[PATCH] spi: spi-qpic-snand: Increase ECC strength for large OOB SPI-NAND devices

[Md Sadre Alam <md.alam@oss.qualcomm.com>]

Some SPI-NAND devices with large OOB areas require a stronger ECC
configuration than the default one provided through firmware
description. For example, Macronix devices with a 256-byte OOB area
report that 4-bit ECC is insufficient and trigger:

  nand: WARNING: the ECC used on your system is too weak compared
  to the one required by the NAND chip

The QPIC SPI-NAND controller supports both 4-bit and 8-bit BCH ECC
modes. When a device exposes an OOB area of at least 128 bytes, there
is sufficient space to accommodate 8-bit ECC without exceeding the OOB
layout constraints.

Automatically increase the ECC strength to 8 bits when the detected OOB
size is 128 bytes or larger and the current configuration requests a
weaker ECC level. This avoids ECC capability mismatches on devices that
require stronger error correction and improves reliability.

Signed-off-by: Md Sadre Alam <md.alam@oss.qualcomm.com>
---
 drivers/spi/spi-qpic-snand.c | 13 +++++++++++++
 1 file changed, 13 insertions(+)

diff --git a/drivers/spi/spi-qpic-snand.c b/drivers/spi/spi-qpic-snand.c
index 6cc53586b8a8..19812400124f 100644
--- a/drivers/spi/spi-qpic-snand.c
+++ b/drivers/spi/spi-qpic-snand.c
@@ -274,6 +274,19 @@ static int qcom_spi_ecc_init_ctx_pipelined(struct nand_device *nand)
 		ecc_cfg->strength = 4;
 	}
 
+	/*
+	 * Override ECC strength based on OOB size to avoid weak ECC warning.
+	 * If OOB size is more than 128 bytes, use 8-bit ECC for better
+	 * error correction capability, which is required by chips with
+	 * larger OOB areas like Macronix SPI NAND with 256 bytes OOB.
+	 */
+	if (mtd->oobsize >= 128 && ecc_cfg->strength < 8) {
+		dev_info(snandc->dev,
+			 "Upgrading ECC strength from %d to 8 bits (OOB size: %d bytes)\n",
+			 ecc_cfg->strength, mtd->oobsize);
+		ecc_cfg->strength = 8;
+	}
+
 	if (ecc_cfg->step_size != NANDC_STEP_SIZE) {
 		dev_err(snandc->dev,
 			"only %u bytes ECC step size is supported\n",

---
base-commit: 19827e7930a5511c68e12aac6e4522f3661a1709
change-id: 20260716-8bitecc-b9be3d2e7690

Best regards,
-- 
Md Sadre Alam <md.alam@oss.qualcomm.com>