Hi Ghorai, I am the initial author of this patch. And I guess this patch still uses most of my work. Thanks and Regards, Vimal On Thu, Jan 20, 2011 at 3:48 PM, Sukumar Ghorai <s-ghorai@xxxxxx> wrote: > bch error correction (t=4 and t=8) for 512 bytes support added. > Tested in omap-3630 es-1.1 silicon. > > Need to select the bch-ecc from board file. E.g. > arch/arm/mach-omap2/board-flash.c: board_nand_init() > board_nand_data.ecc_opt = OMAP_ECC_BCH4_CODE_HW > > This patch has dependency on - > http://www.mail-archive.com/linux-omap@xxxxxxxxxxxxxxx/msg42658.html > > Signed-off-by: Sukumar Ghorai <s-ghorai@xxxxxx> > --- > arch/arm/mach-omap2/gpmc.c | 126 ++++++++--- > arch/arm/plat-omap/include/plat/gpmc.h | 6 +- > drivers/mtd/nand/Makefile | 1 + > drivers/mtd/nand/omap2.c | 119 ++++++++-- > drivers/mtd/nand/omap_bch_decoder.c | 393 ++++++++++++++++++++++++++++++++ > 5 files changed, 583 insertions(+), 62 deletions(-) > create mode 100644 drivers/mtd/nand/omap_bch_decoder.c > > diff --git a/arch/arm/mach-omap2/gpmc.c b/arch/arm/mach-omap2/gpmc.c > index 29c9732..91cfdca 100644 > --- a/arch/arm/mach-omap2/gpmc.c > +++ b/arch/arm/mach-omap2/gpmc.c > @@ -48,6 +48,7 @@ > #define GPMC_ECC_CONTROL 0x1f8 > #define GPMC_ECC_SIZE_CONFIG 0x1fc > #define GPMC_ECC1_RESULT 0x200 > +#define GPMC_ECC_BCH_RESULT_0 0x240 > > #define GPMC_CS0_OFFSET 0x60 > #define GPMC_CS_SIZE 0x30 > @@ -94,7 +95,6 @@ static struct resource gpmc_mem_root; > static struct resource gpmc_cs_mem[GPMC_CS_NUM]; > static DEFINE_SPINLOCK(gpmc_mem_lock); > static unsigned int gpmc_cs_map; /* flag for cs which are initialized */ > -static int gpmc_ecc_used = -EINVAL; /* cs using ecc engine */ > > static void __iomem *gpmc_base; > > @@ -832,52 +832,77 @@ void omap3_gpmc_restore_context(void) > > /** > * gpmc_enable_hwecc - enable hardware ecc functionality > + * @ecc_type: ecc type e.g. Hamming, BCH > * @cs: chip select number > * @mode: read/write mode > * @dev_width: device bus width(1 for x16, 0 for x8) > * @ecc_size: bytes for which ECC will be generated > */ > -int gpmc_enable_hwecc(int cs, int mode, int dev_width, int ecc_size) > +int gpmc_enable_hwecc(int ecc_type, int cs, int mode, > + int dev_width, int ecc_size) > { > - unsigned int val; > - > - /* check if ecc module is in used */ > - if (gpmc_ecc_used != -EINVAL) > - return -EINVAL; > - > - gpmc_ecc_used = cs; > - > - /* clear ecc and enable bits */ > - val = ((0x00000001<<8) | 0x00000001); > - gpmc_write_reg(GPMC_ECC_CONTROL, val); > - > - /* program ecc and result sizes */ > - val = ((((ecc_size >> 1) - 1) << 22) | (0x0000000F)); > - gpmc_write_reg(GPMC_ECC_SIZE_CONFIG, val); > + unsigned int bch_mod = 0, bch_wrapmode = 0, eccsize1 = 0, eccsize0 = 0; > + unsigned int ecc_conf_val = 0, ecc_size_conf_val = 0; > > switch (mode) { > case GPMC_ECC_READ: > - gpmc_write_reg(GPMC_ECC_CONTROL, 0x101); > + if (ecc_type == OMAP_ECC_BCH4_CODE_HW) { > + eccsize1 = 0xD; eccsize0 = 0x48; > + bch_mod = 0; > + bch_wrapmode = 0x09; > + } else if (ecc_type == OMAP_ECC_BCH8_CODE_HW) { > + eccsize1 = 0x1A; eccsize0 = 0x18; > + bch_mod = 1; > + bch_wrapmode = 0x04; > + } else > + eccsize1 = ((ecc_size >> 1) - 1) << 22; > break; > + > case GPMC_ECC_READSYN: > - gpmc_write_reg(GPMC_ECC_CONTROL, 0x100); > break; > + > case GPMC_ECC_WRITE: > - gpmc_write_reg(GPMC_ECC_CONTROL, 0x101); > + if (ecc_type == OMAP_ECC_BCH4_CODE_HW) { > + eccsize1 = 0x20; eccsize0 = 0x00; > + bch_mod = 0; > + bch_wrapmode = 0x06; > + } else if (ecc_type == OMAP_ECC_BCH8_CODE_HW) { > + eccsize1 = 0x20; eccsize0 = 0x00; > + bch_mod = 1; > + bch_wrapmode = 0x06; > + } else > + eccsize1 = ((ecc_size >> 1) - 1) << 22; > break; > + > default: > printk(KERN_INFO "Error: Unrecognized Mode[%d]!