[PATCH v3] console: use first console if stdout-path device doesn't appear

[Michael Ellerman]

Paul Burton <paul.burton at imgtec.com> writes:

> If a device tree specified a preferred device for kernel console output
> via the stdout-path or linux,stdout-path chosen node properties there's
> no guarantee that it will have specified a device for which we have a
> driver. It may also be the case that we do have a driver but it doesn't
> call of_console_check() to register as a preferred console (eg. offb
> driver as used on powermac systems).
>
> In these cases try to ensure that we provide some console output by
> enabling the first usable registered console, which we keep track of
> with the of_fallback_console variable. Affected systems will enable
> their console later than they did prior to commit 05fd007e4629
> ("console: don't prefer first registered if DT specifies stdout-path")
> but should otherwise produce the same output.
>
> Tested in QEMU with a PowerPC pseries_defconfig kernel.

Hi Paul,

This does "work", as in it boots and I get a console. But the delay in
getting output on the VGA is not workable. I get pretty much no output
until the machine is booted entirely to userspace, meaning any crash
prior to that will be undebuggable.

I also note Andreas reports it doesn't work at all on PowerMac.

Please send a revert and we can try again next cycle.

cheers