mtd: nand: fix NAND_BUSWIDTH_AUTO for x16 devices

[Linux-MTD Mailing List]

Gitweb:     http://git.infradead.org/?p=mtd-2.6.git;a=commit;h=68e8078072e802e77134664f11d2ffbfbd2f8fbe
Commit:     68e8078072e802e77134664f11d2ffbfbd2f8fbe
Parent:     9d40349681ea44d80ef84e7a9eb3786165ba79d1
Author:     Brian Norris <computersforpeace at gmail.com>
AuthorDate: Thu Jul 18 01:17:02 2013 -0700
Committer:  David Woodhouse <David.Woodhouse at intel.com>
CommitDate: Mon Aug 5 21:02:31 2013 +0100

    mtd: nand: fix NAND_BUSWIDTH_AUTO for x16 devices
    
    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:
    
      http://lists.infradead.org/pipermail/linux-mtd/2013-July/047515.html
    
    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>
    Cc: <stable at vger.kernel.org> # v3.8+
    Signed-off-by: Artem Bityutskiy <artem.bityutskiy at linux.intel.com>
    Signed-off-by: David Woodhouse <David.Woodhouse at intel.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 1cbacff..0980ae3 100644
--- a/drivers/mtd/nand/nand_base.c
+++ b/drivers/mtd/nand/nand_base.c
@@ -2786,7 +2786,9 @@ 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;
@@ -2794,9 +2796,9 @@ 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;