mtd: spi-nor: core: Allow specifying the byte order in Octal DTR mode

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: JaimeLiao <jaimeliao@mxic.com.tw>
Signed-off-by: AlvinZhou <alvinzhou@mxic.com.tw>
Link: https://lore.kernel.org/r/20240926141956.2386374-4-alvinzhou.tw@gmail.com
Signed-off-by: Tudor Ambarus <tudor.ambarus@linaro.org>

diff --git a/drivers/mtd/spi-nor/core.c b/drivers/mtd/spi-nor/core.c
index 9d6e85bf227b92d5ae847314f4d1869950b0bdaa..b6f374ded390a0c0429a61dd0579204e0e98bfa1 100644 (file)
--- a/drivers/mtd/spi-nor/core.c
+++ b/drivers/mtd/spi-nor/core.c
@@ -113,6 +113,9 @@ void spi_nor_spimem_setup_op(const struct spi_nor *nor,
                op->cmd.opcode = (op->cmd.opcode << 8) | ext;
                op->cmd.nbytes = 2;
        }
+
+       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 1516b6d0dc37a3dc7cec3a92e18dd5b9911aac11..5c33740ed7f5f420b1e1d10ae452a9d0f41cd55a 100644 (file)
--- 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 {