On Tue, 19 May 2020 09:45:43 +0200
Miquel Raynal <miquel.raynal@xxxxxxxxxxx> wrote:
> It seems that several hardware ECC engine use a swapped representation
> of bytes compared to software. This might having to do with how the
> ECC engine is wired to the NAND controller or the order the bits are
> passed to the hardware BCH logic.
>
> This means that when the software BCH engine is working in conjunction
> with data generated with hardware, sometimes we might need to swap the
> bits inside bytes, eg:
>
> 0x0A = b0000_1010 -> b0101_0000 = 0x50
>
> Make it possible by adding a boolean to the BCH initialization routine.
>
> Regarding the implementation itself, this is a rather simple approach
> that can probably be enhanced in the future by preparing the
> ->a_{mod,pow}_tab tables with the swapping in mind.
>
> Suggested-by: Boris Brezillon <boris.brezillon@xxxxxxxxxxxxx>
> Signed-off-by: Miquel Raynal <miquel.raynal@xxxxxxxxxxx>
Reviewed-by: Boris Brezillon <boris.brezillon@xxxxxxxxxxxxx>
> ---
> drivers/mtd/devices/docg3.c | 2 +-
> drivers/mtd/nand/raw/nand_bch.c | 2 +-
> include/linux/bch.h | 5 +-
> lib/bch.c | 90 ++++++++++++++++++++++++++++-----
> 4 files changed, 82 insertions(+), 17 deletions(-)
>
> diff --git a/drivers/mtd/devices/docg3.c b/drivers/mtd/devices/docg3.c
> index 799df8d03357..a030792115bc 100644
> --- a/drivers/mtd/devices/docg3.c
> +++ b/drivers/mtd/devices/docg3.c
> @@ -1985,7 +1985,7 @@ static int __init docg3_probe(struct platform_device *pdev)
> cascade->base = base;
> mutex_init(&cascade->lock);
> cascade->bch = bch_init(DOC_ECC_BCH_M, DOC_ECC_BCH_T,
> - DOC_ECC_BCH_PRIMPOLY);
> + DOC_ECC_BCH_PRIMPOLY, false);
> if (!cascade->bch)
> return ret;
>
> diff --git a/drivers/mtd/nand/raw/nand_bch.c b/drivers/mtd/nand/raw/nand_bch.c
> index d95fcc7358e9..d5af8c5fd02f 100644
> --- a/drivers/mtd/nand/raw/nand_bch.c
> +++ b/drivers/mtd/nand/raw/nand_bch.c
> @@ -130,7 +130,7 @@ struct nand_bch_control *nand_bch_init(struct mtd_info *mtd)
> if (!nbc)
> goto fail;
>
> - nbc->bch = bch_init(m, t, 0);
> + nbc->bch = bch_init(m, t, 0, false);
> if (!nbc->bch)
> goto fail;
>
> diff --git a/include/linux/bch.h b/include/linux/bch.h
> index 9c35e7cd5890..85fdce83d4e2 100644
> --- a/include/linux/bch.h
> +++ b/include/linux/bch.h
> @@ -33,6 +33,7 @@
> * @cache: log-based polynomial representation buffer
> * @elp: error locator polynomial
> * @poly_2t: temporary polynomials of degree 2t
> + * @swap_bits: swap bits within data and syndrome bytes
> */
> struct bch_control {
