linuxにおけるspiの駆動開発例M 25 P 10

m 25 p 10駆動テスト
目的:S 5 PC 100プラットフォーム上で簡単なspi駆動モジュールを作成し、probe段階でm 25 p 10のID番号検出、flash消去、flash状態読取、flash書き込み、flash読み取りなどの操作を実現する.コードはテスト済みで、2.6.35カーネルで実行されています.次のコードを理解するには、m 25 p 10のチップマニュアルを参照する必要があります.実は次のコードはプロセッサとあまり関係がありません.これもspiサブシステムの階層化の特徴です.

urning its value in the location
 * Return the status register value.
 * Returns negative if error occurred.
 */
static int read_sr(struct m25p10a *flash)
{
	ssize_t retval;
	u8 code = CMD_RDSR;
	u8 val;

	retval = spi_write_then_read(flash->spi, &code, 1, &val, 1);

	if (retval < 0) {
		dev_err(&flash->spi->dev, "error %d reading SR
",
				(int) retval);
		return retval;
	}

	return val;
}

/*
 * Service routine to read status register until ready, or timeout occurs.
 * Returns non-zero if error.
 */
static int wait_till_ready(struct m25p10a *flash)
{
	int count;
	int sr; 

	/* one chip guarantees max 5 msec wait here after page writes,
	 * but potentially three seconds (!) after page erase.
	 */
	for (count = 0; count < MAX_READY_WAIT_COUNT; count++) {
		if ((sr = read_sr(flash)) < 0)
			break;
		else if (!(sr & SR_WIP))
			return 0;

		/* REVISIT sometimes sleeping would be best */
	}   
	printk( "in (%s): count = %d
", count );

	return 1;
}

/*
 * Set write enable latch with Write Enable command.
 * Returns negative if error occurred.
 */
static inline int write_enable( struct m25p10a *flash )
{
	flash->cmd[0] = CMD_WRITE_ENABLE;
	return spi_write( flash->spi, flash->cmd, 1 );
}

/*
 * Erase the whole flash memory
 *
 * Returns 0 if successful, non-zero otherwise.
 */
static int erase_chip( struct m25p10a *flash )
{
	/* Wait until finished previous write command. */
	if (wait_till_ready(flash))
		return -1;

	/* Send write enable, then erase commands. */
	write_enable( flash );
	flash->cmd[0] = CMD_BULK_ERASE;
	return spi_write( flash->spi, flash->cmd, 1 );
}

/*
 * Read an address range from the flash chip.  The address range
 * may be any size provided it is within the physical boundaries.
 */
static int m25p10a_read( struct m25p10a *flash, loff_t from, 
		size_t len, char *buf )
{
	int r_count = 0, i;

	flash->cmd[0] = CMD_READ_BYTES;
	flash->cmd[1] = from >> 16;
	flash->cmd[2] = from >> 8;
	flash->cmd[3] = from;
	
#if 1
	struct spi_transfer st[2];
	struct spi_message  msg;
	
	spi_message_init( &msg );
	memset( st, 0, sizeof(st) );

	flash->cmd[0] = CMD_READ_BYTES;
	flash->cmd[1] = from >> 16;
	flash->cmd[2] = from >> 8;
	flash->cmd[3] = from;

	st[ 0 ].tx_buf = flash->cmd;
	st[ 0 ].len = CMD_SZ;
	spi_message_add_tail( &st[0], &msg );

	st[ 1 ].rx_buf = buf;
	st[ 1 ].len = len;
	spi_message_add_tail( &st[1], &msg );

	mutex_lock( &flash->lock );
	
