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

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Date:   Thu, 1 Feb 2018 12:27:23 +0530
From:   Jassi Brar <jassisinghbrar@...il.com>
To:     Georgi Djakov <georgi.djakov@...aro.org>
Cc:     Bjorn Andersson <bjorn.andersson@...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

On Thu, Feb 1, 2018 at 12:10 AM, Georgi Djakov <georgi.djakov@...aro.org> wrote:
>
> Hi Jassi,
>
> On 01/27/2018 05:44 AM, Jassi Brar wrote:
> > On Thu, Jan 4, 2018 at 10:26 PM, Georgi Djakov <georgi.djakov@...aro.org> wrote:
> >> Hi Jassi,
> >>
> >> On 12/29/2017 08:14 AM, Jassi Brar wrote:
> >>> 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.
> >>
> >> The APCS is one separate register block related to the CPU cluster. I
> >> haven't seen any strict guidelines for such cases in the DT docs, and
> >> during the discussion got the impression that this is the preferred
> >> binding. Rob has also reviewed the binding, so we should be fine to move
> >> forward with this one.
> >>
> > Well, I can't overrule Rob. But I am really not happy with random
> > device spawning from mailbox drivers. I know there are such instances
> > already in the kernel but that doesn't make it legit... unless there
> > is some hard dependency. Is there?
>
> The dependency is that on this SoC, these functionalities are combined
> into this "CPU subsystem" block.
>
I see the register space is shared between mailbox and the clock. So I
guess, yes, simply creating a device here and passing the common
regmap is tidier. Which patches are already picked up?

Cheers!