Messages in this thread | | | Date | Thu, 14 May 2015 11:43:03 +0200 | From | Richard Weinberger <> | Subject | Re: [PATCH 2/3] mtd: nand: implement 'max_bad_blocks' mtd function |
| |
Am 11.05.2015 um 17:19 schrieb Ben Shelton: > From: Jeff Westfahl <jeff.westfahl@ni.com> > > Implement the new mtd function 'max_bad_blocks'. Use the "bad blocks > maximum per LUN" field in the ONFI parameter page to find the maximum > number of bad blocks to reserve for an MTD, taking into account the > number of LUNs in the NAND device and how many LUNs the MTD spans. > > From the ONFI 1.0 spec: "This field contains the maximum number of > blocks that may be defective at manufacture and over the life of the > device per LUN. The maximum rating assumes that the host is following > the block endurance requirements and the ECC requirements reported in > the parameter page." > > Signed-off-by: Jeff Westfahl <jeff.westfahl@ni.com> > --- > drivers/mtd/nand/nand_base.c | 35 +++++++++++++++++++++++++++++++++++ > 1 file changed, 35 insertions(+) > > diff --git a/drivers/mtd/nand/nand_base.c b/drivers/mtd/nand/nand_base.c > index c2e1232..a97d08e 100644 > --- a/drivers/mtd/nand/nand_base.c > +++ b/drivers/mtd/nand/nand_base.c > @@ -2884,6 +2884,40 @@ static int nand_block_markbad(struct mtd_info *mtd, loff_t ofs) > } > > /** > + * nand_max_bad_blocks - [MTD Interface] Max number of bad blocks for an mtd > + * @mtd: MTD device structure > + * @ofs: offset relative to mtd start > + * @len: length of mtd > + */ > +static int nand_max_bad_blocks(struct mtd_info *mtd, loff_t ofs, size_t len) > +{ > + struct nand_chip *chip = mtd->priv; > + uint32_t part_start_block; > + uint32_t part_end_block; > + uint32_t part_start_lun; > + uint32_t part_end_lun; > + > + /* ONFI is used to determine the maximum bad block count. */ > + if (!chip->onfi_version) > + return -ENOTSUPP; > + > + /* Get the start and end of the partition in erase blocks. */ > + part_start_block = mtd_div_by_eb(ofs, mtd); > + part_end_block = mtd_div_by_eb(len, mtd) + part_start_block - 1; > + > + /* Get the start and end LUNs of the partition. */ > + part_start_lun = part_start_block / chip->onfi_params.blocks_per_lun; > + part_end_lun = part_end_block / chip->onfi_params.blocks_per_lun; > + > + /* > + * Look up the bad blocks per unit and multiply by the number of units > + * that the partition spans. > + */ > + return chip->onfi_params.bb_per_lun * > + (part_end_lun - part_start_lun + 1);
Hmm, doesn't that calculation assume that all bad blocks are uniformly distributed across the whole chip? Not sure if is a good idea to focus on the best case. Currently UBI assumes the worst case.
Thanks, //richard
| |