Segher Boessenkool segher@kernel.crashing.org writes:
we are going to have to learn USB debug port. This problem is not going away.
The EHCI debug port requires slightly _more_ setup than plugin PCI 16550 cards do...
True. But it is generally available and you don't need DMA to use it. It would not too be hard for bring up to use a plug in PCI serial port card. But it doesn't solve the problem in general and you would have take out all of the serial port code when you are done.
Has anyone made in progress sorting out the EHCI USB debug port yet. I'm about 1/4 of the way from implementing kernel support. Currently I have just gotten as far as a user space client that can detect debug port support and send characters across. A low level driver you can use early I have yet to implement, possibly in the next couple of days. But if someone has done something I can compare notes with that would be great.
As far as LinuxBIOS goes going from a simple kernel driver to a driver you can use during memory initialization shouldn't be too hard. Just a little more setup.
Eric