On Sun, Feb 12, 2017 at 05:45:06PM +0100, Wolfgang Schnitker wrote:

Dear serial developers,

my suggestion is now following:

My box has 3 physical serial IO ports, 1 on MB and 2 on PCI IO board.

dmesg | grep ttyS shows this:

(rmmod parport_serial and modprobe it again)

[    0.833923] 00:00: ttyS3 at I/O 0x2e8 (irq = 3, base_baud = 115200)
is a 16550A
[    9.498473] 0000:03:00.0: ttyS0 at I/O 0xcc00 (irq = 17, base_baud =
115200) is a 16550A
[    9.519894] 0000:03:00.0: ttyS1 at I/O 0xc880 (irq = 17, base_baud =
115200) is a 16550A
[   17.519943] ttyS0: LSR safety check engaged!
[   17.521182] ttyS0: LSR safety check engaged!
[   30.043754] ttyS0: LSR safety check engaged!
[   30.044734] ttyS0: LSR safety check engaged!
[   30.044956] ttyS0: LSR safety check engaged!
[   30.045153] ttyS0: LSR safety check engaged!
[   30.045344] ttyS0: LSR safety check engaged!
[   41.594802] ttyS0: LSR safety check engaged!
[  273.130756] 0000:03:00.0: ttyS1 at I/O 0xcc00 (irq = 17, base_baud =
115200) is a 16550A
[  273.153032] 0000:03:00.0: ttyS2 at I/O 0xc880 (irq = 17, base_baud =
115200) is a 16550A

ttyS3 is on the MB, ttyS0/S1 are the one on he IO card.

It happens right after activating LSR safety check.

[   16.522925] EXT4-fs (sda5): mounted filesystem with ordered data
mode. Opts: (null)
[   16.552462] EXT4-fs (sda7): mounted filesystem with ordered data
mode. Opts: errors=remount-ro
[   17.097626] systemd-journald[216]: Received request to flush runtime
journal from PID 1
[   17.519943] ttyS0: LSR safety check engaged!
[   17.521182] ttyS0: LSR safety check engaged!
[   17.523884] ------------[ cut here ]------------

So look up PCI values for this board:

03:00.0 Communication controller: MosChip Semiconductor Technology Ltd.
PCI 9835 Multi-I/O Controller (rev 01)
    Subsystem: LSI Logic / Symbios Logic 1P2S
    Control: I/O+ Mem+ BusMaster- SpecCycle- MemWINV- VGASnoop- ParErr-
Stepping- SERR+ FastB2B- DisINTx-
    Status: Cap- 66MHz- UDF- FastB2B+ ParErr- DEVSEL=medium >TAbort-
<TAbort- <MAbort- >SERR- <PERR- INTx-
    Interrupt: pin A routed to IRQ 17
    Region 0: I/O ports at cc00 [size=8]
    Region 1: I/O ports at c880 [size=8]
    Region 2: I/O ports at c800 [size=8]
    Region 3: I/O ports at c480 [size=8]
    Region 4: I/O ports at c400 [size=8]
    Region 5: I/O ports at c080 [size=16]
    Kernel driver in use: parport_serial
 

Please tell me, if you need more information.

What exactly is the problem here?