linux-kernel - Re: [RFC PATCH v2 1/2] dt-bindings: nand: meson: support for 512B ECC step size

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Message-ID: <20230706080539.11b57e10@xps-13>
Date:   Thu, 6 Jul 2023 08:05:39 +0200
From:   Miquel Raynal <miquel.raynal@...tlin.com>
To:     Arseniy Krasnov <avkrasnov@...rdevices.ru>
Cc:     Liang Yang <liang.yang@...ogic.com>,
        Richard Weinberger <richard@....at>,
        Vignesh Raghavendra <vigneshr@...com>,
        Rob Herring <robh+dt@...nel.org>,
        Krzysztof Kozlowski <krzysztof.kozlowski+dt@...aro.org>,
        Conor Dooley <conor+dt@...nel.org>,
        Neil Armstrong <neil.armstrong@...aro.org>,
        Kevin Hilman <khilman@...libre.com>,
        Jerome Brunet <jbrunet@...libre.com>,
        Martin Blumenstingl <martin.blumenstingl@...glemail.com>,
        <oxffffaa@...il.com>, <kernel@...rdevices.ru>,
        <linux-mtd@...ts.infradead.org>, <devicetree@...r.kernel.org>,
        <linux-arm-kernel@...ts.infradead.org>,
        <linux-amlogic@...ts.infradead.org>, <linux-kernel@...r.kernel.org>
Subject: Re: [RFC PATCH v2 1/2] dt-bindings: nand: meson: support for 512B
 ECC step size

Hi Arseniy,

avkrasnov@...rdevices.ru wrote on Thu, 6 Jul 2023 08:57:00 +0300:

> On 05.07.2023 11:22, Miquel Raynal wrote:
> > Hi Arseniy,
> > 
> > avkrasnov@...rdevices.ru wrote on Wed, 5 Jul 2023 11:03:30 +0300:
> >   
> >> On 05.07.2023 10:37, Miquel Raynal wrote:  
> >>> Hi Arseniy,
> >>>
> >>> AVKrasnov@...rdevices.ru wrote on Wed, 5 Jul 2023 09:54:33 +0300:
> >>>     
> >>>> Meson NAND supports both 512B and 1024B ECC step size, so replace
> >>>> 'const' for only 1024B step size with enum for both sizes.
> >>>>
> >>>> Signed-off-by: Arseniy Krasnov <AVKrasnov@...rdevices.ru>
> >>>> ---
> >>>>  Documentation/devicetree/bindings/mtd/amlogic,meson-nand.yaml | 4 +++-
> >>>>  1 file changed, 3 insertions(+), 1 deletion(-)
> >>>>
> >>>> diff --git a/Documentation/devicetree/bindings/mtd/amlogic,meson-nand.yaml b/Documentation/devicetree/bindings/mtd/amlogic,meson-nand.yaml
> >>>> index 3bec8af91bbb..81ca8828731a 100644
> >>>> --- a/Documentation/devicetree/bindings/mtd/amlogic,meson-nand.yaml
> >>>> +++ b/Documentation/devicetree/bindings/mtd/amlogic,meson-nand.yaml
> >>>> @@ -49,7 +49,8 @@ patternProperties:
> >>>>          const: hw
> >>>>  
> >>>>        nand-ecc-step-size:
> >>>> -        const: 1024
> >>>> +        enum: [512, 1024]
> >>>> +        default: 1024    
> >>>
> >>> I was actually wrong in my previous review, there is no strong default
> >>> here as the existing binding (and code) try to use the closest
> >>> parameters required by the NAND chip: we pick the "optimal"
> >>> configuration. So if you don't provide any value here, we expect
> >>> the strength and step size advertized by the chip to be used. This is a
> >>> common default in the raw NAND subsystem.
> >>>
> >>> Please drop the default line, re-integrate the missing R-by tag from
> >>> Rob and in a separate patch please mark nand-ecc-step-size and
> >>> nand-ecc-strength mandatory if the other is provide. IOW, we expect
> >>> either both, or none of them, but not a single one.    
> >>
> >> I see, no problem! "mandatory" means update description of both fields like:
> >>
> >>     description:                                                        
> >>       Mandatory if nand-ecc-step-size is set.  
> > 
> > Nope :-)
> > 
> > Something along:
> > 
> > allOf:
> >   - if:
> >     <nand-chip>:
> >       properties:
> >         contains:
> >           - nand-ecc-step-size
> >     then:
> >       required:
> >         <nand-chip>:
> >           properties:
> >             - nand-ecc-strength
> > 
> > And same with the opposite logic.  
> 
> I see, thanks! And this should be for all nand chips, not only Amlogic? I mean in
> nand-chip.yaml? 

Some drivers can directly manage the user requests in terms of either
step size *or* strength, so I would keep this into the Amlogic file for
now.

> I'll include it as third patch in this patchset.
> 
> Thanks, Arseniy

Thanks,
Miquèl