Le Mon, 17 Jul 2017 19:48:09 +0200,
Boris Brezillon [off-list ref] a ?crit :

+Ludovic, Nicolas and Alexandre

Hi Romain,

Le Mon, 17 Jul 2017 18:11:26 +0200,
Romain Izard [off-list ref] a ?crit :

quoted

Hello,

On a custom board based on Microchip's SAMA5D2 SoC, I am encountering
ECC problems with the NAND Flash controller. The board is currently
working with Linux v4.9.x, but it does not with Linux 4.12.

Some pages on the NAND Flash memory chip of the device have bitflips.
With Linux 4.9.x, the bitflips are fixed by the PMECC code, but with
Linux 4.12, the errors are reported as uncorrectable.

From my end, I updated the board's device tree to include the
sama5d2.dtsi as it exists in Linux 4.12, but the rest of the file is
the same as for Linux 4.9. From my understanding, it should be
sufficient as the legacy DTB binding for the NAND controller is
supported.  

I know Ludovic add some problems with the NAND controller on sama5d2,
but it was with the new bindings (see the fixes here [1]).

Your problem seems a bit different since you're using the backward
compat code.

Can you try with the following patch applied?

--->8---

From cb95a16cdd497137872c44d5dd4e251ec73c79c1 Mon Sep 17 00:00:00 2001

From: Boris Brezillon <redacted>
Date: Mon, 17 Jul 2017 20:09:59 +0200
Subject: [PATCH] mtd: nand: atmel: Fix DT backward compatibility in pmecc.c

PMECC caps extraction from old DT bindings is broken, thus leading to
erroneous EL registers offset, which in turn make HW ECC unusable on
sama5d2 when old bindings are in use.

Passing the NAND dev node instead of the NFC node to of_match_node()
solves the problem.

Signed-off-by: Boris Brezillon <redacted>
Fixes: f88fc122cc34 ("mtd: nand: Cleanup/rework the atmel_nand driver")
Cc: <redacted>
---
 drivers/mtd/nand/atmel/pmecc.c | 21 ++++++---------------
 1 file changed, 6 insertions(+), 15 deletions(-)

diff --git a/drivers/mtd/nand/atmel/pmecc.c b/drivers/mtd/nand/atmel/pmecc.c
index 55a8ee5306ea..8c210a5776bc 100644
--- a/drivers/mtd/nand/atmel/pmecc.c
+++ b/drivers/mtd/nand/atmel/pmecc.c

@@ -945,6 +945,7 @@ struct atmel_pmecc *devm_atmel_pmecc_get(struct device *userdev)
 		 */
 		struct platform_device *pdev = to_platform_device(userdev);
 		const struct atmel_pmecc_caps *caps;
+		const struct of_device_id *match;
 
 		/* No PMECC engine available. */
 		if (!of_property_read_bool(userdev->of_node,

@@ -953,21 +954,11 @@ struct atmel_pmecc *devm_atmel_pmecc_get(struct device *userdev)
 
 		caps = &at91sam9g45_caps;
 
-		/*
-		 * Try to find the NFC subnode and extract the associated caps
-		 * from there.
-		 */
-		np = of_find_compatible_node(userdev->of_node, NULL,
-					     "atmel,sama5d3-nfc");
-		if (np) {
-			const struct of_device_id *match;
-
-			match = of_match_node(atmel_pmecc_legacy_match, np);
-			if (match && match->data)
-				caps = match->data;
-
-			of_node_put(np);
-		}
+		/* Find the caps associated to the NAND dev node. */
+		match = of_match_node(atmel_pmecc_legacy_match,
+				      userdev->of_node);
+		if (match && match->data)
+			caps = match->data;
 
 		pmecc = atmel_pmecc_create(pdev, caps, 1, 2);
 	}