[LTP] [PATCH v2] device-drivers/cpufreq_boost: Don't hardcode to CPU0

[Mike Tipton]

Some systems don't support boost on every CPU, such as on many Qualcomm
chipsets. And if boost isn't supported on CPU0, then the test will fail
since there's no performance improvement.

Instead of hardcoding CPU0, find the first CPU that belongs to a cpufreq
policy with boost enabled.

Signed-off-by: Mike Tipton <mike.tipton@oss.qualcomm.com>
---
Changes in v2:
- Use proper maxspeed buf size in snprintf.
- Link to v1: https://lore.kernel.org/ltp/20250626194707.3053036-1-mike.tipton@oss.qualcomm.com/

 .../device-drivers/cpufreq/cpufreq_boost.c    | 58 ++++++++++++++++---
 1 file changed, 50 insertions(+), 8 deletions(-)

diff --git a/testcases/kernel/device-drivers/cpufreq/cpufreq_boost.c b/testcases/kernel/device-drivers/cpufreq/cpufreq_boost.c
index 67917b3fea25..bbb5f602de4b 100644
--- a/testcases/kernel/device-drivers/cpufreq/cpufreq_boost.c
+++ b/testcases/kernel/device-drivers/cpufreq/cpufreq_boost.c
@@ -55,10 +55,14 @@ static int id = -1;
 
 static int boost_value;
 
-const char governor[]	= SYSFS_CPU_DIR "cpu0/cpufreq/scaling_governor";
+static int cpu;
+
+static const char _governor[] = SYSFS_CPU_DIR "cpu%d/cpufreq/scaling_governor";
+static char governor[64];
 static char governor_name[16];
 
-const char maxspeed[]	= SYSFS_CPU_DIR "cpu0/cpufreq/scaling_max_freq";
+static const char _maxspeed[] = SYSFS_CPU_DIR "cpu%d/cpufreq/scaling_max_freq";
+static char maxspeed[64];
 
 static void check_set_turbo(char *file, char *off)
 {
@@ -84,6 +88,40 @@ static void cleanup(void)
 		FILE_PRINTF(governor, "%s", governor_name);
 }
 
+static int find_boost_cpu(void)
+{
+	char buf[64];
+	int fd, i;
+
+	/*
+	 * The files we're looking for only exist for acpi_cpufreq. Continue
+	 * assuming CPU0 for intel_pstate.
+	 */
+	if (!strcmp(cdrv[id].name, "intel_pstate"))
+		return 0;
+
+	for (i = 0;; i++) {
+		snprintf(buf, sizeof(buf), SYSFS_CPU_DIR "cpu%d", i);
+		fd = open(buf, O_RDONLY);
+		if (fd == -1)
+			break;
+
+		close(fd);
+
+		snprintf(buf, sizeof(buf), SYSFS_CPU_DIR "cpu%d/cpufreq/boost", i);
+		fd = open(buf, O_RDONLY);
+		if (fd == -1)
+			continue;
+
+		close(fd);
+		tst_resm(TINFO, "found boost-capable CPU (CPU%d)", i);
+		return i;
+	}
+
+	tst_resm(TINFO, "didn't find boost-capable CPU (assuming CPU0)");
+	return 0;
+}
+
 static void setup(void)
 {
 	int fd;
@@ -109,6 +147,10 @@ static void setup(void)
 	tst_resm(TINFO, "found '%s' driver, sysfs knob '%s'",
 		cdrv[id].name, cdrv[id].file);
 
+	cpu = find_boost_cpu();
+	snprintf(governor, sizeof(governor), _governor, cpu);
+	snprintf(maxspeed, sizeof(maxspeed), _maxspeed, cpu);
+
 	tst_sig(FORK, DEF_HANDLER, cleanup);
 
 	SAFE_FILE_SCANF(NULL, cdrv[i].file, "%d", &boost_value);
@@ -120,16 +162,16 @@ static void setup(void)
 	if (!strcmp(cdrv[i].name, "intel_pstate") && boost_value == cdrv[i].off)
 		check_set_turbo(cdrv[i].file, cdrv[i].off_str);
 
-	/* change cpu0 scaling governor */
+	/* change cpu scaling governor */
 	SAFE_FILE_SCANF(NULL, governor, "%s", governor_name);
 	SAFE_FILE_PRINTF(cleanup, governor, "%s", "performance");
 
-	/* use only cpu0 */
+	/* use only a single cpu */
 	cpu_set_t set;
 	CPU_ZERO(&set);
-	CPU_SET(0, &set);
+	CPU_SET(cpu, &set);
 	if (sched_setaffinity(0, sizeof(cpu_set_t), &set) < 0)
-		tst_brkm(TBROK | TERRNO, cleanup, "failed to set CPU0");
+		tst_brkm(TBROK | TERRNO, cleanup, "failed to set CPU%d", cpu);
 
 	struct sched_param params;
 	params.sched_priority = sched_get_priority_max(SCHED_FIFO);
@@ -176,12 +218,12 @@ static void test_run(void)
 	/* Enable boost */
 	if (boost_value == cdrv[id].off)
 		SAFE_FILE_PRINTF(cleanup, cdrv[id].file, "%s", cdrv[id].on_str);
-	tst_resm(TINFO, "load CPU0 with boost enabled");
+	tst_resm(TINFO, "load CPU%d with boost enabled", cpu);
 	boost_time = load_cpu(max_freq_khz);
 
 	/* Disable boost */
 	SAFE_FILE_PRINTF(cleanup, cdrv[id].file, "%s", cdrv[id].off_str);
-	tst_resm(TINFO, "load CPU0 with boost disabled");
+	tst_resm(TINFO, "load CPU%d with boost disabled", cpu);
 	boost_off_time = load_cpu(max_freq_khz);
 
 	boost_off_time *= .98;
-- 
2.34.1