Re: [PATCH 4/6] arm64/io: Provide a WC friendly __iowriteXX_copy()
From: Catalin Marinas <catalin.marinas@arm.com>
Date: 2024-02-27 10:38:00
Also in:
linux-arch, linux-patches, linux-rdma, linux-s390, llvm, netdev
On Tue, Feb 20, 2024 at 09:17:08PM -0400, Jason Gunthorpe wrote:
+/*
+ * This generates a memcpy that works on a from/to address which is aligned to
+ * bits. Count is in terms of the number of bits sized quantities to copy. It
+ * optimizes to use the STR groupings when possible so that it is WC friendly.
+ */
+#define memcpy_toio_aligned(to, from, count, bits) \
+ ({ \
+ volatile u##bits __iomem *_to = to; \
+ const u##bits *_from = from; \
+ size_t _count = count; \
+ const u##bits *_end_from = _from + ALIGN_DOWN(_count, 8); \
+ \
+ for (; _from < _end_from; _from += 8, _to += 8) \
+ __const_memcpy_toio_aligned##bits(_to, _from, 8); \
+ if ((_count % 8) >= 4) { \
+ __const_memcpy_toio_aligned##bits(_to, _from, 4); \
+ _from += 4; \
+ _to += 4; \
+ } \
+ if ((_count % 4) >= 2) { \
+ __const_memcpy_toio_aligned##bits(_to, _from, 2); \
+ _from += 2; \
+ _to += 2; \
+ } \
+ if (_count % 2) \
+ __const_memcpy_toio_aligned##bits(_to, _from, 1); \
+ })Do we actually need all this if count is not constant? If it's not performance critical anywhere, I'd rather copy the generic implementation, it's easier to read. Otherwise, apart from the __raw_writeq() typo that Will mentioned, the patch looks fine to me. -- Catalin _______________________________________________ linux-arm-kernel mailing list linux-arm-kernel@lists.infradead.org http://lists.infradead.org/mailman/listinfo/linux-arm-kernel