drivers/mtd/devices/at91_dataflash26.c - maze/linux - Git at Google

 /*
  * Atmel DataFlash driver for Atmel AT91RM9200 (Thunder)
  * This is a largely modified version of at91_dataflash.c that
  * supports AT26xxx dataflash chips. The original driver supports
  * AT45xxx chips.
  *
  * Note: This driver was only tested with an AT26F004. It should be
  * easy to make it work with other AT26xxx dataflash devices, though.
  *
  * Copyright (C) 2007 Hans J. Koch <hjk@linutronix.de>
  * original Copyright (C) SAN People (Pty) Ltd
  *
  * 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 <linux/config.h>
 #include <linux/module.h>
 #include <linux/init.h>
 #include <linux/mtd/mtd.h>

 #include <asm/arch/at91_spi.h>

 #define DATAFLASH_MAX_DEVICES	4	/* max number of dataflash devices */

 #define MANUFACTURER_ID_ATMEL		0x1F

 /* command codes */

 #define AT26_OP_READ_STATUS		0x05
 #define AT26_OP_READ_DEV_ID		0x9F
 #define AT26_OP_ERASE_PAGE_4K		0x20
 #define AT26_OP_READ_ARRAY_FAST		0x0B
 #define AT26_OP_SEQUENTIAL_WRITE	0xAF
 #define AT26_OP_WRITE_ENABLE		0x06
 #define AT26_OP_WRITE_DISABLE		0x04
 #define AT26_OP_SECTOR_PROTECT		0x36
 #define AT26_OP_SECTOR_UNPROTECT	0x39

 /* status register bits */

 #define AT26_STATUS_BUSY		0x01
 #define AT26_STATUS_WRITE_ENABLE	0x02

 struct dataflash_local
 {
 	int spi;			/* SPI chip-select number */
 	unsigned int page_size;		/* number of bytes per page */
 };


 /* Detected DataFlash devices */
 static struct mtd_info* mtd_devices[DATAFLASH_MAX_DEVICES];
 static int nr_devices = 0;

 /* Allocate a single SPI transfer descriptor.  We're assuming that if multiple
    SPI transfers occur at the same time, spi_access_bus() will serialize them.
    If this is not valid, then either (i) each dataflash 'priv' structure
    needs it's own transfer descriptor, (ii) we lock this one, or (iii) use
    another mechanism.   */
 static struct spi_transfer_list* spi_transfer_desc;

 /*
  * Perform a SPI transfer to access the DataFlash device.
  */
 static int do_spi_transfer(int nr, char* tx, int tx_len, char* rx, int rx_len,
 		char* txnext, int txnext_len, char* rxnext, int rxnext_len)
 {
 	struct spi_transfer_list* list = spi_transfer_desc;

 	list->tx[0] = tx;	list->txlen[0] = tx_len;
 	list->rx[0] = rx;	list->rxlen[0] = rx_len;

 	list->tx[1] = txnext; 	list->txlen[1] = txnext_len;
 	list->rx[1] = rxnext;	list->rxlen[1] = rxnext_len;

 	list->nr_transfers = nr;
 	/* Note: spi_transfer() always returns 0, there are no error checks */
 	return spi_transfer(list);
 }

 /*
  * Return the status of the DataFlash device.
  */
 static unsigned char at91_dataflash26_status(void)
 {
 	unsigned char command[2];

 	command[0] = AT26_OP_READ_STATUS;
 	command[1] = 0;

 	do_spi_transfer(1, command, 2, command, 2, NULL, 0, NULL, 0);

 	return command[1];
 }

 /*
  * Poll the DataFlash device until it is READY.
  */
 static unsigned char at91_dataflash26_waitready(void)
 {
 	unsigned char status;

 	while (1) {
 		status = at91_dataflash26_status();
 		if (!(status & AT26_STATUS_BUSY))
 			return status;
 	}
 }

 /*
  * Enable/disable write access
  */
  static void at91_dataflash26_write_enable(int enable)
 {
 	unsigned char cmd[2];

