ztimer: add benchmarking tool

tests/ztimer_ondemand_benchmark/Makefile

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+include ../Makefile.tests_common
+
+# required modules
+USEMODULE += ztimer
+USEMODULE += ztimer_ondemand
+USEMODULE += ztimer_ondemand_timer
+USEMODULE += ztimer_ondemand_rtt
+USEMODULE += ztimer_ondemand_rtc
+FEATURES_REQUIRED = periph_timer
+DEFAULT_MODULE += test_utils_interactive_sync
+
+# Select clock to benchmark:
+# - ztimer_usec
+USEMODULE += ztimer_usec
+# - ztimer_msec
+#USEMODULE += ztimer_msec
+# - ztimer_sec
+#USEMODULE += ztimer_sec
+
+# You may sepcify the compare timer device
+#CFLAGS += '-DCOMPARE_TIMER_DEV=TIMER_DEV(2)'
+
+# You may sepcify the compare timer frequency
+#CFLAGS += '-DCOMPARE_TIMER_FREQ=9750000'
+
+include $(RIOTBASE)/Makefile.include

tests/ztimer_ondemand_benchmark/README.md

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+ztimer_ondemand_benchmark
+=========================
+
+This application measures latencies introduced by `ztimer_acquire()` and
+`ztimer_release()`. Since it is directly interacting with the underlying
+peripheral, you need at least two `periph_timer` instances if you're
+benchmarking a ztimer clock based on `ztimer_periph_timer`.
+
+The application tries to select a unused timer automatically. If this selection
+process fails, users may specify device and frequency in this test's Makefile.

tests/ztimer_ondemand_benchmark/main.c

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+/*
+ * Copyright (C) 2022 SSV Software Systems GmbH
+ *
+ * This file is subject to the terms and conditions of the GNU Lesser
+ * General Public License v2.1. See the file LICENSE in the top level
+ * directory for more details.
+ */
+
+/**
+ * @ingroup     tests
+ * @{
+ *
+ * @file
+ * @brief       Benchmarks ztimer_acquire() and ztimer_release()
+ *
+ * @author      Juergen Fitschen <me@jue.yt>
+ *
+ * @}
+ */
+
+#include <stdio.h>
+#include <inttypes.h>
+#include "ztimer.h"
+#include "ztimer/config.h"
+#include "periph/timer.h"
+#include "periph_conf.h"
+
+#if IS_ACTIVE(MODULE_ZTIMER_SEC)
+#  define CLOCK ZTIMER_SEC
+#elif IS_ACTIVE(MODULE_ZTIMER_MSEC)
+#  define CLOCK ZTIMER_MSEC
+#elif IS_ACTIVE(MODULE_ZTIMER_USEC)
+#  define CLOCK ZTIMER_USEC
+#  define CLOCK_IS_ZTIMER_USEC
+#else
+#  error "No ztimer clock selected!"
+#endif
+
+#ifndef COMPARE_TIMER_DEV
+#  if IS_ACTIVE(MODULE_ZTIMER_PERIPH_TIMER)
+#    if CONFIG_ZTIMER_USEC_DEV == TIMER_DEV(0)
+#      define COMPARE_TIMER_DEV TIMER_DEV(1)
+#    else
+#      define COMPARE_TIMER_DEV TIMER_DEV(0)
+#    endif
+#  else
+#    define COMPARE_TIMER_DEV TIMER_DEV(0)
+#  endif
+#endif
+
+#ifndef COMPARE_TIMER_FREQ
+#  define COMPARE_TIMER_FREQ 1000000U
+#endif
+
+static inline uint32_t bench_start(uint32_t adjust)
+{
+    return timer_read(COMPARE_TIMER_DEV) + adjust;
+}
+
+static inline uint32_t bench_finish(const char *name, uint32_t start)
+{
+    uint32_t stop = timer_read(COMPARE_TIMER_DEV);
+    uint32_t diff = stop - start;
+    if (name) {
+        printf(" - %s took %"PRIu32" ticks\n", name, diff);
+    }
+    return diff;
+}
+
+static inline uint32_t bench_overhead(void) {
+    uint32_t start = bench_start(0);
+    uint32_t diff = bench_finish(NULL, start);
+    return diff;
+}
+
+int main(void)
+{
+    uint32_t start, adjust;
+    uint32_t first_acquire, second_acquire;
+    uint32_t poweron_diff;
+
+    timer_init(COMPARE_TIMER_DEV, COMPARE_TIMER_FREQ, NULL, NULL);
+
+    adjust = bench_overhead();
+
+    printf("Compare timer frequency: %"PRIu32"Hz\n", (uint32_t) COMPARE_TIMER_FREQ);
+    printf("Compare timer overhead: %"PRIu32" ticks (will be taken into account)\n", adjust);
+
+    puts("---");
+
+    puts("Benchmarking:");
+
+    start = bench_start(adjust);
+    ztimer_acquire(CLOCK);
+    first_acquire = bench_finish("ztimer_acquire() on inactive clock", start);
+
+    start = bench_start(adjust);
+    ztimer_acquire(CLOCK);
+    second_acquire = bench_finish("ztimer_acquire() on active clock", start);
+
+    start = bench_start(adjust);
+    ztimer_release(CLOCK);
+    bench_finish("ztimer_release() with users left", start);
+
+    start = bench_start(adjust);
+    ztimer_release(CLOCK);
+    bench_finish("ztimer_release() with no users left", start);
+
+    puts("---");
+    poweron_diff = first_acquire - second_acquire;
+
+#if defined(CLOCK_IS_ZTIMER_USEC) && COMPARE_TIMER_FREQ == 1000000U
+    printf("Add this to you board.h:\n");
+    printf("   #define CONFIG_ZTIMER_USEC_ADJUST_CLOCK_START %"PRIu32"\n", poweron_diff);
+#else
+    printf("If the ztimer clock runs with with a frequency of %"PRIu32"Hz, set\n",
+           (uint32_t) COMPARE_TIMER_FREQ);
+    printf("   clock->adjust_clock_start = %"PRIu32"\n", poweron_diff);
+#endif
+
+    return 0;
+}