Re: ARC no console output (was Re: [PATCH 1/2] init/console: Use ttynull as a fallback when there is no console)

[Vineet Gupta]

On 1/7/21 7:48 PM, Sergey Senozhatsky wrote:
> On (21/01/07 09:58), Vineet Gupta wrote:
> > On 1/7/21 9:04 AM, Petr Mladek wrote:
> > > On Thu 2021-01-07 08:43:16, Vineet Gupta wrote:
> > > > Hi John,
> > > >
> > > > On 1/7/21 1:02 AM, John Ogness wrote:
> > > > > Hi Vineet,
> > > > >
> > > > > On 2021-01-06, Vineet Gupta <vgupta@xxxxxxxxxxxx> wrote:
> > > > > > This breaks ARC booting (no output on console).
> > > > >
> > > > > Could you provide the kernel boot arguments that you use? This series is
> > > > > partly about addressing users that have used boot arguments that are
> > > > > technically incorrect (even if had worked). Seeing the boot arguments of
> > > > > users that are not experiencing problems may help to reveal some of the
> > > > > unusual console usages until now.
> > > >
> > > >
> > > > Kernel command line: earlycon=uart8250,mmio32,0xf0005000,115200n8
> > > > console=ttyS0,115200n8 debug print-fatal-signals=1
> > >
> > > This is strange, the problematic patch should use ttynull
> > > only as a fallback. It should not be used when a particular console
> > > is defined on the command line.
> >
> > What happens in my case is console_on_rootfs() doesn't find /dev/console and
> > switching to ttynull. /dev is not present because devtmpfs doesn't automount
> > for initramfs.
>
> I wonder if we'll move the nulltty fallback logic into printk code [1]
> will it fix the problem?
>
> [1] https://lore.kernel.org/lkml/X6x%2FAxD1qanC6evJ@jagdpanzerIV.localdomain/

Your reasoning in the post above makes total sense.

I tired the patch: adding register_ttynull_console() call in 
console_device(), removing from console_on_rootfs() band that works too.


| Warning: unable to open an initial console. Fallback to ttynull.
| Warning: Failed to add ttynull console. No stdin, stdout, and stderr 
for the init process!
| Freeing unused kernel memory: 3096K
| This architecture does not have kernel memory protection.
| Run /init as init process
| with arguments:
|    /init
|  with environment:
|    HOME=/
|    TERM=linux
| Starting System logger (syslogd)
| Bringing up loopback device
| Starting inetd
| Mounting Posix Mqueue filesys
| 
CONFIG_INITRAMFS_SOURCE="~/arc/RAMFS/archs/ramfs_2011-GNU-2020-03-glibc-2.32-tiny"
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