mtd: spi-nor: sfdp: get command opcode extension type from BFPT

Some devices in DTR mode expect an extra command byte called the
extension. The extension can either be same as the opcode, bitwise
inverse of the opcode, or another additional byte forming a 16-byte
opcode. Get the extension type from the BFPT. For now, only flashes with
"repeat" and "inverse" extensions are supported.
Signed-off-by: Pratyush Yadav <p.yadav@ti.com>
Signed-off-by: Vignesh Raghavendra <vigneshr@ti.com>
Reviewed-by: Tudor Ambarus <tudor.ambarus@microchip.com>
Link: https://lore.kernel.org/r/20201005153138.6437-5-p.yadav@ti.com

drivers/mtd/spi-nor/sfdp.c

@@ -606,6 +606,24 @@ static int spi_nor_parse_bfpt(struct spi_nor *nor,
 	if (bfpt_header->length == BFPT_DWORD_MAX_JESD216B)
 		return spi_nor_post_bfpt_fixups(nor, bfpt_header, &bfpt,
 						params);
+	/* 8D-8D-8D command extension. */
+	switch (bfpt.dwords[BFPT_DWORD(18)] & BFPT_DWORD18_CMD_EXT_MASK) {
+	case BFPT_DWORD18_CMD_EXT_REP:
+		nor->cmd_ext_type = SPI_NOR_EXT_REPEAT;
+		break;
+
+	case BFPT_DWORD18_CMD_EXT_INV:
+		nor->cmd_ext_type = SPI_NOR_EXT_INVERT;
+		break;
+
+	case BFPT_DWORD18_CMD_EXT_RES:
+		dev_dbg(nor->dev, "Reserved command extension used\n");
+		break;
+
+	case BFPT_DWORD18_CMD_EXT_16B:
+		dev_dbg(nor->dev, "16-bit opcodes not supported\n");
+		return -EOPNOTSUPP;
+	}
 
 	return spi_nor_post_bfpt_fixups(nor, bfpt_header, &bfpt, params);
 }

drivers/mtd/spi-nor/sfdp.h

@@ -90,6 +90,12 @@ struct sfdp_bfpt {
 #define BFPT_DWORD15_QER_SR2_BIT1_NO_RD		(0x4UL << 20)
 #define BFPT_DWORD15_QER_SR2_BIT1		(0x5UL << 20) /* Spansion */
 
+#define BFPT_DWORD18_CMD_EXT_MASK		GENMASK(30, 29)
+#define BFPT_DWORD18_CMD_EXT_REP		(0x0UL << 29) /* Repeat */
+#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 */
+
 struct sfdp_parameter_header {
 	u8		id_lsb;
 	u8		minor;