Messages in this thread | | | From | Yanjiantao <> | Subject | questions about [PATCH]mtd: nand: fix SCAN2NDPAGE check for BBM | Date | Tue, 13 Oct 2015 11:33:54 +0000 |
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Dear Brian,
i read the patch: " mtd: nand: fix SCAN2NDPAGE check for BBM " And i am confused about the markbad flows.
xxxxx; if (chip->bbt_options & NAND_BBT_SCANLASTPAGE) ofs += mtd->erasesize - mtd->writesize;
xxxxx;
do { if (chip->options & NAND_BUSWIDTH_16) { chip->cmdfunc(mtd, NAND_CMD_READOOB, chip->badblockpos & 0xFE, page); bad = cpu_to_le16(chip->read_word(mtd)); if (chip->badblockpos & 0x1) bad >>= 8; else bad &= 0xFF; } else { chip->cmdfunc(mtd, NAND_CMD_READOOB, chip->badblockpos, page); bad = chip->read_byte(mtd); }
if (likely(chip->badblockbits == 8)) res = bad != 0xFF; else res = hweight8(bad) < chip->badblockbits; ofs += mtd->writesize; page = (int)(ofs >> chip->page_shift) & chip->pagemask; i++; } while (!res && i < 2 && (chip->bbt_options & NAND_BBT_SCAN2NDPAGE)); mark bad flows is the same.
If I understand the patch right, then I think that: 1. when NAND_BBT_SCANLASTPAGE is set, markbad and checkbad on the last page only. 2. when NAND_BBT_SCAN2NDPAGE is set, markbad and checkbad on the 1st and 2nd page.
I checked some datasheets of different manufacturers(such as SAMSUNG/HYNIX/MICRON/TOSHIBA), they claim that bad block marker is on 1st/2nd, or 1st/last, or 1st/2nd/last(for spansion). the checkbad method may check fail in some cases: for example,: 1. for spansion nand(bad block marker is on 1st or 2nd or last page), set NAND_BBT_SCAN2NDPAGE while badblock marker is on last page or set NAND_BBT_SCANLASTPAGE while badblock marker is on 1st/2nd page may cause badblock chech failed. 2. for HYNIX (H27UBG8T2CTR) nand (bad block marker is on 1st or last page), check may failed whether NAND_BBT_SCANLASTPAGE is set or not.
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