[PATCH v3 11/17] mtd: spinand: Allow enabling/disabling Octal DTR mode in the core

[Apurva Nandan <a-nandan@ti.com>]

Enable Octal DTR SPI mode, i.e. 8D-8D-8D mode, if the SPI NAND flash
device supports it. Mixed OSPI (1S-1S-8S & 1S-8S-8S), mixed DTR modes
(1S-1D-8D), etc. aren't supported yet.

The method to switch to Octal DTR SPI mode may vary across
manufacturers. For example, for Winbond, it is enabled by writing
values to the volatile configuration register. So, let the
manufacturer's code have their own implementation for switching to
Octal DTR SPI mode.

Check for the SPI NAND device's support for Octal DTR mode using
spinand flags, and if the data_ops and ctrl_ops are 8D-8D-8D, call
change_mode() manufacturer op. If the SPI controller doesn't
supports these modes, the selected data_ops and ctrl_ops will
prevent switching to the Octal DTR mode. And finally update the
spinand protocol and ctrl_ops on success. Similarly, for disabling
Octal DTR mode, call change_mode(), and update protocol and ctrl_ops.

Signed-off-by: Apurva Nandan <a-nandan@ti.com>
---
 drivers/mtd/nand/spi/core.c | 79 +++++++++++++++++++++++++++++++++++++
 include/linux/mtd/spinand.h |  1 +
 2 files changed, 80 insertions(+)

diff --git a/drivers/mtd/nand/spi/core.c b/drivers/mtd/nand/spi/core.c
index 1a602e4dd6bd..2fd08085db6f 100644
--- a/drivers/mtd/nand/spi/core.c
+++ b/drivers/mtd/nand/spi/core.c
@@ -1067,6 +1067,81 @@ spinand_select_ctrl_ops_variant(struct spinand_device *spinand,
 	return NULL;
 }
 
+static bool spinand_op_is_octal_dtr(const struct spi_mem_op *op)
+{
+	return  op->cmd.buswidth == 8 && op->cmd.dtr &&
+		op->addr.buswidth == 8 && op->addr.dtr &&
+		op->data.buswidth == 8 && op->data.dtr;
+}
+
+static int spinand_init_octal_dtr_enable(struct spinand_device *spinand)
+{
+	struct device *dev = &spinand->spimem->spi->dev;
+	const struct spinand_ctrl_ops *octal_dtr_ctrl_ops;
+	int ret;
+
+	if (!(spinand->flags & SPINAND_HAS_OCTAL_DTR_BIT))
+		return 0;
+
+	if (!(spinand_op_is_octal_dtr(spinand->data_ops.read_cache) &&
+	      spinand_op_is_octal_dtr(spinand->data_ops.write_cache) &&
+	      spinand_op_is_octal_dtr(spinand->data_ops.update_cache)))
+		return 0;
+
+	octal_dtr_ctrl_ops = spinand_select_ctrl_ops_variant(spinand,
+					spinand->desc_entry->ctrl_ops_variants,
+					SPINAND_8D_8D_8D);
+
+	if (!octal_dtr_ctrl_ops)
+		return 0;
+
+	if (!spinand->manufacturer->ops->change_mode) {
+		dev_dbg(dev,
+			"Missing ->change_mode(), unable to switch mode\n");
+		return -EINVAL;
+	}
+
+	ret = spinand->manufacturer->ops->change_mode(spinand,
+						      SPINAND_8D_8D_8D);
+	if (ret) {
+		dev_err(dev,
+			"Failed to enable Octal DTR SPI mode (err = %d)\n",
+			ret);
+		return ret;
+	}
+
+	spinand->protocol = SPINAND_8D_8D_8D;
+	spinand->ctrl_ops = octal_dtr_ctrl_ops;
+
+	dev_dbg(dev,
+		"%s SPI NAND switched to Octal DTR SPI (8D-8D-8D) mode\n",
+		spinand->manufacturer->name);
+	return 0;
+}
+
+static int spinand_init_octal_dtr_disable(struct spinand_device *spinand)
+{
+	struct device *dev = &spinand->spimem->spi->dev;
+	int ret;
+
+	if (!spinand->manufacturer->ops->change_mode)
+		return -EINVAL;
+
+	ret = spinand->manufacturer->ops->change_mode(spinand,
+						      SPINAND_1S_1S_1S);
+
+	if (ret) {
+		dev_err(dev,
+			"Failed to disable Octal DTR SPI mode (err = %d)\n",
+			ret);
+		return ret;
+	}
+
+	spinand->protocol = SPINAND_1S_1S_1S;
+	spinand->ctrl_ops = &spinand_default_ctrl_ops;
+	return 0;
+}
+
 /**
  * spinand_match_and_init() - Try to find a match between a device ID and an
  *			      entry in a spinand_info table
@@ -1203,6 +1278,10 @@ static int spinand_init_flash(struct spinand_device *spinand)
 			break;
 	}
 
+	ret = spinand_init_octal_dtr_enable(spinand);
+	if (ret)
+		return ret;
+
 	if (ret)
 		spinand_manufacturer_cleanup(spinand);
 
diff --git a/include/linux/mtd/spinand.h b/include/linux/mtd/spinand.h
index a8c071983a27..f12aa4516fab 100644
--- a/include/linux/mtd/spinand.h
+++ b/include/linux/mtd/spinand.h
@@ -417,6 +417,7 @@ struct spinand_ecc_info {
 
 #define SPINAND_HAS_QE_BIT		BIT(0)
 #define SPINAND_HAS_CR_FEAT_BIT		BIT(1)
+#define SPINAND_HAS_OCTAL_DTR_BIT	BIT(2)
 
 /**
  * struct spinand_ondie_ecc_conf - private SPI-NAND on-die ECC engine structure
-- 
2.25.1