linux-kernel - [PATCH v4 6/6] mtd: rawnand: micron: detect forced on-die ECC

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Date:   Thu, 21 Jun 2018 22:33:28 +1200
From:   Chris Packham <chris.packham@...iedtelesis.co.nz>
To:     miquel.raynal@...tlin.com, boris.brezillon@...tlin.com,
        dwmw2@...radead.org, computersforpeace@...il.com,
        linux-mtd@...ts.infradead.org
Cc:     linux-kernel@...r.kernel.org,
        Chris Packham <chris.packham@...iedtelesis.co.nz>,
        Richard Weinberger <richard@....at>,
        Marek Vasut <marek.vasut@...il.com>
Subject: [PATCH v4 6/6] mtd: rawnand: micron: detect forced on-die ECC

Some Micron NAND chips have on-die ECC forceably enabled. The detect
these based on chip ID as there seems to be no other way of
distinguishing these chips from those that have optional support for
on-die ECC.

When a chip with mandatory on-die ECC is detected change the current ECC
mode to on-die.

Signed-off-by: Chris Packham <chris.packham@...iedtelesis.co.nz>
---
I'm not convinced that just changing chip->ecc.mode is sensible. An
alternative I considered was only proceeding if the ecc.mode is set to
ON_DIE.

Changes in v4:
- New

 drivers/mtd/nand/raw/nand_micron.c | 17 +++++++++++++++--
 1 file changed, 15 insertions(+), 2 deletions(-)

diff --git a/drivers/mtd/nand/raw/nand_micron.c b/drivers/mtd/nand/raw/nand_micron.c
index f1ecd4986b50..9ba9007a9a06 100644
--- a/drivers/mtd/nand/raw/nand_micron.c
+++ b/drivers/mtd/nand/raw/nand_micron.c
@@ -227,6 +227,14 @@ enum {
 	MICRON_ON_DIE_MANDATORY,
 };
 
+/*
+ * These parts are known to have on-die ECC forceably enabled
+ */
+static u8 micron_on_die_ecc[] = {
+	0xd1, /* MT29F1G08ABAFA */
+	0xa1, /* MT29F1G08ABBFA */
+};
+
 /*
  * Try to detect if the NAND support on-die ECC. To do this, we enable
  * the feature, and read back if it has been enabled as expected. We
@@ -241,6 +249,11 @@ static int micron_supports_on_die_ecc(struct nand_chip *chip)
 {
 	u8 feature[ONFI_SUBFEATURE_PARAM_LEN] = { 0, };
 	int ret;
+	int i;
+
+	for (i = 0; i < ARRAY_SIZE(micron_on_die_ecc); i++)
+		if (chip->id.data[1] == micron_on_die_ecc[i])
+			return MICRON_ON_DIE_MANDATORY;
 
 	if (!chip->parameters.onfi.version)
 		return MICRON_ON_DIE_UNSUPPORTED;
@@ -289,8 +302,8 @@ static int micron_nand_init(struct nand_chip *chip)
 	ondie = micron_supports_on_die_ecc(chip);
 
 	if (ondie == MICRON_ON_DIE_MANDATORY) {
-		pr_err("On-die ECC forcefully enabled, not supported\n");
-		return -EINVAL;
+		pr_info("On-die ECC forcefully enabled\n");
+		chip->ecc.mode = NAND_ECC_ON_DIE;
 	}
 
 	if (chip->ecc.mode == NAND_ECC_ON_DIE) {
-- 
2.17.1