video: rockchip: mpp: report zero load for idle devices

The per-device statistics shown in /proc/mpp_service/load are only ever
recomputed inside mpp_dev_load(), which is called exclusively from the
task-completion paths (mpp_common.c task worker and the rkvdec2 link/ccu
workers). Within that function the load and utilization figures are only
refreshed when a task finishes *and* at least one load_interval has
elapsed; the result is stored in mpp->load_info and reset for the next
window. There is no timer, runtime-PM hook, or reader-side logic that
ages the value out, so mpp->load_info.load is a snapshot of the last
completed interval, not a live measurement.

As a consequence, once a device stops receiving tasks its stored load is
never updated again and /proc/mpp_service/load keeps reporting the last
busy interval indefinitely (until load_interval is toggled, which clears
the stats via mpp_dev_load_clear()).

This is most visible on the standalone AV1 decoder (fdc70000.av1d). It
is driven one task at a time by the default worker, so when playback
stops the final frame's completion is genuinely the last event that will
ever call mpp_dev_load() for that core, and its load freezes at the busy
value. Multi-core rkvdec2 decoders in link/ccu mode keep draining their
queued task list after playback ends, which happens to log a further,
near-idle interval and pulls the figure back down, so the staleness goes
unnoticed there. The underlying defect is common to every device.

Rather than introduce a periodic recompute (a per-core timer with the
associated runtime-PM interactions), detect the idle case in the reader.
A device whose load_info has not been updated for more than one full
load_interval has, by definition, completed no task in that window and
is idle; report zero for it instead of the stale snapshot. Devices that
never started load tracking (!load_en) are likewise reported as zero.

Signed-off-by: Ricardo Pardini <ricardo@pardini.net>
Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>

Author: rpardini

drivers/video/rockchip/mpp/mpp_service.c

@@ -329,13 +329,33 @@ static int mpp_show_device_load(struct seq_file *file, void *v)
 
 		for (j = 0; j < MPP_MAX_CORE_NUM; j++) {
 			struct mpp_dev *mpp = queue->cores[j];
+			struct mpp_load_info *load_info;
+			u32 load, load_frac, util, util_frac;
 
 			if (!mpp)
 				continue;
+
+			load_info = &mpp->load_info;
+			load = load_info->load;
+			load_frac = load_info->load_frac;
+			util = load_info->utilization;
+			util_frac = load_info->utilization_frac;
+
+			/*
+			 * load_info is only refreshed by mpp_dev_load() on task
+			 * completion, so an idle device keeps reporting the last
+			 * busy interval forever. If no task has updated the stats
+			 * for more than one load_interval, the device has gone
+			 * idle: report zero instead of the stale snapshot.
+			 */
+			if (!mpp->load_en ||
+			    ktime_us_delta(ktime_get(), load_info->load_time) >
+			    (s64)srv->load_interval * 1000 * 2)
+				load = load_frac = util = util_frac = 0;
+
 			seq_printf(file, "%-25s load: %3d.%02d%% utilization: %3d.%02d%%\n",
 				   dev_name(mpp->dev),
-				   mpp->load_info.load, mpp->load_info.load_frac,
-				   mpp->load_info.utilization, mpp->load_info.utilization_frac);
+				   load, load_frac, util, util_frac);
 		}
 	}