linux-kernel - Re: [PATCH 11/13] dt-bindings: mips: Add loongson cpus & boards

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Date:   Wed, 4 Sep 2019 11:33:20 +0800
From:   Huacai Chen <chenhc@...ote.com>
To:     Paul Burton <paul.burton@...s.com>
Cc:     Rob Herring <robh+dt@...nel.org>,
        Jiaxun Yang <jiaxun.yang@...goat.com>,
        "open list:MIPS" <linux-mips@...r.kernel.org>,
        Thomas Gleixner <tglx@...utronix.de>,
        Jason Cooper <jason@...edaemon.net>,
        Marc Zyngier <maz@...nel.org>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
        Mark Rutland <mark.rutland@....co>,
        "devicetree@...r.kernel.org" <devicetree@...r.kernel.org>
Subject: Re: [PATCH 11/13] dt-bindings: mips: Add loongson cpus & boards

On Tue, Sep 3, 2019 at 5:08 PM Paul Burton <paul.burton@...s.com> wrote:
>
> Hi Rob,
>
> On Mon, Sep 02, 2019 at 03:50:47PM +0100, Rob Herring wrote:
> > > In general on MIPS we detect CPU properties at runtime from coprocessor
> > > 0 registers & similar sources of information, so there's not really a
> > > need to specify anything about the CPU in devicetree.
> >
> > We thought the same thing initially for Arm... Mostly what is in DT is
> > not what is discoverable. Are clock speeds, power domains, low power
> > states, etc. all discoverable?
>
> No, that's a good point - clocks etc may need to be specified in DT. I
> just don't see any of that in this patchset - it appears all that is
> specified is cache sizes which we already detect. So in this case I
> don't see a need for including CPUs in DT at all.
>
> Jiaxun - did you add all this information to DT to avoid the "cacheinfo:
> Unable to detect cache hierarchy for CPU" messages during boot? If so
> that should be fixed by commit b8bea8a5e5d9 ("mips: fix cacheinfo"). If
> not, could you describe why the CPU nodes are needed here?

Yes, this can avoid "cacheinfo: Unable to detect cache hierarchy for CPU".
In our own git repository we have already reverted commit b8bea8a5e5d9
("mips: fix cacheinfo")

Huacai

>
> Thanks,
>     Paul