From: Paul Burton <paul.burton@imgtec.com>
Subject: Re: [PATCH 2/6] crypto: jz4780-rng: Make ingenic CGU driver use syscon
Date: Mon, 21 Aug 2017 09:04:16 -0700
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References: <20170817182520.20102-1-prasannatsmkumar@gmail.com> <3563032.h0vdzx9HfC@np-p-burton> <CANc+2y6tRe_kkWyGX+-BT-ugb5JiZhKpPoHWkAn=2ZC6cb6uKA@mail.gmail.com>
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Cc: <linux-mips@linux-mips.org>,
        Herbert Xu <herbert@gondor.apana.org.au>,
        Rob Herring <robh+dt@kernel.org>,
        Mark Rutland <mark.rutland@arm.com>,
        Ralf Baechle <ralf@linux-mips.org>,
        Michael Turquette <mturquette@baylibre.com>,
        <sboyd@codeaurora.org>, "David S . Miller" <davem@davemloft.net>,
        Paul Cercueil <paul@crapouillou.net>,
        <linux-crypto@vger.kernel.org>
To: PrasannaKumar Muralidharan <prasannatsmkumar@gmail.com>
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Hi PrasannaKumar,

On Sunday, 20 August 2017 09:12:12 PDT PrasannaKumar Muralidharan wrote:
> > Could you instead perhaps:
> >  - Just add "syscon" as a second compatible string to the CGU node in the
> >  
> >    device tree, but otherwise leave it as-is without the extra
> >    cgu_registers
> >    node.
> >  
> >  - Have your RNG device node as a child of the CGU node, which should let
> >  it
> >  
> >    pick up the regmap via syscon_node_to_regmap() as it already does.
> >  
> >  - Leave the CGU driver as-is, so it can continue accessing memory
> >  directly
> >  
> >    rather than via regmap.
> 
> As per my understanding, CGU driver and syscon will map the same
> register set. Is that fine?

That should work fine.

It's only risky if you have 2 drivers using the same registers in ways that 
might race with one another or clobber one another's data. In this case each 
of the 2 drivers is using a different subset of registers that just happen to 
be in the same address range, so there shouldn't be an issue.

Thanks,
    Paul
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