linux-kernel - Re: Charge counter on droid 4

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Message-ID: <20180618065827.GN112168@atomide.com>
Date:   Sun, 17 Jun 2018 23:58:27 -0700
From:   Tony Lindgren <tony@...mide.com>
To:     Pavel Machek <pavel@....cz>
Cc:     kernel list <linux-kernel@...r.kernel.org>,
        linux-arm-kernel <linux-arm-kernel@...ts.infradead.org>,
        linux-omap@...r.kernel.org, sre@...nel.org, nekit1000@...il.com,
        mpartap@....net, merlijn@...zup.org
Subject: Re: Charge counter on droid 4

* Pavel Machek <pavel@....cz> [180615 08:34]:
> On Fri 2018-06-15 10:00:14, Pavel Machek wrote:
> > Hi!
> > 
> > Droid 4 has non-removable battery, yet the charge counter is reset to
> > near zero on each boot of linux.

Not sure if we actively do anything to reset it. I'm guessing
it's the Motorola bootloader that resets everything on boot.

> > Unfortunately, that makes charge counter pretty much useless on d4, as
> > the "battery full" and "battery empty" limits will be different during
> > each boot.

>From what I've seen also the stock kernel starts only with
voltage based estimate initially after a reboot?

> Hmm, and could we refrain from providing "power" values?
> 
> I was thinking great, we have hardware that does proper power
> measuerement for us. No.... it is driver providing synthetic
> values. As userland has enough information to do that itself, I
> believe we should not do this in kernel.

Hmm I don't follow you, why would we want to remove these as
they implement a standard sysfs interface?

I use the sysfs interface all the time to monitor the power
consumption and the output seems to match what I was seeing
with my power supply.

Note that we also have the IIO raw data also available if that
might help.

Regards,

Tony