linux-kernel - Re: [PATCH v11 2/6] mailbox: qcom: Create APCS child device for clock controller

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Date:   Fri, 29 Dec 2017 11:44:40 +0530
From:   Jassi Brar <jassisinghbrar@...il.com>
To:     Bjorn Andersson <bjorn.andersson@...aro.org>
Cc:     Georgi Djakov <georgi.djakov@...aro.org>,
        Stephen Boyd <sboyd@...eaurora.org>,
        Michael Turquette <mturquette@...libre.com>,
        Rob Herring <robh@...nel.org>, linux-clk@...r.kernel.org,
        Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
        linux-arm-msm@...r.kernel.org,
        Devicetree List <devicetree@...r.kernel.org>
Subject: Re: [PATCH v11 2/6] mailbox: qcom: Create APCS child device for clock controller

Hi Bjorn,

On Sun, Dec 24, 2017 at 10:36 AM, Bjorn Andersson
<bjorn.andersson@...aro.org> wrote:
> On Fri 22 Dec 20:57 PST 2017, Jassi Brar wrote:
>
>> On Tue, Dec 5, 2017 at 9:16 PM, Georgi Djakov <georgi.djakov@...aro.org> wrote:
>> > There is a clock controller functionality provided by the APCS hardware
>> > block of msm8916 devices. The device-tree would represent an APCS node
>> > with both mailbox and clock provider properties.
>> >
>> The spec might depict a 'clock' box and 'mailbox' box inside the
>> bigger APCS box. However, from the code I see in this patchset, they
>> are orthogonal and can & should be represented as independent DT
>> nodes.
>
> The APCS consists of a number of different hardware blocks, one of them
> being the "APCS global" block, which is what this node and drivers
> relate to. On 8916 this contains both the IPC register and clock
> control. But it's still just one block according to the hardware
> specification.
>
> As such DT should describe the one hardware block by one node IMHO.
>
In my even humbler opinion, DT should describe a h/w functional unit
which _could_ be seen as a standalone component.
For example, if this APCS had a mac controller, would we also populate
a netdev from mailbox driver? And what if next revision moves/drops
this clock controller out of APCS, keeping mailbox controller exactly
same?

Maybe some DT maintainer could enlighten either of us.

Cheers!