On Thu, Jun 02, 2016 at 11:07:25PM +0100, Gordan Bobic wrote: > 4.4.12 kernel introduces a regression that seems to break this. When > booting 4.4.12 with: > > earlycon=uart8250,mmio32,0x1c020000 > > it locks up solid before anything appears on the console output. [...] > Has anybody got any ideas on any extra troubleshooting or options to > be passed for initializing the UART that would produce a more > meaningful bug report? The cynic in me, supported by past > experience, suspects that if I file a bug on kernel.org it won't > even get triaged for months, if ever, especially since the problem > is manifesting on hardware few have access to. Although I don't think the underlying bug is related, I'll just note there is a similar thing happening with RHEL 7.3 kernels (which are 4.5.0 plus lots of backports from upstream): https://bugzilla.redhat.com/show_bug.cgi?id=1337705 The difference being I was able to get a stack trace using the same earlycon line you are using, and it turns out to be caused by PCI probing, I think reading from a non-existent config space address or device. Rich. -- Richard Jones, Virtualization Group, Red Hat http://people.redhat.com/~rjones Read my programming and virtualization blog: http://rwmj.wordpress.com virt-builder quickly builds VMs from scratch http://libguestfs.org/virt-builder.1.html