linux-kernel - Re: Zaurus suspend saga

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Date:	Wed, 09 Sep 2009 11:28:12 +0200
From:	Stanislav Brabec <utx@...guin.cz>
To:	Pavel Machek <pavel@....cz>
Cc:	Richard Purdie <rpurdie@...ys.net>, lenz@...wisc.edu,
	kernel list <linux-kernel@...r.kernel.org>,
	Dirk@...er-Online.de, arminlitzel@....de,
	Cyril Hrubis <metan@....cz>, thommycheck@...il.com,
	linux-arm-kernel <linux-arm-kernel@...ts.arm.linux.org.uk>,
	dbaryshkov@...il.com, omegamoon@...il.com, eric.miao@...vell.com,
	Andrea Adami <andrea.adami@...il.com>
Subject: Re: Zaurus suspend saga

Pavel Machek wrote:

>Well, overnight charge (online) seems to result in pretty much empty
>battery...

Which kernel? I did the same in 2.6.26-RP and the battery was charged
overnight from about 60% to 100%.

I think that it is not possible to drain battery if an AC adapter
provides a sufficient voltage. But it's possible to disable charging by
a bad setting of the software.

>Is CHRG_ON pin reversed?

I am not sure, but it looks so. Both CHRG_ON resp. JK_B travel from
SCOOP PA pins to the gate of FET transistors with pull-up (probably
acts as an invertor and voltage converter) and end in EN resp. PRGM pins
of in the charging chip (SC801). You have to consult SC801 data sheet.

You can also verify both with a voltmeter connected to the battery.
CHRG_ON should cause rise of voltage on the battery pins. The rise
value should be dependent on JK_B.

Also both CP resp. STAT pins of SC801 travel through FET transistors
before it become AC_IN and CHRG_FULL.

> With my AA charger, I get "AC Status: 0", as long as battery is not
> full. It draws power for it (and battery percentage goes higher) but
> it is not even detected as charger :-(.

You have to have about 4.2V on the AC connector to get AC_IN. When
trying fast online charging, your AA charger must provide more than 4.2V
at possibly more than 1A current. Switching to slow charging, it
decreases to say >500mA online and 120mA offline. In the worst case,
your Zaurus may need nearly 2A.

You can hack the kernel to send CHRG_ON even if AC_IN is 0. But I am not
sure what will charging chip do then (data sheet will probably tell it
to you).

You can try to set SPITZ_SCP_JK_B to slow charging. Maybe voltage will
become sufficient.

> [But charge LED is lit. WTF?]

One pole of the LED is connected to AC power input, the seconds one to
the GPIO. So the logic is following:

IF (kernel says that LED should light) AND (there is sufficient voltage
on AC input) THEN (LED lights)

________________________________________________________________________
Stanislav Brabec
http://www.penguin.cz/~utx/zaurus

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