Remove camera capture GPIO interrupt when the rate is higher than 5kHz

If the capture GPIO is exposed to a signal with high frequency changes, a lot of
interrupts are scheduled and the handling of these call can worst-case
starve flight critical processes leading to a loss of control. Since camera capture
is not flight critical, we now give up the capture
functionality and stop the interrupts to prevent the starvation of other processes.

src/drivers/camera_capture/camera_capture.cpp

@@ -40,11 +40,15 @@
  */
 
 #include "camera_capture.hpp"
+#include <px4_platform_common/events.h>
+#include <systemlib/mavlink_log.h>
 
 #include <board_config.h>
 
 #define commandParamToInt(n) static_cast<int>(n >= 0 ? n + 0.5f : n - 0.5f)
 
+using namespace time_literals;
+
 namespace camera_capture
 {
 CameraCapture *g_camera_capture{nullptr};
@@ -104,6 +108,21 @@ CameraCapture::~CameraCapture()
 void
 CameraCapture::capture_callback(uint32_t chan_index, hrt_abstime edge_time, uint32_t edge_state, uint32_t overflow)
 {
+	// Maximum acceptable rate is 5kHz
+	if ((edge_time - _trigger.hrt_edge_time) < 200_us) {
+		++_trigger_rate_exceeded_counter;
+
+		if (_trigger_rate_exceeded_counter > 100) {
+
+			// Trigger rate too high, stop future interrupts
+			up_input_capture_set(_capture_channel, Disabled, 0, nullptr, nullptr);
+			_trigger_rate_failure.store(true);
+		}
+
+	} else if (_trigger_rate_exceeded_counter > 0) {
+		--_trigger_rate_exceeded_counter;
+	}
+
 	_trigger.chan_index = chan_index;
 	_trigger.hrt_edge_time = edge_time;
 	_trigger.edge_state = edge_state;
@@ -140,6 +159,13 @@ CameraCapture::publish_trigger()
 {
 	bool publish = false;
 
+	if (_trigger_rate_failure.load()) {
+		mavlink_log_warning(&_mavlink_log_pub, "Hardware fault: Camera capture disabled\t");
+		events::send(events::ID("camera_capture_trigger_rate_exceeded"),
+			     events::Log::Error, "Hardware fault: Camera capture disabled");
+		_trigger_rate_failure.store(false);
+	}
+
 	camera_trigger_s trigger{};
 
 	// MODES 1 and 2 are not fully tested

src/drivers/camera_capture/camera_capture.hpp

@@ -134,6 +134,10 @@ private:
 
 	hrt_abstime	_pps_hrt_timestamp{0};
 	uint64_t		_pps_rtc_timestamp{0};
+	uint8_t			_trigger_rate_exceeded_counter{0};
+	px4::atomic<bool> _trigger_rate_failure{false};
+
+	orb_advert_t _mavlink_log_pub{nullptr};
 
 	// Signal capture callback
 	void			capture_callback(uint32_t chan_index, hrt_abstime edge_time, uint32_t edge_state, uint32_t overflow);