SPI Nor FLASH

SPI Nor FLASH

参考内核 dervices/mtd/devices/m25p80.c
M25P64 datasheet

由于M25P64属于SPI Nor Flash linux内核对于Flash采用Mtd驱动进行管理。
分析m25p80.c 省略了MTD Nor Flash Jedec与CFI 分析 这块分析可以参考韦东山老师Nor flash驱动的讲解 ,对于SPI falsh 驱动已经支持的很好了，只需要去添加以下设备注册
驱动硬件接口属于SPI设备驱动

static struct spi_driver m25p80_driver = {
	.driver = {
		.name	= "m25p80",
		.bus	= &spi_bus_type,
		.owner	= THIS_MODULE,
	},
	.probe	= m25p_probe,
	.remove	= __devexit_p(m25p_remove),
};


static int m25p80_init(void)
{
	return spi_register_driver(&m25p80_driver);
}


static void m25p80_exit(void)
{
	spi_unregister_driver(&m25p80_driver);
}


module_init(m25p80_init);
module_exit(m25p80_exit);

MODULE_LICENSE("GPL");
MODULE_AUTHOR("Mike Lavender");
MODULE_DESCRIPTION("MTD SPI driver for ST M25Pxx flash chips");

对于MTD Nor Flash设备驱动核心在于分配，设置mtd_info，注册。 MTD设备读写均使用MTD注册字符设备进行读写，最终调用mtd_info中注册的底层设备读写方法。

struct m25p {
	struct spi_device	*spi;
	struct semaphore	lock;
	struct mtd_info		mtd;
	unsigned		partitioned;
	u8			command[4];
};

/*
 * board specific setup should have ensured the SPI clock used here
 * matches what the READ command supports, at least until this driver
 * understands FAST_READ (for clocks over 25 MHz).
 */
static int __devinit m25p_probe(struct spi_device *spi)
{
	struct flash_platform_data	*data;
	struct m25p			*flash;
	struct flash_info		*info;
	unsigned			i;

	/* Platform data helps sort out which chip type we have, as
	 * well as how this board partitions it.
	 */
	data = spi->dev.platform_data;
	if (!data || !data->type) {
		/* FIXME some chips can identify themselves with RES
		 * or JEDEC get-id commands.  Try them ...
		 */
		DEBUG(MTD_DEBUG_LEVEL1, "%s: no chip id\n",
				spi->dev.bus_id);
		return -ENODEV;
	}

	for (i = 0, info = m25p_data; i < ARRAY_SIZE(m25p_data); i++, info++) {
		if (strcmp(data->type, info->name) == 0)
			break;
	}
	if (i == ARRAY_SIZE(m25p_data)) {
		DEBUG(MTD_DEBUG_LEVEL1, "%s: unrecognized id %s\n",
				spi->dev.bus_id, data->type);
		return -ENODEV;
	}

	flash = kzalloc(sizeof *flash, GFP_KERNEL);  //分配mtd_info 
	if (!flash)
		return -ENOMEM;

	flash->spi = spi;
	init_MUTEX(&flash->lock);
	dev_set_drvdata(&spi->dev, flash);
//设置mtd_info
	if (data->name)
		flash->mtd.name = data->name;
	else
		flash->mtd.name = spi->dev.bus_id;

	flash->mtd.type = MTD_NORFLASH;
	flash->mtd.writesize = 1;
	flash->mtd.flags = MTD_CAP_NORFLASH;
	flash->mtd.size = info->sector_size * info->n_sectors;
	flash->mtd.erasesize = info->sector_size;
	flash->mtd.erase = m25p80_erase;
	flash->mtd.read = m25p80_read;
	flash->mtd.write = m25p80_write;

	dev_info(&spi->dev, "%s (%d Kbytes)\n", info->name,
			flash->mtd.size / 1024);

	DEBUG(MTD_DEBUG_LEVEL2,
		"mtd .name = %s, .size = 0x%.8x (%uM) "
			".erasesize = 0x%.8x (%uK) .numeraseregions = %d\n",
		flash->mtd.name,
		flash->mtd.size, flash->mtd.size / (1024*1024),
		flash->mtd.erasesize, flash->mtd.erasesize / 1024,
		flash->mtd.numeraseregions);

	if (flash->mtd.numeraseregions)
		for (i = 0; i < flash->mtd.numeraseregions; i++)
			DEBUG(MTD_DEBUG_LEVEL2,
				"mtd.eraseregions[%d] = { .offset = 0x%.8x, "
				".erasesize = 0x%.8x (%uK), "
				".numblocks = %d }\n",
				i, flash->mtd.eraseregions[i].offset,
				flash->mtd.eraseregions[i].erasesize,
				flash->mtd.eraseregions[i].erasesize / 1024,
				flash->mtd.eraseregions[i].numblocks);

//设置mtd设备分区
	/* partitions should match sector boundaries; and it may be good to
	 * use readonly partitions for writeprotected sectors (BP2..BP0).
	 */
	if (mtd_has_partitions()) {
		struct mtd_partition	*parts = NULL;
		int			nr_parts = 0;

#ifdef CONFIG_MTD_CMDLINE_PARTS
		static const char *part_probes[] = { "cmdlinepart", NULL, };

		nr_parts = parse_mtd_partitions(&flash->mtd,
				part_probes, &parts, 0);
#endif

		if (nr_parts <= 0 && data && data->parts) {
			parts = data->parts;
			nr_parts = data->nr_parts;
		}

		if (nr_parts > 0) {
			for (i = 0; i < data->nr_parts; i++) {
				DEBUG(MTD_DEBUG_LEVEL2, "partitions[%d] = "
					"{.name = %s, .offset = 0x%.8x, "
						".size = 0x%.8x (%uK) }\n",
					i, data->parts[i].name,
					data->parts[i].offset,
					data->parts[i].size,
					data->parts[i].size / 1024);
			}
			flash->partitioned = 1;
			return add_mtd_partitions(&flash->mtd, parts, nr_parts);
		}
	} else if (data->nr_parts)
		dev_warn(&spi->dev, "ignoring %d default partitions on %s\n",
				data->nr_parts, data->name);
//添加MTD设备
	return add_mtd_device(&flash->mtd) == 1 ? -ENODEV : 0;
}

设置mtd分区

static struct mtd_partition mini6410_nand_part[] = {
	[0] = {
		.name	= "uboot",
		.size	= SZ_1M,
		.offset	= 0,
	},
	[1] = {
		.name	= "kernel",
		.size	= SZ_2M,
		.offset	= SZ_1M,
	},
	[2] = {
		.name	= "rootfs",
		.size	= MTDPART_SIZ_FULL,
		.offset	= SZ_1M + SZ_2M,
	},
};

参考韦东山的Nor Flash分析

来源：https://blog.csdn.net/hehelizn/article/details/98957811