[PATCH v10 14/27] mtd: spi-nor-core: Add support for DTR protocol

[Pratyush Yadav <p.yadav@ti.com>]

Double Transfer Rate (DTR) is SPI protocol in which data is transferred
on each clock edge as opposed to on each clock cycle. Make
framework-level changes to allow supporting flashes in DTR mode.

Right now, mixed DTR modes are not supported. So, for example a mode
like 4S-4D-4D will not work. All phases need to be either DTR or STR.

Signed-off-by: Pratyush Yadav <p.yadav@ti.com>
---
 drivers/mtd/spi/sf_internal.h  |   1 +
 drivers/mtd/spi/spi-nor-core.c | 178 +++++++++++++++++++++++++--------
 include/linux/mtd/spi-nor.h    |  50 ++++++---
 3 files changed, 175 insertions(+), 54 deletions(-)

diff --git a/drivers/mtd/spi/sf_internal.h b/drivers/mtd/spi/sf_internal.h
index 0b63e1bfc2..d3ef69ec74 100644
--- a/drivers/mtd/spi/sf_internal.h
+++ b/drivers/mtd/spi/sf_internal.h
@@ -68,6 +68,7 @@ struct flash_info {
 #define USE_CLSR		BIT(14)	/* use CLSR command */
 #define SPI_NOR_HAS_SST26LOCK	BIT(15)	/* Flash supports lock/unlock via BPR */
 #define SPI_NOR_OCTAL_READ	BIT(16)	/* Flash supports Octal Read */
+#define SPI_NOR_OCTAL_DTR_READ	BIT(17)	/* Flash supports Octal DTR Read */
 };
 
 extern const struct flash_info spi_nor_ids[];
diff --git a/drivers/mtd/spi/spi-nor-core.c b/drivers/mtd/spi/spi-nor-core.c
index d795ecbc9f..c2eae885e4 100644
--- a/drivers/mtd/spi/spi-nor-core.c
+++ b/drivers/mtd/spi/spi-nor-core.c
@@ -177,6 +177,76 @@ struct spi_nor_fixups {
 			  struct spi_nor_flash_parameter *params);
 };
 
+/**
+ * spi_nor_get_cmd_ext() - Get the command opcode extension based on the
+ *			   extension type.
+ * @nor:		pointer to a 'struct spi_nor'
+ * @op:			pointer to the 'struct spi_mem_op' whose properties
+ *			need to be initialized.
+ *
+ * Right now, only "repeat" and "invert" are supported.
+ *
+ * Return: The opcode extension.
+ */
+static u8 spi_nor_get_cmd_ext(const struct spi_nor *nor,
+			      const struct spi_mem_op *op)
+{
+	switch (nor->cmd_ext_type) {
+	case SPI_NOR_EXT_INVERT:
+		return ~op->cmd.opcode;
+
+	case SPI_NOR_EXT_REPEAT:
+		return op->cmd.opcode;
+
+	default:
+		dev_dbg(nor->dev, "Unknown command extension type\n");
+		return 0;
+	}
+}
+
+/**
+ * spi_nor_setup_op() - Set up common properties of a spi-mem op.
+ * @nor:		pointer to a 'struct spi_nor'
+ * @op:			pointer to the 'struct spi_mem_op' whose properties
+ *			need to be initialized.
+ * @proto:		the protocol from which the properties need to be set.
+ */
+static void spi_nor_setup_op(const struct spi_nor *nor,
+			     struct spi_mem_op *op,
+			     const enum spi_nor_protocol proto)
+{
+	u8 ext;
+
+	op->cmd.buswidth = spi_nor_get_protocol_inst_nbits(proto);
+
+	if (op->addr.nbytes)
+		op->addr.buswidth = spi_nor_get_protocol_addr_nbits(proto);
+
+	if (op->dummy.nbytes)
+		op->dummy.buswidth = spi_nor_get_protocol_addr_nbits(proto);
+
+	if (op->data.nbytes)
+		op->data.buswidth = spi_nor_get_protocol_data_nbits(proto);
+
+	if (spi_nor_protocol_is_dtr(proto)) {
+		/*
+		 * spi-mem supports mixed DTR modes, but right now we can only
+		 * have all phases either DTR or STR. IOW, spi-mem can have
+		 * something like 4S-4D-4D, but spi-nor can't. So, set all 4
+		 * phases to either DTR or STR.
+		 */
+		op->cmd.dtr = op->addr.dtr = op->dummy.dtr =
+			op->data.dtr = true;
+
+		/* 2 bytes per clock cycle in DTR mode. */
+		op->dummy.nbytes *= 2;
+
+		ext = spi_nor_get_cmd_ext(nor, op);
+		op->cmd.opcode = (op->cmd.opcode << 8) | ext;
+		op->cmd.nbytes = 2;
+	}
+}
+
 static int spi_nor_read_write_reg(struct spi_nor *nor, struct spi_mem_op
 		*op, void *buf)
 {
@@ -189,12 +259,14 @@ static int spi_nor_read_write_reg(struct spi_nor *nor, struct spi_mem_op
 
