Merge branch 'refactor/rtc_init_before_mspi_tuning' into 'master'

fix(startup): move rtc initialization before MSPI timing tuning to improve stability

See merge request espressif/esp-idf!31200

components/esp_hw_support/include/esp_private/rtc_clk.h

@@ -74,12 +74,6 @@ uint32_t rtc_clk_mpll_get_freq(void);
 
 #endif  //#if SOC_CLK_MPLL_SUPPORTED
 
-/**
- * @brief Workaround for C2, S3, C6, H2. Trigger the calibration of PLL. Should be called when the bootloader doesn't provide a good enough PLL accuracy.
-*/
-void rtc_clk_recalib_bbpll(void);
-
-
 #ifdef __cplusplus
 }
 #endif

components/esp_hw_support/port/esp32c2/rtc_clk.c

@@ -356,24 +356,6 @@ bool rtc_dig_8m_enabled(void)
     return clk_ll_rc_fast_digi_is_enabled();
 }
 
-// Workaround for bootloader not calibrated well issue.
-// Placed in IRAM because disabling BBPLL may influence the cache
-void rtc_clk_recalib_bbpll(void)
-{
-    rtc_cpu_freq_config_t old_config;
-    rtc_clk_cpu_freq_get_config(&old_config);
-
-    // There are two paths we arrive here: 1. CPU reset. 2. Other reset reasons.
-    // - For other reasons, the bootloader will set CPU source to BBPLL and enable it. But there are calibration issues.
-    //   Turn off the BBPLL and do calibration again to fix the issue.
-    // - For CPU reset, the CPU source will be set to XTAL, while the BBPLL is kept to meet USB Serial JTAG's
-    //   requirements. In this case, we don't touch BBPLL to avoid USJ disconnection.
-    if (old_config.source == SOC_CPU_CLK_SRC_PLL) {
-        rtc_clk_cpu_freq_set_xtal();
-        rtc_clk_cpu_freq_set_config(&old_config);
-    }
-}
-
 /* Name used in libphy.a:phy_chip_v7.o
  * TODO: update the library to use rtc_clk_xtal_freq_get
  */

components/esp_hw_support/port/esp32c6/rtc_clk.c

@@ -422,25 +422,6 @@ bool rtc_dig_8m_enabled(void)
     return clk_ll_rc_fast_digi_is_enabled();
 }
 
-// Workaround for bootloader not calibrated well issue.
-// Placed in IRAM because disabling BBPLL may influence the cache
-void rtc_clk_recalib_bbpll(void)
-{
-    rtc_cpu_freq_config_t old_config;
-    rtc_clk_cpu_freq_get_config(&old_config);
-
-    // There are two paths we arrive here: 1. CPU reset. 2. Other reset reasons.
-    // - For other reasons, the bootloader will set CPU source to BBPLL and enable it. But there are calibration issues.
-    //   Turn off the BBPLL and do calibration again to fix the issue.
-    // - For CPU reset, the CPU source will be set to XTAL, while the BBPLL is kept to meet USB Serial JTAG's
-    //   requirements. In this case, we don't touch BBPLL to avoid USJ disconnection.
-    if (old_config.source == SOC_CPU_CLK_SRC_PLL) {
-        rtc_clk_cpu_freq_set_xtal();
-        rtc_clk_cpu_freq_set_config(&old_config);
-    }
-}
-
-
 /* Name used in libphy.a:phy_chip_v7.o
  * TODO: update the library to use rtc_clk_xtal_freq_get
  */

components/esp_hw_support/port/esp32c61/rtc_clk.c

@@ -427,25 +427,6 @@ bool rtc_dig_8m_enabled(void)
     return clk_ll_rc_fast_digi_is_enabled();
 }
 
-// Workaround for bootloader not calibrated well issue.
-// Placed in IRAM because disabling BBPLL may influence the cache
-void rtc_clk_recalib_bbpll(void)
-{
-    rtc_cpu_freq_config_t old_config;
-    rtc_clk_cpu_freq_get_config(&old_config);
-
-    // There are two paths we arrive here: 1. CPU reset. 2. Other reset reasons.
-    // - For other reasons, the bootloader will set CPU source to BBPLL and enable it. But there are calibration issues.
-    //   Turn off the BBPLL and do calibration again to fix the issue.
-    // - For CPU reset, the CPU source will be set to XTAL, while the BBPLL is kept to meet USB Serial JTAG's
-    //   requirements. In this case, we don't touch BBPLL to avoid USJ disconnection.
-    if (old_config.source == SOC_CPU_CLK_SRC_PLL) {
-        rtc_clk_cpu_freq_set_xtal();
-        rtc_clk_cpu_freq_set_config(&old_config);
-    }
-}
-
-
 /* Name used in libphy.a:phy_chip_v7.o
  * TODO: update the library to use rtc_clk_xtal_freq_get
  */

