linux-kernel - Re: [PATCH v2] rtc: da9063: add as wakeup source

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Message-ID: <20211126132308.7b265f17@redslave.neermore.group>
Date:   Fri, 26 Nov 2021 13:23:08 +0300
From:   Nikita Shubin <nikita.shubin@...uefel.me>
To:     Adam Thomson <Adam.Thomson.Opensource@...semi.com>
Cc:     David Abdurachmanov <david.abdurachmanov@...ive.com>,
        Support Opensource <Support.Opensource@...semi.com>,
        Alessandro Zummo <a.zummo@...ertech.it>,
        Alexandre Belloni <alexandre.belloni@...tlin.com>,
        "linux-rtc@...r.kernel.org" <linux-rtc@...r.kernel.org>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH v2] rtc: da9063: add as wakeup source

Hello Adam!

On Fri, 26 Nov 2021 09:50:18 +0000
Adam Thomson <Adam.Thomson.Opensource@...semi.com> wrote:

> On 26 November 2021 09:10, Nikita Shubin wrote:
> 
> > > Can you please make the commit message more detailed, explaining
> > > why you're making this change; what it adds/fixes/removes/etc.?
> > > Right now just reading this I'm unclear as to why you're adding a
> > > call to device_init_wakeup() here. The generic I2C client code
> > > will mark the parent MFD device as a wake source, if the relevant
> > > boolean 'wakeup' is defined in DT, so what does this add?  
> > 
> > Sorry for long response had to double check setting wakeup-source in
> > case i have missed something.
> > 
> > I2C_CLIENT_WAKE is set in of_i2c_get_board_info - the place da9063
> > rtc would never get to.
> > 
> > Setting "wakeup-source" for pmic indeed marks it as wakeup source,
> > but that's not exactly we want.
> > 
> > What we want is "wakealarm" in RTC sysfs directory, to be able to
> > set alarm so we can wake up from SHUTDOWN/DELIVERY/RTC mode of
> > da9063.
> > 
> > We do have /sys/class/rtc/rtc0/wakealarm if marking da9063-rtc as
> > device_init_wakeup.
> > 
> > Unfortunately marking pmic or rtc as wakeup-source in device tree
> > gives us nothing.
> > 
> > ls /proc/device-tree/soc/i2c\@10030000/pmic\@58/
> > compatible            interrupt-parent  name  regulators
> > wakeup-source interrupt-controller  interrupts        reg   rtc
> >     wdt
> > 
> > ls /proc/device-tree/soc/i2c\@10030000/pmic\@58/rtc/
> > compatible  name  wakeup-source
> > 
> > ls /sys/class/rtc/rtc0/wakealarm
> > ls: cannot access '/sys/class/rtc/rtc0/wakealarm': No such file or
> > directory
> > 
> > So i currently see that either da9063 RTC should be marked as wakeup
> > source, or the da9063 MFD should somehow set that for RTC.
> > 
> > And we want this even if CONFIG_PM is off.
> > 
> > Mentioning "/sys/class/rtc/rtc0/wakealarm" in commit message would
> > be enough ?  
> 
> Thanks for the detailed response; it helped a lot. Having reviewed
> the core code along with your description I know understand what's
> happening here. Basically marking as 'wakeup-source' is simply a
> means to expose the sysfs attribute to user-space.
> 
> Yes I think in the commit message you should be clear that there's a
> need to access the sys attribute 'wakealarm' in the RTC core and
> clarify exactly why there is that need. Your commit log should be
> good enough so that if anyone else needs to look at this later they
> completely understand the intention behind the change.
> 
> By the way, I assume the functionality you're looking for could also
> have been achieved through using the /dev/rtcX instance for DA9063?

Thank you for pointing this out, indeed i missed that obvious thing.

We can also simply set alarm via rtcwake, even if CONFIG_PM is off:

rtcwake -m no -s 60

Now i am not sure we should make changes to da9063-rtc driver - what do
you think ?