\n", mode); > break; > } > > - /* (ECC 16 or 8 bit col) | ( CS ) | ECC Enable */ > - val = (dev_width << 7) | (cs << 1) | (0x1); > - gpmc_write_reg(GPMC_ECC_CONFIG, val); > + /* clear ecc and enable bits */ > + if ((ecc_type == OMAP_ECC_BCH4_CODE_HW) || > + (ecc_type == OMAP_ECC_BCH8_CODE_HW)) { > + gpmc_write_reg(GPMC_ECC_CONTROL, 0x00000001); > + ecc_size_conf_val = (eccsize1 << 22) | (eccsize0 << 12); > + ecc_conf_val = ((0x01 << 16) | (bch_mod << 12) > + | (bch_wrapmode << 8) | (dev_width << 7) > + | (0x03 << 4) | (cs << 1) | (0x1)); > + } else { > + gpmc_write_reg(GPMC_ECC_CONTROL, 0x00000101); > + ecc_size_conf_val = (eccsize1 << 22) | 0x0000000F; > + ecc_conf_val = (dev_width << 7) | (cs << 1) | (0x1); > + } > + > + gpmc_write_reg(GPMC_ECC_SIZE_CONFIG, ecc_size_conf_val); > + gpmc_write_reg(GPMC_ECC_CONFIG, ecc_conf_val); > + gpmc_write_reg(GPMC_ECC_CONTROL, 0x00000101); > + > return 0; > } > > /** > * gpmc_calculate_ecc - generate non-inverted ecc bytes > + * @ecc_type: ecc type e.g. Hamming, BCH > * @cs: chip select number > * @dat: data pointer over which ecc is computed > * @ecc_code: ecc code buffer > @@ -888,20 +913,51 @@ int gpmc_enable_hwecc(int cs, int mode, int dev_width, int ecc_size) > * an erased page will produce an ECC mismatch between generated and read > * ECC bytes that has to be dealt with separately. > */ > -int gpmc_calculate_ecc(int cs, const u_char *dat, u_char *ecc_code) > +int gpmc_calculate_ecc(int ecc_type, int cs, > + const u_char *dat, u_char *ecc_code) > { > - unsigned int val = 0x0; > - > - if (gpmc_ecc_used != cs) > - return -EINVAL; > + unsigned int reg; > + unsigned int val1 = 0x0, val2 = 0x0; > + unsigned int val3 = 0x0, val4 = 0x0; > + int i; > > - /* read ecc result */ > - val = gpmc_read_reg(GPMC_ECC1_RESULT); > - *ecc_code++ = val; /* P128e, ..., P1e */ > - *ecc_code++ = val >> 16; /* P128o, ..., P1o */ > - /* P2048o, P1024o, P512o, P256o, P2048e, P1024e, P512e, P256e */ > - *ecc_code++ = ((val >> 8) & 0x0f) | ((val >> 20) & 0xf0); > + if ((ecc_type == OMAP_ECC_BCH4_CODE_HW) || > + (ecc_type == OMAP_ECC_BCH8_CODE_HW)) { > + for (i = 0; i < 4; i++) { > + /* > + * Reading HW ECC_BCH_Results > + * 0x240-0x24C, 0x250-0x25C, 0x260-0x26C, 0x270-0x27C > + */ > + reg = GPMC_ECC_BCH_RESULT_0 + (0x10 * i); > + val1 = gpmc_read_reg(reg); > + val2 = gpmc_read_reg(reg + 4); > + if (ecc_type == OMAP_ECC_BCH8_CODE_HW) { > + val3 = gpmc_read_reg(reg + 8); > + val4 = gpmc_read_reg(reg + 12); > + > + *ecc_code++ = (val4 & 0xFF); > + *ecc_code++ = ((val3 >> 24) & 0xFF); > + *ecc_code++ = ((val3 >> 16) & 0xFF); > + *ecc_code++ = ((val3 >> 8) & 0xFF); > + *ecc_code++ = (val3 & 0xFF); > + *ecc_code++ = ((val2 >> 24) & 0xFF); > + } > + *ecc_code++ = ((val2 >> 16) & 0xFF); > + *ecc_code++ = ((val2 >> 8) & 0xFF); > + *ecc_code++ = (val2 & 0xFF); > + *ecc_code++ = ((val1 >> 24) & 0xFF); > + *ecc_code++ = ((val1 >> 16) & 0xFF); > + *ecc_code++ = ((val1 >> 8) & 0xFF); > + *ecc_code++ = (val1 & 0xFF); > + } > + } else { > + /* read ecc result */ > + val1 = gpmc_read_reg(GPMC_ECC1_RESULT); > + *ecc_code++ = val1; /* P128e, ..., P1e */ > + *ecc_code++ = val1 >> 16; /* P128o, ..., P1o */ > + /* P2048o, P1024o, P512o, P256o, P2048e, P1024e, P512e, P256e */ > + *ecc_code++ = ((val1 >> 8) & 0x0f) | ((val1 >> 20) & 0xf0); > + } > > - gpmc_ecc_used = -EINVAL; > return 0; > } > diff --git a/arch/arm/plat-omap/include/plat/gpmc.h b/arch/arm/plat-omap/include/plat/gpmc.h > index 49aea09..838c185 100644 > --- a/arch/arm/plat-omap/include/plat/gpmc.h > +++ b/arch/arm/plat-omap/include/plat/gpmc.h > @@ -92,6 +92,8 @@ enum omap_ecc { > OMAP_ECC_HAMMING_CODE_HW, /* gpmc to detect the error */ > /* 1-bit ecc: stored at begining of spare area as romcode */ > OMAP_ECC_HAMMING_CODE_HW_ROMCODE, /* gpmc method & romcode layout */ > + OMAP_ECC_BCH4_CODE_HW, /* gpmc bch detection & s/w method correction */ > + OMAP_ECC_BCH8_CODE_HW, /* gpmc bch detection & s/w method correction */ > }; > > /* > @@ -156,6 +158,6 @@ extern int gpmc_cs_configure(int cs, int cmd, int wval); > extern int gpmc_nand_read(int cs, int cmd); > extern int gpmc_nand_write(int cs, int cmd, int wval); > > -int gpmc_enable_hwecc(int cs, int mode, int dev_width, int ecc_size); > -int gpmc_calculate_ecc(int cs, const u_char *dat, u_char *ecc_code); > +int gpmc_enable_hwecc(int ecc, int cs, int mode, int dev_width, int ecc_size); > +int gpmc_calculate_ecc(int ecc, int cs, const u_char *dat, u_char *ecc_code); > #endif > diff --git a/drivers/mtd/nand/Makefile b/drivers/mtd/nand/Makefile > index 8ad6fae..ae02711 100644 > --- a/drivers/mtd/nand/Makefile > +++ b/drivers/mtd/nand/Makefile > @@ -29,6 +29,7 @@ obj-$(CONFIG_MTD_NAND_NDFC) += ndfc.o > obj-$(CONFIG_MTD_NAND_ATMEL) += atmel_nand.o > obj-$(CONFIG_MTD_NAND_GPIO) += gpio.o > obj-$(CONFIG_MTD_NAND_OMAP2) += omap2.o > +obj-$(CONFIG_MTD_NAND_OMAP2) += omap_bch_decoder.o > obj-$(CONFIG_MTD_NAND_CM_X270) += cmx270_nand.o > obj-$(CONFIG_MTD_NAND_PXA3xx) += pxa3xx_nand.o > obj-$(CONFIG_MTD_NAND_TMIO) += tmio_nand.o > diff --git a/drivers/mtd/nand/omap2.c b/drivers/mtd/nand/omap2.c > index 4e33972..14c7dfe 100644 > --- a/drivers/mtd/nand/omap2.c > +++ b/drivers/mtd/nand/omap2.c > @@ -98,6 +98,8 @@ > static const char *part_probes[] = { "cmdlinepart", NULL }; > #endif > > +int decode_bch(int select_4_8, unsigned char *ecc, unsigned int *err_loc); > + > /* oob info generated runtime depending on ecc algorithm and layout selected */ > static struct nand_ecclayout omap_oobinfo; > /* Define some generic bad / good block scan pattern which are used > @@ -130,7 +132,8 @@ struct omap_nand_info { > OMAP_NAND_IO_WRITE, /* write */ > } iomode; > u_char *buf; > - int buf_len; > + int buf_len; > + int ecc_opt; > }; > > /** > @@ -529,7 +532,6 @@ static void omap_read_buf_irq_pref(struct mtd_info *mtd, u_char *buf, int len) > struct omap_nand_info *info = container_of(mtd, > struct omap_nand_info, mtd); > int ret = 0; > - > if (len <= mtd->oobsize) { > omap_read_buf_pref(mtd, buf, len); > return; > @@ -803,6 +805,8 @@ static int omap_correct_data(struct mtd_info *mtd, u_char *dat, > struct omap_nand_info *info = container_of(mtd, struct omap_nand_info, > mtd); > int blockCnt = 0, i = 0, ret = 0; > + int j, eccsize, eccflag, count; > + unsigned int err_loc[8]; > > /* Ex NAND_ECC_HW12_2048 */ > if ((info->nand.ecc.mode == NAND_ECC_HW) && > @@ -811,16 +815,57 @@ static int omap_correct_data(struct mtd_info *mtd, u_char *dat, > else > blockCnt = 