From: Andrei Botila <andrei.botila@oss.nxp.com>
To: Fabio Estevam <festevam@gmail.com>
Cc: Frank Li <Frank.Li@nxp.com>,
Sascha Hauer <s.hauer@pengutronix.de>,
Conor Dooley <conor+dt@kernel.org>, Rob Herring <robh@kernel.org>,
Krzysztof Kozlowski <krzk+dt@kernel.org>,
Ghennadi Procopciuc <ghennadi.procopciuc@oss.nxp.com>,
NXP S32 Linux Team <s32@nxp.com>,
Chester Lin <chester62515@gmail.com>,
Matthias Brugger <mbrugger@suse.com>,
Pengutronix Kernel Team <kernel@pengutronix.de>,
linux-arm-kernel@lists.infradead.org, imx@lists.linux.dev,
devicetree@vger.kernel.org, linux-kernel@vger.kernel.org
Subject: Re: [PATCH] arm64: dts: s32g: force S32G RTC as rtc0
Date: Tue, 10 Mar 2026 17:21:15 +0200 [thread overview]
Message-ID: <d5bb01c1-17c9-4d76-8a49-00ffd85c7580@oss.nxp.com> (raw)
In-Reply-To: <CAOMZO5CHGssc3Tuf6fJg2_P=bp7=itfDVRANqQOiK2b-2ooeFA@mail.gmail.com>
On 3/10/2026 4:02 PM, Fabio Estevam wrote:
> On Tue, Mar 10, 2026 at 10:50 AM Andrei Botila
> <andrei.botila@oss.nxp.com> wrote:
>
>> Regarding the I2C RTC(PCA85073A) commands like hwclock or rtcwake use by
>> default /dev/rtc, /dev/rtc0 so they will try to use PCA and fail.
>
> These commands should not fail.
rtcwake -s 10 -m mem
rtcwake: cannot open /sys/class/rtc/rtc0/device/power/wakeup: No such file or directory
rtcwake: /dev/rtc0 not enabled for wakeup events
Through this patch what I am trying to do is to get rid of the need of specifying
the rtc (-d rtcX).
>
> date -s "2026-03-10 11:00:00"
> hwclock -w
>
> Power-cycle the board. Does the "date" command retain the correct time?
date -> Tue Mar 10 11:12:43 UTC 2026
date -s "2026-03-10 11:00:00" -> Tue Mar 10 11:00:00 UTC 2026
hwclock -w
date -> Tue Mar 10 11:00:06 UTC 2026
<Power cycle>
hwclock -r -> 2026-03-10 11:00:31.104653+00:00
So looks like it does retain the date between power cycles.
>
>> Also from what I could find online PCA85073A is also not battery-backed.
>
> I haven't checked, but this looks strange. How will the board retain
> the time then, after a power cycle?
next prev parent reply other threads:[~2026-03-10 15:21 UTC|newest]
Thread overview: 6+ messages / expand[flat|nested] mbox.gz Atom feed top
2026-03-10 12:49 Andrei Botila
2026-03-10 13:14 ` Fabio Estevam
2026-03-10 13:49 ` Andrei Botila
2026-03-10 14:02 ` Fabio Estevam
2026-03-10 15:21 ` Andrei Botila [this message]
2026-03-10 16:03 ` Fabio Estevam
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