[PATCH v4 1/5] mtd: rawnand: gpmi: Refactor bch geometry settings function

[Han Xu]

The code change refactor the bch geometry setting function, which
doesn't change the default behavior, while user may choose to use chips
required minimum ecc strength by DT flag "fsl,use-minimum-ecc".

The default way to set bch geometry need to set the data chunk
size(step_size) larger than oob size to make sure BBM locates in data
chunk, then set the maximum ecc strength oob can hold. It always use
unbalanced ECC layout, which ecc0 will cover both meta and data0 chunk.
But the default bch setting is deprecated for large oobsize NAND
(oobsize >1KB), so in the patch set, there is a split commit that
introduces a new way to set bch geometry for large oob size NAND.

For all other cases,set the bch geometry by chip required strength and
step size, which uses the minimum ecc strength chip required. It can be
explicitly enabled by DT flag "fsl,use-minimum-ecc", but need to be
en/disabled in both u-boot and kernel at the same time.

Signed-off-by: Han Xu <han.xu at nxp.com>
Tested-by: Sean Nyekjaer <sean at geanix.com>

---
Changes since v3:
 - don't use the term legacy in commit log
 - mention the split commit for large oob NAND

Changes since v2:
 - split the ecc check to a single patch

Changes since v1:
 - split the patch to two parts
 - change the commit log
 - add test tag
---
---
 drivers/mtd/nand/raw/gpmi-nand/gpmi-nand.c | 32 ++++++++++++++--------
 1 file changed, 20 insertions(+), 12 deletions(-)

diff --git a/drivers/mtd/nand/raw/gpmi-nand/gpmi-nand.c b/drivers/mtd/nand/raw/gpmi-nand/gpmi-nand.c
index 44b14c9dc9a7..66ebd569858d 100644
--- a/drivers/mtd/nand/raw/gpmi-nand/gpmi-nand.c
+++ b/drivers/mtd/nand/raw/gpmi-nand/gpmi-nand.c
@@ -514,24 +514,32 @@ static int legacy_set_geometry(struct gpmi_nand_data *this)
 static int common_nfc_set_geometry(struct gpmi_nand_data *this)
 {
 	struct nand_chip *chip = &this->nand;
+	struct mtd_info *mtd = nand_to_mtd(&this->nand);
 	const struct nand_ecc_props *requirements =
 		nanddev_get_ecc_requirements(&chip->base);
+	bool use_minimun_ecc;
+	int err;
 
-	if (chip->ecc.strength > 0 && chip->ecc.size > 0)
-		return set_geometry_by_ecc_info(this, chip->ecc.strength,
-						chip->ecc.size);
-
-	if ((of_property_read_bool(this->dev->of_node, "fsl,use-minimum-ecc"))
-				|| legacy_set_geometry(this)) {
-		if (!(requirements->strength > 0 && requirements->step_size > 0))
-			return -EINVAL;
+	use_minimun_ecc = of_property_read_bool(this->dev->of_node,
+						"fsl,use-minimum-ecc");
 
-		return set_geometry_by_ecc_info(this,
-						requirements->strength,
-						requirements->step_size);
+	/* use legacy bch geometry settings by default*/
+	if ((!use_minimun_ecc && mtd->oobsize < 1024) ||
+	    !(requirements->strength > 0 && requirements->step_size > 0)) {
+		dev_dbg(this->dev, "use legacy bch geometry\n");
+		err = legacy_set_geometry(this);
+		if (!err)
+			return 0;
 	}
 
-	return 0;
+	/* otherwise use the minimum ecc nand chip required */
+	dev_dbg(this->dev, "use minimum ecc bch geometry\n");
+	err = set_geometry_by_ecc_info(this, requirements->strength,
+					requirements->step_size);
+	if (err)
+		dev_err(this->dev, "none of the bch geometry setting works\n");
+
+	return err;
 }
 
 /* Configures the geometry for BCH.  */
-- 
2.17.1