From: Sarah Sharp
> On Wed, Jan 22, 2014 at 03:22:53PM -0800, walt wrote:
> > On 01/22/2014 12:56 PM, Sarah Sharp wrote:
> > > Walt, can you turn on xHCI debugging and look for whether the NEC host
> > > that worked with David's patch is a 1.0 host? You'll see a line like:
> > >
> > > // @%p = 0x%x (CAPLENGTH AND HCIVERSION)
> >
> > Hi Sarah. This is from the NEC host controller, *not* the ASMedia:
> >
> > [ 9.089178] xhci_hcd 0000:04:00.0: // @ffffc90004f88000 = 0x960020
> > (CAPLENGTH AND HCIVERSION)
>
> Ok, so that's also a 0.96 host, but it's not impacted by the no-op TRBs.
> Still, I think disabling the recently added code for everything but 1.0
> hosts makes sense.
Actually it might be best to use a urb flag to indicate that the request
isn't 'aligned', and only add the NOP for unaligned transfers.
There is already a usb device flag usb_device_no_sg_constraint() to indicate
that scatter gather transfers may be misaligned.
The only code that looks at it is the ax88179_178a ethernet driver.
There is, of course, no definition of what the 'constraint' is, but
I think all the other requests are in 4k+ blocks.
The only problem is that this requires simultaneous updates of the xhci
and usbnet code.
David
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