xhci: align the last trb before link if it is easily splittable.
TD fragments section 4.11.7.1 in xhci specs have additional requirements on how trbs in TDs must be organized. TD fragments shall not span transfer ring segments and TD fragments must be packet aligned. Normally we don't care about TD fragments, on TD is one big fragment, but if a TD spans ring segments it will be treated as two fragments, and we need to comply with the alignment requirements. For us this means that the payload data must be packet aligned in the last trb before a link trb. In most mass storage bulk tranfers we are lucky as the block size aligns nicely with packet size, and there are no issues. However, usb network adapters using scatterlists can hit this alignment issue, and usbtest in kernel triggers this in minutes. This patch is a partial solution, it solves the easy case when the last trb before the link trb contains a packet boundary. If that is the case then just split the trb at the boundary. If not, then just print a debug message and continue as we have always done, hoping for the best Signed-off-by:Mathias Nyman <mathias.nyman@linux.intel.com> Signed-off-by:
Greg Kroah-Hartman <gregkh@linuxfoundation.org>
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86065c27