linux-kernel - Re: [PATCH v3 35/42] ARM: dts: ep93xx: add ts7250 board

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Date:   Mon, 31 Jul 2023 14:55:34 +0300
From:   Nikita Shubin <nikita.shubin@...uefel.me>
To:     Linus Walleij <linus.walleij@...aro.org>
Cc:     Rob Herring <robh+dt@...nel.org>,
        Krzysztof Kozlowski <krzysztof.kozlowski+dt@...aro.org>,
        Conor Dooley <conor+dt@...nel.org>,
        Hartley Sweeten <hsweeten@...ionengravers.com>,
        Lennert Buytenhek <kernel@...tstofly.org>,
        Alexander Sverdlin <alexander.sverdlin@...il.com>,
        Michael Peters <mpeters@...eddedts.com>,
        Kris Bahnsen <kris@...eddedts.com>, devicetree@...r.kernel.org,
        linux-kernel@...r.kernel.org
Subject: Re: [PATCH v3 35/42] ARM: dts: ep93xx: add ts7250 board

Hello Linus!

On Sat, 2023-07-29 at 22:59 +0200, Linus Walleij wrote:
> On Mon, Jul 24, 2023 at 3:45 PM Nikita Shubin
> <nikita.shubin@...uefel.me> wrote:
> 
> > > > +       nand-controller@...00000 {
> > > 
> > > Where is this address? It does not work like that. If this is
> > > part of
> > > SoC, then should be in DTSI and part of soc node. If not, then it
> > > is
> > > some other bus which needs some description. Top-level is not a
> > > bus.
> > > 
> > 
> > It's some kind of EBI, but it doesn't need a driver it is
> > transparent
> > on ts7250, the logic is controlled through installed CPLD.
> > 
> > The EBI it self is a part of the SoC through:
> > 
> > https://elixir.bootlin.com/linux/v6.5-rc3/source/arch/arm/mach-ep93xx/soc.h#L35
> > 
> > EP93XX_CS0_PHYS_BASE_ASYNC to EP93XX_CS0_PHYS_BASE_SYNC.
> > 
> > So for ts7250 this includes:
> > 
> > - NAND
> > - m48t86
> > - watchdog
> > 
> > I don't even know how to represent it correctly, would "simple-bus"
> > with "ranges" defined suit here, so it will represent hierarchy but
> > won't do anything ?
> 
> Check how I solved this on the IXP4xx EBI for an example:
> Documentation/devicetree/bindings/memory-controllers/intel,ixp4xx-
> expansion-bus-controller.yaml
> 
> Top level bus inside soc:
> arch/arm/boot/dts/intel/ixp/intel-ixp4xx.dtsi
> Example platform:
> arch/arm/boot/dts/intel/ixp/intel-ixp42x-linksys-nslu2.dts
> 
> Notice chip select number in first cell.
> 
> I think you want to do something similar here?

Thank you - it looks like what i need !

> 
> Yours,
> Linus Walleij