With increase in NAND flash densities occurence of bit-flips has increased.
Thus stronger ECC schemes are required for detecting and correcting multiple
simultaneous bit-flips in same NAND page. But stronger ECC schemes have large
ECC syndrome which require more space in OOB/Spare.
This patch add support for BCH16_ECC:
(a) BCH16_ECC can correct 16 bit-flips per 512Bytes of data.
(b) BCH16_ECC generates 26-bytes of ECC syndrome / 512B.
Due to (b) this scheme can only be used with NAND devices which have enough
OOB to satisfy following equation:
OOBsize per page >= 26 * (page-size / 512)
Signed-off-by: Pekon Gupta <pekon@xxxxxx>
---
drivers/mtd/nand/omap2.c | 104 +++++++++++++++++++++++++++++++++++++++++++----
1 file changed, 96 insertions(+), 8 deletions(-)
diff --git a/drivers/mtd/nand/omap2.c b/drivers/mtd/nand/omap2.c
index c2c3c6bb..a0cf487 100644
--- a/drivers/mtd/nand/omap2.c
+++ b/drivers/mtd/nand/omap2.c
@@ -130,9 +130,13 @@
#define BADBLOCK_MARKER_LENGTH 0x2
#ifdef CONFIG_MTD_NAND_OMAP_BCH
-static u_char bch8_vector[] = {0xf3, 0xdb, 0x14, 0x16, 0x8b, 0xd2, 0xbe, 0xcc,
- 0xac, 0x6b, 0xff, 0x99, 0x7b};
-static u_char bch4_vector[] = {0x00, 0x6b, 0x31, 0xdd, 0x41, 0xbc, 0x10};
+static u_char bch4_vector[] = {0x00, 0x6b, 0x31, 0xdd, 0x41, 0xbc, 0x10};
+static u_char bch8_vector[] = {0xf3, 0xdb, 0x14, 0x16, 0x8b, 0xd2, 0xbe, 0xcc,
+ 0xac, 0x6b, 0xff, 0x99, 0x7b};
+static u_char bch16_vector[] = {0xf5, 0x24, 0x1c, 0xd0, 0x61, 0xb3, 0xf1, 0x55,
+ 0x2e, 0x2c, 0x86, 0xa3, 0xed, 0x36, 0x1b, 0x78,
+ 0x48, 0x76, 0xa9, 0x3b, 0x97, 0xd1, 0x7a, 0x93,
+ 0x07, 0x0e};
#endif
static u8 bch4_polynomial[] = {0x28, 0x13, 0xcc, 0x39, 0x96, 0xac, 0x7f};
static u8 bch8_polynomial[] = {0xef, 0x51, 0x2e, 0x09, 0xed, 0x93, 0x9a, 0xc2,
@@ -1066,6 +1070,19 @@ static void omap_enable_hwecc(struct mtd_info *mtd, int mode)
eccsize1 = 28; /* OOB bits in nibbles per sector */
}
break;
+ case OMAP_ECC_BCH16_CODE_HW:
+ ecc_algo = 0x1;
+ bch_type = 0x2;
+ if (mode == GPMC_ECC_READ) {
+ bch_wrapmode = 0x01;
+ eccsize0 = 52; /* ECC bits in nibbles per sector */
+ eccsize1 = 0; /* non-ECC bits in nibbles per sector */
+ } else if (mode == GPMC_ECC_WRITE) {
+ bch_wrapmode = 0x01;
+ eccsize0 = 0; /* extra bits in nibbles per sector */
+ eccsize1 = 52; /* OOB bits in nibbles per sector */
+ }
+ break;
default:
pr_err("selected ECC scheme not supported or not enabled\n");
}
@@ -1159,6 +1176,41 @@ static int omap_calculate_ecc_bch(struct mtd_info *mtd, const u_char *dat,
*(ecc_ptr++) = ((val >> 8) & 0xFF);
*(ecc_ptr++) = ((val >> 0) & 0xFF);
break;
+ case OMAP_ECC_BCH16_CODE_HW:
+ val = readl(gpmc_regs->gpmc_bch_result6[i]);
+ *(ecc_ptr++) = ((val >> 8) & 0xFF);
+ *(ecc_ptr++) = ((val >> 0) & 0xFF);
+ val = readl(gpmc_regs->gpmc_bch_result5[i]);
+ *(ecc_ptr++) = ((val >> 24) & 0xFF);
+ *(ecc_ptr++) = ((val >> 16) & 0xFF);
+ *(ecc_ptr++) = ((val >> 8) & 0xFF);
+ *(ecc_ptr++) = ((val >> 0) & 0xFF);
+ val = readl(gpmc_regs->gpmc_bch_result4[i]);
+ *(ecc_ptr++) = ((val >> 24) & 0xFF);
+ *(ecc_ptr++) = ((val >> 16) & 0xFF);
+ *(ecc_ptr++) = ((val >> 8) & 0xFF);
+ *(ecc_ptr++) = ((val >> 0) & 0xFF);
+ val = readl(gpmc_regs->gpmc_bch_result3[i]);
+ *(ecc_ptr++) = ((val >> 24) & 0xFF);
+ *(ecc_ptr++) = ((val >> 16) & 0xFF);
+ *(ecc_ptr++) = ((val >> 8) & 0xFF);
+ *(ecc_ptr++) = ((val >> 0) & 0xFF);
+ val = readl(gpmc_regs->gpmc_bch_result2[i]);
+ *(ecc_ptr++) = ((val >> 24) & 0xFF);
+ *(ecc_ptr++) = ((val >> 16) & 0xFF);
+ *(ecc_ptr++) = ((val >> 8) & 0xFF);
+ *(ecc_ptr++) = ((val >> 0) & 0xFF);
