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 <computersforpeace@gmail.com> (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 <pekon@ti.com>

1 files changed, 1 insertions, 1 deletions

diff --git a/drivers/mtd/nand/nand_spl_simple.c b/drivers/mtd/nand/nand_spl_simple.c
index cead4b5..700ca32 100644
--- a/drivers/mtd/nand/nand_spl_simple.c
+++ b/drivers/mtd/nand/nand_spl_simple.c
@@ -78,7 +78,7 @@ static int nand_command(int block, int page, uint32_t offs,
 	}
 
 	/* Shift the offset from byte addressing to word addressing. */
-	if (this->options & NAND_BUSWIDTH_16)
+	if ((this->options & NAND_BUSWIDTH_16) && !nand_opcode_8bits(cmd))
 		offs >>= 1;
 
 	/* Begin command latch cycle */