components/esp_hw_support/port/esp32h2/rtc_clk.c

@@ -238,7 +238,7 @@ static void rtc_clk_cpu_freq_to_pll_mhz(int cpu_freq_mhz)
 /**
  * Switch to FLASH_PLL as cpu clock source.
  * On ESP32H2, FLASH_PLL frequency is 64MHz.
- * PLL must alreay be enabled.
+ * PLL must already be enabled.
  */
 static void rtc_clk_cpu_freq_to_flash_pll(uint32_t cpu_freq_mhz, uint32_t cpu_divider)
 {
@@ -474,21 +474,3 @@ bool rtc_dig_8m_enabled(void)
 {
     return clk_ll_rc_fast_digi_is_enabled();
 }
-
-// Workaround for bootloader not calibrated well issue.
-// Placed in IRAM because disabling BBPLL may influence the cache
-void rtc_clk_recalib_bbpll(void)
-{
-    rtc_cpu_freq_config_t old_config;
-    rtc_clk_cpu_freq_get_config(&old_config);
-
-    // There are two paths we arrive here: 1. CPU reset. 2. Other reset reasons.
-    // - For other reasons, the bootloader will set CPU source to BBPLL and enable it. But there are calibration issues.
-    //   Turn off the BBPLL and do calibration again to fix the issue. Flash_PLL comes from the same source as PLL.
-    // - For CPU reset, the CPU source will be set to XTAL, while the BBPLL is kept to meet USB Serial JTAG's
-    //   requirements. In this case, we don't touch BBPLL to avoid USJ disconnection.
-    if (old_config.source == SOC_CPU_CLK_SRC_PLL || old_config.source == SOC_CPU_CLK_SRC_FLASH_PLL) {
-        rtc_clk_cpu_freq_set_xtal();
-        rtc_clk_cpu_freq_set_config(&old_config);
-    }
-}

components/esp_hw_support/port/esp32s3/rtc_clk.c

@@ -187,7 +187,7 @@ static void rtc_clk_bbpll_configure(soc_xtal_freq_t xtal_freq, int pll_freq)
 static void rtc_clk_cpu_freq_to_pll_mhz(int cpu_freq_mhz)
 {
 
-    /* There are totally 6 LDO slaves(all on by default). At the moment of swithing LDO slave, LDO voltage will also change instantaneously.
+    /* There are totally 6 LDO slaves(all on by default). At the moment of switching LDO slave, LDO voltage will also change instantaneously.
      * LDO slave can reduce the voltage change caused by switching frequency.
      * CPU frequency <= 40M : just open 3 LDO slaves; CPU frequency = 80M : open 4 LDO slaves; CPU frequency = 160M : open 5 LDO slaves; CPU frequency = 240M : open 6 LDO slaves;
      *
@@ -460,25 +460,6 @@ bool rtc_dig_8m_enabled(void)
     return clk_ll_rc_fast_digi_is_enabled();
 }
 
-// Workaround for bootloader not calibrated well issue.
-// Placed in IRAM because disabling BBPLL may influence the cache
-void rtc_clk_recalib_bbpll(void)
-{
-    rtc_cpu_freq_config_t old_config;
-    rtc_clk_cpu_freq_get_config(&old_config);
-
-    // There are two paths we arrive here: 1. CPU reset. 2. Other reset reasons.
-    // - For other reasons, the bootloader will set CPU source to BBPLL and enable it. But there are calibration issues.
-    //   Turn off the BBPLL and do calibration again to fix the issue.
-    // - For CPU reset, the CPU source will be set to XTAL, while the BBPLL is kept to meet USB Serial JTAG's
-    //   requirements. In this case, we don't touch BBPLL to avoid USJ disconnection.
-    if (old_config.source == SOC_CPU_CLK_SRC_PLL) {
-        rtc_clk_cpu_freq_set_xtal();
-        rtc_clk_cpu_freq_set_config(&old_config);
-    }
-}
-
-
 /* Name used in libphy.a:phy_chip_v7.o
  * TODO: update the library to use rtc_clk_xtal_freq_get
  */

components/esp_system/fpga_overrides_clk.c

@@ -62,14 +62,18 @@ void bootloader_clock_configure(void)
     REG_WRITE(RTC_XTAL_FREQ_REG, (xtal_freq_mhz) | ((xtal_freq_mhz) << 16));
 }
 
