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 for linux-mtd@lists.infradead.org; Fri, 10 Aug 2012 01:41:27 +0000
From: Marek Vasut <marex@denx.de>
To: Fabio Estevam <festevam@gmail.com>
Subject: Re: Kernel crashes when CONFIG_MTD_NAND_VERIFY_WRITE=y
Date: Fri, 10 Aug 2012 03:41:22 +0200
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Cc: Shawn Guo <shawn.guo@linaro.org>, Subodh Nijsure <snijsure@grid-net.com>,
 Huang Shijie <b32955@freescale.com>, linux-mtd@lists.infradead.org,
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Dear Fabio Estevam,

> Hi Marek,
> 
> On Thu, Aug 9, 2012 at 8:53 PM, Marek Vasut <marex@denx.de> wrote:
> > This problem is there because the GPMI NAND code doesn't implement verify
> > buffer
> 
> > function and defaults to nand_verify_buf() call in nand_base.c:
> Yes, you are right.
> 
> > Now the chip->IO_ADDR_R is zero, making the kernel access bogus location,
> > and therefore crash. So the correct solution is to properly implement
> > the struct nand_chip *'s verify_buf function.
> 
> Right, the patch below prevents the kernel to happen:
> 
> --- a/drivers/mtd/nand/gpmi-nand/gpmi-nand.c
> +++ b/drivers/mtd/nand/gpmi-nand/gpmi-nand.c
> @@ -857,6 +857,15 @@ static uint8_t gpmi_read_byte(struct mtd_info *mtd)
>         return buf[0];
>  }
> 
> +/* Used by the upper layer to verify the data in NAND Flash
> + * with the data in the buf. */
> +static int gpmi_verify_buf(struct mtd_info *mtd,
> +                               const u_char *buf, int len)
> +{
> +       /* TODO: implement verify_buf mechanism */
> +       return 0;
> +}


NAK! This is only a workaround, proper implementation is needed. If it's not 
implemented now, I'm pretty sure such workaround will be there forever.

>  /*
>   * Handles block mark swapping.
>   * It can be called in swapping the block mark, or swapping it back,
> @@ -1568,6 +1577,7 @@ static int __devinit gpmi_nfc_init(struct
> gpmi_nand_data *this)
>         chip->ecc.size          = 1;
>         chip->ecc.strength      = 8;
>         chip->ecc.layout        = &gpmi_hw_ecclayout;
> +       chip->verify_buf        = gpmi_verify_buf;
>         if (of_get_nand_on_flash_bbt(this->dev->of_node))
>                 chip->bbt_options |= NAND_BBT_USE_FLASH | NAND_BBT_NO_OOB;
> 
> Now we need to come up with a real  gpmi_verify_buf function ;-)
> 
> Regards,
> 
> Fabio Estevam

Best regards,
Marek Vasut