[LTP] [PATCH v5] cpufreq.c: add new test for cpufreq sysfs interface validation

[Piotr Kubaj <piotr.kubaj@intel.com>]

Runs various sanity checks for intel_pstate cpufreq sysfs interface.

Checks whether intel_pstate driver is used, whether it is possible
to switch scaling_governor to powersave and performance,
whether it is possible to disable turbo frequency and
whether it is possible to change scaling_min_freq and scaling_max_freq
to its minimal valid and maximal valid values.

Signed-off-by: Piotr Kubaj <piotr.kubaj@intel.com>
---
Address bot review.
 runtest/power_management_tests               |   1 +
 testcases/kernel/power_management/.gitignore |   1 +
 testcases/kernel/power_management/cpufreq.c  | 396 +++++++++++++++++++
 3 files changed, 398 insertions(+)
 create mode 100644 testcases/kernel/power_management/.gitignore
 create mode 100644 testcases/kernel/power_management/cpufreq.c

diff --git a/runtest/power_management_tests b/runtest/power_management_tests
index b670da6ec..0bc7dd0c8 100644
--- a/runtest/power_management_tests
+++ b/runtest/power_management_tests
@@ -1,4 +1,5 @@
 #POWER_MANAGEMENT
+cpufreq cpufreq
 runpwtests03 runpwtests03.sh
 runpwtests04 runpwtests04.sh
 runpwtests06 runpwtests06.sh
diff --git a/testcases/kernel/power_management/.gitignore b/testcases/kernel/power_management/.gitignore
new file mode 100644
index 000000000..7f34e4c2f
--- /dev/null
+++ b/testcases/kernel/power_management/.gitignore
@@ -0,0 +1 @@
+cpufreq
diff --git a/testcases/kernel/power_management/cpufreq.c b/testcases/kernel/power_management/cpufreq.c
new file mode 100644
index 000000000..dde87ceea
--- /dev/null
+++ b/testcases/kernel/power_management/cpufreq.c
@@ -0,0 +1,396 @@
+// SPDX-License-Identifier: GPL-2.0-or-later
+/*
+ * Copyright (c) 2026 Piotr Kubaj <piotr.kubaj@intel.com>
+ */
+
+/*\
+ * Runs various sanity checks for intel_pstate cpufreq sysfs interface.
+ *
+ * Checks whether intel_pstate driver is used, whether it is possible to switch
+ * scaling_governor to powersave and performance, whether it is possible
+ * to disable turbo frequency and whether it is possible to change
+ * scaling_min_freq and scaling_max_freq to its minimal valid and maximal valid
+ * values.
+ *
+ * Motivation: LTP has no regression coverage for the intel_pstate cpufreq
+ * sysfs interface, so breakage in any of these attributes (driver exposure,
+ * governor switching, active/passive mode transitions, no_turbo toggling or
+ * scaling_{min,max}_freq writes) can reach users undetected. This test
+ * exercises the interface end-to-end to catch such regressions.
+ */
+
+#include "tst_test.h"
+
+static bool *online;
+static bool setup_done;
+static char intel_pstate_status[16];
+static char (*previous_scaling_governor)[16];
+static int no_turbo, nproc;
+static long *previous_scaling_max_freq, *previous_scaling_min_freq;
+
+static void cleanup(void)
+{
+	char path[PATH_MAX];
+
+	if (!setup_done) {
+		free(online);
+		free(previous_scaling_max_freq);
+		free(previous_scaling_min_freq);
+		free(previous_scaling_governor);
+		return;
+	}
+
+	SAFE_FILE_PRINTF("/sys/devices/system/cpu/intel_pstate/status", "%s", intel_pstate_status);
+	SAFE_FILE_PRINTF("/sys/devices/system/cpu/intel_pstate/no_turbo", "%d", no_turbo);
+
+	for (int i = 0; i < nproc; i++) {
+		if (!online[i])
+			continue;
+
+		snprintf(path, sizeof(path), "/sys/devices/system/cpu/cpu%d/cpufreq/scaling_governor", i);
