嵌入式

Linux移植添加norflash MTD分区

2019-07-13 06:55发布

站内文章 / 嵌入式Linux
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    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。 /* * $Id: edb7312.c,v 1.14 2005/11/07 11:14:27 gleixner Exp $ * * Handle mapping of the NOR flash on Cogent EDB7312 boards * * Copyright 2002 SYSGO Real-Time Solutions GmbH * * This program is free software; you can redistribute it and/or modify * it under the terms of the GNU General Public License version 2 as * published by the Free Software Foundation. */ #include #include #include #include #include #include #include #ifdef CONFIG_MTD_PARTITIONS #include #endif #define WINDOW_ADDR 0x00000000 /* NOR FLASH物理地址 */ #define WINDOW_SIZE 0x01000000 /* NOR FLASH大小 */ #define BUSWIDTH 2 #define FLASH_BLOCKSIZE_MAIN 0x20000 #define FLASH_NUMBLOCKS_MAIN 128 /* can be "cfi_probe", "jedec_probe", "map_rom", NULL }; */ #define PROBETYPES { "cfi_probe", NULL } /* 探测的接口类型，可以是"cfi_probe", "jedec_probe", "map_rom", NULL }; */ #define MSG_PREFIX "EDB7312-NOR:" /* prefix for our printk()'s */ /*printk的前缀 */ #define MTDID "edb7312-nor" /* for mtdparts= partitioning */ /*MTD驱动*/ static struct mtd_info *mymtd; /*定义一个map_info，代表一块norflash*/ struct map_info edb7312nor_map = { .name = "NOR flash on EDB7312", .size = WINDOW_SIZE, .bankwidth = BUSWIDTH, .phys = WINDOW_ADDR, }; #ifdef CONFIG_MTD_PARTITIONS /* * MTD partitioning stuff */ /* 默认分区信息*/ static struct mtd_partition static_partitions[3] = { { .name = "ARMboot", .size = 0x40000, //256K .offset = 0 }, { .name = "Kernel", .size = 0x200000, //2M .offset = 0x40000 }, { .name = "RootFS", .size = 0xDC0000, //13M .offset = 0x240000 }, }; static const char *probes[] = { "RedBoot", "cmdlinepart", NULL }; #endif static int mtd_parts_nb = 0; static struct mtd_partition *mtd_parts = 0; /*Norflash模型初始化函数 *<1>物理地址映射为虚拟地址: mini2440nor_map.virt = ioremap(WINDOW_ADDR, WINDOW_SIZE); *<2>探测norflash芯片: do_map_probe(), 得到mtd_info; *<3>探测分区信息: parse_mtd_partitions(), 得到mtd_partition; *<4>利用mtd_info和mtd_partition注册设备:add_mtd_device(); */ int __init init_edb7312nor(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 ", WINDOW_SIZE, WINDOW_ADDR); edb7312nor_map.virt = ioremap(WINDOW_ADDR, WINDOW_SIZE); /*物理地址映射为虚拟地址*/ if (!edb7312nor_map.virt) { printk(MSG_PREFIX "failed to ioremap "); return -EIO; } simple_map_init(&edb7312nor_map); mymtd = 0; type = rom_probe_types; for(; !mymtd && *type; type++) { mymtd = do_map_probe(*type, &edb7312nor_map); /*根据map_info探测norflash芯片，若成功则返回mtd_info*/ } if (mymtd) { mymtd->owner = THIS_MODULE; #ifdef CONFIG_MTD_PARTITIONS 　 /*探测分区信息，若探测成功，则mtd_parts中保存了分区信息；若探测失败，使用数组定义的默认分区信息*/ mtd_parts_nb = parse_mtd_partitions(mymtd, probes, &mtd_parts, 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 /*注册设备*/ add_mtd_device(mymtd); if (mtd_parts_nb == 0) printk(KERN_NOTICE MSG_PREFIX "no partition info available "); else { printk(KERN_NOTICE MSG_PREFIX "using %s partition definition ", part_type); add_mtd_partitions(mymtd, mtd_parts, mtd_parts_nb); } return 0; } iounmap((void *)edb7312nor_map.virt); return -ENXIO; } /*Norflash模块卸载函数 *<1>注销设备:del_mtd_device(); *<2>销毁map_info:map_destroy(); *<3>取消映射:iounmap(); */ static void __exit cleanup_edb7312nor(void) { if (mymtd) { del_mtd_device(mymtd); /*注销设备*/ map_destroy(mymtd); /*销毁map_info*/ } if (edb7312nor_map.virt) { iounmap((void *)edb7312nor_map.virt); edb7312nor_map.virt = 0; } } module_init(init_edb7312nor); module_exit(cleanup_edb7312nor); MODULE_LICENSE("GPL"); MODULE_AUTHOR("Marius Groeger "); MODULE_DESCRIPTION("Generic configurable MTD map driver");

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