	/* Wait until finished previous write command. */
	if (wait_till_ready(flash)) {
		mutex_unlock( &flash->lock );
		return -1;
	}

	spi_sync( flash->spi, &msg );
	r_count = msg.actual_length - CMD_SZ;
	printk( "in (%s): read %d bytes
", __func__, r_count );
	for( i = 0; i < r_count; i++ ) {
		printk( "0x%02x
", buf[ i ] );
	}

	mutex_unlock( &flash->lock );
#endif

	return 0;
}

/*
 * Write an address range to the flash chip.  Data must be written in
 * FLASH_PAGE_SIZE chunks.  The address range may be any size provided
 * it is within the physical boundaries.
 */
static int m25p10a_write( struct m25p10a *flash, loff_t to, 
		size_t len, const char *buf )
{
	int w_count = 0, i, page_offset;
	struct spi_transfer st[2];
	struct spi_message  msg;
#if 1
	if (wait_till_ready(flash)) {    // ， ready
		mutex_unlock( &flash->lock );
		return -1;
	}
#endif
	write_enable( flash );  // 
	
	spi_message_init( &msg );
	memset( st, 0, sizeof(st) );

	flash->cmd[0] = CMD_PAGE_PROGRAM;
	flash->cmd[1] = to >> 16;
	flash->cmd[2] = to >> 8;
	flash->cmd[3] = to;

	st[ 0 ].tx_buf = flash->cmd;
	st[ 0 ].len = CMD_SZ;
	spi_message_add_tail( &st[0], &msg );

	st[ 1 ].tx_buf = buf;
	st[ 1 ].len = len;
	spi_message_add_tail( &st[1], &msg );

	mutex_lock( &flash->lock );

	/* get offset address inside a page */
	page_offset = to % FLASH_PAGE_SIZE; 	

	/* do all the bytes fit onto one page? */
	if( page_offset + len <= FLASH_PAGE_SIZE ) {	// yes
		st[ 1 ].len = len; 
		printk("%d, cmd = %d
", st[ 1 ].len, *(char *)st[0].tx_buf);
		//while(1)
		{
		spi_sync( flash->spi, &msg );
		}
		w_count = msg.actual_length - CMD_SZ;
	}
	else {	// no
	}
	printk( "in (%s): write %d bytes to flash in total
", __func__, w_count );
	mutex_unlock( &flash->lock );
	return 0;
}

static int check_id( struct m25p10a *flash ) 
{ 
	char buf[10] = {0}; 
	flash->cmd[0] = CMD_READ_ID;
	spi_write_then_read( flash->spi, flash->cmd, 1, buf, 3 ); 
	printk( "Manufacture ID: 0x%x
", buf[0] );
	printk( "Device ID: 0x%x
", buf[1] | buf[2]  << 8 );
	return buf[2] << 16 | buf[1] << 8 | buf[0]; 
} 

static int m25p10a_probe(struct spi_device *spi) 
{ 
	int ret = 0;
	struct m25p10a	*flash;
	char buf[ 256 ];
	printk( "%s was called
", __func__ );
	flash = kzalloc( sizeof(struct m25p10a), GFP_KERNEL );
	if( !flash ) {
		return -ENOMEM;
	}
	flash->spi = spi;
	mutex_init( &flash->lock );
	/* save flash as driver's private data */
	spi_set_drvdata( spi, flash );
	
	check_id( flash );    // ID
#if 1
	ret = erase_chip( flash );  // 
	if( ret < 0 ) {
		printk( "erase the entirely chip failed
" );
	}
	printk( "erase the whole chip done
" );
	memset( buf, 0x7, 256 );
	m25p10a_write( flash, 0, 20, buf); //0 20 7
	memset( buf, 0, 256 );
	m25p10a_read( flash, 0, 25, buf ); //0 25 
#endif
	return 0; 
} 

static int m25p10a_remove(struct spi_device *spi) 
{ 
	return 0; 
} 

static struct spi_driver m25p10a_driver = { 
	.probe = m25p10a_probe, 
	.remove = m25p10a_remove, 
	.driver = { 
		.name = "m25p10a", 
	}, 
}; 

static int __init m25p10a_init(void) 
{ 
	return spi_register_driver(&m25p10a_driver); 
} 

static void __exit m25p10a_exit(void) 
{ 
	spi_unregister_driver(&m25p10a_driver); 
} 

module_init(m25p10a_init); 
module_exit(m25p10a_exit); 

MODULE_DESCRIPTION("m25p10a driver for FS_S5PC100"); 
MODULE_LICENSE("GPL");

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