-void esp_clk_init(void)
+void esp_rtc_init(void)
 {
-    s_warn();
 #if SOC_PMU_SUPPORTED
     pmu_init();
 #endif
 }
 
+void esp_clk_init(void)
+{
+    s_warn();
+}
+
 void esp_perip_clk_init(void)
 {
 }

components/esp_system/port/cpu_start.c

@@ -541,6 +541,10 @@ void IRAM_ATTR call_start_cpu0(void)
     // For Octal flash, it's hard to implement a read_id function in OPI mode for all vendors.
     // So we have to read it here in SPI mode, before entering the OPI mode.
     bootloader_flash_update_id();
+
+    // Configure the power related stuff. After this the MSPI timing tuning can be done.
+    esp_rtc_init();
+
     /**
      * This function initialise the Flash chip to the user-defined settings.
      *
@@ -549,14 +553,9 @@ void IRAM_ATTR call_start_cpu0(void)
      * In this stage, we re-configure the Flash (and MSPI) to required configuration
      */
     spi_flash_init_chip_state();
-
-    // In earlier version of ESP-IDF, the PLL provided by bootloader is not stable enough.
-    // Do calibration again here so that we can use better clock for the timing tuning.
-#if CONFIG_ESP_SYSTEM_BBPLL_RECALIB
-    rtc_clk_recalib_bbpll();
-#endif
 #if SOC_MEMSPI_SRC_FREQ_120M
-    // This function needs to be called when PLL is enabled
+    // This function needs to be called when PLL is enabled. Needs to be called after spi_flash_init_chip_state in case
+    // some state of flash is modified.
     mspi_timing_flash_tuning();
 #endif
 

components/esp_system/port/include/esp_clk_internal.h

@@ -18,6 +18,15 @@ extern "C" {
  * Private clock-related functions
  */
 
+/**
+ * @brief Initialize rtc-related settings
+ *
+ * Called from cpu_start.c, not intended to be called from other places.
+ * This function configures the power related stuff.
+ * After this the MSPI timing tuning can be done.
+ */
+void esp_rtc_init(void);
+
 /**
  * @brief Initialize clock-related settings
  *

components/esp_system/port/soc/esp32/clk.c

@@ -106,11 +106,14 @@ static void select_rtc_slow_clk(slow_clk_sel_t slow_clk)
     esp_clk_slowclk_cal_set(cal_val);
 }
 
-__attribute__((weak)) void esp_clk_init(void)
+void esp_rtc_init(void)
 {
     rtc_config_t cfg = RTC_CONFIG_DEFAULT();
     rtc_init(cfg);
+}
 
+__attribute__((weak)) void esp_clk_init(void)
+{
 #if (CONFIG_APP_COMPATIBLE_PRE_V2_1_BOOTLOADERS || CONFIG_APP_INIT_CLK)
     /* Check the bootloader set the XTAL frequency.
 

components/esp_system/port/soc/esp32c2/clk.c

@@ -51,11 +51,18 @@ typedef enum {
 } slow_clk_sel_t;
 
 static void select_rtc_slow_clk(slow_clk_sel_t slow_clk);
+static __attribute__((unused)) void recalib_bbpll(void);
 
 static const char *TAG = "clk";
 
-__attribute__((weak)) void esp_clk_init(void)
+void esp_rtc_init(void)
 {
+#if CONFIG_ESP_SYSTEM_BBPLL_RECALIB
+    // In earlier version of ESP-IDF, the PLL provided by bootloader is not stable enough.
+    // Do calibration again here so that we can use better clock for the timing tuning.
+    recalib_bbpll();
+#endif
+
 #if !CONFIG_IDF_ENV_FPGA
     rtc_config_t cfg = RTC_CONFIG_DEFAULT();
     soc_reset_reason_t rst_reas;
@@ -64,7 +71,12 @@ __attribute__((weak)) void esp_clk_init(void)
         cfg.cali_ocode = 1;
     }
     rtc_init(cfg);
+#endif
+}
 
