mtd: nand: force NAND_CMD_READID onto 8-bit bus

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. Note that I don't touch sh_flctl.c, since it already
handles this problem slightly differently (note its comment "READID is
always performed using an 8-bit bus").

I have not tested this patch, as I only have x8 parts up for testing at
this point. Hopefully that can change soon...

Signed-off-by: Brian Norris <computersforpeace@gmail.com>
Tested-by: Ezequiel Garcia <ezequiel.garcia@free-electrons.com>
Tested-By: Pekon Gupta <pekon@ti.com>

include/linux/mtd/nand.h

@@ -832,4 +832,14 @@ static inline bool nand_is_slc(struct nand_chip *chip)
 {
 	return chip->bits_per_cell == 1;
 }
+
+/**
+ * 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 */