[PATCH v9 3/6] mtd: spi-nor: core: Allow specifying the byte order in Octal DTR mode

AlvinZhou
2024-07-18T03:47:53Z

From: AlvinZhou <alvinzhou@mxic.com.tw>

From: Tudor Ambarus <tudor.ambarus@linaro.org>

Macronix swaps bytes on a 16-bit boundary when configured in Octal DTR.
The byte order of 16-bit words is swapped when read or written in 8D-8D-8D
mode compared to STR modes. Allow operations to specify the byte order in
DTR mode, so that controllers can swap the bytes back at run-time to
address the flash's endianness requirements, if they are capable. If the
controller is not capable of swapping the bytes, the protocol is downgrade
via spi_nor_spimem_adjust_hwcaps(). When available, the swapping of the
bytes is always done regardless if it's a data or register access, so that
it comply with the JESD216 requirements: "Byte order of 16-bit words is
swapped when read in 8D-8D-8D mode compared to 1-1-1".

Merge Tudor's patch and add modifications for suiting newer version
of Linux kernel.

Suggested-by: Michael Walle <mwalle@kernel.org>
Signed-off-by: Tudor Ambarus <tudor.ambarus@linaro.org>
Signed-off-by: JaimeLiao <jaimeliao@mxic.com.tw>
Signed-off-by: AlvinZhou <alvinzhou@mxic.com.tw>
---
drivers/mtd/spi-nor/core.c | 4 ++++
drivers/mtd/spi-nor/core.h | 1 +
2 files changed, 5 insertions(+)

diff --git a/drivers/mtd/spi-nor/core.c b/drivers/mtd/spi-nor/core.c
index 028514c6996f..31f57b17023f 100644
--- a/drivers/mtd/spi-nor/core.c
+++ b/drivers/mtd/spi-nor/core.c
@@ -113,6 +113,10 @@ void spi_nor_spimem_setup_op(const struct spi_nor *nor,
op->cmd.opcode = (op->cmd.opcode << 8) | ext;
op->cmd.nbytes = 2;
}
+
+ /* SWAP16 is only applicable when Octal DTR mode */
+ if (proto == SNOR_PROTO_8_8_8_DTR && nor->flags & SNOR_F_SWAP16)
+ op->data.swap16 = true;
}

/**
diff --git a/drivers/mtd/spi-nor/core.h b/drivers/mtd/spi-nor/core.h
index 442786685515..baf6c4b5912b 100644
--- a/drivers/mtd/spi-nor/core.h
+++ b/drivers/mtd/spi-nor/core.h
@@ -140,6 +140,7 @@ enum spi_nor_option_flags {
SNOR_F_RWW = BIT(14),
SNOR_F_ECC = BIT(15),
SNOR_F_NO_WP = BIT(16),
+ SNOR_F_SWAP16 = BIT(17),
};

struct spi_nor_read_command {
--
2.25.1