[ 3.8.y.z extended stable ] Patch "mtd: nand: fix NAND_BUSWIDTH_AUTO for x16 devices" has been added to staging queue

Kamal Mostafa kamal at canonical.com
Thu Sep 19 00:03:20 UTC 2013

This is a note to let you know that I have just added a patch titled

    mtd: nand: fix NAND_BUSWIDTH_AUTO for x16 devices

to the linux-3.8.y-queue branch of the 3.8.y.z extended stable tree 
which can be found at:


This patch is scheduled to be released in version

If you, or anyone else, feels it should not be added to this tree, please 
reply to this email.

For more information about the 3.8.y.z tree, see



>From df451e65ca13fa35ab931a3c7764d40c1cbf6512 Mon Sep 17 00:00:00 2001
From: Brian Norris <computersforpeace at gmail.com>
Date: Thu, 18 Jul 2013 01:17:02 -0700
Subject: mtd: nand: fix NAND_BUSWIDTH_AUTO for x16 devices

commit 68e8078072e802e77134664f11d2ffbfbd2f8fbe upstream.

The code for NAND_BUSWIDTH_AUTO is broken. According to Alexander:

  "I have a problem with attach NAND UBI in 16 bit mode.
   NAND works fine if I specify NAND_BUSWIDTH_16 option, but not
   working with NAND_BUSWIDTH_AUTO option. In second case NAND
   chip is identifyed with ONFI."

See his report for the rest of the details:


Anyway, the problem is that nand_set_defaults() is called twice, we
intend it to reset the chip functions to their x16 buswidth verions
if the buswidth changed from x8 to x16; however, nand_set_defaults()
does exactly nothing if called a second time.

Fix this by hacking nand_set_defaults() to reset the buswidth-dependent
functions if they were set to the x8 version the first time. Note that
this does not do anything to reset from x16 to x8, but that's not the
supported use case for NAND_BUSWIDTH_AUTO anyway.

Signed-off-by: Brian Norris <computersforpeace at gmail.com>
Reported-by: Alexander Shiyan <shc_work at mail.ru>
Tested-by: Alexander Shiyan <shc_work at mail.ru>
Cc: Matthieu Castet <matthieu.castet at parrot.com>
Signed-off-by: Artem Bityutskiy <artem.bityutskiy at linux.intel.com>
Signed-off-by: David Woodhouse <David.Woodhouse at intel.com>
Signed-off-by: Kamal Mostafa <kamal at canonical.com>
 drivers/mtd/nand/nand_base.c | 8 +++++---
 1 file changed, 5 insertions(+), 3 deletions(-)

diff --git a/drivers/mtd/nand/nand_base.c b/drivers/mtd/nand/nand_base.c
index db04f53..d831091 100644
--- a/drivers/mtd/nand/nand_base.c
+++ b/drivers/mtd/nand/nand_base.c
@@ -2810,7 +2810,9 @@ static void nand_set_defaults(struct nand_chip *chip, int busw)

 	if (!chip->select_chip)
 		chip->select_chip = nand_select_chip;
-	if (!chip->read_byte)
+	/* If called twice, pointers that depend on busw may need to be reset */
+	if (!chip->read_byte || chip->read_byte == nand_read_byte)
 		chip->read_byte = busw ? nand_read_byte16 : nand_read_byte;
 	if (!chip->read_word)
 		chip->read_word = nand_read_word;
@@ -2818,9 +2820,9 @@ static void nand_set_defaults(struct nand_chip *chip, int busw)
 		chip->block_bad = nand_block_bad;
 	if (!chip->block_markbad)
 		chip->block_markbad = nand_default_block_markbad;
-	if (!chip->write_buf)
+	if (!chip->write_buf || chip->write_buf == nand_write_buf)
 		chip->write_buf = busw ? nand_write_buf16 : nand_write_buf;
-	if (!chip->read_buf)
+	if (!chip->read_buf || chip->read_buf == nand_read_buf)
 		chip->read_buf = busw ? nand_read_buf16 : nand_read_buf;
 	if (!chip->scan_bbt)
 		chip->scan_bbt = nand_default_bbt;

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