linux-kernel - Re: [PATCH v3 10/10] mtd: rawnand: brcmnand: allow for on-die ecc

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Date: Fri, 26 Jan 2024 07:19:13 +0100
From: Miquel Raynal <miquel.raynal@...tlin.com>
To: David Regan <dregan@...adcom.com>
Cc: dregan@...l.com, Richard Weinberger <richard@....at>, Vignesh
 Raghavendra <vigneshr@...com>, robh+dt@...nel.org,
 krzysztof.kozlowski+dt@...aro.org, conor+dt@...nel.org,
 computersforpeace@...il.com, kdasu.kdev@...il.com,
 linux-mtd@...ts.infradead.org, devicetree@...r.kernel.org, Linux Kernel
 Mailing List <linux-kernel@...r.kernel.org>, Joel Peshkin
 <joel.peshkin@...adcom.com>, Tomer Yacoby <tomer.yacoby@...adcom.com>, Dan
 Beygelman <dan.beygelman@...adcom.com>, William Zhang
 <william.zhang@...adcom.com>, Anand Gore <anand.gore@...adcom.com>, Kursad
 Oney <kursad.oney@...adcom.com>, Florian Fainelli
 <florian.fainelli@...adcom.com>, rafal@...ecki.pl,
 bcm-kernel-feedback-list@...adcom.com, andre.przywara@....com,
 baruch@...s.co.il, linux-arm-kernel@...ts.infradead.org, Dan Carpenter
 <dan.carpenter@...aro.org>
Subject: Re: [PATCH v3 10/10] mtd: rawnand: brcmnand: allow for on-die ecc

Hi David,

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

> Hi Miquèl,
> 
> On Wed, Jan 24, 2024 at 9:40 AM Miquel Raynal <miquel.raynal@...tlin.com> wrote:
> >
> > Hi David,
> >
> > dregan@...adcom.com wrote on Tue, 23 Jan 2024 19:04:58 -0800:
> >  
> > > 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@...adcom.com>
> > > Reviewed-by: William Zhang <william.zhang@...adcom.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/nand/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 = get_blk_adr_bytes(mtd->size, mtd->writesize);
> > >
> > >       if (chip->ecc.engine_type != 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);  
> >
> > Can you use a more formal string? Also clarify it because I don't
> > really understand what it leads to.  
> 
> How about:
> 
> 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.

> 
> >  
> > > +                     return -EINVAL;
> > > +             }
> > >       }
> > >
> > >       if (chip->ecc.algo == 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 == NAND_ECC_ENGINE_TYPE_ON_DIE) {
> > > +             dev_dbg(ctrl->dev, "Disable HW ECC for on-die ECC\n");  
> >
> > Not needed.  
> 
> Will remove.
> 
> >  
> > > +             brcmnand_set_ecc_enabled(host, 0);
> > > +     } else
> > > +             brcmnand_set_ecc_enabled(host, 1);  
> >
> > 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.  
> 
> 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,
Miquèl