1; > > - for (i = 0; i < blockCnt; i++) { > - if (memcmp(read_ecc, calc_ecc, 3) != 0) { > - ret = omap_compare_ecc(read_ecc, calc_ecc, dat); > - if (ret < 0) > - return ret; > + switch (info->ecc_opt) { > + case OMAP_ECC_HAMMING_CODE_HW: > + case OMAP_ECC_HAMMING_CODE_HW_ROMCODE: > + for (i = 0; i < blockCnt; i++) { > + if (memcmp(read_ecc, calc_ecc, 3) != 0) { > + ret = omap_compare_ecc(read_ecc, calc_ecc, dat); > + if (ret < 0) > + return ret; > + } > + read_ecc += 3; > + calc_ecc += 3; > + dat += 512; > } > - read_ecc += 3; > - calc_ecc += 3; > - dat += 512; > + break; > + > + case OMAP_ECC_BCH4_CODE_HW: > + eccsize = 7; > + gpmc_calculate_ecc(info->ecc_opt, info->gpmc_cs, dat, calc_ecc); > + for (i = 0; i < blockCnt; i++) { > + /* check if any ecc error */ > + eccflag = 0; > + for (j = 0; (j < eccsize) && (eccflag == 0); j++) > + if (calc_ecc[j] != 0) > + eccflag = 1; > + > + if (eccflag == 1) { > + eccflag = 0; > + for (j = 0; (j < eccsize) && > + (eccflag == 0); j++) > + if (read_ecc[j] != 0xFF) > + eccflag = 1; > + } > + > + count = 0; > + if (eccflag == 1) > + count = decode_bch(0, calc_ecc, err_loc); > + > + for (j = 0; j < count; j++) { > + if (err_loc[j] < 4096) > + dat[err_loc[j] >> 3] ^= > + 1 << (err_loc[j] & 7); > + /* else, not interested to correct ecc */ > + } > + > + calc_ecc = calc_ecc + eccsize; > + read_ecc = read_ecc + eccsize; > + dat += 512; > + } > + break; > } > + > return 0; > } > > @@ -841,7 +886,7 @@ static int omap_calculate_ecc(struct mtd_info *mtd, const u_char *dat, > { > struct omap_nand_info *info = container_of(mtd, struct omap_nand_info, > mtd); > - return gpmc_calculate_ecc(info->gpmc_cs, dat, ecc_code); > + return gpmc_calculate_ecc(info->ecc_opt, info->gpmc_cs, dat, ecc_code); > } > > /** > @@ -856,7 +901,8 @@ static void omap_enable_hwecc(struct mtd_info *mtd, int mode) > struct nand_chip *chip = mtd->priv; > unsigned int dev_width = (chip->options & NAND_BUSWIDTH_16) ? 1 : 0; > > - gpmc_enable_hwecc(info->gpmc_cs, mode, dev_width, info->nand.ecc.size); > + gpmc_enable_hwecc(info->ecc_opt, info->gpmc_cs, mode, > + dev_width, info->nand.ecc.size); > } > > /** > @@ -953,6 +999,7 @@ static int __devinit omap_nand_probe(struct platform_device *pdev) > info->mtd.priv = &info->nand; > info->mtd.name = dev_name(&pdev->dev); > info->mtd.owner = THIS_MODULE; > + info->ecc_opt = pdata->ecc_opt; > > info->nand.options = pdata->devsize; > info->nand.options |= NAND_SKIP_BBTSCAN; > @@ -991,7 +1038,6 @@ static int __devinit omap_nand_probe(struct platform_device *pdev) > info->nand.waitfunc = omap_wait; > info->nand.chip_delay = 50; > } > - > switch (pdata->xfer_type) { > case NAND_OMAP_PREFETCH_POLLED: > info->nand.read_buf = omap_read_buf_pref; > @@ -1052,10 +1098,17 @@ static int __devinit omap_nand_probe(struct platform_device *pdev) > /* selsect the ecc type */ > if (pdata->ecc_opt == OMAP_ECC_HAMMING_CODE_DEFAULT) > info->nand.ecc.mode = NAND_ECC_SOFT; > - else if ((pdata->ecc_opt == OMAP_ECC_HAMMING_CODE_HW) || > - (pdata->ecc_opt == OMAP_ECC_HAMMING_CODE_HW_ROMCODE)) { > - info->nand.ecc.bytes = 3; > - info->nand.ecc.size = 512; > + else { > + if (pdata->ecc_opt == OMAP_ECC_BCH4_CODE_HW) { > + info->nand.ecc.bytes = 4*7; > + info->nand.ecc.size = 4*512; > + } else if (pdata->ecc_opt == OMAP_ECC_BCH8_CODE_HW) { > + info->nand.ecc.bytes = 13; > + info->nand.ecc.size = 4*512; > + } else { > + info->nand.ecc.bytes = 3; > + info->nand.ecc.size = 512; > + } > info->nand.ecc.calculate = omap_calculate_ecc; > info->nand.ecc.hwctl = omap_enable_hwecc; > info->nand.ecc.correct = omap_correct_data; > @@ -1073,8 +1126,8 @@ static int __devinit omap_nand_probe(struct platform_device *pdev) > } > } > > - /* rom code layout */ > - if (pdata->ecc_opt == OMAP_ECC_HAMMING_CODE_HW_ROMCODE) { > + /* select ecc lyout */ > + if (info->nand.ecc.mode != NAND_ECC_SOFT) { > > if (info->nand.options & NAND_BUSWIDTH_16) > offset = 2; > @@ -1082,15 +1135,31 @@ static int __devinit omap_nand_probe(struct platform_device *pdev) > offset = 1; > info->nand.badblock_pattern = &bb_descrip_flashbased; > } > - omap_oobinfo.eccbytes = 3 * (info->mtd.oobsize/16); > - for (i = 0; i < omap_oobinfo.eccbytes; i++) > - omap_oobinfo.eccpos[i] = i+offset; > > - omap_oobinfo.oobfree->offset = offset + omap_oobinfo.eccbytes; > - omap_oobinfo.oobfree->length = info->mtd.oobsize - > - (offset + omap_oobinfo.eccbytes); > + if (info->mtd.oobsize == 64) > + omap_oobinfo.eccbytes = info->nand.ecc.bytes * > + 2048/info->nand.ecc.size; > + else > + omap_oobinfo.eccbytes = info->nand.ecc.bytes; > + > + if (pdata->ecc_opt == OMAP_ECC_HAMMING_CODE_HW_ROMCODE) { > + for (i = 0; i < omap_oobinfo.eccbytes; i++) > + omap_oobinfo.eccpos[i] = i + offset; > + omap_oobinfo.oobfree->offset = > + offset + omap_oobinfo.eccbytes; > + omap_oobinfo.oobfree->length = info->mtd.oobsize - > + offset - omap_oobinfo.eccbytes; > + } else { > > + omap_oobinfo.oobfree->offset = offset; > + omap_oobinfo.oobfree->length = info->mtd.oobsize - > + offset - omap_oobinfo.eccbytes; > + offset = info->mtd.oobsize - omap_oobinfo.eccbytes; > + for (i = 0; i < omap_oobinfo.eccbytes; i++) > + omap_oobinfo.eccpos[i] = i + offset; > + } > info->nand.ecc.layout = &omap_oobinfo; > + > } > > #ifdef CONFIG_MTD_PARTITIONS > diff --git a/drivers/mtd/nand/omap_bch_decoder.c b/drivers/mtd/nand/omap_bch_decoder.c > new file mode 100644 > index 0000000..da42bda > --- /dev/null > +++ b/drivers/mtd/nand/omap_bch_decoder.c > @@ -0,0 +1,393 @@ > +/* > + * drivers/mtd/nand/omap_omap_bch_decoder.c > + * > + * Whole BCH ECC Decoder (Post hardware generated syndrome decoding) > + * > + * Copyright (c) 2007 Texas Instruments > + * > + * Author: Sukumar Ghorai <s-ghorai@xxxxxx > + * Michael Fillinger <m-fillinger@xxxxxx> > + * > + * This program is free software; you can redistribute it and/or modify > + * it under the terms of the GNU General Public License version 2 as > + * published by the Free Software Foundation. > + */ > +#undef DEBUG > + > +#include <linux/kernel.h> > +#include <linux/module.h> > + > +#define mm 13 > +#define kk_shorten 4096 > +#define nn 8191 /* Length of codeword, n = 2**mm - 1 */ > + > +#define PPP 0x201B /* Primary Polynomial : x^13 + x^4 + x^3 + x + 1 */ > +#define P 0x001B /* With omitted x^13 */ > +#define POLY 12 /* degree of the primary Polynomial less one */ > + > +/** > + * mpy_mod_gf - GALOIS field multiplier > + * Input : A(x), B(x) > + * Output : A(x)*B(x) mod P(x) > + */ > +static unsigned int mpy_mod_gf(unsigned int a, unsigned int b) > +{ > + unsigned int R = 0; > + unsigned int R1 = 0; > + unsigned int k = 0; > + > + for (k = 0; k < mm; k++) { > + > + R = (R << 1) & 0x1FFE; > + if (R1 == 1) > + R ^= P; > + > + if (((a >> (POLY - k)) & 1) == 1) > + R ^= b; > + > + if (k < POLY) > + R1 = (R >> POLY) & 