Re: [PATCH 002/002] de2104x: support for systems lacking cache coherence

[Krzysztof Halasa <khc@pm.waw.pl>]

Risto Suominen <risto.suominen@gmail.com> writes:

>> 1) {pci,dma}_alloc_{consistent,coherent}() give kernel mappings of
>>   the buffer with the cache disabled.
                ^^^^^^^^^^^^^^^^^^^^^^^

> Sounds good, but does not seem to help. My theory is that when the cpu
> is writing to one descriptor, it accidentally overwrites another
> descriptor, that has already been written to by the device, as there
> is only a single dirty bit, that makes the whole cacheline to be
> flushed.

That means the consistent/coherent mapping isn't really
consistent/coherent (uncached), right? Perhaps there is some way to fix
this instead of changing the drivers to avoid the problematic area?

Potentially any driver is affected by such coherency problem, this can't
be specific to 21040.
-- 
Krzysztof Halasa