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Commit 49aac4ae authored by Graf Yang's avatar Graf Yang Committed by David Woodhouse
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mtd: m25p80: add support for AAI programming with SST SPI flashes 



The SST SPI flashes are a bit non-standard in that they can be programmed
one byte at a time (including address!), or they can be written two bytes
at a time with auto address incrementing (AAI).  The latter form is
obviously much better for performance, so let's use it when possible.

Signed-off-by: default avatarGraf Yang <graf.yang@analog.com>
Signed-off-by: default avatarMike Frysinger <vapier@gentoo.org>
Signed-off-by: default avatarDavid Woodhouse <David.Woodhouse@intel.com>
parent 80f53da0

drivers/mtd/devices/m25p80.c

+125 −1
Original line number Diff line number Diff line
@@ -44,6 +44,11 @@ 
#define	OPCODE_SE		0xd8	/* Sector erase (usually 64KiB) */

#define	OPCODE_RDID		0x9f	/* Read JEDEC ID */



/* Used for SST flashes only. */

#define	OPCODE_BP		0x02	/* Byte program */

#define	OPCODE_WRDI		0x04	/* Write disable */

#define	OPCODE_AAI_WP		0xad	/* Auto address increment word program */



/* Status Register bits. */

#define	SR_WIP			1	/* Write in progress */

#define	SR_WEL			2	/* Write enable latch */
@@ -132,6 +137,15 @@ static inline int write_enable(struct m25p *flash) 
	return spi_write_then_read(flash->spi, &code, 1, NULL, 0);

}



/*

 * Send write disble instruction to the chip.

 */

static inline int write_disable(struct m25p *flash)

{

	u8	code = OPCODE_WRDI;



	return spi_write_then_read(flash->spi, &code, 1, NULL, 0);

}



/*

 * Service routine to read status register until ready, or timeout occurs.
@@ -454,6 +468,111 @@ static int m25p80_write(struct mtd_info *mtd, loff_t to, size_t len, 
	return 0;

}



static int sst_write(struct mtd_info *mtd, loff_t to, size_t len,

		size_t *retlen, const u_char *buf)

{

	struct m25p *flash = mtd_to_m25p(mtd);

	struct spi_transfer t[2];

	struct spi_message m;

	size_t actual;

	int cmd_sz, ret;



	if (retlen)

		*retlen = 0;



	/* sanity checks */

	if (!len)

		return 0;



	if (to + len > flash->mtd.size)

		return -EINVAL;



	spi_message_init(&m);

	memset(t, 0, (sizeof t));



	t[0].tx_buf = flash->command;

	t[0].len = CMD_SIZE;

	spi_message_add_tail(&t[0], &m);



	t[1].tx_buf = buf;

	spi_message_add_tail(&t[1], &m);



	mutex_lock(&flash->lock);



	/* Wait until finished previous write command. */

	ret = wait_till_ready(flash);

	if (ret)

		goto time_out;



	write_enable(flash);



	actual = to % 2;

	/* Start write from odd address. */

	if (actual) {

		flash->command[0] = OPCODE_BP;

		flash->command[1] = to >> 16;

		flash->command[2] = to >> 8;

		flash->command[3] = to;



		/* write one byte. */

		t[1].len = 1;

		spi_sync(flash->spi, &m);

		ret = wait_till_ready(flash);

		if (ret)

			goto time_out;

		*retlen += m.actual_length - CMD_SIZE;

	}

	to += actual;



	flash->command[0] = OPCODE_AAI_WP;

	flash->command[1] = to >> 16;

	flash->command[2] = to >> 8;

	flash->command[3] = to;



	/* Write out most of the data here. */

	cmd_sz = CMD_SIZE;

	for (; actual < len - 1; actual += 2) {

		t[0].len = cmd_sz;

		/* write two bytes. */

		t[1].len = 2;

		t[1].tx_buf = buf + actual;



		spi_sync(flash->spi, &m);

		ret = wait_till_ready(flash);

		if (ret)

			goto time_out;

		*retlen += m.actual_length - cmd_sz;

		cmd_sz = 1;

		to += 2;

	}

	write_disable(flash);

	ret = wait_till_ready(flash);

	if (ret)

		goto time_out;



	/* Write out trailing byte if it exists. */

	if (actual != len) {

		write_enable(flash);

		flash->command[0] = OPCODE_BP;

		flash->command[1] = to >> 16;

		flash->command[2] = to >> 8;

		flash->command[3] = to;

		t[0].len = CMD_SIZE;

		t[1].len = 1;

		t[1].tx_buf = buf + actual;



		spi_sync(flash->spi, &m);

		ret = wait_till_ready(flash);

		if (ret)

			goto time_out;

		*retlen += m.actual_length - CMD_SIZE;

		write_disable(flash);

	}



time_out:

	mutex_unlock(&flash->lock);

	return ret;

}



/****************************************************************************/
@@ -670,6 +789,11 @@ static int __devinit m25p_probe(struct spi_device *spi) 
	flash->mtd.size = info->sector_size * info->n_sectors;

	flash->mtd.erase = m25p80_erase;

	flash->mtd.read = m25p80_read;



	/* sst flash chips use AAI word program */

	if (info->jedec_id >> 16 == 0xbf)

		flash->mtd.write = sst_write;

	else

		flash->mtd.write = m25p80_write;



	/* prefer "small sector" erase if possible */