perf tests: Add a DRM PMU test

The test opens any DRM devices so that the shell has fdinfo files
containing the DRM data. The test then uses perf stat to make sure the
events can be read.

Signed-off-by: Ian Rogers <irogers@google.com>
Link: https://lore.kernel.org/r/20250624231837.179536-4-irogers@google.com
Signed-off-by: Namhyung Kim <namhyung@kernel.org>

tools/perf/tests/shell/drm_pmu.sh

@@ -0,0 +1,78 @@
+#!/bin/bash
+# DRM PMU
+# SPDX-License-Identifier: GPL-2.0
+
+set -e
+
+output=$(mktemp /tmp/perf.drm_pmu.XXXXXX.txt)
+
+cleanup() {
+  rm -f "${output}"
+
+  trap - EXIT TERM INT
+}
+
+trap_cleanup() {
+  echo "Unexpected signal in ${FUNCNAME[1]}"
+  cleanup
+  exit 1
+}
+trap trap_cleanup EXIT TERM INT
+
+# Array to store file descriptors and device names
+declare -A device_fds
+
+# Open all devices and store file descriptors. Opening the device will create a
+# /proc/$$/fdinfo file containing the DRM statistics.
+fd_count=3 # Start with file descriptor 3
+for device in /dev/dri/*
+do
+  if [[ ! -c "$device" ]]
+  then
+    continue
+  fi
+  major=$(stat -c "%Hr" "$device")
+  if [[ "$major" != 226 ]]
+  then
+    continue
+  fi
+  echo "Opening $device"
+  eval "exec $fd_count<\"$device\""
+  echo "fdinfo for: $device (FD: $fd_count)"
+  cat "/proc/$$/fdinfo/$fd_count"
+  echo
+  device_fds["$device"]="$fd_count"
+  fd_count=$((fd_count + 1))
+done
+
+if [[ ${#device_fds[@]} -eq 0 ]]
+then
+  echo "No DRM devices found [Skip]"
+  cleanup
+  exit 2
+fi
+
+# For each DRM event
+err=0
+for p in $(perf list --raw-dump drm-)
+do
+  echo -n "Testing perf stat of $p. "
+  perf stat -e "$p" --pid=$$ true > "$output" 2>&1
+  if ! grep -q "$p" "$output"
+  then
+    echo "Missing DRM event in: [Failed]"
+    cat "$output"
+    err=1
+  else
+    echo "[OK]"
+  fi
+done
+
+# Close all file descriptors
+for fd in "${device_fds[@]}"; do
+  eval "exec $fd<&-"
+done
+
+# Finished
+cleanup
+exit $err