1; > + } > + return R; > +} > + > +/** > + * chien - CHIEN search > + * > + * @location - Error location vector pointer > + * > + * Inputs : ELP(z) > + * No. of found errors > + * Size of input codeword > + * Outputs : Up to 8 locations > + * No. of errors > + */ > +static int chien(unsigned int select_4_8, int err_nums, > + unsigned int err[], unsigned int *location) > +{ > + int i, count; /* Number of dectected errors */ > + /* Contains accumulation of evaluation at x^i (i:1->8) */ > + unsigned int gammas[8] = {0}; > + unsigned int alpha; > + unsigned int bit, ecc_bits; > + unsigned int elp_sum; > + > + ecc_bits = (select_4_8 == 0) ? 52 : 104; > + > + /* Start evaluation at Alpha**8192 and decreasing */ > + for (i = 0; i < 8; i++) > + gammas[i] = err[i]; > + > + count = 0; > + for (i = 1; (i <= nn) && (count < err_nums); i++) { > + > + /* Result of evaluation at root */ > + elp_sum = 1 ^ gammas[0] ^ gammas[1] ^ > + gammas[2] ^ gammas[3] ^ > + gammas[4] ^ gammas[5] ^ > + gammas[6] ^ gammas[7]; > + > + alpha = PPP >> 1; > + gammas[0] = mpy_mod_gf(gammas[0], alpha); > + alpha = mpy_mod_gf(alpha, (PPP >> 1)); /* x alphha^-2 */ > + gammas[1] = mpy_mod_gf(gammas[1], alpha); > + alpha = mpy_mod_gf(alpha, (PPP >> 1)); /* x alphha^-2 */ > + gammas[2] = mpy_mod_gf(gammas[2], alpha); > + alpha = mpy_mod_gf(alpha, (PPP >> 1)); /* x alphha^-3 */ > + gammas[3] = mpy_mod_gf(gammas[3], alpha); > + alpha = mpy_mod_gf(alpha, (PPP >> 1)); /* x alphha^-4 */ > + gammas[4] = mpy_mod_gf(gammas[4], alpha); > + alpha = mpy_mod_gf(alpha, (PPP >> 1)); /* x alphha^-5 */ > + gammas[5] = mpy_mod_gf(gammas[5], alpha); > + alpha = mpy_mod_gf(alpha, (PPP >> 1)); /* x alphha^-6 */ > + gammas[6] = mpy_mod_gf(gammas[6], alpha); > + alpha = mpy_mod_gf(alpha, (PPP >> 1)); /* x alphha^-7 */ > + gammas[7] = mpy_mod_gf(gammas[7], alpha); > + > + if (elp_sum == 0) { > + /* calculate bit position in main data area */ > + bit = ((i-1) & ~7)|(7-((i-1) & 7)); > + if (i >= 2 * ecc_bits) > + location[count++] = > + kk_shorten - (bit - 2 * ecc_bits) - 1; > + } > + } > + > + /* Failure: No. of detected errors != No. or corrected errors */ > + if (count != err_nums) { > + count = -1; > + printk(KERN_ERR "BCH decoding failed\n"); > + } > + for (i = 0; i < count; i++) > + pr_debug("%d ", location[i]); > + > + return count; > +} > + > +/* synd : 16 Syndromes > + * return: gamaas - Coefficients to the error polynomial > + * return: : Number of detected errors > +*/ > +static unsigned int berlekamp(unsigned int select_4_8, > + unsigned int synd[], unsigned int err[]) > +{ > + int loop, iteration; > + unsigned int LL = 0; /* Detected errors */ > + unsigned int d = 0; /* Distance between Syndromes and ELP[n](z) */ > + unsigned int invd = 0; /* Inverse of d */ > + /* Intermediate ELP[n](z). > + * Final ELP[n](z) is Error Location Polynomial > + */ > + unsigned int gammas[16] = {0}; > + /* Intermediate normalized ELP[n](z) : D[n](z) */ > + unsigned int D[16] = {0}; > + /* Temporary value that holds an ELP[n](z) coefficient */ > + unsigned int next_gamma = 0; > + > + int e = 0; > + unsigned int sign = 0; > + unsigned int u = 0; > + unsigned int v = 0; > + unsigned int C1 = 0, C2 = 0; > + unsigned int ss = 0; > + unsigned int tmp_v = 0, tmp_s = 0; > + unsigned int tmp_poly; > + > + /*-------------- Step 0 ------------------*/ > + for (loop = 0; loop < 16; loop++) > + gammas[loop] = 0; > + gammas[0] = 1; > + D[1] = 1; > + > + iteration = 0; > + LL = 0; > + while ((iteration < ((select_4_8+1)*2*4)) && > + (LL <= ((select_4_8+1)*4))) { > + > + pr_debug("\nIteration.............