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Date: Fri, 26 Jan 2024 07:19:13 +0100
From: Miquel Raynal <miquel.raynal@bootlin.com>
To: David Regan <dregan@broadcom.com>
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Subject: Re: [PATCH v3 10/10] mtd: rawnand: brcmnand: allow for on-die ecc
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Hi David,

dregan@broadcom.com wrote on Thu, 25 Jan 2024 11:47:46 -0800:

> Hi Miqu=C3=A8l,
>=20
> On Wed, Jan 24, 2024 at 9:40=E2=80=AFAM Miquel Raynal <miquel.raynal@boot=
lin.com> wrote:
> >
> > Hi David,
> >
> > dregan@broadcom.com wrote on Tue, 23 Jan 2024 19:04:58 -0800:
> > =20
> > > Allow settings for on-die ecc such that if on-die ECC is selected
> > > don't error out but require ECC strap setting of zero
> > >
> > > Signed-off-by: David Regan <dregan@broadcom.com>
> > > Reviewed-by: William Zhang <william.zhang@broadcom.com>
> > > ---
> > > Changes in v3: None
> > > ---
> > > Changes in v2:
> > > - Added to patch series
> > > ---
> > >  drivers/mtd/nand/raw/brcmnand/brcmnand.c | 14 ++++++++++----
> > >  1 file changed, 10 insertions(+), 4 deletions(-)
> > >
> > > diff --git a/drivers/mtd/nand/raw/brcmnand/brcmnand.c b/drivers/mtd/n=
and/raw/brcmnand/brcmnand.c
> > > index a4e311b6798c..42526f3250c9 100644
> > > --- a/drivers/mtd/nand/raw/brcmnand/brcmnand.c
> > > +++ b/drivers/mtd/nand/raw/brcmnand/brcmnand.c
> > > @@ -2727,9 +2727,11 @@ static int brcmnand_setup_dev(struct brcmnand_=
host *host)
> > >       cfg->blk_adr_bytes =3D get_blk_adr_bytes(mtd->size, mtd->writes=
ize);
> > >
> > >       if (chip->ecc.engine_type !=3D NAND_ECC_ENGINE_TYPE_ON_HOST) {
> > > -             dev_err(ctrl->dev, "only HW ECC supported; selected: %d=
\n",
> > > -                     chip->ecc.engine_type);
> > > -             return -EINVAL;
> > > +             if (chip->ecc.strength) {
> > > +                     dev_err(ctrl->dev, "ERROR!!! HW ECC must be set=
 to zero for non-hardware ECC; selected: %d\n",
> > > +                             chip->ecc.strength); =20
> >
> > Can you use a more formal string? Also clarify it because I don't
> > really understand what it leads to. =20
>=20
> How about:
>=20
> dev_err(ctrl->dev, "HW ECC set to %d, must be zero for on-die ECC\n",

Actually I am wondering how legitimate this is. Just don't enable the
on host ECC engine if it's not in use. No need to check the core's
choice.

>=20
> > =20
> > > +                     return -EINVAL;
> > > +             }
> > >       }
> > >
> > >       if (chip->ecc.algo =3D=3D NAND_ECC_ALGO_UNKNOWN) {
> > > @@ -2797,7 +2799,11 @@ static int brcmnand_setup_dev(struct brcmnand_=
host *host)
> > >       if (ret)
> > >               return ret;
> > >
> > > -     brcmnand_set_ecc_enabled(host, 1);
> > > +     if (chip->ecc.engine_type =3D=3D NAND_ECC_ENGINE_TYPE_ON_DIE) {
> > > +             dev_dbg(ctrl->dev, "Disable HW ECC for on-die ECC\n"); =
=20
> >
> > Not needed. =20
>=20
> Will remove.
>=20
> > =20
> > > +             brcmnand_set_ecc_enabled(host, 0);
> > > +     } else
> > > +             brcmnand_set_ecc_enabled(host, 1); =20
> >
> > Style is wrong, but otherwise I think ECC should be kept disabled while
> > not in active use, so I am a bit surprised by this line. =20
>=20
> This is a double check to turn on/off our hardware ECC.

I expect the engine to be always disabled. Enable it only when you
need (may require an additional patch before this one).

Thanks,
Miqu=C3=A8l