linux-kernel - Re: [PATCH V2 1/2] power: twl4030_charger: detect battery presence prior to enabling charger

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Message-ID: <20140724063250.GG22006@atomide.com>
Date:	Wed, 23 Jul 2014 23:32:51 -0700
From:	Tony Lindgren <tony@...mide.com>
To:	Sebastian Reichel <sre@...nel.org>
Cc:	Nishanth Menon <nm@...com>, dbaryshkov@...il.com, balbi@...com,
	linux@....linux.org.uk, dwmw2@...radead.org,
	linux-arm-kernel@...ts.infradead.org, linux-kernel@...r.kernel.org,
	linux-omap@...r.kernel.org
Subject: Re: [PATCH V2 1/2] power: twl4030_charger: detect battery presence
 prior to enabling charger

* Sebastian Reichel <sre@...nel.org> [140723 05:05]:
> On Wed, Jul 23, 2014 at 02:24:20AM -0700, Tony Lindgren wrote:
> > * Nishanth Menon <nm@...com> [140528 14:48]:
> > > TWL4030's Battery Charger seems to be designed for non-hotpluggable
> > > batteries.
> > > 
> > > If battery is not present in the system, BATSTS is always set with the
> > > expectation that software will take actions to move to a required safe
> > > state (could be power down or disable various charger paths).
> > > 
> > > It does not seem possible even by manipulating the edge detection
> > > of the event (using BCIEDR2 register) to have a consistent hotplug
> > > handling. This seems to be the result of BATSTS interrupt generated
> > > when the thermistor of the battery pack is disconnected from the
> > > dedicated ADIN1 pin. Clearing the status just results in the status
> > > being regenerated by the monitoring ADC(MADC) and disabling the
> > > edges of event just makes hotplug no longer function. The only
> > > other option is to disable the detection of the MADC by disabling
> > > BCIMFEN4::BATSTSMCHGEN (battery presence detector) - but then, we can
> > > never again detect battery reconnection.
> > > 
> > > So, detect battery presence based on precharge(which is hardware
> > > automatic state) or default main charger configuration at the time of
> > > probe and enable charger logic only if battery was present.
> > > 
> > > Reported-by: Russell King <linux@....linux.org.uk>
> > > Tested-by: Tony Lindgren <tony@...mide.com>
> > > Signed-off-by: Nishanth Menon <nm@...com>
> > 
> > Dmitry, can we please get this first patch merged? This is needed
> > on some omap3 platforms for DT based booting when no battery is
> > present.
> > 
> > Only the second patch in this series is still being discussed AFAIK.
> 
> applied to battery-2.6.git:
> 
> http://git.infradead.org/battery-2.6.git/commit/61a7784efd3c89ffb6242f29bcee170dd7f55e6b

Thanks!

Tony
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