xref: /openbmc/u-boot/doc/README.serial_multi (revision a562e1bd)
1The support for multiple serial interfaces as implemented is mainly
2intended to allow for modem dial-in / dial-out while still being able
3to use a serial console on a (different) serial port.
4
5At the moment, the ports must be split on a SMC and a SCC port  on  a
68xx processor; other configurations are not (yet) supported.
7
8Support for hardware handshake has not been implemented yet (but is
9in the works).
10
11*) The default console depends on the keys pressed:
12	- SMC if keys not pressed (modem not enabled)
13	- SCC if keys pressed (modem enabled)
14
15*) The console can be switched to SCC by any of the following commands:
16
17	setenv stdout serial_scc
18	setenv stdin serial_scc
19	setenv stderr serial_scc
20
21*) The console can be switched to SMC by any of the following commands:
22
23	setenv stdout serial_smc
24	setenv stdin serial_smc
25	setenv stderr serial_smc
26
27*) If a file descriptor is set to "serial" then the current serial device
28will be used which, in turn, can be switched by above commands.
29
30*) The baudrate is the same for all serial devices. But it can be switched
31just after switching the console:
32
33	setenv sout serial_scc; setenv baudrate 38400
34
35After that press 'enter' at the SCC console. Note that baudrates <38400
36are not allowed on LWMON with watchdog enabled (see CFG_BAUDRATE_TABLE in
37include/configs/lwmon.h).
38