linux-kernel - Re: [PATCH V2 2/2] power: twl4030_charger: attempt to power off in case of critical events

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Date:	Thu, 5 Jun 2014 01:30:40 +0300
From:	Grazvydas Ignotas <notasas@...il.com>
To:	Nishanth Menon <nm@...com>
Cc:	dbaryshkov@...il.com, Tony Lindgren <tony@...mide.com>,
	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
	Felipe Balbi <balbi@...com>,
	"linux-omap@...r.kernel.org" <linux-omap@...r.kernel.org>,
	dwmw2@...radead.org,
	"linux-arm-kernel@...ts.infradead.org" 
	<linux-arm-kernel@...ts.infradead.org>
Subject: Re: [PATCH V2 2/2] power: twl4030_charger: attempt to power off in
 case of critical events

On Wed, Jun 4, 2014 at 4:01 PM, Nishanth Menon <nm@...com> wrote:
> On 06/04/2014 05:04 AM, Grazvydas Ignotas wrote:
>> On Thu, May 29, 2014 at 12:46 AM, Nishanth Menon <nm@...com> wrote:
>>> Attempt to power off in case of critical events such as battery removal,
>>> over voltage events.
>>>
>>> There is no guarentee that we'd be in a safe scenario here, but the very
>>> least we can try to do is to power off the device to prevent damage to
>>> the system instead of just printing a message and hoping for the best.
>>
>> At least "battery temperature out of range" does seem to happen quite
>> often while charging on hot summer day. I'd prefer my pandora to not
>> shutdown in such case, it could just stop charging instead.
> Yeah, We could call
>   twl4030_charger_enable_ac(false);
>   twl4030_charger_enable_usb(bci, false);
>
> But then, is that sufficient?
> From the TRM:
> 7.5.8 Battery Temperature Out-of-Range Detection
> Battery temperature out-of-range detection detects whether the battery
> temperature is within a specific
> range. Detection is possible for two temperature ranges. When the
> battery temperature is not in the
> 2–50°C range or is in the 3–43°C range, the TBATOR1 and TBATOR2 status
> bits rise and an interrupt is
> generated.
> This MADC monitoring function can be enabled by writing to the
> TBATOR1EN (BCIMFEN2[3]) and
> TBATOR2EN (BCIMFEN2[1]) fields.
>
> Battery pack at high temperature is a risk, no? and it may not be just
> charger that might be causing such a condition. Is'nt it safer to shut
> the device down in such a case?

I don't know, so far nobody has complained about the battery exploding
and anybody getting hurt, but it would make the device unusable for
people in hot climates. From what I remember the automatic charge is
stopped automatically on this condition, as some people complained
they couldn't charge their device and saw these messages in dmesg. I
guess mainline could choose the safer option and shutdown, no strong
opinion about this.

-- 
Gražvydas
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