From 27ce9e4290b168a1241699d411678959aaf9649b Mon Sep 17 00:00:00 2001 From: Brian Norris Date: Tue, 6 May 2014 00:46:17 +0530 Subject: mtd: nand: force NAND_CMD_READID onto 8-bit bus As per following Sections in ONFI Spec, NAND_CMD_READID should use only lower 8-bit for transfering command, address and data even on x16 NAND device. *Section: Target Initialization" "The Read ID and Read Parameter Page commands only use the lower 8-bits of the data bus. The host shall not issue commands that use a word data width on x16 devices until the host determines the device supports a 16-bit data bus width in the parameter page." *Section: Bus Width Requirements* "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." Thus porting following commit from linux-kernel to ensure that column address is not altered to align to x16 bus when issuing NAND_CMD_READID command. commit 3dad2344e92c6e1aeae42df1c4824f307c51bcc7 mtd: nand: force NAND_CMD_READID onto 8-bit bus Author: Brian Norris (preserving authorship) The NAND command helpers tend to automatically shift the column address for x16 bus devices, since most commands expect a word address, not a byte address. The Read ID command, however, expects an 8-bit address (i.e., 0x00, 0x20, or 0x40 should not be translated to 0x00, 0x10, or 0x20). This fixes the column address for a few drivers which imitate the nand_base defaults. Signed-off-by: Pekon Gupta --- include/linux/mtd/nand.h | 10 ++++++++++ 1 file changed, 10 insertions(+) (limited to 'include/linux') diff --git a/include/linux/mtd/nand.h b/include/linux/mtd/nand.h index 0546565593..4be885823c 100644 --- a/include/linux/mtd/nand.h +++ b/include/linux/mtd/nand.h @@ -719,4 +719,14 @@ static inline int onfi_get_sync_timing_mode(struct nand_chip *chip) } #endif +/** + * Check if the opcode's address should be sent only on the lower 8 bits + * @command: opcode to check + */ +static inline int nand_opcode_8bits(unsigned int command) +{ + return command == NAND_CMD_READID; +} + + #endif /* __LINUX_MTD_NAND_H */ -- cgit