ioremap_wc on arm64
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Cover letter [PATCH 0/2] ioremap_wc on arm64
Quoted 6 lines · Catalin Marinas
Quoted 5 lines · Jayachandran C
From its definition, the device "gather" attribute seems to be a better fit for implementing write combining mapping in
ioremap_wc(). And on ThunderX2, Device GRE mapping has optimizations that makes it much faster than normal uncached mapping.
Quoted 6 lines
Quoted 3 lines
I am not sure of the reasoning behind the original decision to make
ioremap_wcuse "Normal Non-Cached" attribute, since all the other variants of ioremap use device attributes, andioremap_wclooks like an exception.The reason we kept it as Normal NC is that
Device_GREdoes not allow unaligned accesses.
There does not to be an expectation to have unaligned access on __iomem pointers. I also see that memremap can call ioremap_wc (which is a Normal mapping) or ioremap_wt(which is a Device mapping), so that is inconsistent as well.
Was this added for a specific use case? Also, do you think this patchset is acceptable?
Thanks,
JC.