linux-kernel - Re: [PATCH 22/43] dt-bindings: mtd: add DT bindings for ts7250 nand

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Message-ID: <20230522161803.4f13d35a@xps-13>
Date:   Mon, 22 May 2023 16:18:03 +0200
From:   Miquel Raynal <miquel.raynal@...tlin.com>
To:     Nikita Shubin <nikita.shubin@...uefel.me>
Cc:     Arnd Bergmann <arnd@...nel.org>, Linus Walleij <linusw@...nel.org>,
        Alexander Sverdlin <alexander.sverdlin@...il.com>,
        Richard Weinberger <richard@....at>,
        Vignesh Raghavendra <vigneshr@...com>,
        Rob Herring <robh+dt@...nel.org>,
        Krzysztof Kozlowski <krzysztof.kozlowski+dt@...aro.org>,
        Lukasz Majewski <lukma@...x.de>, linux-mtd@...ts.infradead.org,
        devicetree@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH 22/43] dt-bindings: mtd: add DT bindings for ts7250 nand

Hi Nikita,

nikita.shubin@...uefel.me wrote on Mon, 15 May 2023 18:48:31 +0300:

> Hello Miquel!
> 
> Thank you for looking into it.
> 
> On Tue, 2023-05-02 at 11:48 +0200, Miquel Raynal wrote:
> > Hi Nikita,
> > 
> > nikita.shubin@...uefel.me wrote on Mon, 24 Apr 2023 15:34:38 +0300:
> >   
> > > Add YAML bindings for ts7250 NAND.
> > > 
> > > Signed-off-by: Nikita Shubin <nikita.shubin@...uefel.me>
> > > ---
> > >  .../bindings/mtd/technologic,nand.yaml        | 56
> > > +++++++++++++++++++
> > >  1 file changed, 56 insertions(+)
> > >  create mode 100644
> > > Documentation/devicetree/bindings/mtd/technologic,nand.yaml
> > > 
> > > diff --git
> > > a/Documentation/devicetree/bindings/mtd/technologic,nand.yaml
> > > b/Documentation/devicetree/bindings/mtd/technologic,nand.yaml
> > > new file mode 100644
> > > index 000000000000..3234d93a1c21
> > > --- /dev/null
> > > +++ b/Documentation/devicetree/bindings/mtd/technologic,nand.yaml
> > > @@ -0,0 +1,56 @@
> > > +# SPDX-License-Identifier: GPL-2.0-only OR BSD-2-Clause
> > > +%YAML 1.2
> > > +---
> > > +$id: http://devicetree.org/schemas/mtd/technologic,nand.yaml#
> > > +$schema: http://devicetree.org/meta-schemas/core.yaml#
> > > +
> > > +title: Technologic Systems NAND controller
> > > +
> > > +maintainers:
> > > +  - Lukasz Majewski <lukma@...x.de>
> > > +
> > > +properties:
> > > +  compatible:
> > > +    items:
> > > +      - const: technologic,ts7200-nand  
> > 
> > would -nand-controller instead of -nand work as a suffix here?
> > 
> > You mention ts7250 in the title, should we have a more specific
> > compatible than ts7200 as well?
> > 
> > I see by looking at the mtd patch that you actually try to match
> > both,
> > so they should both be defined in the bindings.
> >   
> > > +      - const: gen_nand  
> > 
> > This is a old hack for very simple controllers (converted to DT
> > probing
> > 12 years ago). The logic used by this driver has been deprecated for
> > like 10 years and does not really apply to modern APIs. I would
> > really
> > like to keep this driver contained with platform data coming from
> > arch/
> > data only.
> > 
> > I suggest you create a real NAND controller driver based on the
> > generic one (should not be very complex, just duplicate the code so
> > the
> > migration to the up-to-date API is eased) and you flag it as "must be
> > updated to ->exec_op() somehow. This way if someone starts the
> > conversion, it does not need to cope with the 5 other users of the
> > generic driver which anyway share nothing in common besides the
> > deprecated ->cmd_ctrl() backbone.
> > 
> > I read the comments on the cover letter, people are kind of pushing
> > on
> > having this merged quickly. I am fine accepting a legacy controller
> > driver and migrating it to ->exec_op() later, but the current driver
> > conversion does not fit the approach taken years ago towards a
> > cleaner
> > mtd tree.  
> 
> Did you mean that i should at least implement legacy nand controller,
> like, for example, Xway (xway_nand.c) ?:
> 
>         data->chip.legacy.cmd_ctrl = xway_cmd_ctrl;
>         data->chip.legacy.dev_ready = xway_dev_ready;
>         data->chip.legacy.select_chip = xway_select_chip;
>         data->chip.legacy.write_buf = xway_write_buf;
>         data->chip.legacy.read_buf = xway_read_buf;
>         data->chip.legacy.read_byte = xway_read_byte;
>         data->chip.legacy.chip_delay = 30;

I don't know how urgent this conversion is, this is really the minimal
step...

> And the best solution would be switching to exec_op completely ?

...and this is what I would really prefer, yes. I don't think it's
huge, the controller being very simple and straightforward.

> 
> >   
> > > +
> > > +  reg:
> > > +    maxItems: 1
> > > +
> > > +  '#address-cells': true
> > > +  '#size-cells': true
> > > +
> > > +required:
> > > +  - compatible
> > > +  - reg
> > > +
> > > +unevaluatedProperties: true
> > > +
> > > +examples:
> > > +  - |
> > > +    nand-parts@0 {
> > > +      compatible = "technologic,ts7200-nand", "gen_nand";
> > > +      reg = <0x60000000 0x8000000>;
> > > +      #address-cells = <1>;
> > > +      #size-cells = <1>;
> > > +
> > > +      partition@0 {
> > > +        label = "TS-BOOTROM";
> > > +        reg = <0x00000000 0x00020000>;
> > > +        read-only;
> > > +      };  
> > 
> > Partitions are not useful here, but if you want them, use the
> > partitions container instead, please.
> >   
> > > +
> > > +      partition@...00 {
> > > +        label = "Linux";
> > > +        reg = <0x00020000 0x07d00000>;
> > > +      };
> > > +
> > > +      partition@...0000 {
> > > +        label = "RedBoot";
> > > +        reg = <0x07d20000 0x002e0000>;
> > > +        read-only;
> > > +      };
> > > +    };
> > > +
> > > +...  
> > 
> > 
> > Thanks,
> > Miquèl  
> 


Thanks,
Miquèl