From: Alexandre Belloni <alexandre.belloni@bootlin.com>
To: Peter Geis <pgwipeout@gmail.com>
Cc: a.zummo@towertech.it, "Rafael J. Wysocki" <rjw@rjwysocki.net>,
len.brown@intel.com, pavel@ucw.cz,
Greg KH <gregkh@linuxfoundation.org>,
linux-rtc@vger.kernel.org, linux-pm@vger.kernel.org,
linux-kernel@vger.kernel.org, linux-tegra@vger.kernel.org
Subject: Re: [Question] rtc wake behavior and sysfs
Date: Tue, 6 Oct 2020 00:29:53 +0200 [thread overview]
Message-ID: <20201005222953.GD2804081@piout.net> (raw)
In-Reply-To: <CAMdYzYrYdDYF_Y_TwQ65u=Ymu2_8Rs9KWm_TfXcaPGTwucT=jg@mail.gmail.com>
On 05/10/2020 09:13:08-0400, Peter Geis wrote:
> Good Morning,
>
> While testing suspend to ram on the Ouya, I encountered an interesting
> issue with the rtc-tps65910 driver.
> Attempting to use rtc-wake on the default configuration returned:
> rtcwake: /dev/rtc0 not enabled for wakeup events
> This is due to:
> eb5eba4ef722 drivers/rtc/rtc-tps65910.c: enable/disable wake in suspend/resume
> This commit changed this driver's behavior to not enable wakeup by
> default, but enables it when entering sleep mode.
> This seems to be odd behavior to me.
> Looking at a few other rtc drivers show they simply enable themselves
> as wakeup sources by default.
>
> I also found the sysfs entries are at /sys/devices/ ..
> /tps65910-rtc/power but are missing at /sys/class/rtc/rtc0/power/
>
> I have two questions.
> - Should the sysfs wakeup entries be missing at /sys/class/rtc/rtc0/power/ ?
I would be in /sys/class/rtc/rtc0/device/power
> - Shouldn't a rtc be enabled as a wakeup source by default?
>
The short answer is no, the reason being that not all RTCs are connected
to an IRQ or a pin that can wakeup or start the platform. What should be
done is enabling wakeup only when interrupts are available or the
wakeup-source property is in the rtc device tree node.
--
Alexandre Belloni, Bootlin
Embedded Linux and Kernel engineering
https://bootlin.com
next prev parent reply other threads:[~2020-10-05 22:36 UTC|newest]
Thread overview: 4+ messages / expand[flat|nested] mbox.gz Atom feed top
2020-10-05 13:13 [Question] rtc wake behavior and sysfs Peter Geis
2020-10-05 22:29 ` Alexandre Belloni [this message]
2020-10-06 1:47 ` Peter Geis
2020-10-06 7:03 ` Alexandre Belloni
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