+		SAFE_FILE_PRINTF(path, "%s", previous_scaling_governor[i]);
+
+		snprintf(path, sizeof(path), "/sys/devices/system/cpu/cpu%d/cpufreq/scaling_max_freq", i);
+		SAFE_FILE_PRINTF(path, "%ld", previous_scaling_max_freq[i]);
+
+		snprintf(path, sizeof(path), "/sys/devices/system/cpu/cpu%d/cpufreq/scaling_min_freq", i);
+		SAFE_FILE_PRINTF(path, "%ld", previous_scaling_min_freq[i]);
+	}
+
+	free(online);
+	free(previous_scaling_max_freq);
+	free(previous_scaling_min_freq);
+	free(previous_scaling_governor);
+}
+
+static void setup(void)
+{
+	char path[PATH_MAX];
+
+	SAFE_FILE_SCANF("/sys/devices/system/cpu/intel_pstate/no_turbo", "%d", &no_turbo);
+	SAFE_FILE_SCANF("/sys/devices/system/cpu/intel_pstate/status", "%15s", intel_pstate_status);
+
+	nproc = tst_ncpus_conf();
+	online = SAFE_CALLOC(nproc, sizeof(*online));
+	previous_scaling_max_freq = SAFE_CALLOC(nproc, sizeof(*previous_scaling_max_freq));
+	previous_scaling_min_freq = SAFE_CALLOC(nproc, sizeof(*previous_scaling_min_freq));
+	previous_scaling_governor = SAFE_CALLOC(nproc, sizeof(*previous_scaling_governor));
+	online[0] = true;
+	for (int i = 1; i < nproc; i++) {
+		int tmp;
+
+		snprintf(path, sizeof(path), "/sys/devices/system/cpu/cpu%d/online", i);
+		SAFE_FILE_SCANF(path, "%d", &tmp);
+		online[i] = (bool)tmp;
+	}
+	for (int i = 0; i < nproc; i++) {
+		if (!online[i])
+			continue;
+
+		snprintf(path, sizeof(path), "/sys/devices/system/cpu/cpu%d/cpufreq/scaling_governor", i);
+		SAFE_FILE_SCANF(path, "%15s", previous_scaling_governor[i]);
+		snprintf(path, sizeof(path), "/sys/devices/system/cpu/cpu%d/cpufreq/scaling_max_freq", i);
+		SAFE_FILE_SCANF(path, "%ld", &previous_scaling_max_freq[i]);
+		snprintf(path, sizeof(path), "/sys/devices/system/cpu/cpu%d/cpufreq/scaling_min_freq", i);
+		SAFE_FILE_SCANF(path, "%ld", &previous_scaling_min_freq[i]);
+	}
+
+	SAFE_FILE_PRINTF("/sys/devices/system/cpu/intel_pstate/status", "active");
+
+	setup_done = true;
+}
+
+static void run(void)
+{
+	const char * const cpufreq_nodes[] = {
+		"affected_cpus",
+		"cpuinfo_max_freq",
+		"cpuinfo_min_freq",
+		"cpuinfo_transition_latency",
+		"related_cpus",
+		"scaling_available_governors",
+		"scaling_cur_freq",
+		"scaling_driver",
+		"scaling_governor",
+		"scaling_max_freq",
+		"scaling_min_freq",
+		"scaling_setspeed",
+		NULL
+	};
+	char contents[256] = {0}, path[PATH_MAX], path_cpuinfo_min_freq[PATH_MAX];
+	int fd, no_turbo_val;
+	long cpuinfo_max_freq = 0, cpuinfo_min_freq = 0, scaling_max_freq, scaling_min_freq;
+
+	for (int i = 0; i < nproc; i++) {
+		if (!online[i])
+			continue;
+
+		snprintf(path, sizeof(path), "/sys/devices/system/cpu/cpu%d/cpufreq/scaling_driver", i);
+
+		SAFE_FILE_SCANF(path, "%255s", contents);
+		tst_res(TDEBUG, "Checking whether %s is \"intel_pstate\"", path);
+		if (strstr(contents, "intel_pstate")) {
+			tst_res(TPASS, "%s is intel_pstate", path);
+		} else {
+			tst_res(TINFO, "%s contains: %s", path, contents);
+			tst_res(TFAIL, "%s is not intel_pstate", path);
+		}
+
+		for (int j = 0; cpufreq_nodes[j]; j++) {
+			struct stat stats;
+
+			snprintf(path, sizeof(path), "/sys/devices/system/cpu/cpu%d/cpufreq/%s", i, cpufreq_nodes[j]);
+			tst_res(TDEBUG, "Checking whether %s is a regular file", path);
+			SAFE_STAT(path, &stats);
+			if (!S_ISREG(stats.st_mode)) {
+				tst_res(TINFO, "%s mode: %o", path, stats.st_mode);
