linux-kernel - [PATCH 2/2] mtd: nand: gpmi: add support for specific ECC strength

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Date:   Tue,  6 Feb 2018 18:40:21 +0100
From:   Stefan Agner <stefan@...er.ch>
To:     han.xu@....com, boris.brezillon@...e-electrons.com
Cc:     marek.vasut@...il.com, richard@....at, dwmw2@...radead.org,
        cyrille.pitchen@...ev4u.fr, max.oss.09@...il.com,
        linux-mtd@...ts.infradead.org, linux-kernel@...r.kernel.org,
        Stefan Agner <stefan@...er.ch>
Subject: [PATCH 2/2] mtd: nand: gpmi: add support for specific ECC strength

Add support for specified ECC strength/size using device tree
properties nand-ecc-strength/nand-ecc-step-size.

Signed-off-by: Stefan Agner <stefan@...er.ch>
---
 .../devicetree/bindings/mtd/gpmi-nand.txt          |  5 ++++
 drivers/mtd/nand/gpmi-nand/gpmi-nand.c             | 29 ++++++++++++++--------
 2 files changed, 24 insertions(+), 10 deletions(-)

diff --git a/Documentation/devicetree/bindings/mtd/gpmi-nand.txt b/Documentation/devicetree/bindings/mtd/gpmi-nand.txt
index eb2d9919d063..ea6e9b735160 100644
--- a/Documentation/devicetree/bindings/mtd/gpmi-nand.txt
+++ b/Documentation/devicetree/bindings/mtd/gpmi-nand.txt
@@ -46,6 +46,11 @@ Optional properties:
                        partitions written from Linux with this feature
                        turned on may not be accessible by the BootROM
                        code.
+  - nand-ecc-strength: integer representing the number of bits to correct
+                       per ECC step. Needs to be a multiple of 2.
+  - nand-ecc-step-size: integer representing the number of data bytes
+                       that are covered by a single ECC step. The driver
+                       supports 512 and 1024.
 
 The device tree may optionally contain sub-nodes describing partitions of the
 address space. See partition.txt for more detail.
diff --git a/drivers/mtd/nand/gpmi-nand/gpmi-nand.c b/drivers/mtd/nand/gpmi-nand/gpmi-nand.c
index 50f8d4a1b983..8cb378358e11 100644
--- a/drivers/mtd/nand/gpmi-nand/gpmi-nand.c
+++ b/drivers/mtd/nand/gpmi-nand/gpmi-nand.c
@@ -198,17 +198,15 @@ static inline bool gpmi_check_ecc(struct gpmi_nand_data *this)
  *
  * We may have available oob space in this case.
  */
-static int set_geometry_by_ecc_info(struct gpmi_nand_data *this)
+static int set_geometry_by_ecc_info(struct gpmi_nand_data *this,
+			unsigned int ecc_strength, unsigned int ecc_step)
 {
 	struct bch_geometry *geo = &this->bch_geometry;
 	struct nand_chip *chip = &this->nand;
 	struct mtd_info *mtd = nand_to_mtd(chip);
 	unsigned int block_mark_bit_offset;
 
-	if (!(chip->ecc_strength_ds > 0 && chip->ecc_step_ds > 0))
-		return -EINVAL;
-
-	switch (chip->ecc_step_ds) {
+	switch (ecc_step) {
 	case SZ_512:
 		geo->gf_len = 13;
 		break;
@@ -221,8 +219,8 @@ static int set_geometry_by_ecc_info(struct gpmi_nand_data *this)
 			chip->ecc_strength_ds, chip->ecc_step_ds);
 		return -EINVAL;
 	}
-	geo->ecc_chunk_size = chip->ecc_step_ds;
-	geo->ecc_strength = round_up(chip->ecc_strength_ds, 2);
+	geo->ecc_chunk_size = ecc_step;
+	geo->ecc_strength = round_up(ecc_strength, 2);
 	if (!gpmi_check_ecc(this))
 		return -EINVAL;
 
@@ -230,7 +228,7 @@ static int set_geometry_by_ecc_info(struct gpmi_nand_data *this)
 	if (geo->ecc_chunk_size < mtd->oobsize) {
 		dev_err(this->dev,
 			"unsupported nand chip. ecc size: %d, oob size : %d\n",
-			chip->ecc_step_ds, mtd->oobsize);
+			ecc_step, mtd->oobsize);
 		return -EINVAL;
 	}
 
@@ -423,9 +421,20 @@ static int legacy_set_geometry(struct gpmi_nand_data *this)
 
 int common_nfc_set_geometry(struct gpmi_nand_data *this)
 {
+	struct nand_chip *chip = &this->nand;
+
+	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))
-		return set_geometry_by_ecc_info(this);
+				|| legacy_set_geometry(this)) {
+		if (!(chip->ecc_strength_ds > 0 && chip->ecc_step_ds > 0))
+			return -EINVAL;
+
+		return set_geometry_by_ecc_info(this, chip->ecc_strength_ds,
+						chip->ecc_step_ds);
+	}
 
 	return 0;
 }
-- 
2.16.1