mtd: m25p80: Micron SPI uses Macronix-style 4-byte addressing

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Gitweb:     http://git.infradead.org/?p=mtd-2.6.git;a=commit;h=eedeac3ce94e2a3d4ff28974221b9f309358d8de
Commit:     eedeac3ce94e2a3d4ff28974221b9f309358d8de
Parent:     d6a95080a2fb9fb38b4f279e97e508f6151c1000
Author:     Brian Norris <computersforpeace at gmail.com>
AuthorDate: Sat Aug 17 12:16:29 2013 -0700
Committer:  David Woodhouse <David.Woodhouse at intel.com>
CommitDate: Fri Aug 30 21:41:28 2013 +0100

    mtd: m25p80: Micron SPI uses Macronix-style 4-byte addressing
    
    For SPI NOR flash that are larger than 128Mbit (16MiB), we need 4 bytes
    of address space to reach the entire flash; however, the original SPI
    flash protocol used only 3 bytes for the address. So far, the practice
    for handling this has been either to use new command opcodes that are
    defined to use 4 bytes for their address, or to use special
    mode-switching command to configure all traditionally-3-byte-address
    commands to take 4 bytes instead.
    
    Macronix and Spansion developed two incompatible methods for
    entering/exiting "4-byte address mode." Micron flash uses the Macronix
    method (OPCODE_{EN4B,EX4B}), not the Spansion method.
    
    This patch solves addressing issues on Micron n25q256a and provides the
    ability to support other future Micron SPI flash >16MiB.
    
    Quoting a Micron representative:
    
      "Majority of our NOR that needs 4-byte addressing (256Mb or 32MB and
       higher) enter and exit 4byte through B7h and E9h commands. The
       N25Q256A7xxx and N25Q512A7xxx parts do not support 4-byte addressing
       mode via B7h or E9h command."
    
    They further clarified that those that don't support the enter/exit
    opcodes (B7h/E9h) are manufactured specifically to come up by default in
    4-byte mode. We don't need to treat those parts any diffently, as they
    will discard the EN4B opcode as a no-op.
    
    Signed-off-by: Brian Norris <computersforpeace at gmail.com>
    Acked-by: Marek Vasut <marex at denx.de>
    Signed-off-by: David Woodhouse <David.Woodhouse at intel.com>
---
 drivers/mtd/devices/m25p80.c | 1 +
 1 file changed, 1 insertion(+)

diff --git a/drivers/mtd/devices/m25p80.c b/drivers/mtd/devices/m25p80.c
index b5190c4..a759c1f 100644
--- a/drivers/mtd/devices/m25p80.c
+++ b/drivers/mtd/devices/m25p80.c
@@ -169,6 +169,7 @@ static inline int set_4byte(struct m25p *flash, u32 jedec_id, int enable)
 {
 	switch (JEDEC_MFR(jedec_id)) {
 	case CFI_MFR_MACRONIX:
+	case CFI_MFR_ST: /* Micron, actually */
 	case 0xEF /* winbond */:
 		flash->command[0] = enable ? OPCODE_EN4B : OPCODE_EX4B;
 		return spi_write(flash->spi, flash->command, 1);