[PATCH v3 14/17] mtd: spinand: winbond: Add octal_dtr_enable/disable() in manufacturer_ops

[Apurva Nandan]

Add implementation of octal_dtr_enable() and octal_dtr_disable()
manufacturer_ops for Winbond. To switch to Ocatl DTR mode, setting
programmable dummy cycles and SPI IO mode using the volatile
configuration register is required. To function at max 120MHz SPI clock
in Octal DTR mode, 12 programmable dummy clock cycle setting is
required. (Default number of dummy cycle are 8 clocks)

Set the programmable dummy cycle to 12 clocks, and SPI IO mode to
Octal DTR with Data Strobe in the VCR. Also, perform a READ ID
operation in Octal DTR SPI mode to ensure the switch was successful.
To disable Octal DTR mode, restore the VCR registers to their default
values and verify it using READ ID operation.

Datasheet: https://www.winbond.com/export/sites/winbond/datasheet/W35N01JW_Datasheet_Brief.pdf

Signed-off-by: Apurva Nandan <a-nandan at ti.com>
---
 drivers/mtd/nand/spi/winbond.c | 85 ++++++++++++++++++++++++++++++++++
 1 file changed, 85 insertions(+)

diff --git a/drivers/mtd/nand/spi/winbond.c b/drivers/mtd/nand/spi/winbond.c
index 3e0829f58350..c7478faf6cee 100644
--- a/drivers/mtd/nand/spi/winbond.c
+++ b/drivers/mtd/nand/spi/winbond.c
@@ -16,6 +16,16 @@
 
 #define WINBOND_CFG_BUF_READ		BIT(3)
 
+/* Octal DTR SPI mode (8D-8D-8D) with Data Strobe output*/
+#define WINBOND_VCR_IO_MODE_OCTAL_DTR	0xE7
+#define WINBOND_VCR_IO_MODE_SINGLE_STR	0xFF
+#define WINBOND_VCR_IO_MODE_ADDR	0x00
+
+/* Use 12 dummy clk cycles for using Octal DTR SPI at max 120MHZ */
+#define WINBOND_VCR_DUMMY_CLK_COUNT	12
+#define WINBOND_VCR_DUMMY_CLK_DEFAULT	0xFF
+#define WINBOND_VCR_DUMMY_CLK_ADDR	0x01
+
 static SPINAND_OP_VARIANTS(read_cache_variants,
 		SPINAND_PAGE_READ_FROM_CACHE_QUADIO_OP(0, 2, NULL, 0),
 		SPINAND_PAGE_READ_FROM_CACHE_X4_OP(0, 1, NULL, 0),
@@ -157,6 +167,81 @@ static int winbond_write_vcr_op(struct spinand_device *spinand, u8 reg, u8 val)
 	return 0;
 }
 
+static int winbond_spinand_octal_dtr_enable(struct spinand_device *spinand)
+{
+	int ret;
+	struct spi_mem_op op;
+
+	ret = winbond_write_vcr_op(spinand, WINBOND_VCR_DUMMY_CLK_ADDR,
+				   WINBOND_VCR_DUMMY_CLK_COUNT);
+	if (ret)
+		return ret;
+
+	ret = winbond_write_vcr_op(spinand, WINBOND_VCR_IO_MODE_ADDR,
+				   WINBOND_VCR_IO_MODE_OCTAL_DTR);
+	if (ret)
+		return ret;
+
+	/* Read flash ID to make sure the switch was successful. */
+	op = (struct spi_mem_op)
+		SPI_MEM_OP(SPI_MEM_OP_CMD_DTR(2, 0x9f9f, 8),
+			   SPI_MEM_OP_NO_ADDR,
+			   SPI_MEM_OP_DUMMY_DTR(16, 8),
+			   SPI_MEM_OP_DATA_IN_DTR(SPINAND_MAX_ID_LEN,
+						  spinand->scratchbuf, 8));
+
+	ret = spi_mem_exec_op(spinand->spimem, &op);
+	if (ret)
+		return ret;
+
+	if (memcmp(spinand->scratchbuf, spinand->id.data, SPINAND_MAX_ID_LEN))
+		return -EINVAL;
+
+	return 0;
+}
+
+static int winbond_spinand_octal_dtr_disable(struct spinand_device *spinand)
+{
+	int ret;
+	struct spi_mem_op op =
+		SPI_MEM_OP(SPI_MEM_OP_CMD_DTR(2, 0x8181, 8),
+			   SPI_MEM_OP_ADDR_DTR(4, WINBOND_VCR_IO_MODE_ADDR, 8),
+			   SPI_MEM_OP_NO_DUMMY,
+			   SPI_MEM_OP_DATA_OUT_DTR(2, spinand->scratchbuf, 8));
+
+	*spinand->scratchbuf = WINBOND_VCR_IO_MODE_SINGLE_STR;
+
+	ret = spinand_write_enable_op(spinand);
+	if (ret)
+		return ret;
+
+	ret = spi_mem_exec_op(spinand->spimem, &op);
+	if (ret)
+		return ret;
+
+	ret = winbond_write_vcr_op(spinand, WINBOND_VCR_DUMMY_CLK_ADDR,
+				   WINBOND_VCR_DUMMY_CLK_DEFAULT);
+	if (ret)
+		return ret;
+
+	/* Read flash ID to make sure the switch was successful. */
+	op = (struct spi_mem_op)
+		SPI_MEM_OP(SPI_MEM_OP_CMD(0x9f, 1),
+			   SPI_MEM_OP_NO_ADDR,
+			   SPI_MEM_OP_DUMMY(1, 1),
+			   SPI_MEM_OP_DATA_IN(SPINAND_MAX_ID_LEN,
+					      spinand->scratchbuf, 1));
+
+	ret = spi_mem_exec_op(spinand->spimem, &op);
+	if (ret)
+		return ret;
+
+	if (memcmp(spinand->scratchbuf, spinand->id.data, SPINAND_MAX_ID_LEN))
+		return -EINVAL;
+
+	return 0;
+}
+
 static const struct spinand_manufacturer_ops winbond_spinand_manuf_ops = {
 	.init = winbond_spinand_init,
 };
-- 
2.25.1