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

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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: Uwe Kleine-König <u.kleine-koenig@pengutronix.de>
[Brian: fixed warning]
Tested-by: Brian Norris <computersforpeace@gmail.com>
Signed-off-by: Brian Norris <computersforpeace@gmail.com>
This commit is contained in:
Uwe Kleine-König 2013-12-05 22:22:04 +01:00 committed by Brian Norris
parent e2e6b7b7d6
commit 05f7835975
2 changed files with 58 additions and 2 deletions
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57
drivers/mtd/nand/nand_base.c
View file

@ -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)

3
include/linux/mtd/nand.h
View file

@ -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);