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

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Message-ID: <20091203110332.GO1361@nokia.com>
Date:	Thu, 3 Dec 2009 13:03:32 +0200
From:	Felipe Balbi <felipe.balbi@...ia.com>
To:	ext Grazvydas Ignotas <notasas@...il.com>
Cc:	"Balbi Felipe (Nokia-D/Helsinki)" <felipe.balbi@...ia.com>,
	ext 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

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.

-- 
balbi
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