Problem with console without console=ttyS0 bootarg

[mans0n at gorani.run]

Hi Rafał,

On 2021-01-21 16:57, zajec5 at gmail.com (Rafał Miłecki) wrote:> On 
21.05.2017 22:22, Rafał Miłecki wrote:
>> On 14 March 2017 at 07:37, Rafał Miłecki <zajec5 at gmail.com> wrote:
>>> My current DTS file contains following entry:
>>> bootargs = "console=ttyS0,115200"
>>> and it works in a following way:
>>>
>>> Press the [f] key and hit [enter] to enter failsafe mode
>>> Press the [1], [2], [3] or [4] key and hit [enter] to select the debug level
>>> [    9.320212] procd: - early -
>>> [    9.323174] procd: - watchdog -
>>> [    9.924724] procd: - ubus -
>>> [    9.986055] procd: - init -
>>> Please press Enter to activate this console.
>>> === WARNING! =====================================
>>> There is no root password defined on this device!
>>> Use the "passwd" command to set up a new password
>>> in order to prevent unauthorized SSH logins.
>>> --------------------------------------------------
>>> root at LEDE:/#
>>>
>>>
>>>
>>> If I enable "ttylogin" in /etc/config/system it works quite similarly (just
>>> asks for a login):
>>>
>>> Press the [f] key and hit [enter] to enter failsafe mode
>>> Press the [1], [2], [3] or [4] key and hit [enter] to select the debug level
>>> [    9.362481] procd: - early -
>>> [    9.365550] procd: - watchdog -
>>> [    9.983522] procd: - ubus -
>>> [   10.044877] procd: - init -
>>> Please press Enter to activate this console.
>>> LEDE login:
>>> LEDE login: root
>>> === WARNING! =====================================
>>> There is no root password defined on this device!
>>> Use the "passwd" command to set up a new password
>>> in order to prevent unauthorized SSH logins.
>>> --------------------------------------------------
>>> root at LEDE:~#
>>>
>>>
>>> My problem appears when I drop bootargs and use:
>>> stdout-path = "/chipcommonA/serial at 0300:115200";
>>> instead (which is a non-deprecated DTS solution).
>>> In such case I can't login anymore:
>>>
>>> Press the [f] key and hit [enter] to enter failsafe mode
>>> Press the [1], [2], [3] or [4] key and hit [enter] to select the debug level
>>> [    9.340180] procd: - early -
>>> [    9.343141] procd: - watchdog -
>>> [    9.944758] procd: - ubus -
>>> [   10.006092] procd: - init -
>>>
>>>
>>> Do you know what's the reason for this? Can we have a proper console support
>>> while using upstream preferred syntax for the stdout-path?
>>> Please note entering failsafe mode it not affected by this.
>>
>> Since noone got idea how to handle this, I added workaround as for now
>> in commit 0a05fbd135663 ("bcm53xx: add support for TP-LINK Archer C5
>> V2")
>> https://git.lede-project.org/?p=source.git;a=commit;h=0a05fbd1356631a1f903adcd63ffb05550537667
>>
>> You can find it in the 320-ARM-dts-BCM5301X-Add-serial-to-the-bootargs.patch
> 
> I hit this problem again while working on the bcm4908 target. This time I
> debugged it. It's caused by the procd's askconsole(). That function requires
> console device (e.g. ttyS0) to be specified in cmdline's console.
> 
> I don't know how to fix it. Reading "stdout-path" from "chosen" will return
> "serial0:115200n8". Then it's possible to read "serial0" alias which points
> to some DT node (e.g. /bus at ff800000/serial at 640).
> 
> The problem I have is that my /bus at ff800000/serial at 640 doesn't reference
> /dev/ttyS0 anyhow.
> 

Last year I've also encountered that problem and reached exactly the 
same conclusion.
I wanted to (and would still like to) add support for "stdout-path" to 
askconsole(), but I didn't know how to handle that nicely, so I ditched 
it and forgot about it.

Now you mention it, I had a look at it again briefly. Anyway, we need a 
way to translate DTS node to actual device for the deprecated "label" 
property of gpio-led...
https://github.com/openwrt/openwrt/pull/3437

Maybe we can make use of sysfs here, but this seems a little bit 
complicated and I'm not sure if this always returns the right answer.

root at OpenWrt:/# cat /sys/firmware/devicetree/base/chosen/stdout-path; echo
serial0:115200n8
root at OpenWrt:/# cat /sys/firmware/devicetree/base/aliases/serial0; echo
/ocp at f1000000/serial at 12000
root at OpenWrt:/sys/class/tty# find /sys/class/tty/*/device/of_node
/sys/class/tty/ttyS0/device/of_node
root at OpenWrt:/sys/class/tty# readlink -f /sys/class/tty/ttyS0/device/of_node
/sys/firmware/devicetree/base/ocp at f1000000/serial at 12000

Or perhaps can we just use /dev/console here? It seems to be linked to 
the actual serial port, but I don't know if this applies to all devices...

So this is just my guess, sorry if this does not really help you.

Thanks.