[PATCH] cpufreq: stats: clear statistics

[Markus Mayer <code@mmayer.net>]

From: Markus Mayer <mmayer@broadcom.com>

Allow cpufreq statistics to be cleared by writing anything to
/sys/.../cpufreq/stats/reset. Reading this new sysfs entry returns
nothing.

Resetting the statistics can be useful in a test environment (test
governor, retrieve stats, reset stats, test other governor, etc.). This
feature is not meant for production use.

Signed-off-by: Markus Mayer <mmayer@broadcom.com>
---
 drivers/cpufreq/Kconfig         | 10 ++++++++++
 drivers/cpufreq/cpufreq_stats.c | 32 ++++++++++++++++++++++++++++++++
 2 files changed, 42 insertions(+)

diff --git a/drivers/cpufreq/Kconfig b/drivers/cpufreq/Kconfig
index d8b164a..97a458e 100644
--- a/drivers/cpufreq/Kconfig
+++ b/drivers/cpufreq/Kconfig
@@ -45,6 +45,16 @@ config CPU_FREQ_STAT_DETAILS
 
 	  If in doubt, say N.
 
+config CPU_FREQ_STAT_RESET
+	bool "Allow reset of CPU frequency transition statistics"
+	depends on CPU_FREQ_STAT
+	help
+	  If enabled, writing to /sys/[...]/cpufreq/stats/reset will reset the
+	  current CPUfreq statistics. This is primarily meant for testing. It
+	  should not be enabled on a production system.
+
+	  If in doubt, say N.
+
 choice
 	prompt "Default CPUFreq governor"
 	default CPU_FREQ_DEFAULT_GOV_USERSPACE if ARM_SA1100_CPUFREQ || ARM_SA1110_CPUFREQ
diff --git a/drivers/cpufreq/cpufreq_stats.c b/drivers/cpufreq/cpufreq_stats.c
index 06d3abd..e4e1e3e 100644
--- a/drivers/cpufreq/cpufreq_stats.c
+++ b/drivers/cpufreq/cpufreq_stats.c
@@ -111,6 +111,35 @@ static ssize_t show_trans_table(struct cpufreq_policy *policy, char *buf)
 cpufreq_freq_attr_ro(trans_table);
 #endif
 
+#ifdef CONFIG_CPU_FREQ_STAT_RESET
+static void cpufreq_stats_clear_table(struct cpufreq_policy *policy)
+{
+	struct cpufreq_stats *stats = policy->stats;
+	unsigned int count = stats->max_state;
+
+	memset(stats->time_in_state, 0, count * sizeof(u64));
+#ifdef CONFIG_CPU_FREQ_STAT_DETAILS
+	memset(stats->trans_table, 0, count * count * sizeof(int));
+#endif
+	stats->last_time = get_jiffies_64();
+	stats->total_trans = 0;
+}
+
+static ssize_t show_reset(struct cpufreq_policy *policy, char *buf)
+{
+	buf[0] = '\0';
+	return 0;
+}
+
+static ssize_t store_reset(struct cpufreq_policy *policy, const char *buf,
+			   size_t count)
+{
+	cpufreq_stats_clear_table(policy);
+	return count;
+}
+cpufreq_freq_attr_rw(reset);
+#endif
+
 cpufreq_freq_attr_ro(total_trans);
 cpufreq_freq_attr_ro(time_in_state);
 
@@ -120,6 +149,9 @@ static struct attribute *default_attrs[] = {
 #ifdef CONFIG_CPU_FREQ_STAT_DETAILS
 	&trans_table.attr,
 #endif
+#ifdef CONFIG_CPU_FREQ_STAT_RESET
+	&reset.attr,
+#endif
 	NULL
 };
 static struct attribute_group stats_attr_group = {
-- 
2.7.4