Subject: Re: Zaurus suspend saga
From: Stanislav Brabec <utx@penguin.cz>
To: Pavel Machek <pavel@ucw.cz>
Cc: Richard Purdie <rpurdie@rpsys.net>, lenz@cs.wisc.edu,
       kernel list <linux-kernel@vger.kernel.org>, Dirk@Opfer-Online.de,
       arminlitzel@web.de, Cyril Hrubis <metan@ucw.cz>, thommycheck@gmail.com,
       linux-arm-kernel <linux-arm-kernel@lists.arm.linux.org.uk>,
       dbaryshkov@gmail.com, omegamoon@gmail.com, eric.miao@marvell.com,
       Andrea Adami <andrea.adami@gmail.com>
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Date: Wed, 09 Sep 2009 11:28:12 +0200
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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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