Hello everyone. I'm trying to connect to a switch through a built-in to motherboard serial port using minicom. I have arch running on vanilla kernel. `zgrep -i serial /proc/config.gz` tells me that CONFIG_SERIAL_8250=y, but `dmesg | grep tty` shows only tty0 active. I can't see anything serial port related with neither lspci, lshw, nor lsusb.
I do have /dev/ttyS[0-3] but if I try to cat any of them it gives me input/output error. `setserial /dev/ttyS0` says "/dev/ttyS0, UART: unknown, Port: 0x03f8, IRQ: 4".
Setting uart to 8250 with setserial did not help :-\
I also tried starting agetty@ttyS0.service, no luck either.
It seems like it *should* work out-of-box. But I can't communicate with the switch :-\
Can someone please help me get the serial port working?
-> Hardware serial port
-> Vanilla kernel
-> `dmesg | grep tty` shows only tty0
-> `setserial /dev/ttyS0` says "/dev/ttyS0, UART: unknown, Port: 0x03f8, IRQ: 4"
-> cat: /dev/ttyS0: Input/output error
-> Minicom stays dark.
-> Thanks for help!
Last edited by Hexorg (2013-04-05 15:12:43)
Nevermind... Someone had serial port disabled in BIOS...
It looks like your system is expecting the serial port to exist on the old ISA bus. Most modern architectures use a LPC (Low Pin Count) bus to provide ISA bus services. The kernel sets up the four legacy MSDOS COM: ports of 0x3f8, 0x2f8, 0x3e8 and 0x02e8 sharing iqq's 3 and 4 and maps them to /dev/ttyS[[0-3]; regardless of whether there is really hardware there.
The question is: How is your serial port actually implemented? Do you know for certain that it is implemented as an legacy ISA device ? (Even though the hardware layer may be on the LPC bus?). If it is, is this a BIOS machine? Are the ports enabled in BIOS, mapped to the addresses the Linux kernel expects?
Any chance the serial ports are implemented on a USB or PCI bus interface instead?
Edit: Too slow.... At least I was on the right path
Last edited by ewaller (2013-04-05 15:13:12)
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