+ val = readl(gpmc_regs->gpmc_bch_result1[i]);
+ *(ecc_ptr++) = ((val >> 24) & 0xFF);
+ *(ecc_ptr++) = ((val >> 16) & 0xFF);
+ *(ecc_ptr++) = ((val >> 8) & 0xFF);
+ *(ecc_ptr++) = ((val >> 0) & 0xFF);
+ val = readl(gpmc_regs->gpmc_bch_result0[i]);
+ *(ecc_ptr++) = ((val >> 24) & 0xFF);
+ *(ecc_ptr++) = ((val >> 16) & 0xFF);
+ *(ecc_ptr++) = ((val >> 8) & 0xFF);
+ *(ecc_ptr++) = ((val >> 0) & 0xFF);
+ break;
default:
return -EINVAL;
}
@@ -1184,6 +1236,8 @@ static int omap_calculate_ecc_bch(struct mtd_info *mtd, const u_char *dat,
case OMAP_ECC_BCH8_CODE_HW:
*(ecc_ptr++) = 0x00;
break;
+ case OMAP_ECC_BCH16_CODE_HW:
+ break;
}
/* update pointer to next sector */
ecc_calc += eccbytes;
@@ -1225,7 +1279,6 @@ static int omap_elm_correct_data(struct mtd_info *mtd, u_char *data,
/* Initialize elm error vector to zero */
memset(err_vec, 0, sizeof(err_vec));
-
for (i = 0; i < eccsteps ; i++) {
flag_read_ecc = 0;
ecc = calc_ecc + (i * eccbytes);
@@ -1239,12 +1292,16 @@ static int omap_elm_correct_data(struct mtd_info *mtd, u_char *data,
/* check if its a erased-page */
if (flag_read_ecc) {
switch (ecc_opt) {
+ case OMAP_ECC_BCH4_CODE_HW:
+ if (memcmp(ecc, bch4_vector, eccbytes))
+ err_vec[i].error_reported = true;
+ break;
case OMAP_ECC_BCH8_CODE_HW:
if (memcmp(ecc, bch8_vector, eccbytes))
err_vec[i].error_reported = true;
break;
- case OMAP_ECC_BCH4_CODE_HW:
- if (memcmp(ecc, bch4_vector, eccbytes))
+ case OMAP_ECC_BCH16_CODE_HW:
+ if (memcmp(ecc, bch16_vector, eccbytes))
err_vec[i].error_reported = true;
break;
default:
@@ -1282,6 +1339,10 @@ static int omap_elm_correct_data(struct mtd_info *mtd, u_char *data,
(eccbytes - 1);
pos = err_vec[i].error_loc[j];
break;
+ case OMAP_ECC_BCH16_CODE_HW:
+ error_max = SECTOR_BYTES + eccbytes;
+ pos = err_vec[i].error_loc[j];
+ break;
default:
return -EINVAL;
}
@@ -1757,6 +1818,33 @@ static int omap_nand_probe(struct platform_device *pdev)
omap_oobinfo.eccbytes;
goto custom_ecc_layout;
#endif
+#ifdef CONFIG_MTD_NAND_OMAP_BCH
+ case OMAP_ECC_BCH16_CODE_HW:
+ pr_info("using OMAP_ECC_BCH16_CODE_HW ECC scheme\n");
+ chip->ecc.mode = NAND_ECC_HW;
+ chip->ecc.size = 512;
+ /* 14th bit is kept reserved for ROM-code compatibility */
+ chip->ecc.bytes = 26;
+ chip->ecc.strength = 16;
+ chip->ecc.hwctl = omap_enable_hwecc;
+ chip->ecc.correct = omap_elm_correct_data;
+ chip->ecc.calculate = omap_calculate_ecc_bch;
+ chip->ecc.read_page = omap_read_page_bch;
+ chip->ecc.write_page = omap_write_page_bch;
+ /* ELM H/W engine is used for locating errors */
+ if (is_elm_present(info, BCH16_ECC) < 0) {
+ pr_err("ELM module not detected, required for ECC\n");
+ err = -EINVAL;
+ goto out_release_mem_region;
+ }
+ /* define custom ECC layout */
+ omap_oobinfo.eccbytes = chip->ecc.bytes *
+ (mtd->writesize / chip->ecc.size);
+ omap_oobinfo.eccpos[0] = BADBLOCK_MARKER_LENGTH;
+ omap_oobinfo.oobfree->offset = omap_oobinfo.eccpos[0] +
+ omap_oobinfo.eccbytes;
+ goto custom_ecc_layout;
+#endif
default:
pr_err("%s: selected ECC scheme not supported or not enabled",
DRIVER_NAME);
@@ -1777,8 +1865,8 @@ custom_ecc_layout:
/* check if NAND OOBSIZE meets ECC scheme requirement */
if (mtd->oobsize < (omap_oobinfo.eccbytes +
BADBLOCK_MARKER_LENGTH)) {
- pr_err("not enough OOB bytes required = %d, available=%d\n",
- mtd->oobsize, omap_oobinfo.eccbytes);
+ pr_err("%s: not enough OOB bytes available=%d, required=%d\n",
+ DRIVER_NAME, mtd->oobsize, omap_oobinfo.eccbytes);
err = -EINVAL;
goto out_release_mem_region;
}
--
1.8.1
--
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