On Tuesday 18 December 2012 08:49:31 Andrew Turner wrote:
> Hello,
> 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 [1] 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.
> Andrew
> [1] http://fubar.geek.nz/files/freebsd/ehci_4.diff


Can you dump the DMA tag belonging to the QH via and check wether it is mapped 
coherent or not. Thes QH- and TD- structures should not be cache mapped. Else 
cache has not been disabled on those pages.


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