On Thu, 7 May 2020 13:00:30 +0200
Miquel Raynal <miquel.raynal@xxxxxxxxxxx> wrote:
> There are cases where ECC bytes are not byte-aligned. Indeed, BCH
> implies using a number of ECC bits, which are not always a multiple of
> 8. We then need a helper like nand_extract_bits() to extract these
> syndromes from a buffer.
Do you plan to send a patch to make the GPMI driver use this helper?
>
> Signed-off-by: Miquel Raynal <miquel.raynal@xxxxxxxxxxx>
> ---
> drivers/mtd/nand/raw/nand_base.c | 31 +++++++++++++++++++++++++++++++
> include/linux/mtd/rawnand.h | 4 ++++
> 2 files changed, 35 insertions(+)
>
> diff --git a/drivers/mtd/nand/raw/nand_base.c b/drivers/mtd/nand/raw/nand_base.c
> index 25d298938aa9..b236e1bdddaf 100644
> --- a/drivers/mtd/nand/raw/nand_base.c
> +++ b/drivers/mtd/nand/raw/nand_base.c
> @@ -224,6 +224,37 @@ static int check_offs_len(struct nand_chip *chip, loff_t ofs, uint64_t len)
> return ret;
> }
>
> +/* Copy unaligned bits from one buffer to another one (no overlap) */
> +void nand_extract_bits(u8 *dst, const u8 *src, unsigned int src_off,
> + unsigned int nbits)
> +{
> + unsigned int dst_off = 0, tmp, n;
> +
> + src += src_off / 8;
> + src_off %= 8;
> +
> + while (nbits) {
> + n = min3(8 - dst_off, 8 - src_off, nbits);
> +
> + tmp = (*src >> src_off) & GENMASK(n - 1, 0);
> + *dst |= tmp << dst_off;
> +
> + dst_off += n;
> + if (dst_off >= 8) {
> + dst++;
> + dst_off -= 8;
> + }
> +
> + src_off += n;
> + if (src_off >= 8) {
> + src++;
> + src_off -= 8;
> + }
> +
> + nbits -= n;
> + }
> +}
> +
> /**
> * nand_select_target() - Select a NAND target (A.K.A. die)
> * @chip: NAND chip object
> diff --git a/include/linux/mtd/rawnand.h b/include/linux/mtd/rawnand.h
> index 406e9ff0f45c..734564232545 100644
> --- a/include/linux/mtd/rawnand.h
> +++ b/include/linux/mtd/rawnand.h
> @@ -1404,6 +1404,10 @@ int nand_gpio_waitrdy(struct nand_chip *chip, struct gpio_desc *gpiod,
> void nand_select_target(struct nand_chip *chip, unsigned int cs);
> void nand_deselect_target(struct nand_chip *chip);
>
> +/* Bitops */
> +void nand_extract_bits(u8 *dst, const u8 *src, unsigned int src_off,
> + unsigned int nbits);
> +
> /**
> * nand_get_data_buf() - Get the internal page buffer
> * @chip: NAND chip object
