Hello, I am running Lex 3I380CW motherboard equipped with Intel Atom E3845 CPU and six RS232 ports: [ 3.217402] Serial: 8250/16550 driver, 32 ports, IRQ sharing enabled [ 3.238139] 00:02: ttyS2 at I/O 0x3e8 (irq = 10, base_baud = 115200) is a 16550A [ 3.259009] 00:03: ttyS3 at I/O 0x2e8 (irq = 10, base_baud = 115200) is a 16550A [ 3.279869] 00:04: ttyS4 at I/O 0x4f8 (irq = 10, base_baud = 115200) is a 16550A [ 3.300733] 00:05: ttyS5 at I/O 0x4e8 (irq = 10, base_baud = 115200) is a 16550A [ 3.321579] 00:06: ttyS0 at I/O 0x3f8 (irq = 4, base_baud = 115200) is a 16550A [ 3.342424] 00:07: ttyS1 at I/O 0x2f8 (irq = 3, base_baud = 115200) is a 16550A I've found that ttyS1 (COM2) is never works for me with 4.19 and earlier. ttyS0, ttyS2, ttyS3 work fine. ttyS4 and ttyS5 don't have connectors wired and were not tested. I see the following notification from the kernel in logs: [ 11.110474] do_IRQ: 3.36 No irq handler for vector every time when run my test application [1] as the following: ./tty-test /dev/ttyS1 /dev/ttyUSB0 Appearance of the "No irq handler" line makes me to believe that this could be a kernel issue. The question is how could I further debug the issue? [1] https://gist.github.com/matwey/31c9bc6fd803d9f5178c1232df1f3af3
