lib: Add GPU power measurement

Read the RAPL power metrics courtesy of perf. Or your local HW
equivalent?

v2: uselocale()
v3: Use gpu_power_s(), gpu_power_J(), gpu_power_W() to try and make the
scale factors self-consistent.
v4: Use igt_sysfs
v5: s/tN/sampleN/

Signed-off-by: Chris Wilson <chris@chris-wilson.co.uk>
Cc: Tvrtko Ursulin <tvrtko.ursulin@intel.com>
Reviewed-by: Tvrtko Ursulin <tvrtko.ursulin@intel.com>

1 files changed, 87 insertions, 0 deletions

diff --git a/lib/igt_gpu_power.c b/lib/igt_gpu_power.c
new file mode 100644
index 00000000..7092b75b
--- /dev/null
+++ b/lib/igt_gpu_power.c
@@ -0,0 +1,87 @@
+#include <ctype.h>
+#include <errno.h>
+#include <fcntl.h>
+#include <locale.h>
+#include <math.h>
+#include <unistd.h>
+#include <inttypes.h>
+
+#include "igt_gpu_power.h"
+#include "igt_perf.h"
+#include "igt_sysfs.h"
+
+struct rapl {
+	uint64_t power, type;
+	double scale;
+};
+
+static int rapl_parse(struct rapl *r)
+{
+	locale_t locale, oldlocale;
+	bool result;
+	int dir;
+
+	memset(r, 0, sizeof(*r));
+
+	dir = open("/sys/devices/power", O_RDONLY);
+	if (dir < 0)
+		return -errno;
+
+	/* Replace user environment with plain C to match kernel format */
+	locale = newlocale(LC_ALL, "C", 0);
+	oldlocale = uselocale(locale);
+
+	result = true;
+	result &= igt_sysfs_scanf(dir, "type",
+				  "%"PRIu64, &r->type) == 1;
+	result &= igt_sysfs_scanf(dir, "events/energy-gpu",
+				  "event=%"PRIx64, &r->power) == 1;
+	result &= igt_sysfs_scanf(dir, "events/energy-gpu.scale",
+				  "%lf", &r->scale) == 1;
+
+	uselocale(oldlocale);
+	freelocale(locale);
+
+	close(dir);
+
+	if (!result)
+		return -EINVAL;
+
+	if (isnan(r->scale) || !r->scale)
+		return -ERANGE;
+
+	return 0;
+}
+
+int gpu_power_open(struct gpu_power *power)
+{
+	struct rapl r;
+
+	power->fd = rapl_parse(&r);
+	if (power->fd < 0)
+		goto err;
+
+	power->fd = igt_perf_open(r.type, r.power);
+	if (power->fd < 0) {
+		power->fd = -errno;
+		goto err;
+	}
+
+	power->scale = r.scale;
+
+	return 0;
+
+err:
+	errno = 0;
+	return power->fd;
+}
+
+bool gpu_power_read(struct gpu_power *power, struct gpu_power_sample *s)
+{
+	return read(power->fd, s, sizeof(*s)) == sizeof(*s);
+}
+
+void gpu_power_close(struct gpu_power *power)
+{
+	close(power->fd);
+}