Re: [PATCH v3] mtd: gpmi: add NAND write verify support

[Marek Vasut <marex@denx.de>]

Dear Huang Shijie,

Please re-add credit to Fabio. Also, Fabio fixed the subject to be more 
accurate. Your subject makes this sound like it's adding a feature that can be 
postponed, yet this fixes a serious problem with the driver.

> Add NAND write verify support in gpmi-nand driver.
> 
> This patch fixes a kernel crash when we select
> CONFIG_MTD_NAND_VERIFY_WRITE=y, and do some write tests:
> 
> root@freescale /$ dd if=/dev/zero of=/dev/mtd0 bs=128k count=1
> [   41.070000] Unable to handle kernel NULL pointer dereference at virtual
> addr0 [   41.080000] pgd = c77ac000
> [   41.080000] [00000000] *pgd=4773c831, *pte=00000000, *ppte=00000000
> [   41.090000] Internal error: Oops: 17 [#1] ARM
> [   41.090000] Modules linked in:
> [   41.090000] CPU: 0    Not tainted
> (3.6.0-rc1-next-20120809-00002-ga25d017-d) [   41.090000] PC is at
> nand_verify_buf+0x18/0x5c
> [   41.090000] LR is at nand_write_page+0xc0/0x140
> [   41.090000] pc : [<c023e7d4>]    lr : [<c023fcfc>]    psr: 20000013
> [   41.090000] sp : c7779de4  ip : 00000000  fp : c6e60000
> [   41.090000] r10: 00000000  r9 : 00020000  r8 : 00000000
> [   41.090000] r7 : 00000000  r6 : c6e60000  r5 : c762cb10  r4 : 00000000
> [   41.090000] r3 : c762c8a8  r2 : 00000800  r1 : c6e60000  r0 : 00000000
> [   41.090000] Flags: nzCv  IRQs on  FIQs on  Mode SVC_32  ISA ARM  Segment
> user [   41.090000] Control: 0005317f  Table: 477ac000  DAC: 00000015
> [   41.090000] Process dd (pid: 427, stack limit = 0xc7778270)
> [   41.090000] Stack: (0xc7779de4 to 0xc777a000)
> 	...
> 
> Cc: <stable@vger.kernel.org>
> Signed-off-by: Huang Shijie <shijie8@gmail.com>
> ---
> v2 --> v3:
>     [1] free the verify_buf when we exit.
> 
> v1 --> v2:
>     [1] use the mtd->writesize to allocate the verify buffer.
>     [2] add new field `verify_buf` in gpmi_nand_data{}
> 
>     tested this patch on imx6q-arm2 board.
> ---
>  drivers/mtd/nand/gpmi-nand/gpmi-nand.c |   25 +++++++++++++++++++++++++
>  drivers/mtd/nand/gpmi-nand/gpmi-nand.h |    1 +
>  2 files changed, 26 insertions(+), 0 deletions(-)
> 
> diff --git a/drivers/mtd/nand/gpmi-nand/gpmi-nand.c
> b/drivers/mtd/nand/gpmi-nand/gpmi-nand.c index 8c0d2f0..e1e4c51 100644
> --- a/drivers/mtd/nand/gpmi-nand/gpmi-nand.c
> +++ b/drivers/mtd/nand/gpmi-nand/gpmi-nand.c
> @@ -1512,12 +1512,34 @@ static int gpmi_pre_bbt_scan(struct gpmi_nand_data 
> *this) return nand_boot_init(this);
>  }
> 
> +static int gpmi_verify_buf(struct mtd_info *mtd, const uint8_t *buf, int
> len) +{
> +	struct nand_chip *chip = mtd->priv;
> +	struct gpmi_nand_data *this = chip->priv;
> +	int ret;
> +
> +	ret = chip->ecc.read_page(mtd, chip, this->verify_buf, 0, 0);
> +	if (ret)
> +		return -EFAULT;
> +	if (memcmp(buf, this->verify_buf, len))
> +		return -EFAULT;
> +	return 0;
> +}
> +
>  static int gpmi_scan_bbt(struct mtd_info *mtd)
>  {
>  	struct nand_chip *chip = mtd->priv;
>  	struct gpmi_nand_data *this = chip->priv;
>  	int ret;
> 
> +	/*
> +	 * We have gotten the right page size now, use it to allocate
> +	 * the proper verify buffer.
> +	 */
> +	this->verify_buf = kzalloc(mtd->writesize, GFP_KERNEL);

devm_ will work here just fine.

> +	if (!this->verify_buf)
> +		return -ENOMEM;
> +
>  	/* Prepare for the BBT scan. */
>  	ret = gpmi_pre_bbt_scan(this);
>  	if (ret)
> @@ -1531,6 +1553,8 @@ void gpmi_nfc_exit(struct gpmi_nand_data *this)
>  {
>  	nand_release(&this->mtd);
>  	gpmi_free_dma_buffer(this);
> +	kfree(this->verify_buf);

Then you can drop this altogether.

> +	this->verify_buf = NULL;
>  }
> 
>  static int __devinit gpmi_nfc_init(struct gpmi_nand_data *this)
> @@ -1556,6 +1580,7 @@ static int __devinit gpmi_nfc_init(struct
> gpmi_nand_data *this) chip->read_byte		= gpmi_read_byte;
>  	chip->read_buf		= gpmi_read_buf;
>  	chip->write_buf		= gpmi_write_buf;
> +	chip->verify_buf	= gpmi_verify_buf;
>  	chip->ecc.read_page	= gpmi_ecc_read_page;
>  	chip->ecc.write_page	= gpmi_ecc_write_page;
>  	chip->ecc.read_oob	= gpmi_ecc_read_oob;
> diff --git a/drivers/mtd/nand/gpmi-nand/gpmi-nand.h
> b/drivers/mtd/nand/gpmi-nand/gpmi-nand.h index 1547a60..8ddf115 100644
> --- a/drivers/mtd/nand/gpmi-nand/gpmi-nand.h
> +++ b/drivers/mtd/nand/gpmi-nand/gpmi-nand.h
> @@ -144,6 +144,7 @@ struct gpmi_nand_data {
>  	/* MTD / NAND */
>  	struct nand_chip	nand;
>  	struct mtd_info		mtd;
> +	uint8_t			*verify_buf;
> 
>  	/* General-use Variables */
>  	int			current_chip;

Best regards,
Marek Vasut