linux nand flash驱动编写_Linux

很长一段时间，nand flash都是嵌入式的标配产品。nand flash价格便宜，存储量大，适用于很多的场景。现在很普及的ssd，上面的存储模块其实也是由一块一块nand flash构成的。对于linux嵌入式来说，开始uboot的加载是硬件完成的，中期的kernel加载是由uboot中的nand flash驱动完成的，而后期的rootfs加载，这就要靠kernel自己来完成了。当然，这次还是以三星s3c芯片为例进行说明。

1、nand flash驱动在什么地方，可以从drviers/mtd/Makefile来看

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									obj-y    += chips/ lpddr/ maps/ devices/ nand/ onenand/ tests/

2、nand在mtd下面，是作为一个单独目录保存的，这时应该查看nand下的Kconfig

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									config MTD_NAND_S3C2410 

									  tristate "NAND Flash support for Samsung S3C SoCs" 

									  depends on ARCH_S3C24XX || ARCH_S3C64XX 

									  help 

									   This enables the NAND flash controller on the S3C24xx and S3C64xx 

									   SoCs 

									   No board specific support is done by this driver, each board 

									   must advertise a platform_device for the driver to attach. 

									config MTD_NAND_S3C2410_DEBUG 

									  bool "Samsung S3C NAND driver debug" 

									  depends on MTD_NAND_S3C2410 

									  help 

									   Enable debugging of the S3C NAND driver 

									config MTD_NAND_S3C2410_CLKSTOP 

									  bool "Samsung S3C NAND IDLE clock stop" 

									  depends on MTD_NAND_S3C2410 

									  default n 

									  help 

									   Stop the clock to the NAND controller when there is no chip 

									   selected to save power. This will mean there is a small delay 

									   when the is NAND chip selected or released, but will save 

									   approximately 5mA of power when there is nothing happening.

3、不难发现，MTD_NAND_S3C2410才是那个真正的macro，尝试在Makefile找文件

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									obj-$(CONFIG_MTD_NAND_S3C2410)   += s3c2410.o

4、查看s3c2410.c文件，看看基本结构构成

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									static struct platform_driver s3c24xx_nand_driver = { 

									  .probe   = s3c24xx_nand_probe, 

									  .remove   = s3c24xx_nand_remove, 

									  .suspend  = s3c24xx_nand_suspend, 

									  .resume   = s3c24xx_nand_resume, 

									  .id_table  = s3c24xx_driver_ids, 

									  .driver   = { 

									    .name  = "s3c24xx-nand", 

									    .of_match_table = s3c24xx_nand_dt_ids, 

									  }, 

									}; 

									module_platform_driver(s3c24xx_nand_driver);

5、继续分析s3c24xx_nand_probe函数

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									s3c2410_nand_init_chip(info, nmtd, sets);

6、之所以从中摘出了s3c2410_nand_init_chip这个函数，是因为里面进行了函数注册

类似的函数还有s3c2410_nand_update_chip函数

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									chip->write_buf  = s3c2410_nand_write_buf; 

									chip->read_buf   = s3c2410_nand_read_buf; 

									chip->select_chip = s3c2410_nand_select_chip; 

									chip->chip_delay  = 50; 

									nand_set_controller_data(chip, nmtd); 

									chip->options    = set->options; 

									chip->controller  = &info->controller;  

									switch (info->cpu_type) { 

									case TYPE_S3C2410: 

									  chip->IO_ADDR_W = regs + S3C2410_NFDATA; 

									  info->sel_reg  = regs + S3C2410_NFCONF; 

									  info->sel_bit  = S3C2410_NFCONF_nFCE; 

									  chip->cmd_ctrl = s3c2410_nand_hwcontrol; 

									  chip->dev_ready = s3c2410_nand_devready; 

									  break; 

									case TYPE_S3C2440: 

									  chip->IO_ADDR_W = regs + S3C2440_NFDATA; 

									  info->sel_reg  = regs + S3C2440_NFCONT; 

									  info->sel_bit  = S3C2440_NFCONT_nFCE; 

									  chip->cmd_ctrl = s3c2440_nand_hwcontrol; 

									  chip->dev_ready = s3c2440_nand_devready; 

									  chip->read_buf = s3c2440_nand_read_buf; 

									  chip->write_buf = s3c2440_nand_write_buf; 

									  break;  

									case TYPE_S3C2412: 

									  chip->IO_ADDR_W = regs + S3C2440_NFDATA; 

									  info->sel_reg  = regs + S3C2440_NFCONT; 

									  info->sel_bit  = S3C2412_NFCONT_nFCE0; 

									  chip->cmd_ctrl = s3c2440_nand_hwcontrol; 

									  chip->dev_ready = s3c2412_nand_devready;  

									  if (readl(regs + S3C2410_NFCONF) & S3C2412_NFCONF_NANDBOOT) 

									    dev_info(info->device, "System booted from NAND\n");  

									  break; 

									}