pelt scheduler: add new tests to validate pelt

Runner/suites/Kernel/Scheduler/PELT_config/PELT_config.yaml

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+metadata:
+  name: pelt-config
+  format: "Lava-Test Test Definition 1.0"
+  description: "Validates kernel configuration required for PELT (Per-Entity Load Tracking) scheduler"
+  maintainer:
+    - vnarapar@qti.qualcomm.com
+  os:
+    - linux
+  scope:
+    - functional
+  devices:
+    - rb3gen2
+    - qcs6490
+    - qcs8300
+    - qcs9100
+    - sa8775p
+
+run:
+  steps:
+    - REPO_PATH=$PWD
+    - cd "$REPO_PATH/Runner/suites/Kernel/Scheduler/PELT_config"  || true
+    - ./run.sh
+    - $REPO_PATH/Runner/utils/send-to-lava.sh PELT_config.res

Runner/suites/Kernel/Scheduler/PELT_config/README.md

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+# PELT_config — PELT Kernel Configuration Validation
+
+## Overview
+
+Validates that the kernel is built with the configurations required for
+**PELT (Per-Entity Load Tracking)**, the Linux CFS scheduler mechanism that
+tracks CPU utilization per scheduling entity (tasks and task groups).
+
+## What Is Tested
+
+| Config | Required | Purpose |
+|---|---|---|
+| `CONFIG_SMP` | Yes | Multi-CPU support — PELT load balancing is SMP-only |
+| `CONFIG_FAIR_GROUP_SCHED` | Yes | Per-entity load tracking across scheduling groups |
+| `CONFIG_SCHED_DEBUG` | Optional | Enables `/sys/kernel/debug/sched` and `/proc/<pid>/sched` |
+| `CONFIG_CFS_BANDWIDTH` | Optional | CFS bandwidth control (uses PELT util signals) |
+| `CONFIG_NO_HZ_COMMON` | Optional | Tickless kernel — affects PELT decay accuracy |
+| `CONFIG_SCHED_AUTOGROUP` | Optional | Automatic task group creation |
+| `CONFIG_CGROUP_SCHED` | Optional | cgroup-based scheduling (PELT tracks per cgroup) |
+| `CONFIG_CPU_FREQ_GOV_SCHEDUTIL` | Optional | schedutil governor — consumes PELT util_avg |
+
+## Pass / Fail / Skip Criteria
+
+- **SKIP**: `/proc/config.gz` not present (CONFIG_IKCONFIG not enabled)
+- **FAIL**: `CONFIG_SMP` or `CONFIG_FAIR_GROUP_SCHED` not enabled
+- **PASS**: All required configs enabled (optional configs logged as warnings only)
+
+## Usage
+
+```sh
+./run.sh
+```
+
+## Dependencies
+
+- `/proc/config.gz` (CONFIG_IKCONFIG + CONFIG_IKCONFIG_PROC)
+- `grep`, `zgrep` or `gzip` (provided by functestlib)

Runner/suites/Kernel/Scheduler/PELT_config/run.sh

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+#!/bin/sh
+
+# Copyright (c) Qualcomm Technologies, Inc. and/or its subsidiaries.
+# SPDX-License-Identifier: BSD-3-Clause
+
+# Robustly find and source init_env
+SCRIPT_DIR="$(cd "$(dirname "$0")" && pwd)"
+INIT_ENV=""
+SEARCH="$SCRIPT_DIR"
+while [ "$SEARCH" != "/" ]; do
+    if [ -f "$SEARCH/init_env" ]; then
+        INIT_ENV="$SEARCH/init_env"
+        break
+    fi
+    SEARCH=$(dirname "$SEARCH")
+done
+
+if [ -z "$INIT_ENV" ]; then
+    echo "[ERROR] Could not find init_env (starting at $SCRIPT_DIR)" >&2
+    exit 1
+fi
+
+if [ -z "${__INIT_ENV_LOADED:-}" ]; then
+    # shellcheck disable=SC1090
+    . "$INIT_ENV"
+fi
+
+# shellcheck disable=SC1090,SC1091
+. "$TOOLS/functestlib.sh"
+
+TESTNAME="PELT_config"
+test_path=$(find_test_case_by_name "$TESTNAME")
+cd "$test_path" || exit 1
+res_file="./$TESTNAME.res"
+
+log_info "================================================================================"
+log_info "============ Starting $TESTNAME Testcase ======================================="
+log_info "================================================================================"
+log_info "Validates kernel configuration required for PELT (Per-Entity Load Tracking)"
+
+if ! check_dependencies grep; then
+    echo "$TESTNAME SKIP" > "$res_file"
+    exit 0
+fi
+
+pass="true"
+
+log_info "=== Core PELT / CFS Kernel Configs ==="
+
+if [ ! -f /proc/config.gz ]; then
+    log_warn "/proc/config.gz not found  -  kernel config checks will be skipped"
+    log_warn "Ensure CONFIG_IKCONFIG and CONFIG_IKCONFIG_PROC are enabled in the kernel"
+else
+    CORE_CONFIGS="CONFIG_FAIR_GROUP_SCHED CONFIG_SMP"
+
+    if ! check_kernel_config "$CORE_CONFIGS"; then
+        log_fail "Core Scheduler kernel config validation failed"
+        pass=false
+    else
+        log_pass "Core Scheduler configs available"
+    fi
+
+    OPTIONAL_CONFIGS="CONFIG_SCHED_DEBUG CONFIG_CFS_BANDWIDTH CONFIG_NO_HZ_COMMON CONFIG_SCHED_AUTOGROUP CONFIG_CGROUP_SCHED CONFIG_CPU_FREQ_GOV_SCHEDUTIL"
+
+    log_info "Checking optional Scheduler configurations..."
+    for cfg in $OPTIONAL_CONFIGS; do
+        if zgrep -qE "^${cfg}=(y|m)" /proc/config.gz 2>/dev/null; then
+            log_pass "  Optional config $cfg is enabled"
+        else
+            log_info "  Optional config $cfg is not enabled (optional)"
+        fi
+    done
+fi
+
+if [ "$pass" = "true" ]; then
+    log_pass "$TESTNAME : Test Passed"
+    echo "$TESTNAME PASS" > "$res_file"
+else
+    log_fail "$TESTNAME : Test Failed"
+    echo "$TESTNAME FAIL" > "$res_file"
+fi
+
+log_info "-------------------Completed $TESTNAME Testcase----------------------------"
+exit 0

