[PATCH v3 09/12] mtd: spi-nor: enable octal DTR mode when possible

[Pratyush Yadav <p.yadav@xxxxxx>]

Allow flashes to specify a hook to enable octal DTR mode. Use this hook
whenever possible to get optimal transfer speeds.

Signed-off-by: Pratyush Yadav <p.yadav@xxxxxx>
---
 drivers/mtd/spi-nor/spi-nor.c | 35 +++++++++++++++++++++++++++++++++++
 include/linux/mtd/spi-nor.h   |  2 ++
 2 files changed, 37 insertions(+)

diff --git a/drivers/mtd/spi-nor/spi-nor.c b/drivers/mtd/spi-nor/spi-nor.c
index 16d7516f2470..5e225d1b29f7 100644
--- a/drivers/mtd/spi-nor/spi-nor.c
+++ b/drivers/mtd/spi-nor/spi-nor.c
@@ -5232,6 +5232,35 @@ static void spi_nor_init_params(struct spi_nor *nor)
 	spi_nor_late_init_params(nor);
 }
 
+/** spi_nor_octal_dtr_enable() - enable Octal DTR I/O if needed
+ * @nor:                 pointer to a 'struct spi_nor'
+ * @enable:              whether to enable or disable Octal DTR
+ *
+ * Return: 0 on success, -errno otherwise.
+ */
+static int spi_nor_octal_dtr_enable(struct spi_nor *nor, bool enable)
+{
+	int ret;
+
+	if (!nor->params.octal_dtr_enable)
+		return 0;
+
+	if (!(spi_nor_get_protocol_width(nor->read_proto) == 8 ||
+	      spi_nor_get_protocol_width(nor->write_proto) == 8))
+		return 0;
+
+	ret = nor->params.octal_dtr_enable(nor, enable);
+	if (ret)
+		return ret;
+
+	if (enable)
+		nor->reg_proto = SNOR_PROTO_8_8_8_DTR;
+	else
+		nor->reg_proto = SNOR_PROTO_1_1_1;
+
+	return 0;
+}
+
 /**
  * spi_nor_quad_enable() - enable Quad I/O if needed.
  * @nor:                pointer to a 'struct spi_nor'
@@ -5271,6 +5300,12 @@ static int spi_nor_init(struct spi_nor *nor)
 {
 	int err;
 
+	err = spi_nor_octal_dtr_enable(nor, true);
+	if (err) {
+		dev_dbg(nor->dev, "octal mode not supported\n");
+		return err;
+	}
+
 	err = spi_nor_quad_enable(nor);
 	if (err) {
 		dev_dbg(nor->dev, "quad mode not supported\n");
diff --git a/include/linux/mtd/spi-nor.h b/include/linux/mtd/spi-nor.h
index f1db613e0320..923bd34ced84 100644
--- a/include/linux/mtd/spi-nor.h
+++ b/include/linux/mtd/spi-nor.h
@@ -544,6 +544,7 @@ struct spi_nor_locking_ops {
  *                      higher index in the array, the higher priority.
  * @erase_map:		the erase map parsed from the SFDP Sector Map Parameter
  *                      Table.
+ * @octal_dtr_enable:	enables SPI NOR octal DTR mode.
  * @quad_enable:	enables SPI NOR quad mode.
  * @set_4byte:		puts the SPI NOR in 4 byte addressing mode.
  * @convert_addr:	converts an absolute address into something the flash
@@ -567,6 +568,7 @@ struct spi_nor_flash_parameter {
 
 	struct spi_nor_erase_map        erase_map;
 
+	int (*octal_dtr_enable)(struct spi_nor *nor, bool enable);
 	int (*quad_enable)(struct spi_nor *nor);
 	int (*set_4byte)(struct spi_nor *nor, bool enable);
 	u32 (*convert_addr)(struct spi_nor *nor, u32 addr);
-- 
2.25.0