Re: wake up from a serial port

From: Guennadi Liakhovetski
Date: Thu Sep 13 2007 - 16:29:19 EST


On Wed, 12 Sep 2007, Michael Mauch wrote:

> Guennadi Liakhovetski wrote:
>
> > Enable wakeup from serial ports, make it run-time configurable over sysfs,
> > e.g.,
> >
> > echo enabled > /sys/devices/platform/serial8250.0/tty/ttyS0/power/wakeup
>
> Interesting, but how does that work from a user's/hardware perspective?
>
> Do I have to pull DSR/RI to +12V? Can I use one of the other pins to get
> these +12V (i.e. a switch and a resistor to shorten these pins is
> enough)?
>
> And probably in the BIOS I have to enable "wake on modem ring" (or
> something similar)?

It depends on the hardware. In principle, with this patch _if_ your system
can suspend while keeping the UART powered on and the interrupt from this
UART can wake up your system, then using this patch and the command above
you'll be able to also keep the UART configured, i.e., prevent the driver
from suspending it during suspend and then an interrupt from this UART
will wake up the system. How you generate this interrupt - doesn't matter.
Whether it is a received byte, or a modem line toggle, as long as it
produces an interrupt, the system will wake up.

Don't know whether "normal" PCs can do that and if yes - how.

Thanks
Guennadi
---
Guennadi Liakhovetski
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