Runner/suites/Kernel/Scheduler/PELT_decay/PELT_decay.yaml

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+metadata:
+  name: pelt-decay
+  format: "Lava-Test Test Definition 1.0"
+  description: "Validates PELT exponential decay: util_avg must decrease after CPU load stops"
+  maintainer:
+    - vnarapar@qti.qualcomm.com
+  os:
+    - linux
+  scope:
+    - functional
+  devices:
+    - rb3gen2
+    - qcs6490
+    - qcs8300
+    - qcs9100
+    - sa8775p
+
+run:
+  steps:
+    - REPO_PATH=$PWD
+    - cd "$REPO_PATH/Runner/suites/Kernel/Scheduler/PELT_decay"  || true
+    - ./run.sh
+    - $REPO_PATH/Runner/utils/send-to-lava.sh PELT_decay.res

Runner/suites/Kernel/Scheduler/PELT_decay/README.md

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+# PELT_decay — PELT Exponential Decay Validation
+
+## Overview
+
+Validates that **PELT (Per-Entity Load Tracking) exponential decay** is
+functioning correctly in the kernel. PELT uses a geometric series with a
+~32 ms half-life to track CPU utilization. After a task stops running,
+its `util_avg` must decay toward zero — this is the mechanism that allows
+the scheduler and cpufreq governors to reduce CPU frequency after load drops.
+
+This is the **only** testcase in the PELT suite that explicitly validates
+decay. The other tests (`PELT_load_tracking`, `PELT_schedutil`) only validate
+accumulation (load going up), not the decay direction.
+
+## PELT Decay Theory
+
+```
+util_avg(t) = util_avg(t0) × 0.5^( Δt / 32ms )
+
+Half-life  = 32 ms  (one PELT period = 1024 µs)
+After 100ms idle:  util_avg → 11.5% of peak
+After 200ms idle:  util_avg →  1.3% of peak
+After 1000ms idle: util_avg → ~0%   of peak  (< 0.001%)
+```
+
+## Two Validation Methods
+
+### Method 1: `/proc/self/sched` `se.avg.util_avg` (Primary)
+
+**Requires:** `CONFIG_SCHED_DEBUG`
+
+The test script itself performs a CPU-bound busy loop for ~3 seconds,
+saturating its own PELT `util_avg`. It then reads `util_avg` immediately
+after the loop (should be high), sleeps 1 second, and reads again (should
+be near zero).
+
+```
+1. Read baseline util_avg  (shell is idle → low)
+2. Run arithmetic busy loop for ~3s  (saturates util_avg → near 1024)
+3. Read peak util_avg  (should be > 100/1024)
+4. Sleep 1 second  (~31 PELT half-lives → >99.9% theoretical decay)
+5. Read decayed util_avg  (should be < peak/2)
+6. Assert: decayed_util < peak_util / 2
+```
+
+**Pass threshold:** `decayed_util < peak_util / 2` (50% decay after 1s).
+This is extremely conservative — theoretical decay after 1s is >99.9%.
+
+### Method 2: schedutil Frequency Proxy (Secondary)
+
+**Requires:** `schedutil` cpufreq governor active
+
+`schedutil` translates PELT `util_avg` into CPU frequency requests. When
+`util_avg` decays after load stops, `schedutil` should lower the frequency.
+
+```
+1. Record idle frequency
+2. Spawn background busy loop for 3s → record peak frequency
+3. Kill load, wait 2 seconds
+4. Record post-decay frequency
+5. Assert: post_decay_freq < load_freq
+```
+
+This method is **informational** — a warning is issued if frequency does
+not drop, but it does not cause a FAIL (thermal floors, rate_limit_us, or
+platform-specific governor behaviour can prevent immediate frequency drop).
+
+## Pass / Fail / Skip Criteria
+
+| Condition | Result |
+|---|---|
+| Neither method available | SKIP |
+| Method 1 available, decay ≥ 50% after 1s | PASS |
+| Method 1 available, decay < 50% after 1s | FAIL |
+| Method 2 only, frequency dropped after load | PASS (informational) |
+| Method 2 only, frequency did not drop | WARN (not FAIL) |
+
+## Why Existing Tests Don't Cover Decay
+
+| Test | What it measures | Decay? |
+|---|---|---|
+| `PELT_schedstat` | `rq_cpu_time` (monotonic counter, never decays) | ✗ |
+| `PELT_load_tracking` | `rq_cpu_time` increases under load | ✗ |
+| `PELT_schedutil` | Frequency rises under load | ✗ (rise only) |
+| **`PELT_decay`** | `util_avg` decreases after load stops | **✓** |
+
+## Usage
+
+```sh
+./run.sh
+```
+
+## Dependencies
+
+- `/proc/self/sched` — `CONFIG_SCHED_DEBUG` (Method 1)
+- `schedutil` governor — `CONFIG_CPU_FREQ_GOV_SCHEDUTIL` (Method 2)
+- `grep`, `awk`, `cat`, `date`