+__attribute__((weak)) void esp_clk_init(void)
+{
+#if !CONFIG_IDF_ENV_FPGA
 #ifndef CONFIG_XTAL_FREQ_AUTO
     assert(rtc_clk_xtal_freq_get() == CONFIG_XTAL_FREQ);
 #endif
@@ -265,3 +277,21 @@ __attribute__((weak)) void esp_perip_clk_init(void)
     /* Enable RNG clock. */
     periph_module_enable(PERIPH_RNG_MODULE);
 }
+
+// Workaround for bootloader not calibrated well issue.
+// Placed in IRAM because disabling BBPLL may influence the cache
+static void IRAM_ATTR NOINLINE_ATTR recalib_bbpll(void)
+{
+    rtc_cpu_freq_config_t old_config;
+    rtc_clk_cpu_freq_get_config(&old_config);
+
+    // There are two paths we arrive here: 1. CPU reset. 2. Other reset reasons.
+    // - For other reasons, the bootloader will set CPU source to BBPLL and enable it. But there are calibration issues.
+    //   Turn off the BBPLL and do calibration again to fix the issue.
+    // - For CPU reset, the CPU source will be set to XTAL, while the BBPLL is kept to meet USB Serial JTAG's
+    //   requirements. In this case, we don't touch BBPLL to avoid USJ disconnection.
+    if (old_config.source == SOC_CPU_CLK_SRC_PLL) {
+        rtc_clk_cpu_freq_set_xtal();
+        rtc_clk_cpu_freq_set_config(&old_config);
+    }
+}

components/esp_system/port/soc/esp32c3/clk.c

@@ -56,7 +56,7 @@ static void select_rtc_slow_clk(slow_clk_sel_t slow_clk);
 
 static const char *TAG = "clk";
 
-__attribute__((weak)) void esp_clk_init(void)
+void esp_rtc_init(void)
 {
 #if !CONFIG_IDF_ENV_FPGA
     rtc_config_t cfg = RTC_CONFIG_DEFAULT();
@@ -70,7 +70,10 @@ __attribute__((weak)) void esp_clk_init(void)
         cfg.cali_ocode = 1;
     }
     rtc_init(cfg);
+}
 
+__attribute__((weak)) void esp_clk_init(void)
+{
     assert(rtc_clk_xtal_freq_get() == SOC_XTAL_FREQ_40M);
 
     bool rc_fast_d256_is_enabled = rtc_clk_8md256_enabled();

components/esp_system/port/soc/esp32c5/clk.c

@@ -45,7 +45,7 @@ static void select_rtc_slow_clk(soc_rtc_slow_clk_src_t rtc_slow_clk_src);
 static const char *TAG = "clk";
 
 // TODO: [ESP32C5] IDF-8642
-__attribute__((weak)) void esp_clk_init(void)
+void esp_rtc_init(void)
 {
 #if !CONFIG_IDF_ENV_FPGA
 #if SOC_PMU_SUPPORTED
@@ -54,7 +54,13 @@ __attribute__((weak)) void esp_clk_init(void)
     if (esp_rom_get_reset_reason(0) == RESET_REASON_CHIP_POWER_ON) {
         esp_ocode_calib_init();
     }
+#endif
+}
 
+// TODO: [ESP32C5] IDF-8642
+__attribute__((weak)) void esp_clk_init(void)
+{
+#if !CONFIG_IDF_ENV_FPGA
     assert((rtc_clk_xtal_freq_get() == SOC_XTAL_FREQ_48M) || (rtc_clk_xtal_freq_get() == SOC_XTAL_FREQ_40M));
 
     rtc_clk_8m_enable(true);

components/esp_system/port/soc/esp32c6/clk.c

@@ -58,17 +58,29 @@
 #define MHZ (1000000)
 
 static void select_rtc_slow_clk(soc_rtc_slow_clk_src_t rtc_slow_clk_src);
+static __attribute__((unused)) void recalib_bbpll(void);
 
 static const char *TAG = "clk";
 
-__attribute__((weak)) void esp_clk_init(void)
+void esp_rtc_init(void)
 {
+#if CONFIG_ESP_SYSTEM_BBPLL_RECALIB
+    // In earlier version of ESP-IDF, the PLL provided by bootloader is not stable enough.
+    // Do calibration again here so that we can use better clock for the timing tuning.
+    recalib_bbpll();
+#endif
+
 #if !CONFIG_IDF_ENV_FPGA
     pmu_init();
     if (esp_rom_get_reset_reason(0) == RESET_REASON_CHIP_POWER_ON) {
         esp_ocode_calib_init();
     }
+#endif
+}
 
