Serial Mux Mode in NPCM

Jeremy Kerr jk at
Wed Feb 14 14:50:17 AEDT 2018

Hi Eugene,

> 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). 
> 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?

Code to handle this would not be suitable as a UART driver; it handles
more than a simple UART "endpoint", so we'd need something distinct from
the existing tty device here. Perhaps a separate SoC driver?

However, you may not need dynamic reconfiguration of the UART routing,
depending on what configurations are available and your requirements. If
there's a routing configuration that feeds the necessary UARTs
(host-side and external ports) to the BMC CPU, then obmc-console-server
can handle all the routing in userspace, and you set that HW routing
configuration once on boot. This is what we currently do for phosphor



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