brownout detector: enable by default

Because of errata related to BOD reset function, brownout is handled as follows:

- attach an ISR to brownout interrupt
- when ISR happens, print a message and do a software restart
- esp_restart_nonos enables RTC watchdog, so if restart fails,
  there will be  one more attempt to restart (using the RTC
  watchdog)

components/esp32/Kconfig

@@ -407,7 +407,6 @@ config TASK_WDT_CHECK_IDLE_TASK_CPU1
 config BROWNOUT_DET
     bool "Hardware brownout detect & reset"
     default y
-    depends on NEEDS_ESP32_NEW_SILICON_REV
     help
         The ESP32 has a built-in brownout detector which can detect if the voltage is lower than
         a specific value. If this happens, it will reset the chip in order to prevent unintended
@@ -452,16 +451,6 @@ config BROWNOUT_DET_LVL
     default 7 if BROWNOUT_DET_LVL_SEL_7
 
 
-config BROWNOUT_DET_RESETDELAY
-    int "Brownout reset delay (in uS)"
-    depends on BROWNOUT_DET
-    range 0 6820
-    default 1000
-    help
-        The brownout detector can reset the chip after a certain delay, in order to make sure e.g. a voltage dip has entirely passed
-        before trying to restart the chip. You can set the delay here.
-
-
 choice ESP32_TIME_SYSCALL
     prompt "Timers used for gettimeofday function"
     default ESP32_TIME_SYSCALL_USE_RTC_FRC1

components/esp32/brownout.c

@@ -0,0 +1,61 @@
+// Copyright 2015-2017 Espressif Systems (Shanghai) PTE LTD
+//
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+//     http://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+
+#include <stdint.h>
+#include <stdio.h>
+#include <stdlib.h>
+#include <stdbool.h>
+#include "sdkconfig.h"
+#include "soc/soc.h"
+#include "soc/cpu.h"
+#include "soc/rtc_cntl_reg.h"
+#include "rom/ets_sys.h"
+#include "esp_system.h"
+#include "driver/rtc_cntl.h"
+#include "freertos/FreeRTOS.h"
+
+#ifdef CONFIG_BROWNOUT_DET_LVL
+#define BROWNOUT_DET_LVL CONFIG_BROWNOUT_DET_LVL
+#else
+#define BROWNOUT_DET_LVL 0
+#endif //CONFIG_BROWNOUT_DET_LVL
+
+static void rtc_brownout_isr_handler()
+{
+    /* Normally RTC ISR clears the interrupt flag after the application-supplied
+     * handler returns. Since restart is called here, the flag needs to be
+     * cleared manually.
+     */
+    REG_WRITE(RTC_CNTL_INT_CLR_REG, RTC_CNTL_BROWN_OUT_INT_CLR);
+    /* Stall the other CPU to make sure the code running there doesn't use UART
+     * at the same time as the following ets_printf.
+     */
+    esp_cpu_stall(!xPortGetCoreID());
+    ets_printf("\r\nBrownout detector was triggered\r\n\r\n");
+    esp_restart_noos();
+}
+
+void esp_brownout_init()
+{
+    REG_WRITE(RTC_CNTL_BROWN_OUT_REG,
+            RTC_CNTL_BROWN_OUT_ENA /* Enable BOD */
+            | RTC_CNTL_BROWN_OUT_PD_RF_ENA /* Automatically power down RF */
+            /* Reset timeout must be set to >1 even if BOR feature is not used */
+            | (2 << RTC_CNTL_BROWN_OUT_RST_WAIT_S)
+            | (BROWNOUT_DET_LVL << RTC_CNTL_DBROWN_OUT_THRES_S));
+
+    ESP_ERROR_CHECK( rtc_isr_register(rtc_brownout_isr_handler, NULL, RTC_CNTL_BROWN_OUT_INT_ENA_M) );
+
+    REG_SET_BIT(RTC_CNTL_INT_ENA_REG, RTC_CNTL_BROWN_OUT_INT_ENA_M);
+}

components/esp32/include/esp_system.h

@@ -59,6 +59,17 @@ void system_restore(void) __attribute__ ((deprecated));
   */
 void esp_restart(void) __attribute__ ((noreturn));
 
+/**
+  * @brief  Internal function to restart PRO and APP CPUs.
+  *
+  * @note This function should not be called from FreeRTOS applications.
+  *       Use esp_restart instead.
+  *
+  * This is an internal function called by esp_restart. It is called directly
+  * by the panic handler and brownout detector interrupt.
+  */
+void esp_restart_noos() __attribute__ ((noreturn));
+
 /**
   * @brief  Restart system.
   *

components/esp32/panic.c

@@ -39,6 +39,7 @@
 #include "esp_spi_flash.h"
 #include "esp_cache_err_int.h"
 #include "esp_app_trace.h"
+#include "esp_system.h"
 #if CONFIG_SYSVIEW_ENABLE
 #include "SEGGER_RTT.h"
 #endif
@@ -409,8 +410,6 @@ static void doBacktrace(XtExcFrame *frame)
     panicPutStr("\r\n\r\n");
 }
 
-void esp_restart_noos() __attribute__ ((noreturn));
-
 /*
   We arrive here after a panic or unhandled exception, when no OCD is detected. Dump the registers to the
   serial port and either jump to the gdb stub, halt the CPU or reboot.

components/soc/esp32/brownout.c

@@ -1,39 +0,0 @@
-// Copyright 2015-2016 Espressif Systems (Shanghai) PTE LTD
-//
-// Licensed under the Apache License, Version 2.0 (the "License");
-// you may not use this file except in compliance with the License.
-// You may obtain a copy of the License at
-
-//     http://www.apache.org/licenses/LICENSE-2.0
-//
-// Unless required by applicable law or agreed to in writing, software
-// distributed under the License is distributed on an "AS IS" BASIS,
-// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
-// See the License for the specific language governing permissions and
-// limitations under the License.
-
-
-#include <stdint.h>
-#include <stdio.h>
-#include <stdlib.h>
-#include <stdbool.h>
-#include "sdkconfig.h"
-#include "soc/soc.h"
-#include "soc/rtc_cntl_reg.h"
-
-
-#if CONFIG_BROWNOUT_DET
-/*
-This file is included in esp-idf, but the menuconfig option for this is disabled because a silicon bug
-prohibits the brownout detector from functioning correctly on the ESP32.
-*/
-
-void esp_brownout_init() {
-    WRITE_PERI_REG(RTC_CNTL_BROWN_OUT_REG, 
-            RTC_CNTL_BROWN_OUT_ENA | (CONFIG_BROWNOUT_DET_LVL << RTC_CNTL_DBROWN_OUT_THRES_S) |
-            RTC_CNTL_BROWN_OUT_RST_ENA | (((CONFIG_BROWNOUT_DET_RESETDELAY*150)/1000) << RTC_CNTL_BROWN_OUT_RST_WAIT_S) |
-            RTC_CNTL_BROWN_OUT_PD_RF_ENA|RTC_CNTL_BROWN_OUT_CLOSE_FLASH_ENA);
-
-}
-
-#endif