

.offset = 0x30000,

},

/*2: Rootfs(jffs2): 0x240000-0x7f0000 0x5b0000=5824KB=5.687 5MB*/

{

.name = “Rootfs(jffs2)”,

.size = 0x5b0000,

.offset = 0x240000,

},

/*3: U-Boot Parameters: 0x7f0000-0x800000 0x10000=64KB*/ {.name = “Parameter”,

.size = 0x010000,

.offset = 0x7f0000,

},

};

//static const char *probes[] = { “RedBoot”, “cmdlinepart”, NULL };

static const char *probes[] = { NULL };

#endif

static int mtd_parts_nb = 0;

static struct mtd_partition *mtd_parts = 0;

int __init init_s3c2440nor(void)

{

static const char *rom_probe_types[] = PROBETYPES;

const char **type;

const char *part_type = 0;

printk(KERN_NOTICE MSG_PREFIX “0x%08x at 0x%08xn”, WINDOW_SIZE, WINDOW_ADDR);

s3c2440nor_map.virt = ioremap(WINDOW_ADDR, WINDOW_SI ZE);

if (!s3c2440nor_map.virt) {

printk(MSG_PREFIX “failed to ioremapn”);

return -EIO;

}

simple_map_init(&s3c2440nor_map);

mymtd = 0;

type = rom_probe_types;

for(; !mymtd && *type; type++) {

mymtd = do_map_probe(*type, &s3c2440nor_map);

flash_debug(“func:%s[%d] mymtd:%x

type:%sn”, __func__, __LINE__, mymtd, *type);

}

if (mymtd) {

mymtd->owner = THIS_MODULE;

#ifdef CONFIG_MTD_PARTITIONS

mtd_parts_nb = parse_mtd_partitions(mymtd, probes, &mtd_pa rts, MTDID);

if (mtd_parts_nb > 0)

part_type = “detected”;

if (mtd_parts_nb == 0){

mtd_parts = static_partitions;

mtd_parts_nb = ARRAY_SIZE(static_partitions);

part_type = “static”;

}

#endif

add_mtd_device(mymtd);

if (mtd_parts_nb == 0)

printk(KERN_NOTICE MSG_PREFIX “no partition info availablen”);

else{

printk(KERN_NOTICE MSG_PREFIX

“using %s partition definitionn”, part_type); add_mtd_partitions(mymtd, mtd_parts, mtd_parts_nb);

}

return 0;

}

iounmap((void *)s3c2440nor_map.virt);

return -ENXIO;

}

static void __exit cleanup_s3c2440nor(void)

{

if (mymtd) {

del_mtd_device(mymtd);

map_destroy(mymtd);

}

if (s3c2440nor_map.virt) {

iounmap((void *)s3c2440nor_map.virt);

s3c2440nor_map.virt = 0;

}

}

module_init(init_s3c2440nor);

module_exit(cleanup_s3c2440nor);

MODULE_LICENSE(“GPL”);

MODULE_AUTHOR(“GengYaoJun “);

MODULE_DESCRIPTION(“Generic configurable MTD map driver”);