 static int spi_nor_read_reg(struct spi_nor *nor, u8 code, u8 *val, int len)
 {
-	struct spi_mem_op op = SPI_MEM_OP(SPI_MEM_OP_CMD(code, 1),
+	struct spi_mem_op op = SPI_MEM_OP(SPI_MEM_OP_CMD(code, 0),
 					  SPI_MEM_OP_NO_ADDR,
 					  SPI_MEM_OP_NO_DUMMY,
-					  SPI_MEM_OP_DATA_IN(len, NULL, 1));
+					  SPI_MEM_OP_DATA_IN(len, NULL, 0));
 	int ret;
 
+	spi_nor_setup_op(nor, &op, nor->reg_proto);
+
 	ret = spi_nor_read_write_reg(nor, &op, val);
 	if (ret < 0)
 		dev_dbg(nor->dev, "error %d reading %x\n", ret, code);
@@ -204,10 +276,12 @@ static int spi_nor_read_reg(struct spi_nor *nor, u8 code, u8 *val, int len)
 
 static int spi_nor_write_reg(struct spi_nor *nor, u8 opcode, u8 *buf, int len)
 {
-	struct spi_mem_op op = SPI_MEM_OP(SPI_MEM_OP_CMD(opcode, 1),
+	struct spi_mem_op op = SPI_MEM_OP(SPI_MEM_OP_CMD(opcode, 0),
 					  SPI_MEM_OP_NO_ADDR,
 					  SPI_MEM_OP_NO_DUMMY,
-					  SPI_MEM_OP_DATA_OUT(len, NULL, 1));
+					  SPI_MEM_OP_DATA_OUT(len, NULL, 0));
+
+	spi_nor_setup_op(nor, &op, nor->reg_proto);
 
 	if (len == 0)
 		op.data.dir = SPI_MEM_NO_DATA;
@@ -219,21 +293,19 @@ static ssize_t spi_nor_read_data(struct spi_nor *nor, loff_t from, size_t len,
 				 u_char *buf)
 {
 	struct spi_mem_op op =
-			SPI_MEM_OP(SPI_MEM_OP_CMD(nor->read_opcode, 1),
-				   SPI_MEM_OP_ADDR(nor->addr_width, from, 1),
-				   SPI_MEM_OP_DUMMY(nor->read_dummy, 1),
-				   SPI_MEM_OP_DATA_IN(len, buf, 1));
+			SPI_MEM_OP(SPI_MEM_OP_CMD(nor->read_opcode, 0),
+				   SPI_MEM_OP_ADDR(nor->addr_width, from, 0),
+				   SPI_MEM_OP_DUMMY(nor->read_dummy, 0),
+				   SPI_MEM_OP_DATA_IN(len, buf, 0));
 	size_t remaining = len;
 	int ret;
 
