Glibc 2.17 provides new function to read the frequency at which the Time
Base Register of Power processors is updated.
Signed-off-by: Tulio Magno Quites Machado Filho <tuliom@xxxxxxxxxxxxxxxxxx>
---
man3/__ppc_get_timebase.3 | 66 ++++++++++++++++++++++++++++++++++++++----
man3/__ppc_get_timebase_freq.3 | 1 +
2 files changed, 61 insertions(+), 6 deletions(-)
create mode 100644 man3/__ppc_get_timebase_freq.3
diff --git a/man3/__ppc_get_timebase.3 b/man3/__ppc_get_timebase.3
index 6af2d43..e691a5c 100644
--- a/man3/__ppc_get_timebase.3
+++ b/man3/__ppc_get_timebase.3
@@ -25,30 +25,84 @@
.TH __PPC_GET_TIMEBASE 3 2012-08-13 "GNU C Library" "Linux Programmer's\
Manual"
.SH NAME
-__ppc_get_timebase \- get the current value of the Time Base Register on
-Power architecture
+__ppc_get_timebase, __ppc_get_timebase_freq \- get the current value
+ of the Time Base Register on Power architecture and its frequency.
.SH SYNOPSIS
.B #include <sys/platform/ppc.h>
.sp
.BI "uint64_t __ppc_get_timebase(void)"
+
+.BI "uint64_t __ppc_get_timebase_freq(void);"
.SH DESCRIPTION
.BR __ppc_get_timebase ()
-reads the current value of the Time Base Register and returns its value.
+reads the current value of the Time Base Register and returns its
+value, while
+.BR __ppc_get_timebase_freq ()
+returns the frequency in which the Time Base Register is updated.
+
The Time Base Register is a 64-bit register provided by Power Architecture
processors.
It stores a monotonically incremented value that is updated at a
system-dependent frequency that may be different from the processor
frequency.
.SH RETURN VALUE
-Returns a 64-bit unsigned integer that represents the current value of the
+.BR __ppc_get_timebase ()
+returns a 64-bit unsigned integer that represents the current value of the
Time Base Register.
+
+.BR __ppc_get_timebase_freq ()
+returns a 64-bit unsigned integer that represents the frequency at
+which the Time Base Register is updated.
.SH VERSIONS
GNU C Library support for
.\" commit d9dc34cd569bcfe714fe8c708e58c028106e8b2e
.BR __ppc_get_timebase ()
-has been provided since version 2.16.
+has been provided since version 2.16 and
+.\" commit 8ad11b9a9cf1de82bd7771306b42070b91417c11
+.BR __ppc_get_timebase_freq ()
+has been available since version 2.17.
.SH CONFORMING TO
-This function is a nonstandard GNU extension.
+Both functions are nonstandard GNU extensions.
+.SH EXAMPLE
+The following program will calculate the time, in microseconds, spent
+between two calls to __ppc_get_timebase ().
+.SS Program source
+\&
+.nf
+#include <inttypes.h>
+#include <stdint.h>
+#include <stdio.h>
+#include <sys/platform/ppc.h>
+
+/* Maximum value of the Time Base Register: 2^60 - 1. Source: POWER ISA. */
+#define MAX_TB 0xFFFFFFFFFFFFFFF
+
+int
+main ()
+{
+ uint64_t tb1, tb2, diff;
+
+ uint64_t freq = __ppc_get_timebase_freq ();
+ printf ("Time Base frequency = %"PRIu64" Hz\\n", freq);
+
+ tb1 = __ppc_get_timebase ();
+
+ // Do some stuff...
+
+ tb2 = __ppc_get_timebase ();
+
+ if (tb2 > tb1) {
+ diff = tb2 - tb1;
+ } else {
+ /* Treat Time Base Register overflow. */
+ diff = (MAX_TB - tb2) + tb1;
+ }
+
+ printf ("Elapsed time = %1.2f usecs\\n", (double) diff * 1000000 / freq );
+
+ return 0;
+}
+.fi
.SH SEE ALSO
.BR time (2),
.BR usleep (3)
diff --git a/man3/__ppc_get_timebase_freq.3 b/man3/__ppc_get_timebase_freq.3
new file mode 100644
index 0000000..8599293
--- /dev/null
+++ b/man3/__ppc_get_timebase_freq.3
@@ -0,0 +1 @@
+.so man3/__ppc_get_timebase.3
--
2.1.0
--
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