uboot/doc/README.serial_multi
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   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
  56MPC5xxx Specific
  57================
  58
  59Up to two PSCs can be used as console.
  60
  61Support for hardware handshake has not been implemented yet.
  62
  63*) The first (default) console port is defined by:
  64        #define CONFIG_PSC_CONSOLE <PSC number>
  65
  66*) The second (alternative) console port is defined by:
  67        #define CONFIG_PSC_CONSOLE2 <PSC number>
  68
  69*) Commands to switch to the second console:
  70        setenv stdout serial1
  71        setenv stderr serial1
  72        setenv stdin serial1
  73
  74*) Commands to switch to the first console:
  75        setenv stdout serial0
  76        setenv stderr serial0
  77        setenv stdin serial0
  78
  79*) If a file descriptor is set to "serial" then the
  80   current serial device will be used.
  81