selftests/thermel/intel: Add test to read power floor status

Some SoCs have firmware support to notify, if the system can't lower
power limit to a value requested from user space via RAPL constraints.

This test program waits for notification of power floor and prints. This
program can be used to test this feature and also allows other user space
programs to use as a reference.

Signed-off-by: Srinivas Pandruvada <[e-mail]>
Signed-off-by: Rafael J. Wysocki <[e-mail]>

tools/testing/selftests/Makefile

···
 TARGETS += sysctl
 TARGETS += tc-testing
 TARGETS += tdx
+TARGETS += thermal/intel/power_floor
 TARGETS += thermal/intel/workload_hint
 TARGETS += timens
 ifneq (1, $(quicktest))

tools/testing/selftests/thermal/intel/power_floor/Makefile

···
+# SPDX-License-Identifier: GPL-2.0
+ifndef CROSS_COMPILE
+uname_M := $(shell uname -m 2>/dev/null || echo not)
+ARCH ?= $(shell echo $(uname_M) | sed -e s/i.86/x86/ -e s/x86_64/x86/)
+
+ifeq ($(ARCH),x86)
+TEST_GEN_PROGS := power_floor_test
+
+include ../../../lib.mk
+
+endif
+endif

tools/testing/selftests/thermal/intel/power_floor/power_floor_test.c

···
+// SPDX-License-Identifier: GPL-2.0
+
+#define _GNU_SOURCE
+
+#include <stdio.h>
+#include <string.h>
+#include <stdlib.h>
+#include <unistd.h>
+#include <fcntl.h>
+#include <poll.h>
+#include <signal.h>
+
+#define POWER_FLOOR_ENABLE_ATTRIBUTE "/sys/bus/pci/devices/0000:00:04.0/power_limits/power_floor_enable"
+#define POWER_FLOOR_STATUS_ATTRIBUTE  "/sys/bus/pci/devices/0000:00:04.0/power_limits/power_floor_status"
+
+void power_floor_exit(int signum)
+{
+	int fd;
+
+	/* Disable feature via sysfs knob */
+
+	fd = open(POWER_FLOOR_ENABLE_ATTRIBUTE, O_RDWR);
+	if (fd < 0) {
+		perror("Unable to open power floor enable file\n");
+		exit(1);
+	}
+
+	if (write(fd, "0\n", 2) < 0) {
+		perror("Can' disable power floor notifications\n");
+		exit(1);
+	}
+
+	printf("Disabled power floor notifications\n");
+
+	close(fd);
+}
+
+int main(int argc, char **argv)
+{
+	struct pollfd ufd;
+	char status_str[3];
+	int fd, ret;
+
+	if (signal(SIGINT, power_floor_exit) == SIG_IGN)
+		signal(SIGINT, SIG_IGN);
+	if (signal(SIGHUP, power_floor_exit) == SIG_IGN)
+		signal(SIGHUP, SIG_IGN);
+	if (signal(SIGTERM, power_floor_exit) == SIG_IGN)
+		signal(SIGTERM, SIG_IGN);
+
+	/* Enable feature via sysfs knob */
+	fd = open(POWER_FLOOR_ENABLE_ATTRIBUTE, O_RDWR);
+	if (fd < 0) {
+		perror("Unable to open power floor enable file\n");
+		exit(1);
+	}
+
+	if (write(fd, "1\n", 2) < 0) {
+		perror("Can' enable power floor notifications\n");
+		exit(1);
+	}
+
+	close(fd);
+
+	printf("Enabled power floor notifications\n");
+
+	while (1) {
+		fd = open(POWER_FLOOR_STATUS_ATTRIBUTE, O_RDONLY);
+		if (fd < 0) {
+			perror("Unable to power floor status file\n");
+			exit(1);
+		}
+
+		if ((lseek(fd, 0L, SEEK_SET)) < 0) {
+			fprintf(stderr, "Failed to set pointer to beginning\n");
+			exit(1);
+		}
+
+		if (read(fd, status_str, sizeof(status_str)) < 0) {
+			fprintf(stderr, "Failed to read from:%s\n",
+			POWER_FLOOR_STATUS_ATTRIBUTE);
+			exit(1);
+		}
+
+		ufd.fd = fd;
+		ufd.events = POLLPRI;
+
+		ret = poll(&ufd, 1, -1);
+		if (ret < 0) {
+			perror("poll error");
+			exit(1);
+		} else if (ret == 0) {
+			printf("Poll Timeout\n");
+		} else {
+			if ((lseek(fd, 0L, SEEK_SET)) < 0) {
+				fprintf(stderr, "Failed to set pointer to beginning\n");
+				exit(1);
+			}
+
+			if (read(fd, status_str, sizeof(status_str)) < 0)
+				exit(0);
+
+			printf("power floor status: %s\n", status_str);
+		}
+
+		close(fd);
+	}
+}