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Nor flash 驱动和移植
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??開發板上只有Nor?Flash，所以為了實現層次文件系統，需要為Linux2.6.20增加Nor?Flash?MTD驅動支持。其實工作量并不大，因為已經有現成的程序可供參考。
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????MTD的驅動程序都集中在drivers/mtd里面。我們需要做的，僅僅是在drivers/mtd/maps下增加自己的分區表。因為有參考的代碼，所以比較容易。
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（1）構建配置選項
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????首先，根據edb7312.c構建自己的mtd分區表驅動。
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| $cd?drivers/mtd/maps/
$cp?edb7312.c?at91rm9200.c |
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????然后，修改Kconfig，增加自己的配置選項。
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| //拷貝過EDB7312稍作修改即可
config?MTD_AT91RM9200
????????tristate?"CFI?Flash?device?mapped?on?AT91RM9200"
????????depends?on?ARM?&&?MTD_CFI
????????help
??????????This?enables?access?to?the?CFI?Flash?on?the?ATMEL?AT91RM9200DK?board.
??????????If?you?have?such?a?board,?say?'Y'?here. |
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????最后，修改Makefile，增加編譯項目。
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????這樣，自己建立的MTD分區表驅動就可以編譯進內核了。
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（2）修改分區表信息
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????因為第一步的工作中，at91rm9200.c實際上還是edb7312.c的內容，所以需要根據自己的開發板nor?flash的配置做一下修改。
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| obj-$(CONFIG_MTD_EDB7312)?+=?edb7312.o
obj-$(CONFIG_MTD_AT91RM9200)?+=?at91rm9200.o |
| #include?<linux/module.h>
#include?<linux/types.h>
#include?<linux/kernel.h>
#include?<linux/init.h>
#include?<asm/io.h>
#include?<linux/mtd/mtd.h>
#include?<linux/mtd/map.h>
#ifdef?CONFIG_MTD_PARTITIONS
#include?<linux/mtd/partitions.h>
#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,?&mtd_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?definition\n",?part_type); ?//mymtd為master?mtd_info它不被添加到數組mtd_table[]中，它只用于初始化 ?//每一個分區的mtd_info。而后將每一個分區對應的mtd_info添加到數組mtd_table[] ?//供上層調用。MTD原始設備驅動層的主要工作就是向?mtd_table[]中添加mtd_info。?
????????????????????????add_mtd_partitions(mymtd,?mtd_parts,?mtd_parts_nb);
????????????????}
????????????????return?0;
????????}
????????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?<mag@sysgo.de>");
MODULE_DESCRIPTION("Generic?configurable?MTD?map?driver"); |
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（3）配置內核
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????增加MTD，和相應的文件系統的支持。
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????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?--->
????????????????這里選擇cramfs或者Jffs2的支持。
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（4）編譯，然后加載
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????make?Image編譯，然后制作成uImage。
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????這是JFFS2作為根文件系統的信息：
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| 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* |
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????可以看到MTD分區信息。進入shell界面，然后查看/proc/mtd，如下：
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| 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" |
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????可以看到加載是正確的。
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