arm64: optimize memcpy_{from,to}io() and memset_io()

Optimize memcpy_{from,to}io() and memset_io() by transferring in 64 bit as much as possible with minimized barrier usage. This simplest optimization brings faster throughput compare to current byte-by-byte read and write with barrier in the loop. Code's skeleton is taken from the powerpc. Link: http://lkml.kernel.org/p/20141020133304.GH23751@e104818-lin.cambridge.arm.com Reviewed-by: Catalin Marinas <catalin.marinas@arm.com> Reviewed-by: Trilok Soni <tsoni@codeaurora.org> Signed-off-by: Joonwoo Park <joonwoop@codeaurora.org> Signed-off-by: Will Deacon <will.deacon@arm.com>

Author: Joonwoo Park

arch/arm64/kernel/io.c

@@ -25,12 +25,26 @@
  */
 void __memcpy_fromio(void *to, const volatile void __iomem *from, size_t count)
 {
-unsigned char *t = to;
-while (count) {
+while (count && (!IS_ALIGNED((unsigned long)from, 8) ||
+ !IS_ALIGNED((unsigned long)to, 8))) {
+*(u8 *)to = __raw_readb(from);
+from++;
+to++;
 count--;
-*t = readb(from);
-t++;
+}
+
+while (count >= 8) {
+*(u64 *)to = __raw_readq(from);
+from += 8;
+to += 8;
+count -= 8;
+}
+
+while (count) {
+*(u8 *)to = __raw_readb(from);
 from++;
+to++;
+count--;
 }
 }
 EXPORT_SYMBOL(__memcpy_fromio);
@@ -40,12 +54,26 @@ EXPORT_SYMBOL(__memcpy_fromio);
  */
 void __memcpy_toio(volatile void __iomem *to, const void *from, size_t count)
 {
-const unsigned char *f = from;
-while (count) {
+while (count && (!IS_ALIGNED((unsigned long)to, 8) ||
+ !IS_ALIGNED((unsigned long)from, 8))) {
+__raw_writeb(*(volatile u8 *)from, to);
+from++;
+to++;
 count--;
-writeb(*f, to);
-f++;
+}
+
+while (count >= 8) {
+__raw_writeq(*(volatile u64 *)from, to);
+from += 8;
+to += 8;
+count -= 8;
+}
+
+while (count) {
+__raw_writeb(*(volatile u8 *)from, to);
+from++;
 to++;
+count--;
 }
 }
 EXPORT_SYMBOL(__memcpy_toio);
@@ -55,10 +83,28 @@ EXPORT_SYMBOL(__memcpy_toio);
  */
 void __memset_io(volatile void __iomem *dst, int c, size_t count)
 {
-while (count) {
+u64 qc = (u8)c;
+
+qc |= qc << 8;
+qc |= qc << 16;
+qc |= qc << 32;
+
+while (count && !IS_ALIGNED((unsigned long)dst, 8)) {
+__raw_writeb(c, dst);
+dst++;
 count--;
-writeb(c, dst);
+}
+
+while (count >= 8) {
+__raw_writeq(qc, dst);
+dst += 8;
+count -= 8;
+}
+
+while (count) {
+__raw_writeb(c, dst);
 dst++;
+count--;
 }
 }
 EXPORT_SYMBOL(__memset_io);