 	DEBUG(MTD_DEBUG_LEVEL3, "write_enable: enable=%i\n", enable);

 	if (enable)
 		cmd[0] = AT26_OP_WRITE_ENABLE;
 	else
 		cmd[0] = AT26_OP_WRITE_DISABLE;
 	cmd[1] = 0;

 	do_spi_transfer(1, cmd, 2, cmd, 2, NULL, 0, NULL, 0);
 }

 /*
  * Protect/unprotect sector
  */
  static void at91_dataflash26_sector_protect(loff_t addr, int protect)
 {
 	unsigned char cmd[4];

 	DEBUG(MTD_DEBUG_LEVEL3, "sector_protect: addr=0x%06x prot=%d\n",
 	       addr, protect);

 	if (protect)
 		cmd[0] = AT26_OP_SECTOR_PROTECT;
 	else
 		cmd[0] = AT26_OP_SECTOR_UNPROTECT;
 	cmd[1] = (addr & 0x00FF0000) >> 16;
 	cmd[2] = (addr & 0x0000FF00) >> 8;
 	cmd[3] = (addr & 0x000000FF);

 	do_spi_transfer(1, cmd, 4, cmd, 4, NULL, 0, NULL, 0);
 }

 /*
  * Erase blocks of flash.
  */
 static int at91_dataflash26_erase(struct mtd_info *mtd,
 				  struct erase_info *instr)
 {
 	struct dataflash_local *priv = (struct dataflash_local *) mtd->priv;
 	unsigned char cmd[4];

 	DEBUG(MTD_DEBUG_LEVEL1, "dataflash_erase: addr=0x%06x len=%i\n",
 	       instr->addr, instr->len);

 	/* Sanity checks */
 	if (priv->page_size != 4096)
 		return -EINVAL; /* Can't handle other sizes at the moment */

 	if (   ((instr->len % mtd->erasesize) != 0)
 	    || ((instr->len % priv->page_size) != 0)
 	    || ((instr->addr % priv->page_size) != 0)
 	    || ((instr->addr + instr->len) > mtd->size))
 		return -EINVAL;

 	spi_access_bus(priv->spi);

 	while (instr->len > 0) {
 		at91_dataflash26_write_enable(1);
 		at91_dataflash26_sector_protect(instr->addr, 0);
 		at91_dataflash26_write_enable(1);
 		cmd[0] = AT26_OP_ERASE_PAGE_4K;
 		cmd[1] = (instr->addr & 0x00FF0000) >> 16;
 		cmd[2] = (instr->addr & 0x0000FF00) >> 8;
 		cmd[3] = (instr->addr & 0x000000FF);

 		DEBUG(MTD_DEBUG_LEVEL3, "ERASE: (0x%02x) 0x%02x 0x%02x"
 					"0x%02x\n",
 			cmd[0], cmd[1], cmd[2], cmd[3]);

 		do_spi_transfer(1, cmd, 4, cmd, 4, NULL, 0, NULL, 0);
 		at91_dataflash26_waitready();

 		instr->addr += priv->page_size;	 /* next page */
 		instr->len -= priv->page_size;
 	}

 	at91_dataflash26_write_enable(0);
 	spi_release_bus(priv->spi);

 	/* Inform MTD subsystem that erase is complete */
 	instr->state = MTD_ERASE_DONE;
 	if (instr->callback)
 		instr->callback(instr);

 	return 0;
 }

 /*
  * Read from the DataFlash device.
  *   from   : Start offset in flash device
  *   len    : Number of bytes to read
  *   retlen : Number of bytes actually read
  *   buf    : Buffer that will receive data
  */
 static int at91_dataflash26_read(struct mtd_info *mtd, loff_t from, size_t len,
 				 size_t *retlen, u_char *buf)
 {
 	struct dataflash_local *priv = (struct dataflash_local *) mtd->priv;
 	unsigned char cmd[5];

 	DEBUG(MTD_DEBUG_LEVEL1, "dataflash_read: %lli .. %lli\n",
 	      from, from+len);

 	*retlen = 0;

 	/* Sanity checks */
 	if (!len)
 		return 0;
 	if (from + len > mtd->size)
 		return -EINVAL;

 	cmd[0] = AT26_OP_READ_ARRAY_FAST;
 	cmd[1] = (from & 0x00FF0000) >> 16;
 	cmd[2] = (from & 0x0000FF00) >> 8;
 	cmd[3] = (from & 0x000000FF);
 	/* cmd[4] is a "Don't care" byte  */

