[PATCH v3 13/17] mtd: spi-nor-core: Enable octal DTR mode when possible

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

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@ti.com>
---
 drivers/mtd/spi/spi-nor-core.c | 31 +++++++++++++++++++++++++++++++
 include/linux/mtd/spi-nor.h    |  2 ++
 2 files changed, 33 insertions(+)

diff --git a/drivers/mtd/spi/spi-nor-core.c b/drivers/mtd/spi/spi-nor-core.c
index 9361b5c121..5b995cda3f 100644
--- a/drivers/mtd/spi/spi-nor-core.c
+++ b/drivers/mtd/spi/spi-nor-core.c
@@ -2760,10 +2760,41 @@ static int spi_nor_setup(struct spi_nor *nor, const struct flash_info *info,
 	return nor->setup(nor, info, params, hwcaps);
 }
 
+/** spi_nor_octal_dtr_enable() - enable Octal DTR I/O if needed
+ * @nor:                 pointer to a 'struct spi_nor'
+ *
+ * Return: 0 on success, -errno otherwise.
+ */
+static int spi_nor_octal_dtr_enable(struct spi_nor *nor)
+{
+	int ret;
+
+	if (!nor->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->octal_dtr_enable(nor);
+	if (ret)
+		return ret;
+
+	nor->reg_proto = SNOR_PROTO_8_8_8_DTR;
+
+	return 0;
+}
+
 static int spi_nor_init(struct spi_nor *nor)
 {
 	int err;
 
+	err = spi_nor_octal_dtr_enable(nor);
+	if (err) {
+		dev_dbg(nor->dev, "Octal DTR mode not supported\n");
+		return err;
+	}
+
 	/*
 	 * Atmel, SST, Intel/Numonyx, and others serial NOR tend to power up
 	 * with the software protection bits set
diff --git a/include/linux/mtd/spi-nor.h b/include/linux/mtd/spi-nor.h
index 4b3b81ce67..defd0d2d3d 100644
--- a/include/linux/mtd/spi-nor.h
+++ b/include/linux/mtd/spi-nor.h
@@ -468,6 +468,7 @@ struct flash_info;
  * @flash_is_locked:	[FLASH-SPECIFIC] check if a region of the SPI NOR is
  * @quad_enable:	[FLASH-SPECIFIC] enables SPI NOR quad mode
  *			completely locked
+ * @octal_dtr_enable:	[FLASH-SPECIFIC] enables SPI NOR octal DTR mode.
  * @priv:		the private data
  */
 struct spi_nor {
@@ -515,6 +516,7 @@ struct spi_nor {
 	int (*flash_unlock)(struct spi_nor *nor, loff_t ofs, uint64_t len);
 	int (*flash_is_locked)(struct spi_nor *nor, loff_t ofs, uint64_t len);
 	int (*quad_enable)(struct spi_nor *nor);
+	int (*octal_dtr_enable)(struct spi_nor *nor);
 
 	void *priv;
 /* Compatibility for spi_flash, remove once sf layer is merged with mtd */
-- 
2.25.0