Oleksandr and myself have been looking into why when we enable the
write-back cache on the PandaBoard there are kernel panics with USB. We
have tracked it down to an issue appending the ehci_qh_t to the list at
the end of ehci_setup_standard_chain().
I have a patch at  that allows me to run sha256 on a 40MB file over
NSF using the built in smsc USB ethernet chip. The problem is I have
had to place a call to DELAY before EHCI_APPEND_QH. This is obviously
not the correct solution.
Is anyone able to help me narrow down what is missing? It appears to be
a missing cache invalidate or flush somewhere but I haven't been able
to track down what cache function the DELAY is working around.
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