-	/* get transfer protocols. */
-	op.cmd.buswidth = spi_nor_get_protocol_inst_nbits(nor->read_proto);
-	op.addr.buswidth = spi_nor_get_protocol_addr_nbits(nor->read_proto);
-	op.dummy.buswidth = op.addr.buswidth;
-	op.data.buswidth = spi_nor_get_protocol_data_nbits(nor->read_proto);
+	spi_nor_setup_op(nor, &op, nor->read_proto);
 
 	/* convert the dummy cycles to the number of bytes */
 	op.dummy.nbytes = (nor->read_dummy * op.dummy.buswidth) / 8;
+	if (spi_nor_protocol_is_dtr(nor->read_proto))
+		op.dummy.nbytes *= 2;
 
 	while (remaining) {
 		op.data.nbytes = remaining < UINT_MAX ? remaining : UINT_MAX;
@@ -257,20 +329,17 @@ static ssize_t spi_nor_write_data(struct spi_nor *nor, loff_t to, size_t len,
 				  const u_char *buf)
 {
 	struct spi_mem_op op =
-			SPI_MEM_OP(SPI_MEM_OP_CMD(nor->program_opcode, 1),
-				   SPI_MEM_OP_ADDR(nor->addr_width, to, 1),
+			SPI_MEM_OP(SPI_MEM_OP_CMD(nor->program_opcode, 0),
+				   SPI_MEM_OP_ADDR(nor->addr_width, to, 0),
 				   SPI_MEM_OP_NO_DUMMY,
-				   SPI_MEM_OP_DATA_OUT(len, buf, 1));
+				   SPI_MEM_OP_DATA_OUT(len, buf, 0));
 	int ret;
 
-	/* get transfer protocols. */
-	op.cmd.buswidth = spi_nor_get_protocol_inst_nbits(nor->write_proto);
-	op.addr.buswidth = spi_nor_get_protocol_addr_nbits(nor->write_proto);
-	op.data.buswidth = spi_nor_get_protocol_data_nbits(nor->write_proto);
-
 	if (nor->program_opcode == SPINOR_OP_AAI_WP && nor->sst_write_second)
 		op.addr.nbytes = 0;
 
+	spi_nor_setup_op(nor, &op, nor->write_proto);
+
 	ret = spi_mem_adjust_op_size(nor->spi, &op);
 	if (ret)
 		return ret;
@@ -668,11 +737,13 @@ static int read_bar(struct spi_nor *nor, const struct flash_info *info)
 static int spi_nor_erase_sector(struct spi_nor *nor, u32 addr)
 {
 	struct spi_mem_op op =
-		SPI_MEM_OP(SPI_MEM_OP_CMD(nor->erase_opcode, 1),
-			   SPI_MEM_OP_ADDR(nor->addr_width, addr, 1),
+		SPI_MEM_OP(SPI_MEM_OP_CMD(nor->erase_opcode, 0),
+			   SPI_MEM_OP_ADDR(nor->addr_width, addr, 0),
 			   SPI_MEM_OP_NO_DUMMY,
 			   SPI_MEM_OP_NO_DATA);
 
+	spi_nor_setup_op(nor, &op, nor->write_proto);
+
 	if (nor->erase)
 		return nor->erase(nor, addr);
 
@@ -2194,11 +2265,25 @@ static int spi_nor_init_params(struct spi_nor *nor,
 					  SNOR_PROTO_1_1_8);
 	}
 
+	if (info->flags & SPI_NOR_OCTAL_DTR_READ) {
+		params->hwcaps.mask |= SNOR_HWCAPS_READ_8_8_8_DTR;
+		spi_nor_set_read_settings(&params->reads[SNOR_CMD_READ_8_8_8_DTR],
+					  0, 20, SPINOR_OP_READ_FAST,
+					  SNOR_PROTO_8_8_8_DTR);
+	}
+
 	/* Page Program settings. */
 	params->hwcaps.mask |= SNOR_HWCAPS_PP;
 	spi_nor_set_pp_settings(&params->page_programs[SNOR_CMD_PP],
 				SPINOR_OP_PP, SNOR_PROTO_1_1_1);
 
