From eedeac3ce94e2a3d4ff28974221b9f309358d8de Mon Sep 17 00:00:00 2001 From: Brian Norris Date: Sat, 17 Aug 2013 12:16:29 -0700 Subject: [PATCH] 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 Acked-by: Marek Vasut Signed-off-by: David Woodhouse --- 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 b5190c4bd305..a759c1fb0620 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); -- 2.11.0