linux-kernel - Re: [PATCH] ARM: dts: imx6qdl-hummingboard: Add rtc0 and rtc1 aliases to fix hctosys

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Date: Fri, 19 Jan 2024 12:08:00 +0000
From: Josua Mayer <josua@...id-run.com>
To: "Russell King (Oracle)" <linux@...linux.org.uk>
CC: Rob Herring <robh+dt@...nel.org>, Krzysztof Kozlowski
	<krzysztof.kozlowski+dt@...aro.org>, Conor Dooley <conor+dt@...nel.org>,
	Shawn Guo <shawnguo@...nel.org>, Sascha Hauer <s.hauer@...gutronix.de>,
	Pengutronix Kernel Team <kernel@...gutronix.de>, Fabio Estevam
	<festevam@...il.com>, NXP Linux Team <linux-imx@....com>, Yazan Shhady
	<yazan.shhady@...id-run.com>, Jon Nettleton <jon@...id-run.com>,
	"devicetree@...r.kernel.org" <devicetree@...r.kernel.org>,
	"linux-arm-kernel@...ts.infradead.org"
	<linux-arm-kernel@...ts.infradead.org>, "linux-kernel@...r.kernel.org"
	<linux-kernel@...r.kernel.org>
Subject: Re: [PATCH] ARM: dts: imx6qdl-hummingboard: Add rtc0 and rtc1 aliases
 to fix hctosys

Am 18.01.24 um 17:07 schrieb Russell King (Oracle):
> On Thu, Jan 18, 2024 at 04:01:10PM +0100, Josua Mayer wrote:
>> HummingBoard has two RTCs, first integrated within SoC that can be used to
>> wake up from sleep - and a second on the carrier board including back-up
>> battery which is intended for keeping time during power-off.
>>
>> Add aliases for both, ensuring that the battery-backed clock is primary
>> rtc and used by default during boot for restoring system time.
> Given that the snvs RTC isn't battery backed, should we even be enabling
> that in DT?
In imx6qdl.dtsi it is not disabled.
According to Jon it is useful because it can wake up the soc from sleep,
whereas the external rtc can't.
>
> Also, have you seen any issues such as:
>
> [    0.933249] rtc-pcf8523 0-0068: failed to set xtal load capacitance: -11
> [    0.933505] rtc-pcf8523: probe of 0-0068 failed with error -11
>
> which seems to be exhibiting itself on my SolidSense board?
Not on my HummingBoard Gate Rev. 1.4., but indeed on my solidsense
unit too, which is probably same age as yours.
Only tested imx6dl-hummingboard2-emmc-som-v15.dtb,
but solidsense one should make no difference.