[PATCH v8 4/9] mtd: spi-nor: sfdp: Get the 8D-8D-8D byte order from BFPT

[Jaime Liao <jaimeliao.tw@gmail.com>]

From: JaimeLiao <jaimeliao@mxic.com.tw>

Parse BFPT in order to retrieve the byte order in 8D-8D-8D mode.

This info flag will be used as a basis to determine whether
there is byte swapping of data for SPI NOR flash in octal
DTR mode.

The controller driver will check whether byte swapping is supported
to determin whether the corresponding operation are supported, thus
avoiding the generation of unexpected data order.

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

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

diff --git a/drivers/mtd/spi-nor/sfdp.c b/drivers/mtd/spi-nor/sfdp.c
index 57713de32832..1bdb82c1328c 100644
--- a/drivers/mtd/spi-nor/sfdp.c
+++ b/drivers/mtd/spi-nor/sfdp.c
@@ -677,6 +677,10 @@ static int spi_nor_parse_bfpt(struct spi_nor *nor,
 		return -EOPNOTSUPP;
 	}
 
+	/* Byte order in 8D-8D-8D mode */
+	if (bfpt.dwords[SFDP_DWORD(18)] & BFPT_DWORD18_BYTE_ORDER_SWAPPED)
+		nor->flags |= SNOR_F_SWAP16;
+
 	return spi_nor_post_bfpt_fixups(nor, bfpt_header, &bfpt);
 }
 
diff --git a/drivers/mtd/spi-nor/sfdp.h b/drivers/mtd/spi-nor/sfdp.h
index da0fe5aa9bb0..6089d5bc1e4f 100644
--- a/drivers/mtd/spi-nor/sfdp.h
+++ b/drivers/mtd/spi-nor/sfdp.h
@@ -130,6 +130,7 @@ struct sfdp_bfpt {
 #define BFPT_DWORD18_CMD_EXT_INV		(0x1UL << 29) /* Invert */
 #define BFPT_DWORD18_CMD_EXT_RES		(0x2UL << 29) /* Reserved */
 #define BFPT_DWORD18_CMD_EXT_16B		(0x3UL << 29) /* 16-bit opcode */
+#define BFPT_DWORD18_BYTE_ORDER_SWAPPED		BIT(31) /* Byte order of 16-bit words in 8D-8D-8D mode */
 
 struct sfdp_parameter_header {
 	u8		id_lsb;
-- 
2.25.1