linux-kernel - Re: [PATCH 1/2] dt-bindings: Documentation for qcom,llcc

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Message-ID: <20180213143318.be2dmmmoiafkehqk@lakrids.cambridge.arm.com>
Date:   Tue, 13 Feb 2018 14:33:19 +0000
From:   Mark Rutland <mark.rutland@....com>
To:     Channa <ckadabi@...eaurora.org>
Cc:     Matt Sealey <neko@...uhatsu.net>,
        linux-arm-kernel@...ts.infradead.org,
        linux-arm-msm@...r.kernel.org, linux-arm@...ts.infradead.org,
        linux-kernel@...r.kernel.org, tsoni@...eaurora.org,
        Stephen Boyd <sboyd@...eaurora.org>, kyan@...eaurora.org,
        linux-kernel-owner@...r.kernel.org
Subject: Re: [PATCH 1/2] dt-bindings: Documentation for qcom,llcc

On Thu, Feb 08, 2018 at 04:24:16PM -0800, Channa wrote:
> On 2018-02-08 08:52, Matt Sealey wrote:
> > On 25 January 2018 at 17:55, Channagoud Kadabi <ckadabi@...eaurora.org>
> > wrote:
> > > Documentation for last level cache controller device tree bindings,
> > > client bindings usage examples.
> > 
> > [snippety snip]
> > 
> > > +- llcc-bank-off:
> > > +       Usage: required
> > > +       Value Type: <u32 array>
> > > +       Definition: Offsets of llcc banks from llcc base address
> > > starting from
> > > +                   LLCC bank0.
> > > +
> > > +- llcc-broadcast-off:
> > > +       Usage: required
> > > +       Value Type: <u32>
> > > +       Definition: Offset of broadcast register from LLCC bank0
> > > address.

> > And if you need to describe register offsets... why aren't you able to
> > use the reg property?
> 
> Reg property did not suit well for my need, so I choose to maintain offsets
> instead.
> 
> The registers in the HW block are organized as
>                 (offset1)    (offset2)     (offset3)     (offset4)
> Base(Block0) -- Block1 -- Block 2 -- Block 3 -- Broadcast_Block
> 
> Each block has identical register mapping. You can think of it as 4
> instances of identical HW.

We have similar in other devices (e.g. GICv3 has multiple instances of
the same register block).

If there's nothing between those blocks, using a reg entry sounds
prefectly reasonable. You can list the broadcast block first, then the
others, or use reg-names.

Thanks,
Mark.