linux-kernel - [PATCH] Fix writing mtdoops to nand flash.

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Message-Id: <20171030042343.24551-1-motobud@gmail.com>
Date:   Sun, 29 Oct 2017 23:23:43 -0500
From:   motobud@...il.com
To:     boris.brezillon@...e-electrons.com
Cc:     Brent Taylor <motobud@...il.com>,
        Richard Weinberger <richard@....at>,
        David Woodhouse <dwmw2@...radead.org>,
        Brian Norris <computersforpeace@...il.com>,
        Marek Vasut <marek.vasut@...il.com>,
        Cyrille Pitchen <cyrille.pitchen@...ev4u.fr>,
        linux-mtd@...ts.infradead.org, linux-kernel@...r.kernel.org
Subject: [PATCH] Fix writing mtdoops to nand flash.

From: Brent Taylor <motobud@...il.com>

When mtdoops calls mtd_panic_write, it eventually calls
panic_nand_write in nand_base.c.  In order to properly
wait for the nand chip to be ready in panic_nand_wait,
the chip must first be selected.

When using the atmel nand flash controller, a panic
would occur due to a NULL pointer exception.

Signed-off-by: Brent Taylor <motobud@...il.com>
---
 drivers/mtd/nand/nand_base.c | 5 +++++
 1 file changed, 5 insertions(+)

diff --git a/drivers/mtd/nand/nand_base.c b/drivers/mtd/nand/nand_base.c
index 12edaae17d81..0a8058a66d93 100644
--- a/drivers/mtd/nand/nand_base.c
+++ b/drivers/mtd/nand/nand_base.c
@@ -2802,9 +2802,14 @@ static int panic_nand_write(struct mtd_info *mtd, loff_t to, size_t len,
 	struct mtd_oob_ops ops;
 	int ret;
 
+	int chipnr = (int)(to >> chip->chip_shift);
+	chip->select_chip(mtd, chipnr);
+
 	/* Wait for the device to get ready */
 	panic_nand_wait(mtd, chip, 400);
 
+	chip->select_chip(mtd, -1);
+
 	/* Grab the device */
 	panic_nand_get_device(chip, mtd, FL_WRITING);
 
-- 
2.14.2