 	DEBUG(MTD_DEBUG_LEVEL3, "READ: (0x%02x) 0x%02x 0x%02x 0x%02x\n",
 	       cmd[0], cmd[1], cmd[2], cmd[3]);

 	spi_access_bus(priv->spi);
 	do_spi_transfer(2, cmd, 5, cmd, 5, buf, len, buf, len);
 	spi_release_bus(priv->spi);

 	*retlen = len;
 	return 0;
 }

 /*
  * Write to the DataFlash device.
  *   to     : Start offset in flash device
  *   len    : Number of bytes to write
  *   retlen : Number of bytes actually written
  *   buf    : Buffer containing the data
  */
 static int at91_dataflash26_write(struct mtd_info *mtd, loff_t to, size_t len,
 				  size_t *retlen, const u_char *buf)
 {
 	struct dataflash_local *priv = (struct dataflash_local *) mtd->priv;
 	unsigned int addr, buf_index = 0;
 	int ret = -EIO, sector, last_sector;
 	unsigned char status, cmd[5];

 	DEBUG(MTD_DEBUG_LEVEL1, "dataflash_write: %lli .. %lli\n", to, to+len);

 	*retlen = 0;

 	/* Sanity checks */
 	if (!len)
 		return 0;
 	if (to + len > mtd->size)
 		return -EINVAL;

 	spi_access_bus(priv->spi);

 	addr = to;
 	last_sector = -1;

 	while (buf_index < len) {
 		sector = addr / priv->page_size;
 		/* Write first byte if a new sector begins */
 		if (sector != last_sector) {
 			at91_dataflash26_write_enable(1);
 			at91_dataflash26_sector_protect(addr, 0);
 			at91_dataflash26_write_enable(1);

 			/* Program first byte of a new sector */
 			cmd[0] = AT26_OP_SEQUENTIAL_WRITE;
 			cmd[1] = (addr & 0x00FF0000) >> 16;
 			cmd[2] = (addr & 0x0000FF00) >> 8;
 			cmd[3] = (addr & 0x000000FF);
 			cmd[4] = buf[buf_index++];
 			do_spi_transfer(1, cmd, 5, cmd, 5, NULL, 0, NULL, 0);
 			status = at91_dataflash26_waitready();
 			addr++;
 			/* On write errors, the chip resets the write enable
 			   flag. This also happens after the last byte of a
 			   sector is successfully programmed. */
 			if (   ( !(status & AT26_STATUS_WRITE_ENABLE))
 			    && ((addr % priv->page_size) != 0) ) {
 				DEBUG(MTD_DEBUG_LEVEL1,
 					"write error1: addr=0x%06x, "
 					"status=0x%02x\n", addr, status);
 				goto write_err;
 			}
 			(*retlen)++;
 			last_sector = sector;
 		}

 		/* Write subsequent bytes in the same sector */
 		cmd[0] = AT26_OP_SEQUENTIAL_WRITE;
 		cmd[1] = buf[buf_index++];
 		do_spi_transfer(1, cmd, 2, cmd, 2, NULL, 0, NULL, 0);
 		status = at91_dataflash26_waitready();
 		addr++;

 		if (   ( !(status & AT26_STATUS_WRITE_ENABLE))
 		    && ((addr % priv->page_size) != 0) ) {
 			DEBUG(MTD_DEBUG_LEVEL1, "write error2: addr=0x%06x, "
 				"status=0x%02x\n", addr, status);
 			goto write_err;
 		}

 		(*retlen)++;
 	}

 	ret = 0;
 	at91_dataflash26_write_enable(0);
 write_err:
 	spi_release_bus(priv->spi);
 	return ret;
 }

