feat(hal): add RK3588 (Radxa CM5) HAL with sysfs fan control (#155)

Co-authored-by: Claude Opus 4.5 <noreply@anthropic.com>
Co-authored-by: Cedric Specht <cedric@specht-labs.de>

scripts/find-tach-gpio.sh

@@ -0,0 +1,115 @@
+#!/bin/bash
+# find-tach-gpio.sh - Safely probe GPIOs to find fan tachometer signal
+# Run on Radxa node with fan at 100%: sudo ./find-tach-gpio.sh
+#
+# The tachometer generates 2 pulses per revolution. At 5000 RPM:
+#   5000 RPM / 60 = 83.33 RPS * 2 pulses = ~167 Hz
+# At 3000 RPM: ~100 Hz
+# We look for any GPIO showing periodic edge events.
+
+set -e
+
+PROBE_DURATION=1       # seconds to monitor each GPIO
+MIN_EVENTS=10          # minimum events to consider "active" (10 events in 1s = 600 RPM minimum)
+DELAY_BETWEEN=0.5      # seconds between probes to let system settle
+
+# Colors for output
+RED='\033[0;31m'
+GREEN='\033[0;32m'
+YELLOW='\033[1;33m'
+NC='\033[0m' # No Color
+
+echo "=== Fan Tachometer GPIO Finder ==="
+echo ""
+
+# Check if running as root (needed for gpiomon)
+if [ "$EUID" -ne 0 ]; then
+    echo -e "${RED}Please run as root (sudo)${NC}"
+    exit 1
+fi
+
+# Check fan speed
+FAN_PWM=$(cat /sys/class/hwmon/hwmon8/pwm1 2>/dev/null || echo "unknown")
+echo "Current fan PWM: $FAN_PWM (should be 255 for best detection)"
+if [ "$FAN_PWM" != "255" ]; then
+    echo -e "${YELLOW}Setting fan to 100% for detection...${NC}"
+    echo 255 > /sys/class/hwmon/hwmon8/pwm1
+    sleep 2  # Let fan spin up
+fi
+echo ""
+
+# Get list of gpiochips
+CHIPS=$(ls /dev/gpiochip* | sed 's|/dev/||')
+
+echo "Scanning GPIO chips: $CHIPS"
+echo "Probe duration: ${PROBE_DURATION}s per line, minimum ${MIN_EVENTS} events to flag"
+echo ""
+
+FOUND_CANDIDATES=""
+
+for chip in $CHIPS; do
+    # Get number of lines for this chip
+    NUM_LINES=$(gpioinfo $chip 2>/dev/null | wc -l)
+    NUM_LINES=$((NUM_LINES - 1))  # Subtract header line
+
+    if [ "$NUM_LINES" -le 0 ]; then
+        continue
+    fi
+
+    echo -e "${YELLOW}=== Scanning $chip ($NUM_LINES lines) ===${NC}"
+
+    for line in $(seq 0 $((NUM_LINES - 1))); do
+        # Check if line is already in use
+        LINE_INFO=$(gpioinfo $chip 2>/dev/null | grep "line *$line:" || true)
+        if echo "$LINE_INFO" | grep -q "\[used\]"; then
+            # Skip lines that are in use
+            continue
+        fi
+
+        # Probe the line
+        printf "  Line %2d: " "$line"
+
+        # Run gpiomon with timeout, count events
+        EVENTS=$(timeout ${PROBE_DURATION}s gpiomon --num-events=100 $chip $line 2>&1 | wc -l || echo "0")
+
+        if [ "$EVENTS" -ge "$MIN_EVENTS" ]; then
+            # Calculate approximate frequency
+            FREQ=$((EVENTS / PROBE_DURATION))
+            RPM_ESTIMATE=$((FREQ * 60 / 2))  # 2 pulses per revolution
+            echo -e "${GREEN}ACTIVE! $EVENTS events (~${FREQ} Hz, ~${RPM_ESTIMATE} RPM)${NC}"
+            FOUND_CANDIDATES="$FOUND_CANDIDATES\n  $chip line $line: $EVENTS events (~${RPM_ESTIMATE} RPM)"
+        elif [ "$EVENTS" -gt 0 ]; then
+            echo "$EVENTS events (noise?)"
+        else
+            echo "no events"
+        fi
+
+        # Small delay to let system settle
+        sleep $DELAY_BETWEEN
+    done
+    echo ""
+done
+
+echo "=== Scan Complete ==="
+if [ -n "$FOUND_CANDIDATES" ]; then
+    echo -e "${GREEN}Candidate tachometer GPIOs found:${NC}"
+    echo -e "$FOUND_CANDIDATES"
+    echo ""
+    echo "To verify, try monitoring the candidate with varying fan speeds:"
+    echo "  gpiomon --num-events=50 <chip> <line>"
+    echo ""
+    echo "Then add to device tree or HAL configuration."
+else
+    echo -e "${YELLOW}No active GPIOs found.${NC}"
+    echo "Possible reasons:"
+    echo "  - Fan tachometer not connected on this carrier board"
+    echo "  - Tachometer uses a different interface (I2C, ADC, etc.)"
+    echo "  - Fan doesn't have tachometer wire connected"
+fi
+
+# Restore fan to auto if we changed it
+if [ "$FAN_PWM" != "255" ] && [ "$FAN_PWM" != "unknown" ]; then
+    echo ""
+    echo "Restoring fan PWM to $FAN_PWM"
+    echo "$FAN_PWM" > /sys/class/hwmon/hwmon8/pwm1
+fi