Re: USB 3.0 status in NetBSD-current?

[David Laight <david%l8s.co.uk@localhost>]

On Sun, Jun 15, 2014 at 06:30:22PM -0500, Jonathan A. Kollasch wrote:
> On Wed, Jun 11, 2014 at 05:47:28AM +0000, Thomas Mueller wrote:
> > Is there, or is there supposed to be, USB 3.0 support in the current kernel?
> > 
> > I see xhci in kernel config, but have not yet been able to access anything 
> > on a USB 3.0 port.
> 
> Use a USB 2.0 cable in between to force USB 2.0 speeds.

That may not help.
A USB2 cable should still leave you using the xhci driver - just at the
lower speed.

There is some 'magic' needed to hand over the port from ohci? to xhci
(which probably require correct parsing of ACPI data to work out which
usb2 port the xhci port is linked to).

If the port isn't handed over (ie no xhci support in the kernel) the
USB port should still run at USB2 speeds.

There are also significant differences between the xhci hardware.
Some of which are definitely bugs, some are probably documentedd bugs,
other are just the hardware engineers making life extremely difficult
for the software engineers.

For example:
The xhci controller supports arbitrary scatter gather except:
1) The maximum fragment size is 64k.
2) Fragments can't cross 64k address boundaries.
3) The end of a ring segment must happen at the end of a USB packet.

        David

-- 
David Laight: david%l8s.co.uk@localhost