Best Regards!
Anson Huang

-----Original Message-----
From: Alexandre Belloni [mailto:alexandre.belloni at bootlin.com]
Sent: 2018?11?28? 17:58
To: Anson Huang <redacted>
Cc: Lothar Wa??mann <redacted>; a.zummo at towertech.it;
robh+dt at kernel.org; mark.rutland at arm.com; catalin.marinas at arm.com;
will.deacon at arm.com; Aisheng DONG [off-list ref]; Andy Gross
[off-list ref]; arnd at arndb.de; horms+renesas at verge.net.au;
heiko at sntech.de; bjorn.andersson at linaro.org; enric.balletbo at collabora.com;
amit.kucheria at linaro.org; ezequiel at collabora.com; olof at lixom.net;
shawnguo at kernel.org; linux-rtc at vger.kernel.org; devicetree at vger.kernel.org;
linux-kernel at vger.kernel.org; linux-arm-kernel at lists.infradead.org;
dl-linux-imx [off-list ref]
Subject: Re: [PATCH 4/4] ARM64: dts: imx: add i.MX8QXP system controller
RTC support

On 28/11/2018 09:41:22+0000, Anson Huang wrote:

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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?

quoted

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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.

quoted

Do you mean that the plan is to push support for the external RTCs (e.g.
the i2c ones) to the M4 firmware?

As far as I know, currently there is no such plan/support in system controller (M4) firmware,
and if there are external RTCs, like some PMICs have RTC inside, yes, M4 will
control it and Linux kernel (AP) does NOT need to care about which RTC is used,
same IPC API will be used I think.

Anson.

--
Alexandre Belloni, Bootlin
Embedded Linux and Kernel engineering
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