+	/*
+	 * Since xSPI Page Program opcode is backward compatible with
+	 * Legacy SPI, use Legacy SPI opcode there as well.
+	 */
+	spi_nor_set_pp_settings(&params->page_programs[SNOR_CMD_PP_8_8_8_DTR],
+				SPINOR_OP_PP, SNOR_PROTO_8_8_8_DTR);
+
 	if (info->flags & SPI_NOR_QUAD_READ) {
 		params->hwcaps.mask |= SNOR_HWCAPS_PP_1_1_4;
 		spi_nor_set_pp_settings(&params->page_programs[SNOR_CMD_PP_1_1_4],
@@ -2233,7 +2318,8 @@ static int spi_nor_init_params(struct spi_nor *nor,
 	/* Override the parameters with data read from SFDP tables. */
 	nor->addr_width = 0;
 	nor->mtd.erasesize = 0;
-	if ((info->flags & (SPI_NOR_DUAL_READ | SPI_NOR_QUAD_READ)) &&
+	if ((info->flags & (SPI_NOR_DUAL_READ | SPI_NOR_QUAD_READ |
+	     SPI_NOR_OCTAL_DTR_READ)) &&
 	    !(info->flags & SPI_NOR_SKIP_SFDP)) {
 		struct spi_nor_flash_parameter sfdp_params;
 
@@ -2280,6 +2366,7 @@ static int spi_nor_hwcaps_read2cmd(u32 hwcaps)
 		{ SNOR_HWCAPS_READ_1_8_8,	SNOR_CMD_READ_1_8_8 },
 		{ SNOR_HWCAPS_READ_8_8_8,	SNOR_CMD_READ_8_8_8 },
 		{ SNOR_HWCAPS_READ_1_8_8_DTR,	SNOR_CMD_READ_1_8_8_DTR },
+		{ SNOR_HWCAPS_READ_8_8_8_DTR,	SNOR_CMD_READ_8_8_8_DTR },
 	};
 
 	return spi_nor_hwcaps2cmd(hwcaps, hwcaps_read2cmd,
@@ -2296,6 +2383,7 @@ static int spi_nor_hwcaps_pp2cmd(u32 hwcaps)
 		{ SNOR_HWCAPS_PP_1_1_8,		SNOR_CMD_PP_1_1_8 },
 		{ SNOR_HWCAPS_PP_1_8_8,		SNOR_CMD_PP_1_8_8 },
 		{ SNOR_HWCAPS_PP_8_8_8,		SNOR_CMD_PP_8_8_8 },
+		{ SNOR_HWCAPS_PP_8_8_8_DTR,	SNOR_CMD_PP_8_8_8_DTR },
 	};
 
 	return spi_nor_hwcaps2cmd(hwcaps, hwcaps_pp2cmd,
@@ -2342,17 +2430,17 @@ static int spi_nor_check_op(struct spi_nor *nor,
 static int spi_nor_check_readop(struct spi_nor *nor,
 				const struct spi_nor_read_command *read)
 {
-	struct spi_mem_op op = SPI_MEM_OP(SPI_MEM_OP_CMD(read->opcode, 1),
-					  SPI_MEM_OP_ADDR(3, 0, 1),
-					  SPI_MEM_OP_DUMMY(0, 1),
-					  SPI_MEM_OP_DATA_IN(0, NULL, 1));
+	struct spi_mem_op op = SPI_MEM_OP(SPI_MEM_OP_CMD(read->opcode, 0),
+					  SPI_MEM_OP_ADDR(3, 0, 0),
+					  SPI_MEM_OP_DUMMY(1, 0),
+					  SPI_MEM_OP_DATA_IN(2, NULL, 0));
+
+	spi_nor_setup_op(nor, &op, read->proto);
 