 /*
  * Initialize and register DataFlash device with MTD subsystem.
  */
 static int __init add_dataflash(int channel, char *name, int nr_pages,
 				int pagesize)
 {
 	struct mtd_info *device;
 	struct dataflash_local *priv;

 	if (nr_devices >= DATAFLASH_MAX_DEVICES) {
 		printk(KERN_ERR "at91_dataflash26: Too many devices "
 				"detected\n");
 		return 0;
 	}

 	device = kzalloc(sizeof(struct mtd_info) + strlen(name) + 8,
 			 GFP_KERNEL);
 	if (!device)
 		return -ENOMEM;

 	device->name = (char *)&device[1];
 	sprintf(device->name, "%s.spi%d", name, channel);
 	device->size = nr_pages * pagesize;
 	device->erasesize = pagesize;
 	device->owner = THIS_MODULE;
 	device->type = MTD_DATAFLASH;
 	device->flags = MTD_CAP_NORFLASH;
 	device->erase = at91_dataflash26_erase;
 	device->read = at91_dataflash26_read;
 	device->write = at91_dataflash26_write;

 	priv = (struct dataflash_local *)kzalloc(sizeof(struct dataflash_local),
 		GFP_KERNEL);
 	if (!priv) {
 		kfree(device);
 		return -ENOMEM;
 	}

 	priv->spi = channel;
 	priv->page_size = pagesize;
 	device->priv = priv;

 	mtd_devices[nr_devices] = device;
 	nr_devices++;
 	printk(KERN_INFO "at91_dataflash26: %s detected [spi%i] (%i bytes)\n",
 	       name, channel, device->size);

 	return add_mtd_device(device);
 }

 /*
  * Detect and initialize DataFlash device connected to specified SPI channel.
  *
  */

 struct dataflash26_types {
 	unsigned char id0;
 	unsigned char id1;
 	char *name;
 	int pagesize;
 	int nr_pages;
 };

 struct dataflash26_types df26_types[] = {
 	{
 		.id0 = 0x04,
 		.id1 = 0x00,
 		.name = "AT26F004",
 		.pagesize = 4096,
 		.nr_pages = 128,
 	},
 	{
 		.id0 = 0x45,
 		.id1 = 0x01,
 		.name = "AT26DF081A", /* Not tested ! */
 		.pagesize = 4096,
 		.nr_pages = 256,
 	},
 };

 static int __init at91_dataflash26_detect(int channel)
 {
 	unsigned char status, cmd[5];
 	int i;

 	spi_access_bus(channel);
 	status = at91_dataflash26_status();

 	if (status == 0 || status == 0xff) {
 		printk(KERN_ERR "at91_dataflash26_detect: status error %d\n",
 			status);
 		spi_release_bus(channel);
 		return -ENODEV;
 	}

 	cmd[0] = AT26_OP_READ_DEV_ID;
 	do_spi_transfer(1, cmd, 5, cmd, 5, NULL, 0, NULL, 0);
 	spi_release_bus(channel);

 	if (cmd[1] != MANUFACTURER_ID_ATMEL)
 		return -ENODEV;

 	for (i = 0; i < ARRAY_SIZE(df26_types); i++) {
 		if (   cmd[2] == df26_types[i].id0
 		    && cmd[3] == df26_types[i].id1)
 			return add_dataflash(channel,
 						df26_types[i].name,
 						df26_types[i].nr_pages,
 						df26_types[i].pagesize);
 	}

 	printk(KERN_ERR "at91_dataflash26_detect: Unsupported device "
 			"(0x%02x/0x%02x)\n", cmd[2], cmd[3]);
 	return -ENODEV;
 }

 static int __init at91_dataflash26_init(void)
 {
 	spi_transfer_desc = kmalloc(sizeof(struct spi_transfer_list),
 				    GFP_KERNEL);
 	if (!spi_transfer_desc)
 		return -ENOMEM;

 	/* DataFlash (SPI chip select 0) */
 	at91_dataflash26_detect(0);

 #ifdef CONFIG_MTD_AT91_DATAFLASH_CARD
 	/* DataFlash card (SPI chip select 3) */
 	at91_dataflash26_detect(3);
 #endif
 	return 0;
 }

 static void __exit at91_dataflash26_exit(void)
 {
 	int i;

 	for (i = 0; i < DATAFLASH_MAX_DEVICES; i++) {
 		if (mtd_devices[i]) {
 			del_mtd_device(mtd_devices[i]);
 			kfree(mtd_devices[i]->priv);
 			kfree(mtd_devices[i]);
 		}
 	}
 	nr_devices = 0;
 	kfree(spi_transfer_desc);
 }

 module_init(at91_dataflash26_init);
 module_exit(at91_dataflash26_exit);