+__attribute__((weak)) void esp_clk_init(void)
+{
+#if !CONFIG_IDF_ENV_FPGA
     assert(rtc_clk_xtal_freq_get() == SOC_XTAL_FREQ_40M);
 
     rtc_clk_8m_enable(true);
@@ -302,3 +314,21 @@ __attribute__((weak)) void esp_perip_clk_init(void)
         WRITE_PERI_REG(LP_CLKRST_LP_CLK_PO_EN_REG, 0);
     }
 }
+
+// Workaround for bootloader not calibrated well issue.
+// Placed in IRAM because disabling BBPLL may influence the cache
+static void IRAM_ATTR NOINLINE_ATTR recalib_bbpll(void)
+{
+    rtc_cpu_freq_config_t old_config;
+    rtc_clk_cpu_freq_get_config(&old_config);
+
+    // There are two paths we arrive here: 1. CPU reset. 2. Other reset reasons.
+    // - For other reasons, the bootloader will set CPU source to BBPLL and enable it. But there are calibration issues.
+    //   Turn off the BBPLL and do calibration again to fix the issue.
+    // - For CPU reset, the CPU source will be set to XTAL, while the BBPLL is kept to meet USB Serial JTAG's
+    //   requirements. In this case, we don't touch BBPLL to avoid USJ disconnection.
+    if (old_config.source == SOC_CPU_CLK_SRC_PLL) {
+        rtc_clk_cpu_freq_set_xtal();
+        rtc_clk_cpu_freq_set_config(&old_config);
+    }
+}

components/esp_system/port/soc/esp32c61/clk.c

@@ -41,14 +41,19 @@ static void select_rtc_slow_clk(soc_rtc_slow_clk_src_t rtc_slow_clk_src);
 
 static const char *TAG = "clk";
 
-__attribute__((weak)) void esp_clk_init(void)
+void esp_rtc_init(void)
 {
 #if !CONFIG_IDF_ENV_FPGA
     pmu_init();
     if (esp_rom_get_reset_reason(0) == RESET_REASON_CHIP_POWER_ON) {
         esp_ocode_calib_init();
     }
+#endif
+}
 
+__attribute__((weak)) void esp_clk_init(void)
+{
+#if !CONFIG_IDF_ENV_FPGA
     assert(rtc_clk_xtal_freq_get() == SOC_XTAL_FREQ_40M);
 
     rtc_clk_8m_enable(true);

components/esp_system/port/soc/esp32h2/clk.c

@@ -58,14 +58,26 @@
 #define MHZ (1000000)
 
 static void select_rtc_slow_clk(soc_rtc_slow_clk_src_t rtc_slow_clk_src);
+static __attribute__((unused)) void recalib_bbpll(void);
 
 static const char *TAG = "clk";
 
+void esp_rtc_init(void)
+{
+#if CONFIG_ESP_SYSTEM_BBPLL_RECALIB
+    // In earlier version of ESP-IDF, the PLL provided by bootloader is not stable enough.
+    // Do calibration again here so that we can use better clock for the timing tuning.
+    recalib_bbpll();
+#endif
+
+#if !CONFIG_IDF_ENV_FPGA
+    pmu_init();
+#endif
+}
+
 __attribute__((weak)) void esp_clk_init(void)
 {
 #if !CONFIG_IDF_ENV_FPGA
-    pmu_init();
-
     assert(rtc_clk_xtal_freq_get() == SOC_XTAL_FREQ_32M);
 
     rtc_clk_8m_enable(true);
@@ -290,3 +302,21 @@ __attribute__((weak)) void esp_perip_clk_init(void)
         WRITE_PERI_REG(LP_CLKRST_LP_CLK_PO_EN_REG, 0);
     }
 }
+
+// Workaround for bootloader not calibrated well issue.
+// Placed in IRAM because disabling BBPLL may influence the cache
+static void IRAM_ATTR NOINLINE_ATTR recalib_bbpll(void)
+{
+    rtc_cpu_freq_config_t old_config;
+    rtc_clk_cpu_freq_get_config(&old_config);
+
+    // There are two paths we arrive here: 1. CPU reset. 2. Other reset reasons.
+    // - For other reasons, the bootloader will set CPU source to BBPLL and enable it. But there are calibration issues.
+    //   Turn off the BBPLL and do calibration again to fix the issue. Flash_PLL comes from the same source as PLL.
+    // - For CPU reset, the CPU source will be set to XTAL, while the BBPLL is kept to meet USB Serial JTAG's
+    //   requirements. In this case, we don't touch BBPLL to avoid USJ disconnection.
+    if (old_config.source == SOC_CPU_CLK_SRC_PLL || old_config.source == SOC_CPU_CLK_SRC_FLASH_PLL) {
+        rtc_clk_cpu_freq_set_xtal();
+        rtc_clk_cpu_freq_set_config(&old_config);
+    }
+}

components/esp_system/port/soc/esp32p4/clk.c

@@ -41,12 +41,15 @@ static void select_rtc_slow_clk(soc_rtc_slow_clk_src_t rtc_slow_clk_src);
 
 static const char *TAG = "clk";
 
