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 08:11:35 +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 27/06/2019 02:43, Anson Huang wrote:
> > 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://eur01.safelinks.protection.outlook.com/?url=https%3A%2F%2Fpatc
> >
> hwork.kernel.org%2Fpatch%2F11011703%2F&amp;data=02%7C01%7Canson.
> huang%
> >
> 40nxp.com%7C8b9519ecceb346712be808d6fad675e4%7C686ea1d3bc2b4c6f
> a92cd99
> >
> c5c301635%7C0%7C0%7C636972196338405582&amp;sdata=sOQQzDFxoCqe
> VuHFuYPHh
> > F8Bdj2Zu9WS7Go%2FV9lrWa8%3D&amp;reserved=0
> 
> Sorry, I was unclear. I meant a patch with the timer defined using a clock as
> defined currently in the binding (no clock-frequency).

OK, for i.MX8MM, we use clocks, check below patch series:

https://patchwork.kernel.org/patch/11008519/

code piece as below:

+			system_counter: timer@...a0000 {
+				compatible = "nxp,sysctr-timer";
+				reg = <0x306a0000 0x30000>;
+				interrupts = <GIC_SPI 47 IRQ_TYPE_LEVEL_HIGH>,
+					     <GIC_SPI 48 IRQ_TYPE_LEVEL_HIGH>;
+				clocks = <&clk IMX8MM_CLK_SYS_CTR>;
+				clock-names = "per";
+			};

Thanks,
Anson.