 MODULE_LICENSE("GPL");
 MODULE_AUTHOR("Hans J. Koch");
 MODULE_DESCRIPTION("DataFlash AT26xxx driver for Atmel AT91RM9200");
	/*
	* Atmel DataFlash driver for Atmel AT91RM9200 (Thunder)
	* This is a largely modified version of at91_dataflash.c that
	* supports AT26xxx dataflash chips. The original driver supports
	* AT45xxx chips.
	*
	* Note: This driver was only tested with an AT26F004. It should be
	* easy to make it work with other AT26xxx dataflash devices, though.
	*
	* Copyright (C) 2007 Hans J. Koch <hjk@linutronix.de>
	* original Copyright (C) SAN People (Pty) Ltd
	*
	* 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 <linux/config.h>
	#include <linux/module.h>
	#include <linux/init.h>
	#include <linux/mtd/mtd.h>

	#include <asm/arch/at91_spi.h>

	#define DATAFLASH_MAX_DEVICES 4 /* max number of dataflash devices */

	#define MANUFACTURER_ID_ATMEL 0x1F

	/* command codes */

	#define AT26_OP_READ_STATUS 0x05
	#define AT26_OP_READ_DEV_ID 0x9F
	#define AT26_OP_ERASE_PAGE_4K 0x20
	#define AT26_OP_READ_ARRAY_FAST 0x0B
	#define AT26_OP_SEQUENTIAL_WRITE 0xAF
	#define AT26_OP_WRITE_ENABLE 0x06
	#define AT26_OP_WRITE_DISABLE 0x04
	#define AT26_OP_SECTOR_PROTECT 0x36
	#define AT26_OP_SECTOR_UNPROTECT 0x39

	/* status register bits */

	#define AT26_STATUS_BUSY 0x01
	#define AT26_STATUS_WRITE_ENABLE 0x02

	struct dataflash_local
	{
	int spi; /* SPI chip-select number */
	unsigned int page_size; /* number of bytes per page */
	};


	/* Detected DataFlash devices */
	static struct mtd_info* mtd_devices[DATAFLASH_MAX_DEVICES];
	static int nr_devices = 0;

	/* Allocate a single SPI transfer descriptor. We're assuming that if multiple
	SPI transfers occur at the same time, spi_access_bus() will serialize them.
	If this is not valid, then either (i) each dataflash 'priv' structure
	needs it's own transfer descriptor, (ii) we lock this one, or (iii) use
	another mechanism. */
	static struct spi_transfer_list* spi_transfer_desc;

	/*
	* Perform a SPI transfer to access the DataFlash device.
	*/
	static int do_spi_transfer(int nr, char* tx, int tx_len, char* rx, int rx_len,
	char* txnext, int txnext_len, char* rxnext, int rxnext_len)
	{
	struct spi_transfer_list* list = spi_transfer_desc;

	list->tx[0] = tx; list->txlen[0] = tx_len;
	list->rx[0] = rx; list->rxlen[0] = rx_len;

	list->tx[1] = txnext; list->txlen[1] = txnext_len;
	list->rx[1] = rxnext; list->rxlen[1] = rxnext_len;

	list->nr_transfers = nr;
	/* Note: spi_transfer() always returns 0, there are no error checks */
	return spi_transfer(list);
	}

	/*
	* Return the status of the DataFlash device.
	*/
	static unsigned char at91_dataflash26_status(void)
	{
	unsigned char command[2];

	command[0] = AT26_OP_READ_STATUS;
	command[1] = 0;

	do_spi_transfer(1, command, 2, command, 2, NULL, 0, NULL, 0);

	return command[1];
	}

	/*
	* Poll the DataFlash device until it is READY.
	*/
	static unsigned char at91_dataflash26_waitready(void)
	{
	unsigned char status;

	while (1) {
	status = at91_dataflash26_status();
	if (!(status & AT26_STATUS_BUSY))
	return status;
	}
	}

