Re: [Xen-users] serial console to Dom0 -- connection, but only 'garbage' (� , 'question mark') output. config wrong?

[PGNet Dev <pgnet.dev@xxxxxxxxx>]

On 1/31/20 4:45 PM, Sarah Newman wrote:
> But in newer versions of Xen the syntax you're using should be supported. 
> Looking at the source files docs/misc/xen-command-line.pandoc and 
> xen/drivers/char/ns16550.c, I think there's a problem with hyphens versus 
> underscores.
> 
> Try changing io_base to io-base in your command line.

i was just poking at that myself.

@ https://xenbits.xen.org/docs/4.13-testing/misc/xen-command-line.html#com1

it says

"The accepted name keywords for name=value pairs are:
    ...
    io-base - accepts integer which specified IO base port for UART registers
    ...
"

i.e., hyphenated. then, in the next comment,

        "
        The following are examples of correct specifications:
        
        com1=115200,8n1,0x3f8,4
        com1=115200,8n1,0x3f8,4,reg_width=4,reg_shift=2
        com1=baud=115200,parity=n,stop_bits=1,io_base=0x3f8,reg_width=4
        "

note, *all* underscores :-/

If I use underscores,

        com1=baud=115200,data_bits=8,parity=n,stop_bits=1,io_base=0x03e8,irq=3

the /dev/ttyS2 device *is* defined and probeable on boot.

OTOH, with hyphens, there's no /dev created.

Haven't yet found any *errors* abt it :-S

Need to take a look at the code myself & monkey with logging to understand 
what's right.

> I looked up the ttyS2 port and irq using
> 
> $ cat /sys/class/tty/ttyS2/device/resources
> state = active

here,

        cat /sys/class/tty/ttyS2/device/resources
                state = active
                io 0x3e8-0x3ef
                irq 3
                dma disabled

> serial --unit=2 --speed=115200
> terminal_input serial console
> terminal_output serial console

I mod'd  /etc/default/grub to

        GRUB_TERMINAL_INPUT="serial console "
        GRUB_TERMINAL_OUTPUT="serial console"
        GRUB_SERIAL_COMMAND="serial --unit=2 --speed=115200"

and, switched to the 'shorthand',

        GRUB_CMDLINE_XEN="com1=115200,8n1,0x03e8,3 console=com1,vga ..."

and updated the initrd.

verifying,

        grep serial /boot/grub2/grub.cfg
                serial --unit=2 --speed=115200
                terminal_input serial console
                terminal_output serial console

and

        grep com /boot/grub2/xen-4.13.0_04-lp151.688.cfg
                ... com1=115200,8n1,0x03e8,3 console=com1,vga

after reboot, there's unfortunately NO assigned UART

        setserial -g /dev/ttyS* | grep 03e8
                /dev/ttyS2, UART: unknown, Port: 0x03e8, IRQ: 3

and the /dev can't be written,

        /bin/stty -F /dev/ttyS2 115200 raw -echo
                /bin/stty: /dev/ttyS2: Input/output error

ok, confused.

now to unwind the changes and see why not.

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