On Tue, Jul 18, 2017 at 9:02 AM, Jeffy Chen [off-list ref] wrote:

I was testing earlycon with 8250 dw serial console. And it hangs in
these cases:
1/ kernel hang when calling early write function after free_initmem:
a) the earlycon not disabled after the init code(due to keep_bootcon or
   not specify a real console to switch to)
b) the early write func is marked as __init, for example 8250_early.

This serial fix 1/ case only.

Here is another opinion.
I can tell that conditions to get into the trouble are quite unusual or rare.

Any rationale behind why one needs such a combination of parameters?

P.S. For doulble output ask Sergey and Petr (they are quite concerned
about it). Actually strange I didn't see their names in Cc list for
console related stuff,

-- 
With Best Regards,
Andy Shevchenko