	/*
	* Enable/disable write access
	*/
	static void at91_dataflash26_write_enable(int enable)
	{
	unsigned char cmd[2];

	DEBUG(MTD_DEBUG_LEVEL3, "write_enable: enable=%i\n", enable);

	if (enable)
	cmd[0] = AT26_OP_WRITE_ENABLE;
	else
	cmd[0] = AT26_OP_WRITE_DISABLE;
	cmd[1] = 0;

	do_spi_transfer(1, cmd, 2, cmd, 2, NULL, 0, NULL, 0);
	}

	/*
	* Protect/unprotect sector
	*/
	static void at91_dataflash26_sector_protect(loff_t addr, int protect)
	{
	unsigned char cmd[4];

	DEBUG(MTD_DEBUG_LEVEL3, "sector_protect: addr=0x%06x prot=%d\n",
	addr, protect);

	if (protect)
	cmd[0] = AT26_OP_SECTOR_PROTECT;
	else
	cmd[0] = AT26_OP_SECTOR_UNPROTECT;
	cmd[1] = (addr & 0x00FF0000) >> 16;
	cmd[2] = (addr & 0x0000FF00) >> 8;
	cmd[3] = (addr & 0x000000FF);

	do_spi_transfer(1, cmd, 4, cmd, 4, NULL, 0, NULL, 0);
	}

	/*
	* Erase blocks of flash.
	*/
	static int at91_dataflash26_erase(struct mtd_info *mtd,
	struct erase_info *instr)
	{
	struct dataflash_local priv = (struct dataflash_local ) mtd->priv;
	unsigned char cmd[4];

	DEBUG(MTD_DEBUG_LEVEL1, "dataflash_erase: addr=0x%06x len=%i\n",
	instr->addr, instr->len);

	/* Sanity checks */
	if (priv->page_size != 4096)
	return -EINVAL; /* Can't handle other sizes at the moment */

	if ( ((instr->len % mtd->erasesize) != 0)
	\|\| ((instr->len % priv->page_size) != 0)
	\|\| ((instr->addr % priv->page_size) != 0)
	\|\| ((instr->addr + instr->len) > mtd->size))
	return -EINVAL;

	spi_access_bus(priv->spi);

	while (instr->len > 0) {
	at91_dataflash26_write_enable(1);
	at91_dataflash26_sector_protect(instr->addr, 0);
	at91_dataflash26_write_enable(1);
	cmd[0] = AT26_OP_ERASE_PAGE_4K;
	cmd[1] = (instr->addr & 0x00FF0000) >> 16;
	cmd[2] = (instr->addr & 0x0000FF00) >> 8;
	cmd[3] = (instr->addr & 0x000000FF);

	DEBUG(MTD_DEBUG_LEVEL3, "ERASE: (0x%02x) 0x%02x 0x%02x"
	"0x%02x\n",
	cmd[0], cmd[1], cmd[2], cmd[3]);

	do_spi_transfer(1, cmd, 4, cmd, 4, NULL, 0, NULL, 0);
	at91_dataflash26_waitready();

	instr->addr += priv->page_size; /* next page */
	instr->len -= priv->page_size;
	}

	at91_dataflash26_write_enable(0);
	spi_release_bus(priv->spi);

	/* Inform MTD subsystem that erase is complete */
	instr->state = MTD_ERASE_DONE;
	if (instr->callback)
	instr->callback(instr);

	return 0;
	}

	/*
	* Read from the DataFlash device.
	* from : Start offset in flash device
	* len : Number of bytes to read
	* retlen : Number of bytes actually read
	* buf : Buffer that will receive data
	*/
	static int at91_dataflash26_read(struct mtd_info *mtd, loff_t from, size_t len,
	size_t retlen, u_char buf)
	{
	struct dataflash_local priv = (struct dataflash_local ) mtd->priv;
	unsigned char cmd[5];

	DEBUG(MTD_DEBUG_LEVEL1, "dataflash_read: %lli .. %lli\n",
	from, from+len);

	*retlen = 0;

	/* Sanity checks */
	if (!len)
	return 0;
	if (from + len > mtd->size)
	return -EINVAL;

	cmd[0] = AT26_OP_READ_ARRAY_FAST;
	cmd[1] = (from & 0x00FF0000) >> 16;
	cmd[2] = (from & 0x0000FF00) >> 8;
	cmd[3] = (from & 0x000000FF);
	/* cmd[4] is a "Don't care" byte */

