Re: Grub2 UEFI boot and serial console output

[Matwey V. Kornilov]

2017-01-14 10:55 GMT+03:00 Andrei Borzenkov <address@hidden>:
> 13.01.2017 19:40, Matwey V. Kornilov пишет:
>> 2017-01-13 16:44 GMT+03:00 Andrei Borzenkov <address@hidden>:
>>> 13.01.2017 12:03, Matwey V. Kornilov пишет:
>>>> 2017-01-11 20:16 GMT+03:00 Andrei Borzenkov <address@hidden>:
>>>>> 11.01.2017 19:55, Matwey V. Kornilov пишет:
>>>>>> 2017-01-11 19:45 GMT+03:00 Andrei Borzenkov <address@hidden>:
>>>>>>> 11.01.2017 16:27, Matwey V. Kornilov пишет:
>>>>>>>> Hello,
>>>>>>>>
>>>>>>>> What is the proper way to output GRUB2 menu to serial rs232 console 
>>>>>>>> when
>>>>>>>> UEFI boot is used? I've copy-pasted GRUB_SERIAL_COMMAND="serial 
>>>>>>>> --unit=0
>>>>>>>> --speed=115200" from Google because I didn't find anything else. It
>>>>>>>> doesn't work.
>>>>>>>> Now, reading grub sources, I see that the proper way should probably be
>>>>>>>> something like GRUB_SERIAL_COMMAND="serial efi0".
>>>>>>>>
>>>>>>>
>>>>>>> This is platform dependent. --unit=0 refers to COM1 on PC BIOS platform.
>>>>>>> On EFI grub is using EFI Serial I/O Protocol and enumerates all handles
>>>>>>> with this protocol using efiXX names. Then there is USB serial driver,
>>>>>>> ARC and IEEE1275 where names are provided by firmware etc.
>>>>>>
>>>>>> I just can't understand, term/serial.c: grub_cmd_serial() sets name to
>>>>>> "com%ld" using --unit=value on any platform.
>>>>>>
>>>>>>   if (state[OPTION_UNIT].set)
>>>>>>     {
>>>>>>       grub_snprintf (pname, sizeof (pname), "com%ld",
>>>>>>                      grub_strtoul (state[0].arg, 0, 0));
>>>>>>       name = pname;
>>>>>>    }
>>>>>>
>>>>>> Then this "com0" is put to grub_serial_find(name) call. The question
>>>>>> is how this is going to match with "efi0"?
>>>>>
>>>>> It is not.
>>>>>
>>>>>> Please correct me, if I am wrong.
>>>>>>
>>>>>
>>>>> Again - "--unit=0" is simply alias for "com0". Whether device with name
>>>>> "com0" actually exists depends on platform and loaded drivers.
>>>>>
>>>>> This alias makes no sense on platform that does not include ns8250
>>>>> driver that provides access to device with name "com0". You can check
>>>>> grub-core/Makefile.core.def which platforms include this driver.
>>>>>
>>>>> So on EFI you are not going to use --unit=0 (or you need to add some
>>>>> platform-dependent magic to translate --unit=0 into platform device).
>>>>>
>>>>> And yes, this could use better documentation, both for "serial" command
>>>>> and "Serial terminal" section.
>>>>
>>>> Thank you.
>>>> "serial --speed=115200 efi0" also doesn't work.
>>>
>>> Please define "does not work". What you expect it to do and how you
>>> verify it?
>>>
>>
>> I expect that it will show grub menu on serial port where I wait for
>> it. I believe that the port itself is working because I see linux
>> kernel console output redirected to serial after grub timeout.
>>
>>>> It seems that there is no Serial IO protocol in my Insyde UEFI.
>>>>
>
> You can verify it by loading EFI Shell, and looking in devtree output

It says

Ctrl[186] PciRoot(0x0)/Pci(0x1F,0x0)/Serial(0x0)/Uart(115200,8,N,1)
  Ctrl[187] PC-ANSI Serial Console

> for something like "ISA Serial Port" or similar. You can also list all
> handles with bound Serial IO protocol using
>
> dh -p SerialIO
>

Handle dump by protocol 'SerialIO'
 186: DevPath (..rial(0x0)/Uart(115200,8,N,1))SerialIO
 188: DevPath (..rial(0x0)/Uart(115200,8,N,1))SerialIO

>
>>>
>>> What is output of "terminal_input" and "terminal_output"?
>>>
>>>
>>
>> serial --speed=115200 efi0
>> terminal_input serial
>> terminal_output serial
>>
>
> Well, it is messy indeed. First, I was wrong, and ns8250 driver is
> compiled on EFI x86 platforms. Do you have x86 or ARM system?
>
> Second, terminal names to use with "terminal_input" and
> "terminal_output" are "serial_efi0" for port "efi0". Do you get any
> error from the commands you listed?
>
> Third, "serial" is alias to the first used ns8250 port. So
>
> serial --unit=0
> terminal_input serial
>
> *will* work because the first command makes "serial" alias for
> "serial_com0". But your commands will *not* work because they configure
> port "efi0" but attempt to use port "com0" instead. May be we should
> extend handling and make "serial" consistently to be alias for the first
> used port, so the above sequence would work on each platform.
>
> Finally I am not whether we should support direct hardware access with
> ns8250 on EFI at all.
>
> Here is what I get on x86 OVMF.
>
>
> grub> lsmod
> Name    Ref Count       Dependencies
> minicmd 1
> normal  1               gettext,boot,extcmd,bufio,crypto,terminal
> gzio    0
> gettext 2
> extcmd  2
> crypto  2
> terminal        2
> tar     1               archelp
> archelp 2
> memdisk 1
> efinet  1               net
> net     2               boot,datetime,bufio,priority_queue
> priority_queue  3
> bufio   5
> datetime        3
> boot    5
> grub> terminal_input
> Active input terminals:
> console
> Available input terminals:
> serial_* serial at_keyboard
> grub> serial --speed=115200 efi0
> grub> lsmod
> Name    Ref Count       Dependencies
> serial  1               terminfo,extcmd
> terminfo        2               extcmd
> minicmd 1
> normal  1               gettext,boot,extcmd,bufio,crypto,terminal
> gzio    0
> gettext 2
> extcmd  7
> crypto  2
> terminal        2
> tar     1               archelp
> archelp 2
> memdisk 1
> efinet  1               net
> net     2               boot,datetime,bufio,priority_queue
> priority_queue  3
> bufio   5
> datetime        3
> boot    5
> grub> terminal_input
> Active input terminals:
> console
> Available input terminals:
> serial_efi0 serial_com0 serial at_keyboard
> grub> terminal_output
> Active output terminals:
> console
> Available output terminals:
> serial_efi0 serial_com0 spkmodem serial gfxterm cbmemc audio
> grub> serial --unit=0 --speed=115200
> grub> serial --unit=1 --speed=115200
> error: serial port `com1' isn't found.
>
> Note, I am not sure whether use "serial_com0" will actually work, as it
> obviously competes with EFI for hardware access so result may be
> unpredictable.

I think here is my issue:

terminal_input says that 'console' is active terminal and no other
terminals available.

serial --speed=115200 efi0 says "can't find command `serial'"

-- 
With best regards,
Matwey V. Kornilov
http://blog.matwey.name
xmpp://address@hidden