Messages in this thread | | | Date | Fri, 19 Jun 2015 23:46:41 +0900 | From | KOBAYASHI Yoshitake <> | Subject | Re: [PATCH v2] mtd: nand: support for Toshiba BENAND (Built-in ECC NAND) |
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> Please see my patches how to deal with that. Maybe you can find a better solution.
Thank you for your suggestion. I considered to use your submitted patch on BENAND driver, but I believe reading twice the same page approach will affect read performance. Additionally, BENAND does not support Disable ECC. So, I cannot use same approach.
I consider other solutions.
BENAND Read Status CMD (70h) can report Rewrite Recommend. BENAND also has extended ECC Status CMD (7Ah). This can report number of bit error / sector data. If I can use an extended ECC Status CMD (7Ah) in BENAND driver (nand_benand.c), I suggest to implement it as the follows:
+++ b/drivers/mtd/nand/nand_benand.c .....
+/* ECC Status Read Command */ +#define NAND_CMD_ECC_STATUS 0x7A ..... + chip->ecc.strength = 8; ..... + /* correctable */ + else if (status & NAND_STATUS_RECOM_REWRT) { + if (chip->cmd_ctrl && + IS_ENABLED(CONFIG_MTD_NAND_BENAND_ECC_STATUS)) { + + /* Check Read ECC Status */ + chip->cmd_ctrl(mtd, NAND_CMD_ECC_STATUS, + NAND_NCE | NAND_CLE | NAND_CTRL_CHANGE); + ecc_status = chip->read_byte(mtd); + bitflips = ecc_status & 0xff; + mtd->ecc_stats.corrected += bitflips;
If above implementation cannot be acceptable, I would like to use "mtd->bitflip_threshold" to inform number of bitflip, as the follows:
+ } else { + /* + * If can't use chip->cmd_ctrl, + * we can't get real number of bitflips. + * So, we set bitflips mtd->bitflip_threshold. + */ + bitflips = mtd->bitflip_threshold; + mtd->ecc_stats.corrected += bitflips; + } + } + + return bitflips; +}
-- Yoshi
On 2015/06/16 22:53, Richard Weinberger wrote: > Am 16.06.2015 um 15:33 schrieb KOBAYASHI Yoshitake: >>>> + /* correctable */ >>>> + else if (status & NAND_STATUS_RECOM_REWRT) { >>>> + pr_info("BENAND : Recommended to rewrite!\n"); >>>> + bitflips = chip->ecc.strength; >>> >>> In your case this might be okay, as you set strength to 1. >>> Otherweise you'd have to report the real number of bitflips. >> >> I also thought it is okay in this case. >> BENAND return corrected data to Host NAND Controller till uncorrectable status. >> The current patch uses this Read Status command 70h to abstract BENAND Multi >> bit ECC and Need to Rewrite judgement so BENAND would look like 1bit ECC device. > > The layers above MTD need to know how many bits got repaired. > It seems like BENAND suffers from the same shortcomings than On-Die-ECC. ;-\ > Please see my patches how to deal with that. Maybe you can find a better solution. > > Thanks, > //richard > > >
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