+				tst_res(TFAIL, "%s is not a regular file", path);
+			} else {
+				tst_res(TPASS, "%s is a regular file", path);
+			}
+		}
+
+		snprintf(path, sizeof(path), "/sys/devices/system/cpu/cpu%d/cpufreq/scaling_available_governors", i);
+		memset(contents, 0, sizeof(contents));
+		fd = SAFE_OPEN(path, O_RDONLY);
+		SAFE_READ(0, fd, contents, sizeof(contents));
+		SAFE_CLOSE(fd);
+
+		tst_res(TDEBUG, "Checking whether %s contains \"performance\" and \"powersave\"", path);
+		if (strstr(contents, "performance") && strstr(contents, "powersave")) {
+			tst_res(TPASS, "%s contains: %s", path, contents);
+		} else {
+			tst_res(TINFO, "%s contains: %s", path, contents);
+			tst_res(TFAIL, "%s is not \"performance powersave\"", path);
+		}
+
+		snprintf(path, sizeof(path), "/sys/devices/system/cpu/cpu%d/cpufreq/scaling_governor", i);
+		tst_res(TDEBUG, "Checking %s", path);
+		memset(contents, 0, sizeof(contents));
+		SAFE_FILE_SCANF(path, "%255s", contents);
+		if (strstr(contents, "performance")) {
+			tst_res(TDEBUG, "%s is \"performance\"", path);
+			tst_res(TDEBUG, "Checking whether %s can be switched to \"powersave\"", path);
+			SAFE_FILE_PRINTF(path, "powersave");
+			memset(contents, 0, sizeof(contents));
+			SAFE_FILE_SCANF(path, "%255s", contents);
+			if (strstr(contents, "powersave"))
+				tst_res(TPASS, "Changing scaling_governor from performance to powersave succeeded");
+			else
+				tst_res(TFAIL, "%s: failed to change scaling_governor from performance to powersave, current scaling_governor: %s", path, contents);
+
+		} else if (strstr(contents, "powersave")) {
+			tst_res(TDEBUG, "%s is \"powersave\"", path);
+			tst_res(TDEBUG, "Checking whether %s can be switched to \"performance\"", path);
+			SAFE_FILE_PRINTF(path, "performance");
+			memset(contents, 0, sizeof(contents));
+			SAFE_FILE_SCANF(path, "%255s", contents);
+			if (strstr(contents, "performance"))
+				tst_res(TPASS, "Changing scaling_governor from powersave to performance succeeded");
+			else
+				tst_res(TFAIL, "%s: failed to change scaling_governor from powersave to performance, current scaling_governor: %s", path, contents);
+
+		} else {
+			tst_brk(TBROK, "Unknown scaling_governor: %s", contents);
+		}
+
+		snprintf(path, sizeof(path), "/sys/devices/system/cpu/cpu%d/cpufreq/cpuinfo_max_freq", i);
+		snprintf(path_cpuinfo_min_freq, sizeof(path_cpuinfo_min_freq), "/sys/devices/system/cpu/cpu%d/cpufreq/cpuinfo_min_freq", i);
+		tst_res(TDEBUG, "Checking whether %s is bigger than cpuinfo_min_freq", path);
+		SAFE_FILE_SCANF(path, "%ld", &cpuinfo_max_freq);
+
+		SAFE_FILE_SCANF(path_cpuinfo_min_freq, "%ld", &cpuinfo_min_freq);
+
+		if (cpuinfo_min_freq > cpuinfo_max_freq)
+			tst_res(TFAIL, "Value in %s: %ld, should be bigger than cpuinfo_min_freq: %ld", path, cpuinfo_max_freq, cpuinfo_min_freq);
+		else
+			tst_res(TPASS, "Value in %s: %ld, is bigger than cpuinfo_min_freq: %ld", path, cpuinfo_max_freq, cpuinfo_min_freq);
+	}
+
+	snprintf(path, sizeof(path), "/sys/devices/system/cpu/intel_pstate/status");
+	tst_res(TDEBUG, "Checking whether %s contains \"active\"", path);
+	memset(contents, 0, sizeof(contents));
+	SAFE_FILE_SCANF(path, "%255s", contents);
+
+	if (strstr(contents, "active"))
+		tst_res(TPASS, "%s is \"active\"", path);
+	else
+		tst_res(TFAIL, "%s is not \"active\", but %s", path, contents);
+
+	tst_res(TDEBUG, "Checking whether %s can be switched to \"passive\"", path);
