linux-kernel - Re: [PATCH v2 2/3] bq2415x_charger: Use power

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Message-ID: <20131125171420.GA12995@earth.universe>
Date:	Mon, 25 Nov 2013 18:14:21 +0100
From:	Sebastian Reichel <sre@...g0.de>
To:	Ивайло Димитров 
	<freemangordon@....bg>
Cc:	Pavel Machek <pavel@....cz>, pali.rohar@...il.com,
	anton@...msg.org, dwmw2@...radead.org, tony@...mide.com,
	linux@....linux.org.uk, linux-kernel@...r.kernel.org,
	linux-omap@...r.kernel.org, aaro.koskinen@....fi
Subject: Re: [PATCH v2 2/3] bq2415x_charger: Use power_supply notifier for
 automode

On Mon, Nov 25, 2013 at 07:01:54PM +0200, Ивайло Димитров wrote:
>> Now.. Imagine phone left in car in charger (on sun). Likely
>> temperature will reach high values, kernel is charging, dsme will
>> reboot the system, but kernel will start charging again, dsme will
>> reboot again, ...
>>
>> And it is not only high temperatures that are problem for li-ion
>> charging; battery should not be fast charged below 5C and should not
>> be charged below 0C. (Again, both are likely to happen if you leave
>> your phone in car).
>>
>> AFAICT, we should simply disable charging below 5C or above 45C.
> 
> AFAIK dsme will not restart it, but power it off, so the above
> scenario won't happen.

Just assume what happens, when dsme does not start (e.g. system boot
hangs).

If everything is controlled from userspace, charger would not start
(-> safe!). If everything is controlled by the kernel, temperature
safety checks are taken (-> safe!). But in the currently proposed
variant: No safety checks.

-- Sebastian


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