linux-kernel - Re: [PATCH v9 3/3] dt-bindings: mtd: marvell-nand: Convert to YAML DT scheme

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Message-ID: <20230616102414.222dde21@xps-13>
Date:   Fri, 16 Jun 2023 10:24:14 +0200
From:   Miquel Raynal <miquel.raynal@...tlin.com>
To:     Krzysztof Kozlowski <krzysztof.kozlowski@...aro.org>
Cc:     Chris Packham <Chris.Packham@...iedtelesis.co.nz>,
        "richard@....at" <richard@....at>,
        "vigneshr@...com" <vigneshr@...com>,
        "robh+dt@...nel.org" <robh+dt@...nel.org>,
        "krzysztof.kozlowski+dt@...aro.org" 
        <krzysztof.kozlowski+dt@...aro.org>,
        "andrew@...n.ch" <andrew@...n.ch>,
        "gregory.clement@...tlin.com" <gregory.clement@...tlin.com>,
        "sebastian.hesselbarth@...il.com" <sebastian.hesselbarth@...il.com>,
        "linux-mtd@...ts.infradead.org" <linux-mtd@...ts.infradead.org>,
        "devicetree@...r.kernel.org" <devicetree@...r.kernel.org>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
        "linux-arm-kernel@...ts.infradead.org" 
        <linux-arm-kernel@...ts.infradead.org>,
        Vadym Kochan <vadym.kochan@...ision.eu>
Subject: Re: [PATCH v9 3/3] dt-bindings: mtd: marvell-nand: Convert to YAML
 DT scheme

Hi Krzysztof,

krzysztof.kozlowski@...aro.org wrote on Fri, 16 Jun 2023 10:15:31 +0200:

> On 15/06/2023 23:06, Chris Packham wrote:
> >>  
> >>> +
> >>> +properties:
> >>> +  compatible:
> >>> +    oneOf:
> >>> +      - items:
> >>> +          - const: marvell,armada-8k-nand-controller
> >>> +          - const: marvell,armada370-nand-controller
> >>> +      - enum:
> >>> +          - marvell,armada-8k-nand-controller  
> >> This is wrong. 8k cannot be both: compatible and not compatible with
> >> 370. It's not someone's cat to be in both states at the same time...  
> > 
> > The correct state (IMHO, Miquel correct me if I'm wrong) is `compatible 
> > = "marvell,armada-8k-nand-controller";`  as there are some 8K specific 
> > requirements that aren't present on the 370 (specifically the 
> > system-controller and the 2nd clock).   
> 
> Presence of specific requirements does not invalidate compatibility. Two
> devices are compatible if the 8k can bind and work with 370 compatible
> string, even if this means some lower performance or less features (e.g.
> subset of features).

Quoting myself from 2019 (comment in the driver):
"Some SoCs like A7k/A8k need to enable manually the NAND controller,
gated clocks and reset bits to avoid being bootloader dependent."

So can the 8k controller work using a 370 compatible : yes, if the
booloader enabled the NAND controller already, no otherwise. But in
practice it is the same controller.

Given this information I don't know whether it makes sense to qualify
the 8k controller compatible with the 370 compatible or not.

> Now whether they are really compatible or not - I don't know. I expect
> the answer from you (as plural you).

:-)

> > The only reason `compatible = 
> > "marvell,armada-8k-nand-controller", 
> > "marvell,armada370-nand-controller";` is supported is because that is 
> > what is in use in the existing dtses.  
> 
> Fix the DTS, use here the correct combination and, if it is a deviation
> from old binding, mention this in commit msg.

Fine by me.
 
> Best regards,
> Krzysztof
> 


Thanks,
Miquèl