[PATCH 2/2] mtd: nand: esmt: retrieve ecc requirements from 5th id byte

[Marcel Ziswiler <marcel@ziswiler.com>]

From: Marcel Ziswiler <marcel.ziswiler@toradex.com>

This patch enables support to read the ECC level from the NAND flash
using ESMT SLC NAND ID byte 5 information as documented e.g. in the
following data sheet:

https://www.esmt.com.tw/upload/pdf/ESMT/datasheets/F59L1G81LA(2Y).pdf

Signed-off-by: Marcel Ziswiler <marcel.ziswiler@toradex.com>

---

 drivers/mtd/nand/raw/nand_esmt.c | 46 ++++++++++++++++++++++++++++++++++++++++
 1 file changed, 46 insertions(+)
 create mode 100644 drivers/mtd/nand/raw/nand_esmt.c

diff --git a/drivers/mtd/nand/raw/nand_esmt.c b/drivers/mtd/nand/raw/nand_esmt.c
new file mode 100644
index 000000000000..360d351ac043
--- /dev/null
+++ b/drivers/mtd/nand/raw/nand_esmt.c
@@ -0,0 +1,46 @@
+// SPDX-License-Identifier: GPL-2.0
+/*
+ * Copyright (C) 2018 Toradex AG
+ *
+ * Author: Marcel Ziswiler <marcel.ziswiler@toradex.com>
+ */
+
+#include <linux/mtd/rawnand.h>
+
+static void esmt_nand_decode_id(struct nand_chip *chip)
+{
+	nand_decode_ext_id(chip);
+
+	/* Extract ECC requirements from 5th id byte. */
+	if (chip->id.len >= 5 && nand_is_slc(chip)) {
+		chip->ecc_step_ds = 512;
+		switch (chip->id.data[4] & 0x3) {
+		case 0x0:
+			chip->ecc_strength_ds = 4;
+			break;
+		case 0x1:
+			chip->ecc_strength_ds = 2;
+			break;
+		case 0x2:
+			chip->ecc_strength_ds = 1;
+			break;
+		default:
+			WARN(1, "Could not get ECC info");
+			chip->ecc_step_ds = 0;
+			break;
+		}
+	}
+}
+
+static int esmt_nand_init(struct nand_chip *chip)
+{
+	if (nand_is_slc(chip))
+		chip->bbt_options |= NAND_BBT_SCAN2NDPAGE;
+
+	return 0;
+}
+
+const struct nand_manufacturer_ops esmt_nand_manuf_ops = {
+	.detect = esmt_nand_decode_id,
+	.init = esmt_nand_init,
+};
-- 
2.14.4