%d\n", iteration); > + d = 0; > + /* Step: 0 */ > + for (loop = 0; loop <= LL; loop++) { > + tmp_poly = mpy_mod_gf( > + gammas[loop], synd[iteration - loop]); > + d ^= tmp_poly; > + pr_debug("%02d. s=0 LL=%x poly %x\n", > + loop, LL, tmp_poly); > + } > + > + /* Step 1: 1 cycle only to perform inversion */ > + v = d << 1; > + e = -1; > + sign = 1; > + ss = 0x2000; > + invd = 0; > + u = PPP; > + for (loop = 0; (d != 0) && (loop <= (2 * POLY)); loop++) { > + pr_debug("%02d. s=1 LL=%x poly NULL\n", > + loop, LL); > + C1 = (v >> 13) & 1; > + C2 = C1 & sign; > + > + sign ^= C2 ^ (e == 0); > + > + tmp_v = v; > + tmp_s = ss; > + > + if (C1 == 1) { > + v ^= u; > + ss ^= invd; > + } > + v = (v << 1) & 0x3FFF; > + if (C2 == 1) { > + u = tmp_v; > + invd = tmp_s; > + e = -e; > + } > + invd >>= 1; > + e--; > + } > + > + for (loop = 0; (d != 0) && (loop <= (iteration + 1)); loop++) { > + /* Step 2 > + * Interleaved with Step 3, if L<(n-k) > + * invd: Update of ELP[n](z) = ELP[n-1](z) - d.D[n-1](z) > + */ > + > + /* Holds value of ELP coefficient until precedent > + * value does not have to be used anymore > + */ > + tmp_poly = mpy_mod_gf(d, D[loop]); > + pr_debug("%02d. s=2 LL=%x poly %x\n", > + loop, LL, tmp_poly); > + > + next_gamma = gammas[loop] ^ tmp_poly; > + if ((2 * LL) < (iteration + 1)) { > + /* Interleaving with Step 3 > + * for parallelized update of ELP(z) and D(z) > + */ > + } else { > + /* Update of ELP(z) only -> stay in Step 2 */ > + gammas[loop] = next_gamma; > + if (loop == (iteration + 1)) { > + /* to step 4 */ > + break; > + } > + } > + > + /* Step 3 > + * Always interleaved with Step 2 (case when L<(n-k)) > + * Update of D[n-1](z) = ELP[n-1](z)/d > + */ > + D[loop] = mpy_mod_gf(gammas[loop], invd); > + pr_debug("%02d. s=3 LL=%x poly %x\n", > + loop, LL, D[loop]); > + > + /* Can safely update ELP[n](z) */ > + gammas[loop] = next_gamma; > + > + if (loop == (iteration + 1)) { > + /* If update finished */ > + LL = iteration - LL + 1; > + /* to step 4 */ > + break; > + } > + /* Else, interleaving to step 2*/ > + } > + > + /* Step 4: Update D(z): i:0->L */ > + /* Final update of D[n](z) = D[n](z).z*/ > + for (loop = 0; loop < 15; loop++) /* Left Shift */ > + D[15 - loop] = D[14 - loop]; > + > + D[0] = 0; > + > + iteration++; > + } /* while */ > + > + /* Processing finished, copy ELP to final registers : 0->2t-1*/ > + for (loop = 0; loop < 8; loop++) > + err[loop] = gammas[loop+1]; > + > + pr_debug("\n Err poly:"); > + for (loop = 0; loop < 8; loop++) > + pr_debug("0x%x ", err[loop]); > + > + return LL; > +} > + > +/* > + * syndrome - Generate syndrome components from hw generate syndrome > + * r(x) = c(x) + e(x) > + * s(x) = c(x) mod g(x) + e(x) mod g(x) = e(x) mod g(x) > + * so receiver checks if the syndrome s(x) = r(x) mod g(x) is equal to zero. > + * unsigned int s[16]; - Syndromes > + */ > +static void syndrome(unsigned int select_4_8, > + unsigned char *ecc, unsigned int syn[]) > +{ > + unsigned int k, l, t; > + unsigned int alpha_bit, R_bit; > + int ecc_pos, ecc_min; > + > + /* 2t-1 = 15 (for t=8) minimal polynomials of the first 15 powers of a > + * primitive elemmants of GF(m); Even powers minimal polynomials are > + * duplicate of