> unsigned int m;
> @@ -51,9 +52,11 @@ struct bch_control {
> int *cache;
> struct gf_poly *elp;
> struct gf_poly *poly_2t[4];
> + bool swap_bits;
> };
>
> -struct bch_control *bch_init(int m, int t, unsigned int prim_poly);
> +struct bch_control *bch_init(int m, int t, unsigned int prim_poly,
> + bool swap_bits);
>
> void bch_free(struct bch_control *bch);
>
> diff --git a/lib/bch.c b/lib/bch.c
> index 1091841ac716..7c031ee8b93b 100644
> --- a/lib/bch.c
> +++ b/lib/bch.c
> @@ -114,6 +114,49 @@ struct gf_poly_deg1 {
> unsigned int c[2];
> };
>
> +static u8 swap_bits_table[] = {
> + 0x00, 0x80, 0x40, 0xc0, 0x20, 0xa0, 0x60, 0xe0,
> + 0x10, 0x90, 0x50, 0xd0, 0x30, 0xb0, 0x70, 0xf0,
> + 0x08, 0x88, 0x48, 0xc8, 0x28, 0xa8, 0x68, 0xe8,
> + 0x18, 0x98, 0x58, 0xd8, 0x38, 0xb8, 0x78, 0xf8,
> + 0x04, 0x84, 0x44, 0xc4, 0x24, 0xa4, 0x64, 0xe4,
> + 0x14, 0x94, 0x54, 0xd4, 0x34, 0xb4, 0x74, 0xf4,
> + 0x0c, 0x8c, 0x4c, 0xcc, 0x2c, 0xac, 0x6c, 0xec,
> + 0x1c, 0x9c, 0x5c, 0xdc, 0x3c, 0xbc, 0x7c, 0xfc,
> + 0x02, 0x82, 0x42, 0xc2, 0x22, 0xa2, 0x62, 0xe2,
> + 0x12, 0x92, 0x52, 0xd2, 0x32, 0xb2, 0x72, 0xf2,
> + 0x0a, 0x8a, 0x4a, 0xca, 0x2a, 0xaa, 0x6a, 0xea,
> + 0x1a, 0x9a, 0x5a, 0xda, 0x3a, 0xba, 0x7a, 0xfa,
> + 0x06, 0x86, 0x46, 0xc6, 0x26, 0xa6, 0x66, 0xe6,
> + 0x16, 0x96, 0x56, 0xd6, 0x36, 0xb6, 0x76, 0xf6,
> + 0x0e, 0x8e, 0x4e, 0xce, 0x2e, 0xae, 0x6e, 0xee,
> + 0x1e, 0x9e, 0x5e, 0xde, 0x3e, 0xbe, 0x7e, 0xfe,
> + 0x01, 0x81, 0x41, 0xc1, 0x21, 0xa1, 0x61, 0xe1,
> + 0x11, 0x91, 0x51, 0xd1, 0x31, 0xb1, 0x71, 0xf1,
> + 0x09, 0x89, 0x49, 0xc9, 0x29, 0xa9, 0x69, 0xe9,
> + 0x19, 0x99, 0x59, 0xd9, 0x39, 0xb9, 0x79, 0xf9,
> + 0x05, 0x85, 0x45, 0xc5, 0x25, 0xa5, 0x65, 0xe5,
> + 0x15, 0x95, 0x55, 0xd5, 0x35, 0xb5, 0x75, 0xf5,
> + 0x0d, 0x8d, 0x4d, 0xcd, 0x2d, 0xad, 0x6d, 0xed,
> + 0x1d, 0x9d, 0x5d, 0xdd, 0x3d, 0xbd, 0x7d, 0xfd,
> + 0x03, 0x83, 0x43, 0xc3, 0x23, 0xa3, 0x63, 0xe3,
> + 0x13, 0x93, 0x53, 0xd3, 0x33, 0xb3, 0x73, 0xf3,
> + 0x0b, 0x8b, 0x4b, 0xcb, 0x2b, 0xab, 0x6b, 0xeb,
> + 0x1b, 0x9b, 0x5b, 0xdb, 0x3b, 0xbb, 0x7b, 0xfb,
> + 0x07, 0x87, 0x47, 0xc7, 0x27, 0xa7, 0x67, 0xe7,
> + 0x17, 0x97, 0x57, 0xd7, 0x37, 0xb7, 0x77, 0xf7,
> + 0x0f, 0x8f, 0x4f, 0xcf, 0x2f, 0xaf, 0x6f, 0xef,
> + 0x1f, 0x9f, 0x5f, 0xdf, 0x3f, 0xbf, 0x7f, 0xff,
> +};
> +
> +static u8 swap_bits(struct bch_control *bch, u8 in)
> +{
> + if (!bch->swap_bits)
> + return in;
> +
> + return swap_bits_table[in];
> +}
> +
> /*
> * same as bch_encode(), but process input data one byte at a time
> */
> @@ -126,7 +169,9 @@ static void bch_encode_unaligned(struct bch_control *bch,
