linux-kernel - RE: [PATCH 4/4] ARM64: dts: imx: add i.MX8QXP system controller RTC support

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Message-ID: <DB3PR0402MB3916DE94D437DC51435D00CEF5D10@DB3PR0402MB3916.eurprd04.prod.outlook.com>
Date:   Wed, 28 Nov 2018 09:41:22 +0000
From:   Anson Huang <anson.huang@....com>
To:     Alexandre Belloni <alexandre.belloni@...tlin.com>
CC:     Lothar Wa��mann <LW@...O-electronics.de>,
        "a.zummo@...ertech.it" <a.zummo@...ertech.it>,
        "robh+dt@...nel.org" <robh+dt@...nel.org>,
        "mark.rutland@....com" <mark.rutland@....com>,
        "catalin.marinas@....com" <catalin.marinas@....com>,
        "will.deacon@....com" <will.deacon@....com>,
        Aisheng DONG <aisheng.dong@....com>,
        Andy Gross <andy.gross@...aro.org>,
        "arnd@...db.de" <arnd@...db.de>,
        "horms+renesas@...ge.net.au" <horms+renesas@...ge.net.au>,
        "heiko@...ech.de" <heiko@...ech.de>,
        "bjorn.andersson@...aro.org" <bjorn.andersson@...aro.org>,
        "enric.balletbo@...labora.com" <enric.balletbo@...labora.com>,
        "amit.kucheria@...aro.org" <amit.kucheria@...aro.org>,
        "ezequiel@...labora.com" <ezequiel@...labora.com>,
        "olof@...om.net" <olof@...om.net>,
        "shawnguo@...nel.org" <shawnguo@...nel.org>,
        "linux-rtc@...r.kernel.org" <linux-rtc@...r.kernel.org>,
        "devicetree@...r.kernel.org" <devicetree@...r.kernel.org>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
        "linux-arm-kernel@...ts.infradead.org" 
        <linux-arm-kernel@...ts.infradead.org>,
        dl-linux-imx <linux-imx@....com>
Subject: RE: [PATCH 4/4] ARM64: dts: imx: add i.MX8QXP system controller RTC
 support



Best Regards!
Anson Huang

> -----Original Message-----
> From: Alexandre Belloni [mailto:alexandre.belloni@...tlin.com]
> Sent: 2018年11月28日 17:34
> To: Anson Huang <anson.huang@....com>
> Cc: Lothar Wa��mann <LW@...O-electronics.de>; a.zummo@...ertech.it;
> robh+dt@...nel.org; mark.rutland@....com; catalin.marinas@....com;
> will.deacon@....com; Aisheng DONG <aisheng.dong@....com>; Andy Gross
> <andy.gross@...aro.org>; arnd@...db.de; horms+renesas@...ge.net.au;
> heiko@...ech.de; bjorn.andersson@...aro.org; enric.balletbo@...labora.com;
> amit.kucheria@...aro.org; ezequiel@...labora.com; olof@...om.net;
> shawnguo@...nel.org; linux-rtc@...r.kernel.org; devicetree@...r.kernel.org;
> linux-kernel@...r.kernel.org; linux-arm-kernel@...ts.infradead.org;
> dl-linux-imx <linux-imx@....com>
> Subject: Re: [PATCH 4/4] ARM64: dts: imx: add i.MX8QXP system controller
> RTC support
> 
> On 28/11/2018 09:21:56+0000, Anson Huang wrote:
> > > > This module is NOT depending on any board design, should it be
> > > > enabled by
> > > default in soc dtsi?
> > > > Like wdog etc..
> > > >
> > >
> > > I guess the point is that you may not want it enabled, even if it
> > > should always be working. enabling it by default would affect the RTC
> ordering for example.
> >
> > i.MX SoCs ONLY have 1 RTC. And RTC are always enabled by default for
> > all i.MX SoCs, so do we have to disable it here and enable it in board dts?
> >
> 
> I would say that most of the i.MX based boards include another RTC because
> the SoC one consumes way too much power.
> 
> Note that I don't care too much whether it is enabled by default, I was simply
> explaining why you may want to disable it by default.

OK, this system controller RTC is a little different, it is controlled by system controller firmware,
and system controller firmware will always select the best one for its user(Linux kernel) if there are other
RTCs available, so I think we can keep it enabled by default for now. Thanks.

Anson.

> 
> --
> Alexandre Belloni, Bootlin
> Embedded Linux and Kernel engineering
> https://emea01.safelinks.protection.outlook.com/?url=https%3A%2F%2Fbootl
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