linux-kernel - RE: [PATCH RESEND V2 1/3] clocksource/drivers/sysctr: Add optional clock-frequency property

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Date:   Wed, 26 Jun 2019 01:42:48 +0000
From:   Anson Huang <anson.huang@....com>
To:     Daniel Lezcano <daniel.lezcano@...aro.org>,
        "tglx@...utronix.de" <tglx@...utronix.de>,
        "robh+dt@...nel.org" <robh+dt@...nel.org>,
        "mark.rutland@....com" <mark.rutland@....com>,
        "shawnguo@...nel.org" <shawnguo@...nel.org>,
        "s.hauer@...gutronix.de" <s.hauer@...gutronix.de>,
        "kernel@...gutronix.de" <kernel@...gutronix.de>,
        "festevam@...il.com" <festevam@...il.com>,
        "l.stach@...gutronix.de" <l.stach@...gutronix.de>,
        Abel Vesa <abel.vesa@....com>,
        "ccaione@...libre.com" <ccaione@...libre.com>,
        "angus@...ea.ca" <angus@...ea.ca>,
        "andrew.smirnov@...il.com" <andrew.smirnov@...il.com>,
        "agx@...xcpu.org" <agx@...xcpu.org>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
        "devicetree@...r.kernel.org" <devicetree@...r.kernel.org>,
        "linux-arm-kernel@...ts.infradead.org" 
        <linux-arm-kernel@...ts.infradead.org>
CC:     dl-linux-imx <linux-imx@....com>
Subject: RE: [PATCH RESEND V2 1/3] clocksource/drivers/sysctr: Add optional
 clock-frequency property

Hi, Daniel

> On 23/06/2019 14:38, Anson.Huang@....com wrote:
> > From: Anson Huang <Anson.Huang@....com>
> >
> > Systems which use platform driver model for clock driver require the
> > clock frequency to be supplied via device tree when system counter
> > driver is enabled.
> >
> > This is necessary as in the platform driver model the of_clk
> > operations do not work correctly because system counter driver is
> > initialized in early phase of system boot up, and clock driver using
> > platform driver model is NOT ready at that time, it will cause system
> > counter driver initialization failed.
> >
> > Add the optinal clock-frequency to the device tree bindings of the NXP
> > system counter, so the frequency can be handed in and the of_clk
> > operations can be skipped.
> 
> Isn't it possible to create a fixed-clock and refer to it? So no need to create a
> specific action before calling timer_of_init() ?
> 

As the clock must be ready before the TIMER_OF_DECLARE, so adding a CLK_OF_DECLARE_DRIVER in
clock driver to ONLY register a fixed-clock? The system counter's frequency are different on different
platforms, so adding fixed clock in system counter driver is NOT a good idea, ONLY the DT node or the
clock driver can create this fixed clock according to platforms, can you advise where to create this fixed
clock is better?

Thanks,
Anson