perf drm_pmu: Add a tool like PMU to expose DRM information

DRM clients expose information through usage stats as documented in
Documentation/gpu/drm-usage-stats.rst (available online at
https://docs.kernel.org/gpu/drm-usage-stats.html). Add a tool like
PMU, similar to the hwmon PMU, that exposes DRM information. For
example on a tigerlake laptop:
```
$ perf list drm

List of pre-defined events (to be used in -e or -M):

drm:
  drm-active-stolen-system0
       [Total memory active in one or more engines. Unit: drm_i915]
  drm-active-system0
       [Total memory active in one or more engines. Unit: drm_i915]
  drm-engine-capacity-video
       [Engine capacity. Unit: drm_i915]
  drm-engine-copy
       [Utilization in ns. Unit: drm_i915]
  drm-engine-render
       [Utilization in ns. Unit: drm_i915]
  drm-engine-video
       [Utilization in ns. Unit: drm_i915]
  drm-engine-video-enhance
       [Utilization in ns. Unit: drm_i915]
  drm-purgeable-stolen-system0
       [Size of resident and purgeable memory bufers. Unit: drm_i915]
  drm-purgeable-system0
       [Size of resident and purgeable memory bufers. Unit: drm_i915]
  drm-resident-stolen-system0
       [Size of resident memory bufers. Unit: drm_i915]
  drm-resident-system0
       [Size of resident memory bufers. Unit: drm_i915]
  drm-shared-stolen-system0
       [Size of shared memory bufers. Unit: drm_i915]
  drm-shared-system0
       [Size of shared memory bufers. Unit: drm_i915]
  drm-total-stolen-system0
       [Size of shared and private memory. Unit: drm_i915]
  drm-total-system0
       [Size of shared and private memory. Unit: drm_i915]
```

System wide data can be gathered:
```
$ perf stat -x, -I 1000 -e drm-active-stolen-system0,drm-active-system0,drm-engine-capacity-video,drm-engine-copy,drm-engine-render,drm-engine-video,drm-engine-video-enhance,drm-purgeable-stolen-system0,drm-purgeable-system0,drm-resident-stolen-system0,drm-resident-system0,drm-shared-stolen-system0,drm-shared-system0,drm-total-stolen-system0,drm-total-system0
1.000904910,0,bytes,drm-active-stolen-system0,1,100.00,,
1.000904910,0,bytes,drm-active-system0,1,100.00,,
1.000904910,36,capacity,drm-engine-capacity-video,1,100.00,,
1.000904910,0,ns,drm-engine-copy,1,100.00,,
1.000904910,1472970566175,ns,drm-engine-render,1,100.00,,
1.000904910,0,ns,drm-engine-video,1,100.00,,
1.000904910,0,ns,drm-engine-video-enhance,1,100.00,,
1.000904910,0,bytes,drm-purgeable-stolen-system0,1,100.00,,
1.000904910,38199296,bytes,drm-purgeable-system0,1,100.00,,
1.000904910,0,bytes,drm-resident-stolen-system0,1,100.00,,
1.000904910,4643196928,bytes,drm-resident-system0,1,100.00,,
1.000904910,0,bytes,drm-shared-stolen-system0,1,100.00,,
1.000904910,1886871552,bytes,drm-shared-system0,1,100.00,,
1.000904910,0,bytes,drm-total-stolen-system0,1,100.00,,
1.000904910,4643196928,bytes,drm-total-system0,1,100.00,,
2.264426839,0,bytes,drm-active-stolen-system0,1,100.00,,
```

Or for a particular process:
```
$ perf stat -x, -I 1000 -e drm-active-stolen-system0,drm-active-system0,drm-engine-capacity-video,drm-engine-copy,drm-engine-render,drm-engine-video,drm-engine-video-enhance,drm-purgeable-stolen-system0,drm-purgeable-system0,drm-resident-stolen-system0,drm-resident-system0,drm-shared-stolen-system0,drm-shared-system0,drm-total-stolen-system0,drm-total-system0 -p 200027
1.001040274,0,bytes,drm-active-stolen-system0,6,100.00,,
1.001040274,0,bytes,drm-active-system0,6,100.00,,
1.001040274,12,capacity,drm-engine-capacity-video,6,100.00,,
1.001040274,0,ns,drm-engine-copy,6,100.00,,
1.001040274,1542300,ns,drm-engine-render,6,100.00,,
1.001040274,0,ns,drm-engine-video,6,100.00,,
1.001040274,0,ns,drm-engine-video-enhance,6,100.00,,
1.001040274,0,bytes,drm-purgeable-stolen-system0,6,100.00,,
1.001040274,13516800,bytes,drm-purgeable-system0,6,100.00,,
1.001040274,0,bytes,drm-resident-stolen-system0,6,100.00,,
1.001040274,27746304,bytes,drm-resident-system0,6,100.00,,
1.001040274,0,bytes,drm-shared-stolen-system0,6,100.00,,
1.001040274,0,bytes,drm-shared-system0,6,100.00,,
1.001040274,0,bytes,drm-total-stolen-system0,6,100.00,,
1.001040274,27746304,bytes,drm-total-system0,6,100.00,,
2.016629075,0,bytes,drm-active-stolen-system0,6,100.00,,
```

As with the hwmon PMU, high numbered PMU types are used to encode
multiple possible "DRM" PMUs. The appropriate fdinfo is found by
scanning /proc and filtering which fdinfos to read with stat. To avoid
some unneeding scanning, events not starting with "drm-" are
ignored. The patch builds on commit 57e13264dcea ("perf pmus:
Restructure pmu_read_sysfs to scan fewer PMUs") and later so that only
if full wild carding is being done, the PMU starts with "drm_" or the
event starts with "drm-" will /proc be scanned. That is there should
be little to no cost in this PMU unless DRM events are requested.

Signed-off-by: Ian Rogers <irogers@google.com>
Link: https://lore.kernel.org/r/20250624231837.179536-3-irogers@google.com
Signed-off-by: Namhyung Kim <namhyung@kernel.org>

1 files changed, 9 insertions, 0 deletions

diff --git a/tools/perf/util/evsel.c b/tools/perf/util/evsel.c
index d55482f094bf..9c50c3960487 100644
--- a/tools/perf/util/evsel.c
+++ b/tools/perf/util/evsel.c
@@ -56,6 +56,7 @@
 #include "off_cpu.h"
 #include "pmu.h"
 #include "pmus.h"
+#include "drm_pmu.h"
 #include "hwmon_pmu.h"
 #include "tool_pmu.h"
 #include "rlimit.h"
@@ -1889,6 +1890,9 @@ int evsel__read_counter(struct evsel *evsel, int cpu_map_idx, int thread)
 	if (evsel__is_hwmon(evsel))
 		return evsel__hwmon_pmu_read(evsel, cpu_map_idx, thread);
 
+	if (evsel__is_drm(evsel))
+		return evsel__drm_pmu_read(evsel, cpu_map_idx, thread);
+
 	if (evsel__is_retire_lat(evsel))
 		return evsel__tpebs_read(evsel, cpu_map_idx, thread);
 
@@ -2610,6 +2614,11 @@ fallback_missing_features:
 					     start_cpu_map_idx,
 					     end_cpu_map_idx);
 	}
+	if (evsel__is_drm(evsel)) {
+		return evsel__drm_pmu_open(evsel, threads,
+					   start_cpu_map_idx,
+					   end_cpu_map_idx);
+	}
 
 	for (idx = start_cpu_map_idx; idx < end_cpu_map_idx; idx++) {
 		cpu = perf_cpu_map__cpu(cpus, idx);