linux-kernel - Re: [linux-sunxi] [PATCH 2/4] power: add axp20x-battery driver

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Date:	Tue, 5 Jul 2016 14:43:17 +0200
From:	Bruno Prémont <bonbons@...ux-vserver.org>
To:	Icenowy Zheng <icenowy@...c.xyz>
Cc:	Michael Haas <michael.haas@...lbox.org>, Wens <wens@...e.org>,
	Maxime Ripard <maxime.ripard@...e-electrons.com>,
	sre@...nel.org, dbaryshkov@...il.com, dwmw2@...radead.org,
	robh+dt@...nel.org, Mark Rutland <mark.rutland@....com>,
	linux@...linux.org.uk, devicetree@...r.kernel.org,
	linux-arm-kernel@...ts.infradead.org, linux-kernel@...r.kernel.org,
	linux-pm@...r.kernel.org, linux-sunxi@...glegroups.com
Subject: Re: [linux-sunxi] [PATCH 2/4] power: add axp20x-battery driver

On Tue, 05 Jul 2016 16:47:38 +0800 Icenowy Zheng wrote:
> I read the datasheet of axp20x, and then found that this driver does
> not support backup RTC battery.
> (But maybe backup battery do not need a driver -- at least on IBM PC
> it has no driver)

A driver is needed to enable/disable the RTC battery charging (unless
uboot does it).
However all the driver can do according to datasheet is configure the
charge voltage/current or disable charging completely.
Monitoring RTC battery is not possible, neither is presence detection.

So driver should just apply configuration it finds in device-tree and
eventually share that information via power supply class.

> And I don't know whether the axp20x has default Li-ion/LiPo battery
> OCV parameter. (axp22x seems to be have a set of default OCV)

It seems to have default OCV parameters as well. With empty RTC
battery OCV values are present.

> You can test this driver on AXP20x. (I think I didn't access to
> AXP22x-specified registers in the power supply code)

Bruno