xref: /openbmc/u-boot/doc/README.serial_multi (revision 281e00a3be453a169d854f824a460359d10f92bb)
1*281e00a3SwdenkThe support for multiple serial interfaces as implemented is mainly
2*281e00a3Swdenkintended to allow for modem dial-in / dial-out while still being able
3*281e00a3Swdenkto use a serial console on a (different) serial port.
4*281e00a3Swdenk
5*281e00a3SwdenkAt the moment, the ports must be split on a SMC and a SCC port  on  a
6*281e00a3Swdenk8xx processor; other configurations are not (yet) supported.
7*281e00a3Swdenk
8*281e00a3SwdenkSupport for hardware handshake has not been implemented yet (but is
9*281e00a3Swdenkin the works).
10*281e00a3Swdenk
11*281e00a3Swdenk*) The default console depends on the keys pressed:
12*281e00a3Swdenk	- SMC if keys not pressed (modem not enabled)
13*281e00a3Swdenk	- SCC if keys pressed (modem enabled)
14*281e00a3Swdenk
15*281e00a3Swdenk*) The console can be switched to SCC by any of the following commands:
16*281e00a3Swdenk
17*281e00a3Swdenk	setenv stdout serial_scc
18*281e00a3Swdenk	setenv stdin serial_scc
19*281e00a3Swdenk	setenv stderr serial_scc
20*281e00a3Swdenk
21*281e00a3Swdenk*) The console can be switched to SMC by any of the following commands:
22*281e00a3Swdenk
23*281e00a3Swdenk	setenv stdout serial_smc
24*281e00a3Swdenk	setenv stdin serial_smc
25*281e00a3Swdenk	setenv stderr serial_smc
26*281e00a3Swdenk
27*281e00a3Swdenk*) If a file descriptor is set to "serial" then the current serial device
28*281e00a3Swdenkwill be used which, in turn, can be switched by above commands.
29*281e00a3Swdenk
30*281e00a3Swdenk*) The baudrate is the same for all serial devices. But it can be switched
31*281e00a3Swdenkjust after switching the console:
32*281e00a3Swdenk
33*281e00a3Swdenk	setenv sout serial_scc; setenv baudrate 38400
34*281e00a3Swdenk
35*281e00a3SwdenkAfter that press 'enter' at the SCC console. Note that baudrates <38400
36*281e00a3Swdenkare not allowed on LWMON with watchdog enabled (see CFG_BAUDRATE_TABLE in
37*281e00a3Swdenkinclude/configs/lwmon.h).
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