-__attribute__((weak)) void esp_clk_init(void)
+void esp_rtc_init(void)
 {
 #if SOC_PMU_SUPPORTED
     pmu_init();
 #endif  //SOC_PMU_SUPPORTED
+}
 
+__attribute__((weak)) void esp_clk_init(void)
+{
     assert(rtc_clk_xtal_freq_get() == SOC_XTAL_FREQ_40M);
 
     rtc_clk_8m_enable(true);

components/esp_system/port/soc/esp32s2/clk.c

@@ -59,7 +59,7 @@ typedef enum {
 
 static void select_rtc_slow_clk(slow_clk_sel_t slow_clk);
 
-__attribute__((weak)) void esp_clk_init(void)
+void esp_rtc_init(void)
 {
     rtc_config_t cfg = RTC_CONFIG_DEFAULT();
     soc_reset_reason_t rst_reas = esp_rom_get_reset_reason(0);
@@ -73,7 +73,10 @@ __attribute__((weak)) void esp_clk_init(void)
         }
     }
     rtc_init(cfg);
+}
 
+__attribute__((weak)) void esp_clk_init(void)
+{
     bool rc_fast_d256_is_enabled = rtc_clk_8md256_enabled();
     rtc_clk_8m_enable(true, rc_fast_d256_is_enabled);
     rtc_clk_fast_src_set(SOC_RTC_FAST_CLK_SRC_RC_FAST);

components/esp_system/port/soc/esp32s3/clk.c

@@ -54,9 +54,16 @@ typedef enum {
 } slow_clk_sel_t;
 
 static void select_rtc_slow_clk(slow_clk_sel_t slow_clk);
+static __attribute__((unused)) void recalib_bbpll(void);
 
-__attribute__((weak)) void esp_clk_init(void)
+void esp_rtc_init(void)
 {
+#if CONFIG_ESP_SYSTEM_BBPLL_RECALIB
+    // In earlier version of ESP-IDF, the PLL provided by bootloader is not stable enough.
+    // Do calibration again here so that we can use better clock for the timing tuning.
+    recalib_bbpll();
+#endif
+
     rtc_config_t cfg = RTC_CONFIG_DEFAULT();
     soc_reset_reason_t rst_reas;
     rst_reas = esp_rom_get_reset_reason(0);
@@ -65,7 +72,10 @@ __attribute__((weak)) void esp_clk_init(void)
         cfg.cali_ocode = 1;
     }
     rtc_init(cfg);
+}
 
+__attribute__((weak)) void esp_clk_init(void)
+{
     assert(rtc_clk_xtal_freq_get() == SOC_XTAL_FREQ_40M);
 
     bool rc_fast_d256_is_enabled = rtc_clk_8md256_enabled();
@@ -325,3 +335,21 @@ __attribute__((weak)) void esp_perip_clk_init(void)
     /* Enable RNG clock. */
     periph_module_enable(PERIPH_RNG_MODULE);
 }
+
+// Workaround for bootloader not calibrated well issue.
+// Placed in IRAM because disabling BBPLL may influence the cache
+static void IRAM_ATTR NOINLINE_ATTR recalib_bbpll(void)
+{
+    rtc_cpu_freq_config_t old_config;
+    rtc_clk_cpu_freq_get_config(&old_config);
+
+    // There are two paths we arrive here: 1. CPU reset. 2. Other reset reasons.
+    // - For other reasons, the bootloader will set CPU source to BBPLL and enable it. But there are calibration issues.
+    //   Turn off the BBPLL and do calibration again to fix the issue.
+    // - For CPU reset, the CPU source will be set to XTAL, while the BBPLL is kept to meet USB Serial JTAG's
+    //   requirements. In this case, we don't touch BBPLL to avoid USJ disconnection.
+    if (old_config.source == SOC_CPU_CLK_SRC_PLL) {
+        rtc_clk_cpu_freq_set_xtal();
+        rtc_clk_cpu_freq_set_config(&old_config);
+    }
+}