change(esp_trace): skip unused timer reads on the per-event path

Lock take called esp_timer_get_time() before trying the spinlock, and the
C3 default timestamp went through esp_timer's tick-to-us conversion.
Try the lock first, and read systimer ticks directly.

components/esp_trace/CMakeLists.txt

@@ -33,6 +33,7 @@ set(priv_requires
     "esp_driver_gptimer"
     "esp_hal_usb"
     "esp_driver_usb_serial_jtag"
+    "esp_hal_systimer"
     "esp_timer"
     "esp_system"
 )

components/esp_trace/Kconfig

@@ -142,6 +142,7 @@ menu "ESP Trace Configuration"
         prompt "Trace timestamp source"
         default ESP_TRACE_TS_SOURCE_CCOUNT if ESP_SYSTEM_SINGLE_CORE_MODE && !PM_ENABLE && !IDF_TARGET_ESP32C3
         default ESP_TRACE_TS_SOURCE_GPTIMER if !ESP_SYSTEM_SINGLE_CORE_MODE && !PM_ENABLE && !IDF_TARGET_ESP32C3
+        default ESP_TRACE_TS_SOURCE_SYSTIMER if SOC_SYSTIMER_SUPPORTED && (PM_ENABLE || IDF_TARGET_ESP32C3)
         default ESP_TRACE_TS_SOURCE_ESP_TIMER if PM_ENABLE || IDF_TARGET_ESP32C3
         help
             Select the timestamp source for tracing.
@@ -154,6 +155,15 @@ menu "ESP Trace Configuration"
             bool "General Purpose Timer (Timer Group)"
             depends on !PM_ENABLE && !IDF_TARGET_ESP32C3
 
+        config ESP_TRACE_TS_SOURCE_SYSTIMER
+            bool "Systimer raw ticks"
+            depends on SOC_SYSTIMER_SUPPORTED
+            help
+                Read the systimer counter directly. This is the same clock
+                esp_timer uses, without the tick-to-microsecond conversion.
+                Timestamps are in raw ticks (16 MHz on most targets); host
+                tools get the rate from the trace stream.
+
         config ESP_TRACE_TS_SOURCE_ESP_TIMER
             bool "esp_timer high resolution timer"
 

components/esp_trace/include/esp_trace_util.h

@@ -20,8 +20,8 @@ extern "C" {
  * @brief Initialize the trace timestamp source.
  *
  * This function initializes the trace timestamp source based on the configured
- * source. The timestamp source can be the CPU cycle counter, esp_timer, or
- * Timer Group, depending on configuration.
+ * source. The timestamp source can be the CPU cycle counter, esp_timer,
+ * Timer Group, or systimer, depending on configuration.
  *
  * @return The timestamp frequency in Hz.
  */
@@ -31,7 +31,8 @@ uint32_t esp_trace_timestamp_init(void);
  * @brief Get the current timestamp value from the configured source for ESP trace.
  *
  * This function returns the current timestamp value, which can be sourced from
- * the CPU cycle counter, esp_timer, or Timer Group, depending on configuration.
+ * the CPU cycle counter, esp_timer, Timer Group, or systimer, depending on
+ * configuration.
  *
  * @return The current timestamp value as a 32-bit unsigned integer.
  */

components/esp_trace/src/ports/port_utils.c

@@ -25,12 +25,20 @@
 // Determine which timer to use as timestamp source
 #if CONFIG_ESP_TRACE_TS_SOURCE_CCOUNT
 #define TS_USE_CCOUNT 1
+#elif CONFIG_ESP_TRACE_TS_SOURCE_SYSTIMER
+#define TS_USE_SYSTIMER 1
 #elif CONFIG_ESP_TRACE_TS_SOURCE_ESP_TIMER
 #define TS_USE_ESP_TIMER 1
 #else
 #define TS_USE_TIMERGROUP 1
 #endif
 
+#if TS_USE_SYSTIMER
+#include "hal/systimer_ll.h"
+#include "soc/systimer_struct.h"
+#include "esp_private/systimer.h"
+#endif // TS_USE_SYSTIMER
+
 #if TS_USE_TIMERGROUP
 #include "driver/gptimer.h"
 
@@ -52,13 +60,17 @@ static gptimer_handle_t s_trace_gptimer;
 #define ESP_TRACE_TIMESTAMP_FREQ  (CONFIG_ESP_DEFAULT_CPU_FREQ_MHZ * 1000000)
 #endif // TS_USE_CCOUNT
 
+#if TS_USE_SYSTIMER
+#define ESP_TRACE_TIMESTAMP_FREQ  ((uint32_t)systimer_us_to_ticks(1000000))
+#endif // TS_USE_SYSTIMER
+
 // System Frequency.
 #define ESP_TRACE_CPU_FREQ        (esp_clk_cpu_freq())
 
 uint32_t esp_trace_timestamp_init(void)
 {
     /* We only need to initialize something if we use Timer Group.
-     * esp_timer and ccount can be used as is.
+     * esp_timer, systimer, and ccount can be used as is.
      */
 #if TS_USE_TIMERGROUP
     // get clock source frequency
@@ -83,7 +95,12 @@ uint32_t esp_trace_timestamp_init(void)
 
 uint32_t esp_trace_timestamp_get(void)
 {
-#if TS_USE_TIMERGROUP
+#if TS_USE_SYSTIMER
+    /* Set the "update" bit and wait for acknowledgment */
+    systimer_ll_counter_snapshot(&SYSTIMER, SYSTIMER_COUNTER_ESPTIMER);
+    while (!systimer_ll_is_counter_value_valid(&SYSTIMER, SYSTIMER_COUNTER_ESPTIMER)) {}
+    return systimer_ll_get_counter_value_low(&SYSTIMER, SYSTIMER_COUNTER_ESPTIMER);
+#elif TS_USE_TIMERGROUP
     uint64_t ts = 0;
     gptimer_get_raw_count(s_trace_gptimer, &ts);
     return (uint32_t)ts; // return lower part of counter value
@@ -133,6 +150,11 @@ void esp_trace_lock_init(esp_trace_lock_t *lock)
 
 esp_err_t esp_trace_lock_take(esp_trace_lock_t *lock, uint32_t tmo_us)
 {
+    /* Skip tmo_init's esp_timer read when the lock is free. */
+    if (portTRY_ENTER_CRITICAL(&lock->mux, 0) == pdTRUE) {
+        return ESP_OK;
+    }
+
     esp_trace_tmo_t tmo;
     esp_trace_tmo_init(&tmo, tmo_us);
 

examples/system/tracing/sysview_tracing/sdkconfig.defaults

@@ -3,7 +3,7 @@ CONFIG_FREERTOS_HZ=1000
 # Enable FreeRTOS SystemView Tracing by default
 CONFIG_ESP_TRACE_ENABLE=y
 CONFIG_ESP_TRACE_LIB_EXTERNAL=y
-CONFIG_ESP_TRACE_TS_SOURCE_ESP_TIMER=y
+CONFIG_ESP_TRACE_TS_SOURCE_SYSTIMER=y
 CONFIG_SEGGER_SYSVIEW_EVT_OVERFLOW_ENABLE=y
 CONFIG_SEGGER_SYSVIEW_EVT_ISR_ENTER_ENABLE=y
 CONFIG_SEGGER_SYSVIEW_EVT_ISR_EXIT_ENABLE=y

examples/system/tracing/sysview_tracing/sdkconfig.defaults.esp32

@@ -0,0 +1 @@
+CONFIG_ESP_TRACE_TS_SOURCE_ESP_TIMER=y