-	op.cmd.buswidth = spi_nor_get_protocol_inst_nbits(read->proto);
-	op.addr.buswidth = spi_nor_get_protocol_addr_nbits(read->proto);
-	op.data.buswidth = spi_nor_get_protocol_data_nbits(read->proto);
-	op.dummy.buswidth = op.addr.buswidth;
 	op.dummy.nbytes = (read->num_mode_clocks + read->num_wait_states) *
 			  op.dummy.buswidth / 8;
+	if (spi_nor_protocol_is_dtr(nor->read_proto))
+		op.dummy.nbytes *= 2;
 
 	return spi_nor_check_op(nor, &op);
 }
@@ -2367,14 +2455,12 @@ static int spi_nor_check_readop(struct spi_nor *nor,
 static int spi_nor_check_pp(struct spi_nor *nor,
 			    const struct spi_nor_pp_command *pp)
 {
-	struct spi_mem_op op = SPI_MEM_OP(SPI_MEM_OP_CMD(pp->opcode, 1),
-					  SPI_MEM_OP_ADDR(3, 0, 1),
+	struct spi_mem_op op = SPI_MEM_OP(SPI_MEM_OP_CMD(pp->opcode, 0),
+					  SPI_MEM_OP_ADDR(3, 0, 0),
 					  SPI_MEM_OP_NO_DUMMY,
-					  SPI_MEM_OP_DATA_OUT(0, NULL, 1));
+					  SPI_MEM_OP_DATA_OUT(2, NULL, 0));
 
-	op.cmd.buswidth = spi_nor_get_protocol_inst_nbits(pp->proto);
-	op.addr.buswidth = spi_nor_get_protocol_addr_nbits(pp->proto);
-	op.data.buswidth = spi_nor_get_protocol_data_nbits(pp->proto);
+	spi_nor_setup_op(nor, &op, pp->proto);
 
 	return spi_nor_check_op(nor, &op);
 }
@@ -2404,12 +2490,16 @@ spi_nor_adjust_hwcaps(struct spi_nor *nor,
 	 */
 	*hwcaps = SNOR_HWCAPS_ALL;
 
-	/* DTR modes are not supported yet, mask them all. */
-	*hwcaps &= ~SNOR_HWCAPS_DTR;
-
 	/* X-X-X modes are not supported yet, mask them all. */
 	*hwcaps &= ~SNOR_HWCAPS_X_X_X;
 
+	/*
+	 * If the reset line is broken, we do not want to enter a stateful
+	 * mode.
+	 */
+	if (nor->flags & SNOR_F_BROKEN_RESET)
+		*hwcaps &= ~(SNOR_HWCAPS_X_X_X | SNOR_HWCAPS_X_X_X_DTR);
+
 	for (cap = 0; cap < sizeof(*hwcaps) * BITS_PER_BYTE; cap++) {
 		int rdidx, ppidx;
 
@@ -2649,6 +2739,7 @@ static int spi_nor_init(struct spi_nor *nor)
 	}
 
 	if (nor->addr_width == 4 &&
+	    !(nor->info->flags & SPI_NOR_OCTAL_DTR_READ) &&
 	    (JEDEC_MFR(nor->info) != SNOR_MFR_SPANSION) &&
 	    !(nor->info->flags & SPI_NOR_4B_OPCODES)) {
 		/*
@@ -2767,7 +2858,10 @@ int spi_nor_scan(struct spi_nor *nor)
 	if (ret)
 		return ret;
 
