Serial Mux Mode in NPCM

Joel Stanley joel at
Fri Feb 9 12:43:03 AEDT 2018

Hey Eugene,

On Fri, Feb 9, 2018 at 7:32 AM,  <Eugene.Cho at> wrote:
> Any thoughts how we should handle the serial mux mode (SPMOD in SPSWC) in the NPCM? It seems we need to able to switch between modes runtime (as these are customer configurable options that can change at anytime).

Are we talking about the ability to have characters appear on
different ports on the back of a chassis if a user selects an option?
Or is this more about the system integrator deciding that UART2 goes
to connector X, and UART4 goes to connector Y?

Instead of me guessing, perhaps you describe what this looks like to the user?

> We use almost all the modes in some fashion...
> Could this be a handled like the 8250_aspeed_vuart.c? Maybe another simple sysfs driver? Thoughts?

The vuart driver is about exposing a normal Linux tty serial device
for the UART registers that are part of the LPC bus. This is mostly a
normal 8250 driver, with a pair of sysfs files that configure where
the device appears to the host.

It is then up to userspace (obmc-console) to shuffle characters
to/from that tty device to/from a software console (IPMI SoL", or a
ssh based "SoL"), a physical RS-232 port (exposed to Linux as another
tty device), or log it to a file.





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