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

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Date:   Thu, 27 Jun 2019 00:43:30 +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 26/06/2019 03:42, Anson Huang wrote:
> > 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?
> 
> Can you point me to a DT with the "nxp,sysctr-timer" ?

The DT node of system counter is new added in 3/3 of this patch series, also can be found
from below link:
https://patchwork.kernel.org/patch/11011703/

thanks,
Anson