[profile] Standardise return type of profile_timestamp()

All consumers of profile_timestamp() currently treat the value as an
unsigned long.  Only the elapsed number of ticks is ever relevant: the
absolute value of the timestamp is not used.  Profiling is used to
measure short durations that are generally fewer than a million CPU
cycles, for which an unsigned long is easily large enough.

Standardise the return type of profile_timestamp() as unsigned long
across all CPU architectures.  This allows 32-bit architectures such
as i386 and riscv32 to omit all logic associated with retrieving the
upper 32 bits of the 64-bit hardware counter, which simplifies the
code and allows riscv32 and riscv64 to share the same implementation.

Signed-off-by: Michael Brown <mcb30@ipxe.org>

1 files changed, 28 insertions, 0 deletions

diff --git a/src/arch/riscv/include/bits/profile.h b/src/arch/riscv/include/bits/profile.h
new file mode 100644
index 000000000..e9e003dab
--- /dev/null
+++ b/src/arch/riscv/include/bits/profile.h
@@ -0,0 +1,28 @@
+#ifndef _BITS_PROFILE_H
+#define _BITS_PROFILE_H
+
+/** @file
+ *
+ * Profiling
+ *
+ */
+
+FILE_LICENCE ( GPL2_OR_LATER_OR_UBDL );
+
+#include <stdint.h>
+
+/**
+ * Get profiling timestamp
+ *
+ * @ret timestamp	Timestamp
+ */
+static inline __attribute__ (( always_inline )) unsigned long
+profile_timestamp ( void ) {
+	unsigned long cycles;
+
+	/* Read timestamp counter */
+	__asm__ __volatile__ ( "rdcycle %0" : "=r" ( cycles ) );
+	return cycles;
+}
+
+#endif /* _BITS_PROFILE_H */