xref: /openbmc/u-boot/doc/README.serial_multi (revision 064b55cfcb25c0f7692ecf6d4a38f12cd82739f7)
1281e00a3SwdenkThe support for multiple serial interfaces as implemented is mainly
2281e00a3Swdenkintended to allow for modem dial-in / dial-out while still being able
3281e00a3Swdenkto use a serial console on a (different) serial port.
4281e00a3Swdenk
5ff36fd85SwdenkMPC8XX Specific
6ff36fd85Swdenk===============
7281e00a3SwdenkAt the moment, the ports must be split on a SMC and a SCC port  on  a
8281e00a3Swdenk8xx processor; other configurations are not (yet) supported.
9281e00a3Swdenk
10281e00a3SwdenkSupport for hardware handshake has not been implemented yet (but is
11281e00a3Swdenkin the works).
12281e00a3Swdenk
13281e00a3Swdenk*) The default console depends on the keys pressed:
14281e00a3Swdenk	- SMC if keys not pressed (modem not enabled)
15281e00a3Swdenk	- SCC if keys pressed (modem enabled)
16281e00a3Swdenk
17281e00a3Swdenk*) The console can be switched to SCC by any of the following commands:
18281e00a3Swdenk
19281e00a3Swdenk	setenv stdout serial_scc
20281e00a3Swdenk	setenv stdin serial_scc
21281e00a3Swdenk	setenv stderr serial_scc
22281e00a3Swdenk
23281e00a3Swdenk*) The console can be switched to SMC by any of the following commands:
24281e00a3Swdenk
25281e00a3Swdenk	setenv stdout serial_smc
26281e00a3Swdenk	setenv stdin serial_smc
27281e00a3Swdenk	setenv stderr serial_smc
28281e00a3Swdenk
29281e00a3Swdenk*) If a file descriptor is set to "serial" then the current serial device
30281e00a3Swdenkwill be used which, in turn, can be switched by above commands.
31281e00a3Swdenk
32281e00a3Swdenk*) The baudrate is the same for all serial devices. But it can be switched
33281e00a3Swdenkjust after switching the console:
34281e00a3Swdenk
35281e00a3Swdenk	setenv sout serial_scc; setenv baudrate 38400
36281e00a3Swdenk
37281e00a3SwdenkAfter that press 'enter' at the SCC console. Note that baudrates <38400
38*6d0f6bcfSJean-Christophe PLAGNIOL-VILLARDare not allowed on LWMON with watchdog enabled (see CONFIG_SYS_BAUDRATE_TABLE in
39281e00a3Swdenkinclude/configs/lwmon.h).
40ff36fd85Swdenk
41ff36fd85Swdenk
42ff36fd85SwdenkPPC4XX Specific
43ff36fd85Swdenk===============
44ff36fd85Swdenk*) The default console is UART0
45ff36fd85Swdenk
46ff36fd85Swdenk*) The console can be switched to UART1 by any of the following commands:
47ff36fd85Swdenk	setenv stdout serial1
48ff36fd85Swdenk	setenv stderr serial1
49ff36fd85Swdenk	setenv stdin serial1
50ff36fd85Swdenk
51ff36fd85Swdenk*) The console can be switched to UART0 by any of the following commands:
52ff36fd85Swdenk	setenv stdout serial0
53ff36fd85Swdenk	setenv stderr serial0
54ff36fd85Swdenk	setenv stdin serial0
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