feat(esp_hw_support): compensate the error introduced to LACT during APB frequency switching

Author: esp-wzh

components/esp_hw_support/linker.lf

@@ -16,6 +16,9 @@ entries:
     if PM_SLP_IRAM_OPT = y:
         rtc_clk (noflash)
         rtc_time (noflash_text)
+    if IDF_TARGET_ESP32 = y:
+        rtc_clk:rtc_clk_cpu_freq_to_pll_mhz (noflash)
+        rtc_clk:rtc_clk_cpu_freq_to_xtal (noflash)
     if SOC_CONFIGURABLE_VDDSDIO_SUPPORTED = y:
         rtc_init:rtc_vddsdio_get_config (noflash)
         rtc_init:rtc_vddsdio_set_config (noflash)

components/esp_hw_support/port/esp32/rtc_clk.c

@@ -402,19 +402,49 @@ static void rtc_clk_cpu_freq_to_8m(void)
     rtc_clk_apb_freq_update(SOC_CLK_RC_FAST_FREQ_APPROX);
 }
 
+#ifndef BOOTLOADER_BUILD
+static const DRAM_ATTR int16_t dfs_lact_conpensate_table[3][3] = {   \
+/* From / To 80     160     240*/   \
+/* 10  */   {138,   220,    18},    \
+/* 20  */   {128,   205,    -3579}, \
+/* 40  */   {34,    100,    0},     \
+};
+
+__attribute__((weak)) IRAM_ATTR int16_t rtc_clk_get_lact_compensation_delay(uint32_t cur_freq, uint32_t tar_freq)
+{
+    return dfs_lact_conpensate_table[(cur_freq == 10) ? 0 : (cur_freq == 20) ? 1 : 2][(tar_freq == 80) ? 0 : (tar_freq == 160) ? 1 : 2];
+}
+#endif
+
 /**
  * Switch to one of PLL-based frequencies. Current frequency can be XTAL or PLL.
  * PLL must already be enabled.
  * @param cpu_freq new CPU frequency
  */
-static void rtc_clk_cpu_freq_to_pll_mhz(int cpu_freq_mhz)
+__attribute__((optimize("-O2")))
+NOINLINE_ATTR static void rtc_clk_cpu_freq_to_pll_mhz(int cpu_freq_mhz)
 {
     int dbias = (cpu_freq_mhz == 240) ? DIG_DBIAS_240M : DIG_DBIAS_80M_160M;
     REG_SET_FIELD(RTC_CNTL_REG, RTC_CNTL_DIG_DBIAS_WAK, dbias);
 #ifndef BOOTLOADER_BUILD
-    timer_ll_set_lact_clock_prescale(TIMER_LL_GET_HW(LACT_MODULE), 80 / LACT_TICKS_PER_US);
+    uint32_t cur_freq = esp_rom_get_cpu_ticks_per_us();
+    int16_t delay_cycle = rtc_clk_get_lact_compensation_delay(cur_freq, cpu_freq_mhz);
+    if (cur_freq <= 40 && delay_cycle >= 0) {
+        timer_ll_set_lact_clock_prescale(TIMER_LL_GET_HW(LACT_MODULE), 80 / LACT_TICKS_PER_US);
+        for (int i = 0; i < delay_cycle; ++i) {
+            __asm__ __volatile__("nop");
+        }
+    }
 #endif
     clk_ll_cpu_set_freq_mhz_from_pll(cpu_freq_mhz);
+#ifndef BOOTLOADER_BUILD
+    if (cur_freq <= 40 && delay_cycle < 0) {
+        for (int i = 0; i > delay_cycle; --i) {
+            __asm__ __volatile__("nop");
+        }
+        timer_ll_set_lact_clock_prescale(TIMER_LL_GET_HW(LACT_MODULE), 80 / LACT_TICKS_PER_US);
+    }
+#endif
     /* adjust ref_tick */
     clk_ll_ref_tick_set_divider(SOC_CPU_CLK_SRC_PLL, cpu_freq_mhz);
     /* switch clock source */