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| author | Brian Norris <computersforpeace@gmail.com> | 2013-08-17 23:16:29 +0400 |
|---|---|---|
| committer | David Woodhouse <David.Woodhouse@intel.com> | 2013-08-31 00:41:28 +0400 |
| commit | eedeac3ce94e2a3d4ff28974221b9f309358d8de (patch) | |
| tree | 7725b50529a2090662f08669cf858989649627f1 /drivers/mtd/devices | |
| parent | d6a95080a2fb9fb38b4f279e97e508f6151c1000 (diff) | |
| download | linux-eedeac3ce94e2a3d4ff28974221b9f309358d8de.tar.xz | |
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@gmail.com>
Acked-by: Marek Vasut <marex@denx.de>
Signed-off-by: David Woodhouse <David.Woodhouse@intel.com>
Diffstat (limited to 'drivers/mtd/devices')
| -rw-r--r-- | drivers/mtd/devices/m25p80.c | 1 |
1 files changed, 1 insertions, 0 deletions
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); |