> const int l = BCH_ECC_WORDS(bch)-1;
>
> while (len--) {
> - p = bch->mod8_tab + (l+1)*(((ecc[0] >> 24)^(*data++)) & 0xff);
> + u8 tmp = swap_bits(bch, *data++);
> +
> + p = bch->mod8_tab + (l+1)*(((ecc[0] >> 24)^(tmp)) & 0xff);
>
> for (i = 0; i < l; i++)
> ecc[i] = ((ecc[i] << 8)|(ecc[i+1] >> 24))^(*p++);
> @@ -145,10 +190,16 @@ static void load_ecc8(struct bch_control *bch, uint32_t *dst,
> unsigned int i, nwords = BCH_ECC_WORDS(bch)-1;
>
> for (i = 0; i < nwords; i++, src += 4)
> - dst[i] = (src[0] << 24)|(src[1] << 16)|(src[2] << 8)|src[3];
> + dst[i] = ((u32)swap_bits(bch, src[0]) << 24) |
> + ((u32)swap_bits(bch, src[1]) << 16) |
> + ((u32)swap_bits(bch, src[2]) << 8) |
> + swap_bits(bch, src[3]);
>
> memcpy(pad, src, BCH_ECC_BYTES(bch)-4*nwords);
> - dst[nwords] = (pad[0] << 24)|(pad[1] << 16)|(pad[2] << 8)|pad[3];
> + dst[nwords] = ((u32)swap_bits(bch, pad[0]) << 24) |
> + ((u32)swap_bits(bch, pad[1]) << 16) |
> + ((u32)swap_bits(bch, pad[2]) << 8) |
> + swap_bits(bch, pad[3]);
> }
>
> /*
> @@ -161,15 +212,15 @@ static void store_ecc8(struct bch_control *bch, uint8_t *dst,
> unsigned int i, nwords = BCH_ECC_WORDS(bch)-1;
>
> for (i = 0; i < nwords; i++) {
> - *dst++ = (src[i] >> 24);
> - *dst++ = (src[i] >> 16) & 0xff;
> - *dst++ = (src[i] >> 8) & 0xff;
> - *dst++ = (src[i] >> 0) & 0xff;
> + *dst++ = swap_bits(bch, src[i] >> 24);
> + *dst++ = swap_bits(bch, src[i] >> 16);
> + *dst++ = swap_bits(bch, src[i] >> 8);
> + *dst++ = swap_bits(bch, src[i]);
> }
> - pad[0] = (src[nwords] >> 24);
> - pad[1] = (src[nwords] >> 16) & 0xff;
> - pad[2] = (src[nwords] >> 8) & 0xff;
> - pad[3] = (src[nwords] >> 0) & 0xff;
> + pad[0] = swap_bits(bch, src[nwords] >> 24);
> + pad[1] = swap_bits(bch, src[nwords] >> 16);
> + pad[2] = swap_bits(bch, src[nwords] >> 8);
> + pad[3] = swap_bits(bch, src[nwords]);
> memcpy(dst, pad, BCH_ECC_BYTES(bch)-4*nwords);
> }
>
> @@ -240,7 +291,13 @@ void bch_encode(struct bch_control *bch, const uint8_t *data,
> */
> while (mlen--) {
> /* input data is read in big-endian format */
> - w = r[0]^cpu_to_be32(*pdata++);
> + w = cpu_to_be32(*pdata++);
> + if (bch->swap_bits)
> + w = (u32)swap_bits(bch, w) |
> + ((u32)swap_bits(bch, w >> 8) << 8) |
> + ((u32)swap_bits(bch, w >> 16) << 16) |
> + ((u32)swap_bits(bch, w >> 24) << 24);
> + w ^= r[0];
> p0 = tab0 + (l+1)*((w >> 0) & 0xff);
> p1 = tab1 + (l+1)*((w >> 8) & 0xff);
> p2 = tab2 + (l+1)*((w >> 16) & 0xff);
> @@ -1048,7 +1105,9 @@ int bch_decode(struct bch_control *bch, const uint8_t *data, unsigned int len,