-	if (nor->addr_width) {
+	if (spi_nor_protocol_is_dtr(nor->read_proto)) {
+		 /* Always use 4-byte addresses in DTR mode. */
+		nor->addr_width = 4;
+	} else if (nor->addr_width) {
 		/* already configured from SFDP */
 	} else if (info->addr_width) {
 		nor->addr_width = info->addr_width;
diff --git a/include/linux/mtd/spi-nor.h b/include/linux/mtd/spi-nor.h
index 90b75ec845..4394cb6e16 100644
--- a/include/linux/mtd/spi-nor.h
+++ b/include/linux/mtd/spi-nor.h
@@ -200,6 +200,7 @@ enum spi_nor_protocol {
 	SNOR_PROTO_1_2_2_DTR = SNOR_PROTO_DTR(1, 2, 2),
 	SNOR_PROTO_1_4_4_DTR = SNOR_PROTO_DTR(1, 4, 4),
 	SNOR_PROTO_1_8_8_DTR = SNOR_PROTO_DTR(1, 8, 8),
+	SNOR_PROTO_8_8_8_DTR = SNOR_PROTO_DTR(8, 8, 8),
 };
 
 static inline bool spi_nor_protocol_is_dtr(enum spi_nor_protocol proto)
@@ -267,7 +268,7 @@ struct spi_nor_hwcaps {
  * then Quad SPI protocols before Dual SPI protocols, Fast Read and lastly
  * (Slow) Read.
  */
-#define SNOR_HWCAPS_READ_MASK		GENMASK(14, 0)
+#define SNOR_HWCAPS_READ_MASK		GENMASK(15, 0)
 #define SNOR_HWCAPS_READ		BIT(0)
 #define SNOR_HWCAPS_READ_FAST		BIT(1)
 #define SNOR_HWCAPS_READ_1_1_1_DTR	BIT(2)
@@ -284,11 +285,12 @@ struct spi_nor_hwcaps {
 #define SNOR_HWCAPS_READ_4_4_4		BIT(9)
 #define SNOR_HWCAPS_READ_1_4_4_DTR	BIT(10)
 
-#define SNOR_HWCPAS_READ_OCTO		GENMASK(14, 11)
+#define SNOR_HWCPAS_READ_OCTO		GENMASK(15, 11)
 #define SNOR_HWCAPS_READ_1_1_8		BIT(11)
 #define SNOR_HWCAPS_READ_1_8_8		BIT(12)
 #define SNOR_HWCAPS_READ_8_8_8		BIT(13)
 #define SNOR_HWCAPS_READ_1_8_8_DTR	BIT(14)
+#define SNOR_HWCAPS_READ_8_8_8_DTR	BIT(15)
 
 /*
  * Page Program capabilities.
@@ -299,18 +301,19 @@ struct spi_nor_hwcaps {
  * JEDEC/SFDP standard to define them. Also at this moment no SPI flash memory
  * implements such commands.
  */
-#define SNOR_HWCAPS_PP_MASK	GENMASK(22, 16)
-#define SNOR_HWCAPS_PP		BIT(16)
+#define SNOR_HWCAPS_PP_MASK		GENMASK(23, 16)
+#define SNOR_HWCAPS_PP			BIT(16)
 
-#define SNOR_HWCAPS_PP_QUAD	GENMASK(19, 17)
-#define SNOR_HWCAPS_PP_1_1_4	BIT(17)
-#define SNOR_HWCAPS_PP_1_4_4	BIT(18)
-#define SNOR_HWCAPS_PP_4_4_4	BIT(19)
+#define SNOR_HWCAPS_PP_QUAD		GENMASK(19, 17)
+#define SNOR_HWCAPS_PP_1_1_4		BIT(17)
+#define SNOR_HWCAPS_PP_1_4_4		BIT(18)
+#define SNOR_HWCAPS_PP_4_4_4		BIT(19)
 
-#define SNOR_HWCAPS_PP_OCTO	GENMASK(22, 20)
-#define SNOR_HWCAPS_PP_1_1_8	BIT(20)
-#define SNOR_HWCAPS_PP_1_8_8	BIT(21)
-#define SNOR_HWCAPS_PP_8_8_8	BIT(22)
+#define SNOR_HWCAPS_PP_OCTO		GENMASK(23, 20)
+#define SNOR_HWCAPS_PP_1_1_8		BIT(20)
+#define SNOR_HWCAPS_PP_1_8_8		BIT(21)
+#define SNOR_HWCAPS_PP_8_8_8		BIT(22)
+#define SNOR_HWCAPS_PP_8_8_8_DTR	BIT(23)
 
