On Tue, Feb 08, 2005 at 10:11:25AM -0800, David Brownell wrote:
> On Tuesday 08 February 2005 1:03 am, Andi Kleen wrote:
> >
> > BTW EHCI works, you just shouldn't use any USB 2.0 devices.
>
> That is, the root hub "switch to the companion controller"
> works, but not any other traffic? Then there's no point...
>
>
> > But there are valid reasons in some cases to want to have EHCI
> > even on a 8111, e.g. if you want to use the debug port.
>
> The debug devices are USB 2.0 devices though ... albeit odd
> ones!
My plan was to just drive a normal host2host cable through
debug port. It'll need some hacks, but should not be too bad.
>
>
> > It's annoying
> > to have to fight against such dumb code in the kernel then.
>
> Do you actually have a debug port driver for Linux? And some
> hardware that it can talk to?
Not yet. But I have(had) plans to write one. Unfortunately
it dropped back a bit on the todo list, so not too much has happened
yet:/
>
> I started looking at that issue a while back:
>
> - What model to use for it? OK, "console" for output is
> at least a (unidirectional) start; how about remote GDB?
Not sure I understand the q. (model?) My plan was to start with output
only, and then later implement receiving too.
>
> - But usually one wants consoles that start working well
> before PCI is initialized.
Early console is a different problem. The first goal is to
just get any console at all e.g. on laptops and those new desktops
who don't have a serial port anymore.
For early console you could always use early pci scanning
like the x86-64 code does for some things. It's possible, although
not very pretty. But it's a secondary step really.
>
> - The EHCI driver currently doesn't know how to share
> access to the debug port. ("mode 2" or whatever.)
It would need to be taught. Shouldn't be too hard.
> More hardware seems to come without serial ports lately, so
> it starts to look like Linux could benefit from a solution
> there. (Actually several, but the EHCI debug port option
Yes, a solution is badly needed.
-Andi
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