Re: [PATCH v4] mtd: nand: sunxi: fix OOB handling in ->write_xxx() functions

[Brian Norris <computersforpeace@gmail.com>]

On Mon, Sep 14, 2015 at 10:41:03AM +0200, Boris Brezillon wrote:
> The USER_DATA register cannot be accessed using byte accessors on A13
> SoCs, thus triggering a bug when using memcpy_toio on this register.
> Declare an helper macros to convert an OOB buffer into a suitable
> USER_DATA value and vice-versa.
> 
> This patch also fixes an error in the oob_required logic (some OOB data
> are not written even if the user required it) by removing the
> oob_required condition, which is perfectly valid since the core already
> fill ->oob_poi with FFs when oob_required is false.
> 
> Signed-off-by: Boris Brezillon <boris.brezillon@free-electrons.com>
> Cc: <stable@vger.kernel.org> # 3.19+
> Fixes: 1fef62c1423b ("mtd: nand: add sunxi NAND flash controller support")
> 
> ---
> Changes since v3:
> - drop the NFC_USER_DATA_TO_BUF() macro

I don't have any real objections to this version, and I think some IRC
discussion helped clear up a few questions. I'll take this for 4.3 soon,
unless I see any objections.

> Changes since v2:
> - add the NFC_USER_DATA_TO_BUF() macro and rename NFC_USER_DATA() into
>   NFC_BUF_TO_USER_DATA()
> - rework the commit message
> 
> Changes since v1:
> - drop the !oob_required conditional path
> - replace endianness conversions by a macro relying on byte shifting
>   operations
> ---
>  drivers/mtd/nand/sunxi_nand.c | 26 +++++++++-----------------
>  1 file changed, 9 insertions(+), 17 deletions(-)
> 
> diff --git a/drivers/mtd/nand/sunxi_nand.c b/drivers/mtd/nand/sunxi_nand.c
> index f97a58d..279cafd 100644
> --- a/drivers/mtd/nand/sunxi_nand.c
> +++ b/drivers/mtd/nand/sunxi_nand.c
> @@ -147,6 +147,10 @@
>  #define NFC_ECC_MODE		GENMASK(15, 12)
>  #define NFC_RANDOM_SEED		GENMASK(30, 16)
>  
> +/* NFC_USER_DATA helper macros */
> +#define NFC_BUF_TO_USER_DATA(buf)	((buf)[0] | ((buf)[1] << 8) | \
> +					((buf)[2] << 16) | ((buf)[3] << 24))
> +
>  #define NFC_DEFAULT_TIMEOUT_MS	1000
>  
>  #define NFC_SRAM_SIZE		1024
> @@ -646,15 +650,9 @@ static int sunxi_nfc_hw_ecc_write_page(struct mtd_info *mtd,
>  		offset = layout->eccpos[i * ecc->bytes] - 4 + mtd->writesize;
>  
>  		/* Fill OOB data in */
> -		if (oob_required) {
> -			tmp = 0xffffffff;
> -			memcpy_toio(nfc->regs + NFC_REG_USER_DATA_BASE, &tmp,
> -				    4);
> -		} else {
> -			memcpy_toio(nfc->regs + NFC_REG_USER_DATA_BASE,
> -				    chip->oob_poi + offset - mtd->writesize,
> -				    4);
> -		}
> +		writel(NFC_BUF_TO_USER_DATA(chip->oob_poi +
> +					    layout->oobfree[i].offset),
> +		       nfc->regs + NFC_REG_USER_DATA_BASE);

I believe the few remaining questionable points were:

 * you don't actually need to add the barrier, thus __raw_writel() would
   suffice
 * you're still doing a double swap for the (likely theoretical) big
   endian case

Neither point matters much to me, so as noted above, LGTM.

>  
>  		chip->cmdfunc(mtd, NAND_CMD_RNDIN, offset, -1);
>  
> @@ -784,14 +782,8 @@ static int sunxi_nfc_hw_syndrome_ecc_write_page(struct mtd_info *mtd,
>  		offset += ecc->size;
>  
>  		/* Fill OOB data in */
> -		if (oob_required) {
> -			tmp = 0xffffffff;
> -			memcpy_toio(nfc->regs + NFC_REG_USER_DATA_BASE, &tmp,
> -				    4);
> -		} else {
> -			memcpy_toio(nfc->regs + NFC_REG_USER_DATA_BASE, oob,
> -				    4);
> -		}
> +		writel(NFC_BUF_TO_USER_DATA(oob),
> +		       nfc->regs + NFC_REG_USER_DATA_BASE);

Same here.

>  
>  		tmp = NFC_DATA_TRANS | NFC_DATA_SWAP_METHOD | NFC_ACCESS_DIR |
>  		      (1 << 30);

Brian