[PATCH umr] Prevent reading sensors far too quickly.

[Tom St Denis]

On platforms without GPU_POWER sensors the thread reading sensors would proceed
far too quickly.  So it is now rate limited to 50Hz to be consistent.

Signed-off-by: Tom St Denis <tom.stdenis at amd.com>
---
 src/app/top.c | 12 +++++++++++-
 1 file changed, 11 insertions(+), 1 deletion(-)

diff --git a/src/app/top.c b/src/app/top.c
index 96e33ff2e1da..364180eb70f6 100644
--- a/src/app/top.c
+++ b/src/app/top.c
@@ -293,18 +293,24 @@ static volatile struct umr_bitfield *sensor_bits = NULL;
 static void *gpu_sensor_thread(void *data)
 {
 	struct umr_asic asic = *((struct umr_asic*)data);
-	int size, rem, off, x;
+	int size, rem, off, x, power;
 	char fname[128];
+	struct timespec ts;
+
+	ts.tv_sec = 0;
+	ts.tv_nsec = 1000000000UL / 50; // limit to 50Hz
 
 	snprintf(fname, sizeof(fname)-1, "/sys/kernel/debug/dri/%d/amdgpu_sensors", asic.instance);
 	asic.fd.sensors = open(fname, O_RDWR);
 	while (!sensor_thread_quit) {
 		rem = sizeof gpu_power_data;
 		off = 0;
+		power = 0;
 		for (x = 0; sensor_bits[x].regname; ) {
 			switch (sensor_bits[x].start) {
 				case AMDGPU_PP_SENSOR_GPU_POWER:
 					size = 16;
+					power = 1;
 					break;
 				default:
 					size = 4;
@@ -316,6 +322,10 @@ static void *gpu_sensor_thread(void *data)
 			rem -= size;
 			x   += size / 4;
 		}
+
+		// sleep for 20ms if no GPU power sensor to rate limit things a bit
+		if (!power)
+			nanosleep(&ts, NULL);
 	}
 	close(asic.fd.sensors);
 	return NULL;
-- 
2.12.0