	DEBUG(MTD_DEBUG_LEVEL3, "READ: (0x%02x) 0x%02x 0x%02x 0x%02x\n",
	cmd[0], cmd[1], cmd[2], cmd[3]);

	spi_access_bus(priv->spi);
	do_spi_transfer(2, cmd, 5, cmd, 5, buf, len, buf, len);
	spi_release_bus(priv->spi);

	*retlen = len;
	return 0;
	}

	/*
	* Write to the DataFlash device.
	* to : Start offset in flash device
	* len : Number of bytes to write
	* retlen : Number of bytes actually written
	* buf : Buffer containing the data
	*/
	static int at91_dataflash26_write(struct mtd_info *mtd, loff_t to, size_t len,
	size_t retlen, const u_char buf)
	{
	struct dataflash_local priv = (struct dataflash_local ) mtd->priv;
	unsigned int addr, buf_index = 0;
	int ret = -EIO, sector, last_sector;
	unsigned char status, cmd[5];

	DEBUG(MTD_DEBUG_LEVEL1, "dataflash_write: %lli .. %lli\n", to, to+len);

	*retlen = 0;

	/* Sanity checks */
	if (!len)
	return 0;
	if (to + len > mtd->size)
	return -EINVAL;

	spi_access_bus(priv->spi);

	addr = to;
	last_sector = -1;

	while (buf_index < len) {
	sector = addr / priv->page_size;
	/* Write first byte if a new sector begins */
	if (sector != last_sector) {
	at91_dataflash26_write_enable(1);
	at91_dataflash26_sector_protect(addr, 0);
	at91_dataflash26_write_enable(1);

	/* Program first byte of a new sector */
	cmd[0] = AT26_OP_SEQUENTIAL_WRITE;
	cmd[1] = (addr & 0x00FF0000) >> 16;
	cmd[2] = (addr & 0x0000FF00) >> 8;
	cmd[3] = (addr & 0x000000FF);
	cmd[4] = buf[buf_index++];
	do_spi_transfer(1, cmd, 5, cmd, 5, NULL, 0, NULL, 0);
	status = at91_dataflash26_waitready();
	addr++;
	/* On write errors, the chip resets the write enable
	flag. This also happens after the last byte of a
	sector is successfully programmed. */
	if ( ( !(status & AT26_STATUS_WRITE_ENABLE))
	&& ((addr % priv->page_size) != 0) ) {
	DEBUG(MTD_DEBUG_LEVEL1,
	"write error1: addr=0x%06x, "
	"status=0x%02x\n", addr, status);
	goto write_err;
	}
	(*retlen)++;
	last_sector = sector;
	}

	/* Write subsequent bytes in the same sector */
	cmd[0] = AT26_OP_SEQUENTIAL_WRITE;
	cmd[1] = buf[buf_index++];
	do_spi_transfer(1, cmd, 2, cmd, 2, NULL, 0, NULL, 0);
	status = at91_dataflash26_waitready();
	addr++;

	if ( ( !(status & AT26_STATUS_WRITE_ENABLE))
	&& ((addr % priv->page_size) != 0) ) {
	DEBUG(MTD_DEBUG_LEVEL1, "write error2: addr=0x%06x, "
	"status=0x%02x\n", addr, status);
	goto write_err;
	}

	(*retlen)++;
	}

	ret = 0;
	at91_dataflash26_write_enable(0);
	write_err:
	spi_release_bus(priv->spi);
	return ret;
	}

