On Tue, Apr 08, 2014 at 01:35:47AM +0100, Michael Bohan wrote: > On Fri, Feb 21, 2014 at 10:53:08AM +0000, Catalin Marinas wrote: > > On Fri, Feb 21, 2014 at 09:58:27AM +0000, Zhou Zhu wrote: > > > We faced one issue using memcpy for memory type DEVICE_nGnRnE > > > (pgprot_noncached). If the address is not aligned, exception would > > > happen due to the alignment of this type could not be handled by hardware. > > > > Indeed, that's expected. This memory type is the equivalent of Strongly > > Ordered. > > > > > Is there any plan and ongoing patch to support this or we need to keep > > > address aligned for memcpy using pgprot_noncached memory in drivers? > > > > You either change the memory type to pgprot_writecombine() or use the > > right API (memcpy_toio/memcpy_fromio, these could be further optimised, > > similar to powerpc for example, but I didn't get there yet). > > How should we handle Device Memory with copy_from_user / copy_to_user? > Should we follow the same scheme and create > copy_from_user_io / copy_to_user_io, or rather enforce that the stock > routines handle alignment? We have generic copy_from_user_toio() and copy_to_user_fromio(). Are these what you need? As with the memcpy_(to|from)io, they can be further optimised. -- Catalin -- To unsubscribe from this list: send the line "unsubscribe linux-arm-msm" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
