Re: [PATCH 2/2] [RFC] pl2303 autosuspend

On Thu, Oct 25, 2007 at 02:35:20PM -0700, Greg KH wrote:
> On Thu, Oct 25, 2007 at 10:58:45AM -0700, Sarah Sharp wrote:
> > The other gotcha is that the pl2303 claims to support remote wakeup.  I haven't
> > found a good explanation on any datasheet I've seen about *when* remote wakeup
> > is triggered.  One datasheet for the pl2303-HX [1] lists a register RW_MODE that
> > if set to 0 "When engages remote wakeup, the device issues disconnect signal" or
> > if set to 1 "When engages remote wakeup, the device issues resume signal".  If
> > anyone can help me decode this, it would be appreciated.
> 
> True data sheets for this hardware are very hard to come by.  What you
> found at:
> 
> > [1]
> > http://www.prolific.com.tw/support/files/%5CIO%20Cable%5CPL-2303%5CDoc%5CData%20Sheet%5Cds_pl2303H_v16B.pdf
> 
> Is just the basic hardware spec, and the config register shows how the
> device could be configured at the factory through the internal i2c
> interface on the chip.
> 
> Rumor has it that you can read this information from the chip itself
> through a vendor-specific command, but I have not seen any public
> information on how to do that :(

I'll play around with remote wakeup with my pl2303 converters and see
what I can deduce.  I don't really know if allowing remote wake up is
useful.  If we've autosuspended the serial converter because all ttys
are closed, then no one cares about output from the device on the
other end.  Forcing a wakeup from system suspend might be a useful
thing, or waking up the converter to provide power to a device, but
really I'm just making guesses about the usage model. :)

> So, does this patch work for you with your devices?

My devices work fine after an autosuspend, but I think they won't work
after a suspend.  The urbs will get killed in the suspend function and
then won't get resubmitted in the resume function.  You don't notice in
the autosuspend case because the urbs are submitted when the tty is
opened.  So this patch not ready to be merged; I simply wanted comments
on it.

Sarah Sharp

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