linux-kernel - Re: [PATCH 4/4] ARM: dts: uniphier: change support card to simple-mfd from simple-bus

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Message-ID: <20200624181605.GJ954398@dell>
Date:   Wed, 24 Jun 2020 19:16:05 +0100
From:   Lee Jones <lee.jones@...aro.org>
To:     Masahiro Yamada <masahiroy@...nel.org>
Cc:     linux-arm-kernel <linux-arm-kernel@...ts.infradead.org>,
        Rob Herring <robh+dt@...nel.org>,
        DTML <devicetree@...r.kernel.org>,
        Linux Kernel Mailing List <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH 4/4] ARM: dts: uniphier: change support card to
 simple-mfd from simple-bus

On Thu, 25 Jun 2020, Masahiro Yamada wrote:

> On Tue, Jun 23, 2020 at 9:24 PM Lee Jones <lee.jones@...aro.org> wrote:
> >
> > On Tue, 23 Jun 2020, Masahiro Yamada wrote:
> >
> > > 'make ARCH=arm dtbs_check' emits the following warning:
> > >
> > >   support-card@1,1f00000: $nodename:0: 'support-card@1,1f00000' does not match '^(bus|soc|axi|ahb|apb)(@[0-9a-f]+)?$'
> > >
> > > Maybe, simple-mfd could be a better fit for this device.
> >
> > The two should be equivalent.
> 
> Yes, I know.
> That's why I can change "simple-bus" to "simple-mfd"
> with no risk.
> 
> The difference is schema-check.
> 
> The node name for "simple-bus" is checked by 'make dtbs_check'.
> 
> See this code:
> https://github.com/robherring/dt-schema/blob/v2020.05/schemas/simple-bus.yaml#L17
> 
> Even if I rename the node, it does not accept the
> unit name '1,1f00000'
> 
> > What do you mean by "maybe"?  Does this squash the warning?
> 
> "maybe" means I am not quite sure
> which compatible is a better fit
> to describe this device.
> 
> As mentioned above, simple-bus and simple-mfd
> are interchangeable from a driver point of view.
> 
> This add-on board is integrated with various peripherals
> such as 16550a serial, smsc9115 ether etc.
> The address-decode is implemented in a CPLD device.
> It has chip selects and local addresses, which are mapped to
> the parent.
> 
> It can be either simple-bus or simple-mfd, I think.
> 
> 
> dt-schema checks the node name of simple-bus.
> Currently, there is no check for simple-mfd.
> 
> So, I think this patch is an easy solution
> to fix the warning.

Yes, looking at the documentation it seems as though 'simple-mfd'
would be a better fit.  Is the device a single IP with various
different functions?

> Rob is in Cc. Please add comments if any.
> 
> > Isn't the issue caused by the ','?
> 
> Right.
> 
> The node name of simple-bus
> must meet the regular expression:
> "^(bus|soc|axi|ahb|apb)(@[0-9a-f]+)?$"
> 
> 
> Even if I rename the node
> "support-card@1,1f00000"
> to "bus@1,1f00000", the warning is still
> displayed due to ','
> 
> "1,1f00000" means
> the address 0x01f00000 of chip select 1.

Is this an officially accepted format?

-- 
Lee Jones [李琼斯]
Senior Technical Lead - Developer Services
Linaro.org │ Open source software for Arm SoCs
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