linux-kernel - Re: [PATCH] power_supply: Add driver for TWL4030/TPS65950 BCI charger

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Date:	Thu, 10 Dec 2009 16:09:08 +0200
From:	Grazvydas Ignotas <notasas@...il.com>
To:	felipe.balbi@...ia.com
Cc:	Anton Vorontsov <avorontsov@...mvista.com>,
	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
	Madhusudhan Chikkature <madhu.cr@...com>,
	"linux-omap@...r.kernel.org" <linux-omap@...r.kernel.org>
Subject: Re: [PATCH] power_supply: Add driver for TWL4030/TPS65950 BCI charger

On Thu, Dec 3, 2009 at 1:03 PM, Felipe Balbi <felipe.balbi@...ia.com> wrote:
> Hi,
>
> On Thu, Dec 03, 2009 at 11:55:12AM +0100, ext Grazvydas Ignotas wrote:
>>
>> TPS65950 is catalog part of TWL4030 and has documentation here:
>>
>> http://focus.ti.com/docs/prod/folders/print/tps65950.html#technicaldocuments
>>
>> It says that it is software's responsibility to detect the device and
>> set the right charge mode/current..
>
> yes, the BCI (or bq24xxx) will never be able to know which configuration we
> were enumerated with...
>
>>> yes, that'll work. But how about start charging always with 100mA and if
>>> userland sees that we were enumerated it reconfigures charging as
>>> necessary.
>>> But this would mean that we have the EM daemon started up just after the
>>> driver itself is loaded to avoid the problem with 100ms no enumeration.
>>> How
>>> does that sound ? Do we start making some writeable power_supply sysfs
>>> ???
>>
>> There are also USB chargers that don't enumerate and have D+ and D-
>> shorted with a resistor (see "dedicated charger port" in the charging
>> spec), how do we support those?
>
> dedicated chargers are simple. You kick the charger detection according to
> USB BC 1.x and if it returns true, you configure high current charging.
> Host/Hub chargers are also simple, after kicking charger detection, you
> enable Data pullups (e.g. SOFTCONN bit in musb's power register) and see if
> the host sends a setup packet...
>
> the complicated part is passing the information of which configuration you
> were enumerated with to the charger chip.

Ok since it doesn't look like this will resolve soon, what about
adding some DEVICE_ATTR for the time being and requiring userspace to
write charge current here to start actual charging?
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