fix(esp_pm): safely check ccompare validity in DFS update_ccompare

components/esp_pm/pm_impl.c

@@ -56,10 +56,13 @@
  */
 #define CCOMPARE_UPDATE_TIMEOUT 1000000
 
-/* When changing CCOMPARE, don't allow changes if the difference is less
- * than this. This is to prevent setting CCOMPARE below CCOUNT.
+/* The number of CPU cycles required from obtaining the base ccount to configuring
+   the calculated ccompare value. (In order to avoid ccompare being updated to a value
+   smaller than the current ccount, this update should be discarded if the next tick
+   is too close to this moment, and this value is used to calculate the threshold for
+   determining whether or not a skip is required.)
  */
-#define CCOMPARE_MIN_CYCLES_IN_FUTURE 1000
+#define CCOMPARE_PREPARE_CYCLES_IN_FREQ_UPDATE  60
 #endif // CONFIG_FREERTOS_SYSTICK_USES_CCOUNT
 
 /* When light sleep is used, wake this number of microseconds earlier than
@@ -662,15 +665,17 @@ static void IRAM_ATTR do_switch(pm_mode_t new_mode)
  * would happen without the frequency change.
  * Assumes that the new_frequency = old_frequency * s_ccount_mul / s_ccount_div.
  */
-static void IRAM_ATTR update_ccompare(void)
+static __attribute__((optimize("-O2"))) void IRAM_ATTR update_ccompare(void)
 {
+    uint32_t ccompare_min_cycles_in_future = ((s_ccount_div + s_ccount_mul - 1) / s_ccount_mul) * CCOMPARE_PREPARE_CYCLES_IN_FREQ_UPDATE;
 #if CONFIG_PM_UPDATE_CCOMPARE_HLI_WORKAROUND
     /* disable level 4 and below */
     uint32_t irq_status = XTOS_SET_INTLEVEL(XCHAL_DEBUGLEVEL - 2);
 #endif
     uint32_t ccount = esp_cpu_get_cycle_count();
     uint32_t ccompare = XTHAL_GET_CCOMPARE(XT_TIMER_INDEX);
-    if ((ccompare - CCOMPARE_MIN_CYCLES_IN_FUTURE) - ccount < UINT32_MAX / 2) {
+
+    if ((ccompare - ccompare_min_cycles_in_future) - ccount < UINT32_MAX / 2) {
         uint32_t diff = ccompare - ccount;
         uint32_t diff_scaled = (diff * s_ccount_mul + s_ccount_div - 1) / s_ccount_div;
         if (diff_scaled < _xt_tick_divisor) {