[PATCH v1 1/2] mtd: spi-nor: add Octal DTR support for Macronix flash

[Jaime Liao]

From: JaimeLiao <jaimeliao.tw at gmail.com>

Enable Octal DTR mode with 20 dummy cycles to allow running
at the maximum supported frequency for adding Macronix flash
in Octal DTR mode.

Signed-off-by: JaimeLiao <jaimeliao.tw at gmail.com>
Co-authored-by: Tudor Ambarus <tudor.ambarus at linaro.org>
---
 drivers/mtd/spi-nor/macronix.c | 77 ++++++++++++++++++++++++++++++++++
 1 file changed, 77 insertions(+)

diff --git a/drivers/mtd/spi-nor/macronix.c b/drivers/mtd/spi-nor/macronix.c
index 04888258e891..9010b81e098f 100644
--- a/drivers/mtd/spi-nor/macronix.c
+++ b/drivers/mtd/spi-nor/macronix.c
@@ -8,6 +8,12 @@
 
 #include "core.h"
 
+#define SPINOR_OP_RD_CR2		0x71		/* Read configuration register 2 */
+#define SPINOR_OP_WR_CR2		0x72		/* Write configuration register 2 */
+#define SPINOR_REG_MXIC_CR2_MODE	0x00000000	/* For setting octal DTR mode */
+#define SPINOR_REG_MXIC_OPI_DTR_EN	0x2		/* Enable Octal DTR */
+#define SPINOR_REG_MXIC_SPI_EN		0x0		/* Enable SPI */
+
 static int
 mx25l25635_post_bfpt_fixups(struct spi_nor *nor,
 			    const struct sfdp_parameter_header *bfpt_header,
@@ -32,6 +38,76 @@ static const struct spi_nor_fixups mx25l25635_fixups = {
 	.post_bfpt = mx25l25635_post_bfpt_fixups,
 };
 
+/**
+ * spi_nor_macronix_octal_dtr_enable() - Enable octal DTR on Macronix flashes.
+ * @nor:		pointer to a 'struct spi_nor'
+ * @enable:		whether to enable Octal DTR or switch back to SPI
+ *
+ * Return: 0 on success, -errno otherwise.
+ */
+static int spi_nor_macronix_octal_dtr_enable(struct spi_nor *nor, bool enable)
+{
+	struct spi_mem_op op;
+	u8 *buf = nor->bouncebuf, i;
+	int ret;
+
+	/* Set/unset the octal and DTR enable bits. */
+	ret = spi_nor_write_enable(nor);
+	if (ret)
+		return ret;
+
+	if (enable) {
+		buf[0] = SPINOR_REG_MXIC_OPI_DTR_EN;
+	} else {
+		/*
+		 * The register is 1-byte wide, but 1-byte transactions are not
+		 * allowed in 8D-8D-8D mode. Since there is no register at the
+		 * next location, just initialize the value to 0 and let the
+		 * transaction go on.
+		 */
+		buf[0] = SPINOR_REG_MXIC_SPI_EN;
+		buf[1] = 0x0;
+	}
+
+	op = (struct spi_mem_op)
+		SPI_MEM_OP(SPI_MEM_OP_CMD(SPINOR_OP_WR_CR2, 1),
+			   SPI_MEM_OP_ADDR(4, SPINOR_REG_MXIC_CR2_MODE, 1),
+			   SPI_MEM_OP_NO_DUMMY,
+			   SPI_MEM_OP_DATA_OUT(enable ? 1 : 2, buf, 1));
+
+	if (!enable)
+		spi_nor_spimem_setup_op(nor, &op, SNOR_PROTO_8_8_8_DTR);
+
+	ret = spi_mem_exec_op(nor->spimem, &op);
+	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(SPINOR_OP_RDID, 1),
+			   SPI_MEM_OP_ADDR(enable ? 4 : 0, 0, 1),
+			   SPI_MEM_OP_DUMMY(enable ? 4 : 0, 1),
+			   SPI_MEM_OP_DATA_IN(SPI_NOR_MAX_ID_LEN, buf, 1));
+
+	if (enable)
+		spi_nor_spimem_setup_op(nor, &op, SNOR_PROTO_8_8_8_DTR);
+
+	ret = spi_mem_exec_op(nor->spimem, &op);
+	if (ret)
+		return ret;
+
+	if (enable) {
+		for (i = 0; i < nor->info->id_len; i++)
+			if (buf[i * 2] != nor->info->id[i])
+				return -EINVAL;
+	} else {
+		if (memcmp(buf, nor->info->id, nor->info->id_len))
+			return -EINVAL;
+	}
+
+	return 0;
+}
+
 static const struct flash_info macronix_nor_parts[] = {
 	/* Macronix */
 	{ "mx25l512e",   INFO(0xc22010, 0, 64 * 1024,   1)
@@ -108,6 +184,7 @@ static const struct flash_info macronix_nor_parts[] = {
 static void macronix_nor_default_init(struct spi_nor *nor)
 {
 	nor->params->quad_enable = spi_nor_sr1_bit6_quad_enable;
+	nor->params->octal_dtr_enable = spi_nor_macronix_octal_dtr_enable;
 }
 
 static void macronix_nor_late_init(struct spi_nor *nor)
-- 
2.25.1