On 8 May 2010 06:30, Dr. H. Nikolaus Schaller <h...@computer.org> wrote:
> Does anyone have an idea (from a 2.4 kernel?) how we can command the power
> management chip to turn off power for the CPU and LCM? Does this go through
> a GPIO?
As you have surmised: watchdog for reset, gpio for power off.
I suggest you write a simple sysctl/proc hook that can be used to
whack specific gpio pins.
e.g.
echo "64" > /proc/gpio_high
would cause pin 64 to become an output logic high.
echo "64" > /proc/gpio_low
would cause pin 64 to become an output logic low.
Then you could write a script to loop through all the gpio, trying
them in turn to find out when the board powers off.
for i in `seq 1 120`; do
echo "trying $i high" > /home/foo/halt_attempt
echo $i > /proc/gpio_high
done
for i in `seq 1 120`; do
echo "trying $i low" > /home/foo/halt_attempt
echo $i > /proc/gpio_low
done
Its likely all sorts of peripherals will be disabled when you do this,
but it shouldn't cause any harm. I wouldn't make a habit of doing this
on random devices though, as its not beyond the realms of possibility
that a gpio is hooked to something dumb.
-Graham
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