linux-kernel - Re: [PATCH 2/2] mtd: spi-nand: Add read retry support

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Message-ID: <CAAyq3SZvr3RVUAfMOWQqCqDOyj9QfAmiSdUHwyt=tmrbNRFFOg@mail.gmail.com>
Date: Mon, 7 Oct 2024 13:53:29 +0800
From: Cheng Ming Lin <linchengming884@...il.com>
To: Miquel Raynal <miquel.raynal@...tlin.com>
Cc: vigneshr@...com, linux-mtd@...ts.infradead.org, 
	linux-kernel@...r.kernel.org, richard@....at, alvinzhou@...c.com.tw, 
	leoyu@...c.com.tw, Cheng Ming Lin <chengminglin@...c.com.tw>
Subject: Re: [PATCH 2/2] mtd: spi-nand: Add read retry support

Hi Miquel,

Miquel Raynal <miquel.raynal@...tlin.com> 於 2024年10月1日 週二 下午6:17寫道：
>
> Hi Cheng Ming,
>
> linchengming884@...il.com wrote on Thu,  5 Sep 2024 13:53:33 +0800:
>
> > From: Cheng Ming Lin <chengminglin@...c.com.tw>
> >
> > When the host ECC fails to correct the data error of NAND device,
> > there's a special read for data recovery method which host setups
> > for the next read retry mode and may recover the lost data by host
> > ECC again.
> >
> > Signed-off-by: Cheng Ming Lin <chengminglin@...c.com.tw>
> > ---
> >  drivers/mtd/nand/spi/core.c | 33 +++++++++++++++++++++++++++++++--
> >  1 file changed, 31 insertions(+), 2 deletions(-)
> >
> > diff --git a/drivers/mtd/nand/spi/core.c b/drivers/mtd/nand/spi/core.c
> > index e0b6715e5dfe..2f21ea926132 100644
> > --- a/drivers/mtd/nand/spi/core.c
> > +++ b/drivers/mtd/nand/spi/core.c
> > @@ -640,6 +640,7 @@ static int spinand_mtd_read(struct mtd_info *mtd, loff_t from,
> >       struct nand_io_iter iter;
> >       bool disable_ecc = false;
> >       bool ecc_failed = false;
> > +     u8 retry_mode = 0;
> >       int ret = 0;
> >
> >       if (ops->mode == MTD_OPS_RAW || !spinand->eccinfo.ooblayout)
> > @@ -657,20 +658,45 @@ static int spinand_mtd_read(struct mtd_info *mtd, loff_t from,
>
> This will no longer apply with continuous support added in. However
> please make this only in the non continuous path. I don't think it can
> fly in the other.

Thanks for your helpful suggestions.

>
> >               if (ret)
> >                       break;
> >
> > +read_retry:
> >               ret = spinand_read_page(spinand, &iter.req);
> >               if (ret < 0 && ret != -EBADMSG)
> >                       break;
> >
> > -             if (ret == -EBADMSG)
> > +             if (ret == -EBADMSG && spinand->info->fixups) {
> > +                     if (spinand->read_retries && ((retry_mode + 1) < spinand->read_retries)) {
>
>                                                         ++retry_mode?
> > +                             retry_mode++;
>
> So this can be dropped.
>
> > +                             ret = spinand->info->fixups->setup_read_retry(spinand, retry_mode);
> > +                             if (ret < 0)
> > +                                     break;
>
> No, you need to set ecc_failed here.
>
> > +
> > +                             /* Reset ecc_stats; retry */
> > +                             mtd->ecc_stats = old_stats;
> > +                             goto read_retry;
> > +                     } else {
> > +                             /* No more retry modes; real failure */
> > +                             ecc_failed = true;
> > +                     }
> > +             } else if (ret == -EBADMSG) {
> >                       ecc_failed = true;
> > -             else
> > +             } else {
> >                       max_bitflips = max_t(unsigned int, max_bitflips, ret);
> > +             }
> >
> >               ret = 0;
> >               ops->retlen += iter.req.datalen;
> >               ops->oobretlen += iter.req.ooblen;
> > +
> > +             /* Reset to retry mode 0*/
> > +             if (retry_mode) {
>
>                         retry_mode = 0;
>
> > +                     ret = spinand->info->fixups->setup_read_retry(spinand, 0);
>
>                                                                         retry_mode);
>
> > +                     if (ret < 0)
> > +                             break;
>
> this if clause is useless.
>
> > +                     retry_mode = 0;
>
> And then this can be dropped from here.
>
> > +             }
> >       }
> >
> > +
>
> Spurious line
>
> >       if (ops->stats) {
> >               ops->stats->uncorrectable_errors +=
> >                       mtd->ecc_stats.failed - old_stats.failed;
> > @@ -1095,6 +1121,9 @@ int spinand_match_and_init(struct spinand_device *spinand,
> >               spinand->flags = table[i].flags;
> >               spinand->id.len = 1 + table[i].devid.len;
> >               spinand->select_target = table[i].select_target;
> > +             spinand->info = info;
> > +             if (spinand->info->fixups && spinand->info->fixups->init_read_retry)
> > +                     spinand->read_retries = spinand->info->fixups->init_read_retry(spinand);
>
> Now I get you init. Ok, fine.
>
> >
> >               op = spinand_select_op_variant(spinand,
> >                                              info->op_variants.read_cache);
>

Thank you for all your suggestions.
I will modify the patch according to your advice.

>
> Thanks,
> Miquèl

Thanks,
Cheng Ming Lin