odd powers' minimal polynomials. > + * Odd powers of alpha (1 to 15) > + */ > + unsigned int pow_alpha[8] = {0x0002, 0x0008, 0x0020, 0x0080, > + 0x0200, 0x0800, 0x001B, 0x006C}; > + > + pr_debug("\n ECC[0..n]: "); > + for (k = 0; k < 13; k++) > + pr_debug("0x%x ", ecc[k]); > + > + if (select_4_8 == 0) { > + t = 4; > + ecc_pos = 55; /* bits(52-bits): 55->4 */ > + ecc_min = 4; > + } else { > + t = 8; > + ecc_pos = 103; /* bits: 103->0 */ > + ecc_min = 0; > + } > + > + /* total numbber of syndrom to be used is 2t */ > + /* Step1: calculate the odd syndrome(s) */ > + R_bit = ((ecc[ecc_pos/8] >> (7 - ecc_pos%8)) & 1); > + ecc_pos--; > + for (k = 0; k < t; k++) > + syn[2 * k] = R_bit; > + > + while (ecc_pos >= ecc_min) { > + R_bit = ((ecc[ecc_pos/8] >> (7 - ecc_pos%8)) & 1); > + ecc_pos--; > + > + for (k = 0; k < t; k++) { > + /* Accumulate value of x^i at alpha^(2k+1) */ > + if (R_bit == 1) > + syn[2*k] ^= pow_alpha[k]; > + > + /* Compute a**(2k+1), using LSFR */ > + for (l = 0; l < (2 * k + 1); l++) { > + alpha_bit = (pow_alpha[k] >> POLY) & 1; > + pow_alpha[k] = (pow_alpha[k] << 1) & 0x1FFF; > + if (alpha_bit == 1) > + pow_alpha[k] ^= P; > + } > + } > + } > + > + /* Step2: calculate the even syndrome(s) > + * Compute S(a), where a is an even power of alpha > + * Evenry even power of primitive element has the same minimal > + * polynomial as some odd power of elemets. > + * And based on S(a^2) = S^2(a) > + */ > + for (k = 0; k < t; k++) > + syn[2*k+1] = mpy_mod_gf(syn[k], syn[k]); > + > + pr_debug("\n Syndromes: "); > + for (k = 0; k < 16; k++) > + pr_debug("0x%x ", syn[k]); > +} > + > +/** > + * decode_bch - BCH decoder for 4- and 8-bit error correction > + * > + * @ecc - ECC syndrome generated by hw BCH engine > + * @err_loc - pointer to error location array > + * > + * This function does post sydrome generation (hw generated) decoding > + * for:- > + * Dimension of Galoise Field: m = 13 > + * Length of codeword: n = 2**m - 1 > + * Number of errors that can be corrected: 4- or 8-bits > + * Length of information bit: kk = nn - rr > + */ > +int decode_bch(int select_4_8, unsigned char *ecc, unsigned int *err_loc) > +{ > + int no_of_err; > + unsigned int syn[16] = {0,}; /* 16 Syndromes */ > + unsigned int err_poly[8] = {0,}; > + /* Coefficients to the error polynomial > + * ELP(x) = 1 + err0.x + err1.x^2 + ... + err7.x^8 > + */ > + > + /* Decoting involes three steps > + * 1. Compute the syndrom from teh received codeword, > + * 2. Find the error location polynomial from a set of equations > + * derived from the syndrome, > + * 3. Use the error location polynomial to identify errants bits, > + * > + * And correcttion done by bit flips using error locaiton and expected > + * to be outseide of this implementation. > + */ > + syndrome(select_4_8, ecc, syn); > + no_of_err = berlekamp(select_4_8, syn, err_poly); > + if (no_of_err <= (4 << select_4_8)) > + no_of_err = chien(select_4_8, no_of_err, err_poly, err_loc); > + > + return no_of_err; > +} > +EXPORT_SYMBOL(decode_bch); > + > -- > 1.7.0.4 > > -- > To unsubscribe from this list: send the line "unsubscribe linux-omap" in > the body of a message to majordomo@xxxxxxxxxxxxxxx > More majordomo info at http://vger.kernel.org/majordomo-info.html > -- Regards, Vimal Singh -- To unsubscribe from this list: send the line "unsubscribe linux-omap" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
