Commit 05f78359 authored by Uwe Kleine-König's avatar Uwe Kleine-König Committed by Brian Norris
Browse files

mtd: nand: don't use {read,write}_buf for 8-bit transfers 



According to the Open NAND Flash Interface Specification (ONFI) Revision
3.1 "Parameters are always transferred on the lower 8-bits of the data
bus." for the Get Features and Set Features commands.

So using read_buf and write_buf is wrong for 16-bit wide nand chips as
they use I/O[15:0]. The Get Features command is easily fixed using 4
times the read_byte callback. For Set Features implement a new
overwritable callback "write_byte". Still I expect the default to work
just fine for all controllers and making it overwriteable was just done
for symmetry.

Signed-off-by: default avatarUwe Kleine-König <u.kleine-koenig@pengutronix.de>
[Brian: fixed warning]
Tested-by: default avatarBrian Norris <computersforpeace@gmail.com>
Signed-off-by: default avatarBrian Norris <computersforpeace@gmail.com>
parent e2e6b7b7

drivers/mtd/nand/nand_base.c

+55 −2
Original line number Diff line number Diff line
@@ -203,6 +203,51 @@ static void nand_select_chip(struct mtd_info *mtd, int chipnr) 
	}

}



/**

 * nand_write_byte - [DEFAULT] write single byte to chip

 * @mtd: MTD device structure

 * @byte: value to write

 *

 * Default function to write a byte to I/O[7:0]

 */

static void nand_write_byte(struct mtd_info *mtd, uint8_t byte)

{

	struct nand_chip *chip = mtd->priv;



	chip->write_buf(mtd, &byte, 1);

}



/**

 * nand_write_byte16 - [DEFAULT] write single byte to a chip with width 16

 * @mtd: MTD device structure

 * @byte: value to write

 *

 * Default function to write a byte to I/O[7:0] on a 16-bit wide chip.

 */

static void nand_write_byte16(struct mtd_info *mtd, uint8_t byte)

{

	struct nand_chip *chip = mtd->priv;

	uint16_t word = byte;



	/*

	 * It's not entirely clear what should happen to I/O[15:8] when writing

	 * a byte. The ONFi spec (Revision 3.1; 2012-09-19, Section 2.16) reads:

	 *

	 *    When the host supports a 16-bit bus width, only data is

	 *    transferred at the 16-bit width. All address and command line

	 *    transfers shall use only the lower 8-bits of the data bus. During

	 *    command transfers, the host may place any value on the upper

	 *    8-bits of the data bus. During address transfers, the host shall

	 *    set the upper 8-bits of the data bus to 00h.

	 *

	 * One user of the write_byte callback is nand_onfi_set_features. The

	 * four parameters are specified to be written to I/O[7:0], but this is

	 * neither an address nor a command transfer. Let's assume a 0 on the

	 * upper I/O lines is OK.

	 */

	chip->write_buf(mtd, (uint8_t *)&word, 2);

}



/**

 * nand_write_buf - [DEFAULT] write buffer to chip

 * @mtd: MTD device structure
@@ -2769,6 +2814,7 @@ static int nand_onfi_set_features(struct mtd_info *mtd, struct nand_chip *chip, 
			int addr, uint8_t *subfeature_param)

{

	int status;

	int i;



	if (!chip->onfi_version ||

	    !(le16_to_cpu(chip->onfi_params.opt_cmd)
@@ -2776,7 +2822,9 @@ static int nand_onfi_set_features(struct mtd_info *mtd, struct nand_chip *chip, 
		return -EINVAL;



	chip->cmdfunc(mtd, NAND_CMD_SET_FEATURES, addr, -1);

	chip->write_buf(mtd, subfeature_param, ONFI_SUBFEATURE_PARAM_LEN);

	for (i = 0; i < ONFI_SUBFEATURE_PARAM_LEN; ++i)

		chip->write_byte(mtd, subfeature_param[i]);



	status = chip->waitfunc(mtd, chip);

	if (status & NAND_STATUS_FAIL)

		return -EIO;
@@ -2793,6 +2841,8 @@ static int nand_onfi_set_features(struct mtd_info *mtd, struct nand_chip *chip, 
static int nand_onfi_get_features(struct mtd_info *mtd, struct nand_chip *chip,

			int addr, uint8_t *subfeature_param)

{

	int i;



	if (!chip->onfi_version ||

	    !(le16_to_cpu(chip->onfi_params.opt_cmd)

	      & ONFI_OPT_CMD_SET_GET_FEATURES))
@@ -2802,7 +2852,8 @@ static int nand_onfi_get_features(struct mtd_info *mtd, struct nand_chip *chip, 
	memset(subfeature_param, 0, ONFI_SUBFEATURE_PARAM_LEN);



	chip->cmdfunc(mtd, NAND_CMD_GET_FEATURES, addr, -1);

	chip->read_buf(mtd, subfeature_param, ONFI_SUBFEATURE_PARAM_LEN);

	for (i = 0; i < ONFI_SUBFEATURE_PARAM_LEN; ++i)

		*subfeature_param++ = chip->read_byte(mtd);

	return 0;

}
@@ -2865,6 +2916,8 @@ static void nand_set_defaults(struct nand_chip *chip, int busw) 
		chip->block_markbad = nand_default_block_markbad;

	if (!chip->write_buf || chip->write_buf == nand_write_buf)

		chip->write_buf = busw ? nand_write_buf16 : nand_write_buf;

	if (!chip->write_byte || chip->write_byte == nand_write_byte)

		chip->write_byte = busw ? nand_write_byte16 : nand_write_byte;

	if (!chip->read_buf || chip->read_buf == nand_read_buf)

		chip->read_buf = busw ? nand_read_buf16 : nand_read_buf;

	if (!chip->scan_bbt)

include/linux/mtd/nand.h

+3 −0
Original line number Diff line number Diff line
@@ -456,6 +456,8 @@ struct nand_buffers { 
 *			flash device.

 * @read_byte:		[REPLACEABLE] read one byte from the chip

 * @read_word:		[REPLACEABLE] read one word from the chip

 * @write_byte:		[REPLACEABLE] write a single byte to the chip on the

 *			low 8 I/O lines

 * @write_buf:		[REPLACEABLE] write data from the buffer to the chip

 * @read_buf:		[REPLACEABLE] read data from the chip into the buffer

 * @select_chip:	[REPLACEABLE] select chip nr
@@ -548,6 +550,7 @@ struct nand_chip { 


	uint8_t (*read_byte)(struct mtd_info *mtd);

	u16 (*read_word)(struct mtd_info *mtd);

	void (*write_byte)(struct mtd_info *mtd, uint8_t byte);

	void (*write_buf)(struct mtd_info *mtd, const uint8_t *buf, int len);

	void (*read_buf)(struct mtd_info *mtd, uint8_t *buf, int len);

	void (*select_chip)(struct mtd_info *mtd, int chip);

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