xref: /openbmc/u-boot/doc/README.serial_multi (revision c66f5620)
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
5MPC8XX Specific
6===============
7At the moment, the ports must be split on a SMC and a SCC port  on  a
88xx processor; other configurations are not (yet) supported.
9
10Support for hardware handshake has not been implemented yet (but is
11in the works).
12
13*) The default console depends on the keys pressed:
14	- SMC if keys not pressed (modem not enabled)
15	- SCC if keys pressed (modem enabled)
16
17*) The console can be switched to SCC by any of the following commands:
18
19	setenv stdout serial_scc
20	setenv stdin serial_scc
21	setenv stderr serial_scc
22
23*) The console can be switched to SMC by any of the following commands:
24
25	setenv stdout serial_smc
26	setenv stdin serial_smc
27	setenv stderr serial_smc
28
29*) If a file descriptor is set to "serial" then the current serial device
30will be used which, in turn, can be switched by above commands.
31
32*) The baudrate is the same for all serial devices. But it can be switched
33just after switching the console:
34
35	setenv sout serial_scc; setenv baudrate 38400
36
37After that press 'enter' at the SCC console. Note that baudrates <38400
38are not allowed on LWMON with watchdog enabled (see CONFIG_SYS_BAUDRATE_TABLE in
39include/configs/lwmon.h).
40
41
42PPC4XX Specific
43===============
44*) The default console is UART0
45
46*) The console can be switched to UART1 by any of the following commands:
47	setenv stdout serial1
48	setenv stderr serial1
49	setenv stdin serial1
50
51*) The console can be switched to UART0 by any of the following commands:
52	setenv stdout serial0
53	setenv stderr serial0
54	setenv stdin serial0
55