[coreboot] Super I/O: Winbond LPC Super I/O WPCN381U

Jeremy Moles cubicool at gmail.com
Thu Apr 7 17:16:13 CEST 2011

Hey guys--I hate to bump this so soon, but my current project is pretty
much stalled without being able to approach this issue one way or

Does anyone have any good documentation I can read to learn how to
interact with (either in userspace or kernel-level) LPC devices,
specifically the PC87381 Super I/O device? Perhaps there's some code in
coreboot demonstrating how GPIO ports are manipulated?

On Mon, 2011-04-04 at 19:07 -0400, Jeremy Moles wrote:
> Hello everyone.
> I have my hands on a piece of hardware here using the Super I/O device
> listed in the subject; that is:
> 	Winbond LPC Super I/O WPCN381U
> - My first question is, has anyone else encountered this device?
> - SVN trunk of superiotool detects this device as:
> 	Found NSC PC87382 (sid=0xf4, srid=0x04) at 0x2e
> ...and I know from the manufacturer that the device is actually the one
> mentioned previously. However, I know from the specsheet that the
> hardware is pin-compatible with the Winbond PC87381, which has a very
> similar name to the device it "thinks" it is.
> http://www.winbond-usa.com/products/winbond_products/pdfs/APC/WPCN381U_pba.pdf
> Does this mean that superiotool is actually detecting it properly?
> - Finally, the device I want to use waits for input via the serial port,
> but before this can be initiated the device must be powered on via the
> Super I/O module. According to the manufacturer, I do this by activating
> the GPIO03 pin. I know superiotool is a read-only tool, given I know
> these pieces of data, is there an easy way to ping this particular bit?
> - My first approach to enable this device was to write a small kernel
> module that would call gpio_request(3); however, this always returns
> -ENOSYS or -EINVAL. This clearly isn't the right approach. :)
> I realize this is probably a question for LKML proper, but I figured I'd
> ask here first and see what the Fates have in store. :)

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