[PATCH 07/13] mtd: spinand: Allow enabling Octal DTR mode in the core

[Apurva Nandan <a-nandan@xxxxxx>]

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. Mixed OSPI (1S-1S-8S & 1S-8S-8S), mixed DTR modes
(1S-1D-8D), etc. aren't supported yet.

Check for the SPI NAND device's support for Octal DTR mode using
spinand flags, and if the op_templates allow 8D-8D-8D, call
octal_dtr_enable() manufacturer op. If the SPI controller doesn't
supports these modes, the selected op_templates would prevent switching
to the Octal DTR mode. And finally update the spinand reg_proto
if success.

Signed-off-by: Apurva Nandan <a-nandan@xxxxxx>
---
 drivers/mtd/nand/spi/core.c | 46 +++++++++++++++++++++++++++++++++++++
 include/linux/mtd/spinand.h |  3 +++
 2 files changed, 49 insertions(+)

diff --git a/drivers/mtd/nand/spi/core.c b/drivers/mtd/nand/spi/core.c
index 1e619b6d777f..19d8affac058 100644
--- a/drivers/mtd/nand/spi/core.c
+++ b/drivers/mtd/nand/spi/core.c
@@ -256,6 +256,48 @@ static int spinand_init_quad_enable(struct spinand_device *spinand)
 			       enable ? CFG_QUAD_ENABLE : 0);
 }
 
+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;
+	int ret;
+
+	if (!(spinand->flags & SPINAND_HAS_OCTAL_DTR_BIT))
+		return 0;
+
+	if (!(spinand_op_is_octal_dtr(spinand->op_templates.read_cache) &&
+	      spinand_op_is_octal_dtr(spinand->op_templates.write_cache) &&
+	      spinand_op_is_octal_dtr(spinand->op_templates.update_cache)))
+		return 0;
+
+	if (!spinand->manufacturer->ops->octal_dtr_enable) {
+		dev_err(dev,
+			"Missing ->octal_dtr_enable(), unable to switch mode\n");
+		return -EINVAL;
+	}
+
+	ret = spinand->manufacturer->ops->octal_dtr_enable(spinand);
+	if (ret) {
+		dev_err(dev,
+			"Failed to enable Octal DTR SPI mode (err = %d)\n",
+			ret);
+		return ret;
+	}
+
+	spinand->reg_proto = SPINAND_OCTAL_DTR;
+
+	dev_dbg(dev,
+		"%s SPI NAND switched to Octal DTR SPI (8D-8D-8D) mode\n",
+		spinand->manufacturer->name);
+	return 0;
+}
+
 static int spinand_ecc_enable(struct spinand_device *spinand,
 			      bool enable)
 {
@@ -1189,6 +1231,10 @@ static int spinand_init_flash(struct spinand_device *spinand)
 	if (ret)
 		return ret;
 
+	ret = spinand_init_octal_dtr_enable(spinand);
+	if (ret)
+		return ret;
+
 	ret = spinand_upd_cfg(spinand, CFG_OTP_ENABLE, 0);
 	if (ret)
 		return ret;
diff --git a/include/linux/mtd/spinand.h b/include/linux/mtd/spinand.h
index 35816b8cfe81..daa2ac5c3110 100644
--- a/include/linux/mtd/spinand.h
+++ b/include/linux/mtd/spinand.h
@@ -271,6 +271,7 @@ struct spinand_devid {
  * @init: initialize a SPI NAND device
  * @adjust_op: modify the ops for any variation in their cmd, address, dummy or
  *	       data phase by the manufacturer
+ * @octal_dtr_enable: switch the SPI NAND flash into Octal DTR SPI mode
  * @cleanup: cleanup a SPI NAND device
  *
  * Each SPI NAND manufacturer driver should implement this interface so that
@@ -280,6 +281,7 @@ struct spinand_manufacturer_ops {
 	int (*init)(struct spinand_device *spinand);
 	void (*adjust_op)(struct spi_mem_op *op,
 			  const enum spinand_proto reg_proto);
+	int (*octal_dtr_enable)(struct spinand_device *spinand);
 	void (*cleanup)(struct spinand_device *spinand);
 };
 
@@ -348,6 +350,7 @@ 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
-- 
2.17.1