the imfamous asix ax88179 iommu error

[David Laight]

> >> It appears that my ax88179 is working just fine now with the vendor
> >> driver. So perhaps it's possible to revert the old commit in the linux
> >> kernel and allow the use of scatter gather ? (perhaps for non-intel
> >> hosts ? I'm not sure if this device is effected by intel xhci errata)
> >
> > Thanks for the tip-off - as luck would have it I have an AX88179 dongle
> > to hand! Does the out-of-tree driver behave significantly differently to
> > the mainline driver (CONFIG_USB_NET_AX88179_178A)?
> 
> To answer myself - yes, the out-of-tree driver produces all manner of
> >PAGE_SIZE offsets for dma_map_sg():
> 
> ...
> [  571.019335] xhci_hcd 0000:04:00.0: ####### sg->offset = 0x7770
> [  571.025497] xhci_hcd 0000:04:00.0: ####### sg->offset = 0x7a60
> [  571.031402] xhci_hcd 0000:04:00.0: ####### sg->offset = 0x1100
> [  571.037353] xhci_hcd 0000:04:00.0: ####### sg->offset = 0x1c50
> [  571.043254] xhci_hcd 0000:04:00.0: ####### sg->offset = 0x27a0

I remember a load of XHCI patches I had that were needed to get the
AX88179 working reliably
I think most of the ones to do with the TRB boundaries and ZLP have
been fixed now.
There was a problem with an ASMedia host controller (1b21:1042) that
it needed the command ring doorbell rung in the command completion
code in order to process a second command.
Not sure I've seen a fix for that.
I've still got the host system, but not the dongle.

	David