linux-kernel - Re: [GIT PULL] Greybus driver subsystem for 4.9-rc1

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Date:   Thu, 15 Sep 2016 12:02:55 +0100
From:   Bryan O'Donoghue <pure.logic@...us-software.ie>
To:     Greg KH <gregkh@...uxfoundation.org>, Rob Herring <robh@...nel.org>
Cc:     Mark Rutland <mark.rutland@....com>, Arnd Bergmann <arnd@...db.de>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
        Johan Hovold <johan@...oldconsulting.com>,
        Rui Miguel Silva <rmfrfs@...il.com>,
        Laurent Pinchart <laurent.pinchart@...asonboard.com>,
        Sandeep Patil <sspatil@...gle.com>,
        Matt Porter <mporter@...nel.crashing.org>,
        John Stultz <john.stultz@...aro.org>,
        Viresh Kumar <viresh.kumar@...aro.org>,
        Alex Elder <elder@...aro.org>, David Lin <dtwlin@...gle.com>,
        Vaibhav Agarwal <vaibhav.agarwal@...aro.org>,
        Mark Greer <mgreer@...malcreek.com>,
        Marc Zyngier <marc.zyngier@....com>,
        "linux-arm-kernel@...ts.infradead.org" 
        <linux-arm-kernel@...ts.infradead.org>
Subject: Re: [GIT PULL] Greybus driver subsystem for 4.9-rc1

On Thu, 2016-09-15 at 12:17 +0200, Greg KH wrote:
> This
> > is the first I've heard of timesync having a binding. I can't
> imagine
> > why it needs one.
> 
> Ah, I'll let Bryan answer that one :)

It's possible we could drop the binding. It was needed to describe the
register location of the MMIO architectural register on MSM8994. I have
this binding ATM the describe fact that get_cycles() on MSM8994 returns
a free-running counter, clocked by refclk and that refclk is provided
to each processor that want to do FrameTime - i.e. the clock driving
get_cycles() comes from PMIC and drives the relevant PLLs on the
downstream processors clocking their respective TMR blocks.

static const struct of_device_id arch_timer_of_match[] = {
        { .compatible   = "google,greybus-frame-time-counter", },
        {},
};

I'm not aware of a corresponding kernel API that describes the
frequency get_cycles() operates at but if there is one then there's no
need for this binding.