	/*
	* Initialize and register DataFlash device with MTD subsystem.
	*/
	static int __init add_dataflash(int channel, char *name, int nr_pages,
	int pagesize)
	{
	struct mtd_info *device;
	struct dataflash_local *priv;

	if (nr_devices >= DATAFLASH_MAX_DEVICES) {
	printk(KERN_ERR "at91_dataflash26: Too many devices "
	"detected\n");
	return 0;
	}

	device = kzalloc(sizeof(struct mtd_info) + strlen(name) + 8,
	GFP_KERNEL);
	if (!device)
	return -ENOMEM;

	device->name = (char *)&device[1];
	sprintf(device->name, "%s.spi%d", name, channel);
	device->size = nr_pages * pagesize;
	device->erasesize = pagesize;
	device->owner = THIS_MODULE;
	device->type = MTD_DATAFLASH;
	device->flags = MTD_CAP_NORFLASH;
	device->erase = at91_dataflash26_erase;
	device->read = at91_dataflash26_read;
	device->write = at91_dataflash26_write;

	priv = (struct dataflash_local *)kzalloc(sizeof(struct dataflash_local),
	GFP_KERNEL);
	if (!priv) {
	kfree(device);
	return -ENOMEM;
	}

	priv->spi = channel;
	priv->page_size = pagesize;
	device->priv = priv;

	mtd_devices[nr_devices] = device;
	nr_devices++;
	printk(KERN_INFO "at91_dataflash26: %s detected [spi%i] (%i bytes)\n",
	name, channel, device->size);

	return add_mtd_device(device);
	}

	/*
	* Detect and initialize DataFlash device connected to specified SPI channel.
	*
	*/

	struct dataflash26_types {
	unsigned char id0;
	unsigned char id1;
	char *name;
	int pagesize;
	int nr_pages;
	};

	struct dataflash26_types df26_types[] = {
	{
	.id0 = 0x04,
	.id1 = 0x00,
	.name = "AT26F004",
	.pagesize = 4096,
	.nr_pages = 128,
	},
	{
	.id0 = 0x45,
	.id1 = 0x01,
	.name = "AT26DF081A", /* Not tested ! */
	.pagesize = 4096,
	.nr_pages = 256,
	},
	};

	static int __init at91_dataflash26_detect(int channel)
	{
	unsigned char status, cmd[5];
	int i;

	spi_access_bus(channel);
	status = at91_dataflash26_status();

	if (status == 0 \|\| status == 0xff) {
	printk(KERN_ERR "at91_dataflash26_detect: status error %d\n",
	status);
	spi_release_bus(channel);
	return -ENODEV;
	}

	cmd[0] = AT26_OP_READ_DEV_ID;
	do_spi_transfer(1, cmd, 5, cmd, 5, NULL, 0, NULL, 0);
	spi_release_bus(channel);

	if (cmd[1] != MANUFACTURER_ID_ATMEL)
	return -ENODEV;

	for (i = 0; i < ARRAY_SIZE(df26_types); i++) {
	if ( cmd[2] == df26_types[i].id0
	&& cmd[3] == df26_types[i].id1)
	return add_dataflash(channel,
	df26_types[i].name,
	df26_types[i].nr_pages,
	df26_types[i].pagesize);
	}

	printk(KERN_ERR "at91_dataflash26_detect: Unsupported device "
	"(0x%02x/0x%02x)\n", cmd[2], cmd[3]);
	return -ENODEV;
	}

	static int __init at91_dataflash26_init(void)
	{
	spi_transfer_desc = kmalloc(sizeof(struct spi_transfer_list),
	GFP_KERNEL);
	if (!spi_transfer_desc)
	return -ENOMEM;

	/* DataFlash (SPI chip select 0) */
	at91_dataflash26_detect(0);

	#ifdef CONFIG_MTD_AT91_DATAFLASH_CARD
	/* DataFlash card (SPI chip select 3) */
	at91_dataflash26_detect(3);
	#endif
	return 0;
	}

	static void __exit at91_dataflash26_exit(void)
	{
	int i;

	for (i = 0; i < DATAFLASH_MAX_DEVICES; i++) {
	if (mtd_devices[i]) {
	del_mtd_device(mtd_devices[i]);
	kfree(mtd_devices[i]->priv);
	kfree(mtd_devices[i]);
	}
	}
	nr_devices = 0;
	kfree(spi_transfer_desc);
	}

	module_init(at91_dataflash26_init);
	module_exit(at91_dataflash26_exit);

	MODULE_LICENSE("GPL");
	MODULE_AUTHOR("Hans J. Koch");
	MODULE_DESCRIPTION("DataFlash AT26xxx driver for Atmel AT91RM9200");