 #define SNOR_HWCAPS_X_X_X	(SNOR_HWCAPS_READ_2_2_2 |	\
 				 SNOR_HWCAPS_READ_4_4_4 |	\
@@ -318,6 +321,9 @@ struct spi_nor_hwcaps {
 				 SNOR_HWCAPS_PP_4_4_4 |		\
 				 SNOR_HWCAPS_PP_8_8_8)
 
+#define SNOR_HWCAPS_X_X_X_DTR	(SNOR_HWCAPS_READ_8_8_8_DTR |	\
+				 SNOR_HWCAPS_PP_8_8_8_DTR)
+
 #define SNOR_HWCAPS_DTR		(SNOR_HWCAPS_READ_1_1_1_DTR |	\
 				 SNOR_HWCAPS_READ_1_2_2_DTR |	\
 				 SNOR_HWCAPS_READ_1_4_4_DTR |	\
@@ -360,6 +366,7 @@ enum spi_nor_read_command_index {
 	SNOR_CMD_READ_1_8_8,
 	SNOR_CMD_READ_8_8_8,
 	SNOR_CMD_READ_1_8_8_DTR,
+	SNOR_CMD_READ_8_8_8_DTR,
 
 	SNOR_CMD_READ_MAX
 };
@@ -376,6 +383,7 @@ enum spi_nor_pp_command_index {
 	SNOR_CMD_PP_1_1_8,
 	SNOR_CMD_PP_1_8_8,
 	SNOR_CMD_PP_8_8_8,
+	SNOR_CMD_PP_8_8_8_DTR,
 
 	SNOR_CMD_PP_MAX
 };
@@ -391,6 +399,22 @@ struct spi_nor_flash_parameter {
 	int (*quad_enable)(struct spi_nor *nor);
 };
 
+/**
+ * enum spi_nor_cmd_ext - describes the command opcode extension in DTR mode
+ * @SPI_MEM_NOR_NONE: no extension. This is the default, and is used in Legacy
+ *		      SPI mode
+ * @SPI_MEM_NOR_REPEAT: the extension is same as the opcode
+ * @SPI_MEM_NOR_INVERT: the extension is the bitwise inverse of the opcode
+ * @SPI_MEM_NOR_HEX: the extension is any hex value. The command and opcode
+ *		     combine to form a 16-bit opcode.
+ */
+enum spi_nor_cmd_ext {
+	SPI_NOR_EXT_NONE = 0,
+	SPI_NOR_EXT_REPEAT,
+	SPI_NOR_EXT_INVERT,
+	SPI_NOR_EXT_HEX,
+};
+
 /**
  * struct flash_info - Forward declaration of a structure used internally by
  *		       spi_nor_scan()
@@ -430,6 +454,7 @@ struct spi_flash {
  * @write_proto:	the SPI protocol for write operations
  * @reg_proto		the SPI protocol for read_reg/write_reg/erase operations
  * @cmd_buf:		used by the write_reg
+ * @cmd_ext_type:	the command opcode extension for DTR mode.
  * @fixups:		flash-specific fixup hooks.
  * @prepare:		[OPTIONAL] do some preparations for the
  *			read/write/erase/lock/unlock operations
@@ -472,6 +497,7 @@ struct spi_nor {
 	bool			sst_write_second;
 	u32			flags;
 	u8			cmd_buf[SPI_NOR_MAX_CMD_SIZE];
+	enum spi_nor_cmd_ext	cmd_ext_type;
 	struct spi_nor_fixups	*fixups;
 
 	int (*setup)(struct spi_nor *nor, const struct flash_info *info,
-- 
2.30.0