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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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3
include/linux/mtd/nand.h
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@@ -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);