linux-kernel - Re: [PATCH v2] mtd: nand: Fix writing mtdoops to nand flash.

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Date:   Tue, 31 Oct 2017 11:18:42 +0100
From:   Boris Brezillon <boris.brezillon@...e-electrons.com>
To:     motobud@...il.com
Cc:     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: Re: [PATCH v2] mtd: nand: Fix writing mtdoops to nand flash.

On Mon, 30 Oct 2017 22:32:45 -0500
motobud@...il.com wrote:

> 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>

I'll add

Fixes: 2af7c6539931 ("mtd: Add panic_write for NAND flashes")
Cc: <stable@...r.kernel.org>

when applying the patch.

Thanks,

Boris

> ---
> Changes in v2:
>   - drop deselecting the chip
>   - move select_chip and panic_nand_wait after panic_nand_get_device
> 
>  drivers/mtd/nand/nand_base.c | 8 ++++++--
>  1 file changed, 6 insertions(+), 2 deletions(-)
> 
> diff --git a/drivers/mtd/nand/nand_base.c b/drivers/mtd/nand/nand_base.c
> index 12edaae17d81..2093667e2bcb 100644
> --- a/drivers/mtd/nand/nand_base.c
> +++ b/drivers/mtd/nand/nand_base.c
> @@ -2802,12 +2802,16 @@ static int panic_nand_write(struct mtd_info *mtd, loff_t to, size_t len,
>  	struct mtd_oob_ops ops;
>  	int ret;
>  
> -	/* Wait for the device to get ready */
> -	panic_nand_wait(mtd, chip, 400);
> +	int chipnr = (int)(to >> chip->chip_shift);
>  
>  	/* Grab the device */
>  	panic_nand_get_device(chip, mtd, FL_WRITING);
>  
> +	chip->select_chip(mtd, chipnr);
> +
> +	/* Wait for the device to get ready */
> +	panic_nand_wait(mtd, chip, 400);
> +
>  	memset(&ops, 0, sizeof(ops));
>  	ops.len = len;
>  	ops.datbuf = (uint8_t *)buf;