+	SAFE_FILE_PRINTF(path, "passive");
+	memset(contents, 0, sizeof(contents));
+	SAFE_FILE_SCANF(path, "%255s", contents);
+
+	if (strstr(contents, "passive"))
+		tst_res(TPASS, "%s is \"passive\"", path);
+	else
+		tst_res(TFAIL, "%s is not \"passive\", but %s", path, contents);
+
+	tst_res(TDEBUG, "Checking whether %s can be switched back to \"active\"", path);
+	SAFE_FILE_PRINTF(path, "active");
+	memset(contents, 0, sizeof(contents));
+	SAFE_FILE_SCANF(path, "%255s", contents);
+
+	if (strstr(contents, "active"))
+		tst_res(TPASS, "%s is \"active\"", path);
+	else
+		tst_res(TFAIL, "%s is not \"active\", but %s", path, contents);
+
+	snprintf(path, sizeof(path), "/sys/devices/system/cpu/intel_pstate/no_turbo");
+	tst_res(TDEBUG, "Checking whether %s can be switched to 1", path);
+	SAFE_FILE_PRINTF(path, "1");
+	SAFE_FILE_SCANF(path, "%d", &no_turbo_val);
+
+	if (no_turbo_val == 1)
+		tst_res(TPASS, "%s is \"1\"", path);
+	else
+		tst_res(TFAIL, "%s is not \"1\", but %d", path, no_turbo_val);
+
+	tst_res(TDEBUG, "Checking whether %s can be switched back to 0", path);
+	SAFE_FILE_PRINTF(path, "0");
+	SAFE_FILE_SCANF(path, "%d", &no_turbo_val);
+
+	if (no_turbo_val == 0)
+		tst_res(TPASS, "%s is \"0\"", path);
+	else
+		tst_res(TFAIL, "%s is not \"0\", but %d", path, no_turbo_val);
+
+	tst_res(TDEBUG, "Checking whether scaling_available_governors contains \"performance\" and \"schedutil\" after switching /sys/devices/system/cpu/intel_pstate/status to \"passive\"");
+	snprintf(path, sizeof(path), "/sys/devices/system/cpu/intel_pstate/status");
+	SAFE_FILE_PRINTF(path, "passive");
+
+	for (int i = 0; i < nproc; i++) {
+		if (!online[i])
+			continue;
+
+		snprintf(path, sizeof(path), "/sys/devices/system/cpu/cpu%d/cpufreq/scaling_available_governors", i);
+		memset(contents, 0, sizeof(contents));
+		fd = SAFE_OPEN(path, O_RDONLY);
+		SAFE_READ(0, fd, contents, sizeof(contents));
+		SAFE_CLOSE(fd);
+
+		tst_res(TDEBUG, "Checking whether %s contains \"performance\" and \"schedutil\"", path);
+		if (strstr(contents, "performance") && strstr(contents, "schedutil")) {
+			tst_res(TPASS, "%s contains: %s", path, contents);
+		} else {
+			tst_res(TINFO, "%s contains: %s", path, contents);
+			tst_res(TFAIL, "%s does not contain \"performance\" and \"schedutil\"", path);
+		}
+
+		snprintf(path, sizeof(path), "/sys/devices/system/cpu/cpu%d/cpufreq/scaling_governor", i);
+		tst_res(TDEBUG, "Checking whether %s can be changed to performance", path);
+		SAFE_FILE_PRINTF(path, "performance");
+		memset(contents, 0, sizeof(contents));
+		SAFE_FILE_SCANF(path, "%255s", contents);
+
+		if (strstr(contents, "performance"))
+			tst_res(TPASS, "%s is \"performance\"", path);
+		else
+			tst_res(TFAIL, "%s is not \"performance\", but %s", path, contents);
+
+		tst_res(TDEBUG, "Checking whether %s can be changed to schedutil", path);
+		SAFE_FILE_PRINTF(path, "schedutil");
+		memset(contents, 0, sizeof(contents));
+		SAFE_FILE_SCANF(path, "%255s", contents);
+
+		if (strstr(contents, "schedutil"))
+			tst_res(TPASS, "%s is \"schedutil\"", path);
+		else
+			tst_res(TFAIL, "%s is not \"schedutil\", but %s", path, contents);
+	}
+
+	for (int i = 0; i < nproc; i++) {
+		if (!online[i])
+			continue;
+
+		snprintf(path, sizeof(path), "/sys/devices/system/cpu/cpu%d/cpufreq/cpuinfo_max_freq", i);
