On 20 July 2016 at 07:44, Adrian Chadd <[email protected]> wrote: > Hi, > > dma coherent doesn't /have/ to mean "low 32 bits". It's just supposed > to mean "try really hard to use uncached memory on platforms that > support it."
Good point. Maybe it does on x86, or at least some machines. @Ben: Can you verify if that's the case for you? Can you see what address ranges hostmem chunks get with and without the GFP_DMA32 (and maybe compare it against a revert to compare to dma-coherent as well)? > The ath10k hardware (at least what I've played with thus far) is all > 32 bit DMA hardware, not 64 bit, so it can't be handed 64 bit memory - > contiguous or otherwise. > > So, if dma coherent on linux means 32 bit only physmem, great. > > Now, it also turns out that various platforms that say they do > coherent memory these days do "mostly coherent", and you still need > some flush/sync ops.. Yeah, but since the device has it's own CPU and RAM it has to have a way to distinguish local and host memory in some way using these 32 bits, no? (think about firmware generating local 802.11 frames vs pushing frames coming from host driver) Michał _______________________________________________ ath10k mailing list [email protected] http://lists.infradead.org/mailman/listinfo/ath10k