> break;
> }
> errloc[i] = nbits-1-errloc[i];
> - errloc[i] = (errloc[i] & ~7)|(7-(errloc[i] & 7));
> + if (!bch->swap_bits)
> + errloc[i] = (errloc[i] & ~7) |
> + (7-(errloc[i] & 7));
> }
> }
> return (err >= 0) ? err : -EBADMSG;
> @@ -1240,6 +1299,7 @@ static uint32_t *compute_generator_polynomial(struct bch_control *bch)
> * @m: Galois field order, should be in the range 5-15
> * @t: maximum error correction capability, in bits
> * @prim_poly: user-provided primitive polynomial (or 0 to use default)
> + * @swap_bits: swap bits within data and syndrome bytes
> *
> * Returns:
> * a newly allocated BCH control structure if successful, NULL otherwise
> @@ -1256,7 +1316,8 @@ static uint32_t *compute_generator_polynomial(struct bch_control *bch)
> * BCH control structure, ecc length in bytes is given by member @ecc_bytes of
> * the structure.
> */
> -struct bch_control *bch_init(int m, int t, unsigned int prim_poly)
> +struct bch_control *bch_init(int m, int t, unsigned int prim_poly,
> + bool swap_bits)
> {
> int err = 0;
> unsigned int i, words;
> @@ -1321,6 +1382,7 @@ struct bch_control *bch_init(int m, int t, unsigned int prim_poly)
> bch->syn = bch_alloc(2*t*sizeof(*bch->syn), &err);
> bch->cache = bch_alloc(2*t*sizeof(*bch->cache), &err);
> bch->elp = bch_alloc((t+1)*sizeof(struct gf_poly_deg1), &err);
> + bch->swap_bits = swap_bits;
>
> for (i = 0; i < ARRAY_SIZE(bch->poly_2t); i++)
> bch->poly_2t[i] = bch_alloc(GF_POLY_SZ(2*t), &err);
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Re: [PATCH v5 2/8] lib/bch: Allow easy bit swapping
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- Subject: Re: [PATCH v5 2/8] lib/bch: Allow easy bit swapping
- From: Boris Brezillon <boris.brezillon@xxxxxxxxxxxxx>
- Date: Tue, 19 May 2020 10:41:07 +0200
- Cc: Michal Simek <monstr@xxxxxxxxx>, Vignesh Raghavendra <vigneshr@xxxxxx>, Tudor Ambarus <Tudor.Ambarus@xxxxxxxxxxxxx>, Richard Weinberger <richard@xxxxxx>, linux-mtd@xxxxxxxxxxxxxxxxxxx, Thomas Petazzoni <thomas.petazzoni@xxxxxxxxxxx>, Naga Sureshkumar Relli <nagasure@xxxxxxxxxx>
- In-reply-to: <20200519074549.23673-3-miquel.raynal@bootlin.com>
- Organization: Collabora
- References: <20200519074549.23673-1-miquel.raynal@bootlin.com> <20200519074549.23673-3-miquel.raynal@bootlin.com>
- References:
- [PATCH v5 0/8] New Arasan NAND controller driver
- From: Miquel Raynal
- [PATCH v5 2/8] lib/bch: Allow easy bit swapping
- From: Miquel Raynal
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