+		tst_res(TDEBUG, "Checking whether %s can be assigned to scaling_max_freq and scaling_min_freq", path);
+		SAFE_FILE_SCANF(path, "%ld", &cpuinfo_max_freq);
+
+		snprintf(path, sizeof(path), "/sys/devices/system/cpu/cpu%d/cpufreq/cpuinfo_min_freq", i);
+		SAFE_FILE_SCANF(path, "%ld", &cpuinfo_min_freq);
+
+		snprintf(path, sizeof(path), "/sys/devices/system/cpu/cpu%d/cpufreq/scaling_max_freq", i);
+		SAFE_FILE_PRINTF(path, "%ld", cpuinfo_max_freq);
+		SAFE_FILE_SCANF(path, "%ld", &scaling_max_freq);
+
+		if (cpuinfo_max_freq < scaling_max_freq) {
+			tst_res(TINFO, "cpuinfo_max_freq: %ld", cpuinfo_max_freq);
+			tst_res(TINFO, "scaling_max_freq: %ld", scaling_max_freq);
+			tst_res(TFAIL, "Failure setting %s", path);
+		} else {
+			tst_res(TPASS, "Successfully set up %s", path);
+		}
+
+		snprintf(path, sizeof(path), "/sys/devices/system/cpu/cpu%d/cpufreq/scaling_min_freq", i);
+		SAFE_FILE_PRINTF(path, "%ld", cpuinfo_max_freq);
+		SAFE_FILE_SCANF(path, "%ld", &scaling_min_freq);
+
+		if (cpuinfo_max_freq < scaling_min_freq) {
+			tst_res(TINFO, "cpuinfo_max_freq: %ld", cpuinfo_max_freq);
+			tst_res(TINFO, "scaling_min_freq: %ld", scaling_min_freq);
+			tst_res(TFAIL, "Failure setting %s", path);
+		} else {
+			tst_res(TPASS, "Successfully set up %s", path);
+		}
+
+		snprintf(path, sizeof(path), "/sys/devices/system/cpu/cpu%d/cpufreq/scaling_min_freq", i);
+		SAFE_FILE_PRINTF(path, "%ld", previous_scaling_min_freq[i]);
+
+		snprintf(path, sizeof(path), "/sys/devices/system/cpu/cpu%d/cpufreq/scaling_max_freq", i);
+		SAFE_FILE_PRINTF(path, "%ld", previous_scaling_max_freq[i]);
+	}
+
+	for (int i = 0; i < nproc; i++) {
+		if (!online[i])
+			continue;
+
+		snprintf(path, sizeof(path), "/sys/devices/system/cpu/cpu%d/cpufreq/cpuinfo_max_freq", i);
+		tst_res(TDEBUG, "Checking whether %s can be assigned to scaling_max_freq and scaling_min_freq", path);
+		SAFE_FILE_SCANF(path, "%ld", &cpuinfo_max_freq);
+
+		snprintf(path, sizeof(path), "/sys/devices/system/cpu/cpu%d/cpufreq/cpuinfo_min_freq", i);
+		SAFE_FILE_SCANF(path, "%ld", &cpuinfo_min_freq);
+
+		snprintf(path, sizeof(path), "/sys/devices/system/cpu/cpu%d/cpufreq/scaling_min_freq", i);
+		SAFE_FILE_PRINTF(path, "%ld", cpuinfo_min_freq);
+		SAFE_FILE_SCANF(path, "%ld", &scaling_min_freq);
+
+		if (cpuinfo_min_freq > scaling_min_freq) {
+			tst_res(TINFO, "cpuinfo_min_freq: %ld", cpuinfo_min_freq);
+			tst_res(TINFO, "scaling_min_freq: %ld", scaling_min_freq);
+			tst_res(TFAIL, "Failure setting %s", path);
+		} else {
+			tst_res(TPASS, "Successfully set up %s", path);
+		}
+
+		snprintf(path, sizeof(path), "/sys/devices/system/cpu/cpu%d/cpufreq/scaling_max_freq", i);
+		SAFE_FILE_PRINTF(path, "%ld", cpuinfo_min_freq);
+		SAFE_FILE_SCANF(path, "%ld", &scaling_max_freq);
+
+		if (cpuinfo_min_freq > scaling_max_freq) {
+			tst_res(TINFO, "cpuinfo_min_freq: %ld", cpuinfo_min_freq);
+			tst_res(TINFO, "scaling_max_freq: %ld", scaling_max_freq);
+			tst_res(TFAIL, "Failure setting %s", path);
+		} else {
+			tst_res(TPASS, "Successfully set up %s", path);
+		}
+	}
+}
+
+static struct tst_test test = {
+	.cleanup = cleanup,
+	.needs_kconfigs = (const char *const []) {
+		"CONFIG_X86_INTEL_PSTATE",
+		NULL
+	},
+	.needs_root = 1,
+	.setup = setup,
+	.supported_archs = (const char *const []) {
+		"x86",
+		"x86_64",
+		NULL
+	},
+	.test_all = run
+};
-- 
2.47.3

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