memcpy alignment for DEVICE_nGnRnE

Catalin Marinas catalin.marinas at
Fri Feb 21 05:53:08 EST 2014

Hi Zhou,

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

> 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).


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