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

From: Larry Finger
Date: Mon Nov 07 2016 - 10:26:46 EST

On 11/07/2016 03:18 AM, Paul Burton wrote:
On Monday, 7 November 2016 19:27:32 GMT Michael Ellerman wrote:
Paul Burton <paul.burton@xxxxxxxxxx> 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.


Hi Michael,

A revert was already submitted by Hans de Goede & is being discussed over

I am a little surprised that I was not CCd on that thread. To reiterate, my PowerBook G4 with a PPC32 processor CRASHES on boot. That is a lot more serious than the console output disappearing.

As it seems unlikely that this regression will be fixed in the current cycle, I recommend that the reversion of commit 05fd007e4629 until a proper fix is available.