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Date:   Wed, 20 Nov 2019 23:49:28 +0800
From:   Orson Zhai <orson.zhai@spreadtrum.com>
To:     Arnd Bergmann <arnd@arndb.de>
CC:     Orson Zhai <orson.zhai@unisoc.com>,
        Lee Jones <lee.jones@linaro.org>,
        Rob Herring <robh+dt@kernel.org>,
        Mark Rutland <mark.rutland@arm.com>,
        DTML <devicetree@vger.kernel.org>,
        "linux-kernel@vger.kernel.org" <linux-kernel@vger.kernel.org>,
        <kevin.tang@unisoc.com>
Subject: Re: [PATCH 1/2] dt-bindings: Add syscon-names support
Message-ID: <20191120154928.GC6039@spreadtrum.com>
References: <20191114114525.12675-1-orson.zhai@unisoc.com>
 <20191114114525.12675-2-orson.zhai@unisoc.com>
 <CAK8P3a23jcNgFErik1PFr=tG6n8kc8Pj9fARw47n=ou8t8iV+Q@mail.gmail.com>
 <20191118083952.GB6039@spreadtrum.com>
 <CAK8P3a2d2=BejX=R0jmw0zt64mPF-rjKSi1Eh5Koz1cqku-nRA@mail.gmail.com>
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Hi Arnd,

On Tue, Nov 19, 2019 at 03:46:09PM +0100, Arnd Bergmann wrote:
> On Mon, Nov 18, 2019 at 9:42 AM Orson Zhai <orson.zhai@spreadtrum.com> wrote:
> >
> > Hi Arnd,
> >
> > On Fri, Nov 15, 2019 at 10:33:30AM +0100, Arnd Bergmann wrote:
> > > On Thu, Nov 14, 2019 at 12:48 PM Orson Zhai <orson.zhai@unisoc.com> wrote:
> > > >
> > > >
> > > > Make life easier when syscon consumer want to access multiple syscon
> > > > nodes.
> > > > Add syscon-names and relative properties to help manage complicated
> > > > cases when accessing more one syscon node.
> > > >
> > > > Signed-off-by: Orson Zhai <orson.zhai@unisoc.com>
> > >
> > > Hi Orson,
> > >
> > > Can you explain why the number of cells in this binding is specific
> > > to the syscon node rather than the node referencing it?
> >
> > The story is like this. I found there are too many global registers in
> > Unisoc(former Spreadtrum) chips. Dozens of offset with dozens of modules
> > were needed to be specified. So I thought the dts files would seem "horrible"
> > with a big chunk of syscon-xxx (say more than 20 lines)
> >
> > I learned from reg-names way which might look clean to hold all these mess things.
> > But to implement this, the users need to konw the cell-size if we add arguments to syscon node.
> > I thought to add cell-size into every syscon consumer node is a duplicated work and
> > I wanted to take advantage of of_parse_phandle_with_args.
> > So the bindings were created then.
>
> Ok, that makes sense.
>
> > > The way would otherwise handle the example from your binding
> > > would be with two separate properties in the display node, like
> > >
> > > syscon-enable = <&ap_apb_regs 0x4 0xf00>;
> > > syscon-power = <&aon_regs 0x8>;
> >
> > This is an option for consumers all the time.
> > Acturally my patches are not going to replace this.
> > I'd like to provide another option to save people like desperate engineers in Spreadtrum :)
> >
> > >
> > > in which case, the syscon driver does not need to know anything
> >
> > Whould it be better if I add syscon-cells into consumer's node?
>
> As I see it, there is no reason to put the syscon-cells property into any node,
> as this is implied by the driver binding using the syscon reference.  I would
> only use the #xyz-cells style property if there are multiple interpretations
> that all make sense for the same binding.
>
> > Then I could read the cell size and use "of_parse_phandle_with_fixed_args()" instead.
> > This will not involve syscon node itself at all.
>
> This sounds better to me, yes. I had not even remembered this function
> exists, but I think this is a good idea.
>
> I can also see a point in favor of adding more infrastructure around this,
> possibly naming the entries in a syscon-names property as you suggested,
> combining of_parse_phandle_with_fixed_args() with a name, or
> combining with syscon_regmap_lookup_by_phandle() for convenience.
>
> This should all be possible without adding complexity to the syscon
> DT binding itself, and it would give more structure to the way it
> is used by drivers.

V2 has been sent out per as you suggested.

Free free to review please.

Best Regards,
-Orson
>
>        Arnd
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