linux-kernel - Re: [PATCH v2] mtd: rawnand: xway: No hardcoded ECC engine, use device tree setting

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Date:   Tue, 24 Aug 2021 09:15:49 +0200
From:   Kestrel seventyfour <kestrelseventyfour@...il.com>
To:     Miquel Raynal <miquel.raynal@...tlin.com>
Cc:     Richard Weinberger <richard@....at>,
        Vignesh Raghavendra <vigneshr@...com>,
        linux-mtd@...ts.infradead.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH v2] mtd: rawnand: xway: No hardcoded ECC engine, use
 device tree setting

Hi Miquèl,

Am Mo., 23. Aug. 2021 um 17:24 Uhr schrieb Miquel Raynal
<miquel.raynal@...tlin.com>:
>
> Hi Kestrel,
>
> Kestrel seventyfour <kestrelseventyfour@...il.com> wrote on Mon, 23 Aug
> 2021 13:19:43 +0200:
>
> > Hi Miquèl,
> >
> > Am Do., 19. Aug. 2021 um 10:03 Uhr schrieb Miquel Raynal
> > <miquel.raynal@...tlin.com>:
...
> >
> > thank you for your response.
> > If I remove the nand-ecc-xxx properties in the device tree, the device with
> > the Toshiba NAND chip is working. However, the device with the Micron
> > NAND fails with NO ECC functions supplied; hardware ECC not possible,
> > seems to be at line 5367 or equivalent.
> > https://elixir.bootlin.com/linux/latest/source/drivers/mtd/nand/raw/nand_base.c#L5367
> >
> > It looks like the micron nand driver supports on die only if its
> > specified int the
> > Device tree:
> > https://elixir.bootlin.com/linux/latest/source/drivers/mtd/nand/raw/nand_micron.c#L511
> > The Micron NAND driver probably needs to set the ECC type to ON DIE if the
> > variable ondie contains the supported attribute?!
>
> You're right but I don't see any easy upstream-able solution here.
> Changing the behavior in the Xway driver would certainly break users,
> changing the behavior in the Micron driver would certainly break even
> more users. The root cause being an absence of proper description (the
> integration changed). Honestly I feel stuck, maybe you can try to
> register your device, if it fails, change the integration in the driver
> (to an ondie ecc engine) then retry?
>
> Thanks,
> Miquèl

Do you think adding something like below at the following location
https://elixir.bootlin.com/linux/latest/source/drivers/mtd/nand/raw/xway_nand.c#L223
would be upstreamable (with or without device tree property?)?

        err = nand_scan(&data->chip, 1);
        if (err /* && of_property_read_bool(np, "lantiq,retry-on-die") */) {
                data->chip.ecc.engine_type = NAND_ECC_ENGINE_TYPE_ON_DIE;
                err = nand_scan(&data->chip, 1);
                if (err) return err;
        }

It still throws the kernel warning on first try, but the second try then works.

Thanks Daniel.