esp32s2: add brownout detector support

1. add brownout detector HAL for esp32 and esp32s2
2. enable brownout reset for esp32 rev. 1 and above
3. add approximate brownout detector levels for esp32s2

components/soc/esp32s2/brownout_hal.c

@@ -0,0 +1,46 @@
+
+// Copyright 2020 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 "hal/brownout_hal.h"
+#include "soc/rtc_cntl_struct.h"
+#include "soc/rtc_cntl_reg.h"
+#include "i2c_rtc_clk.h"
+#include "i2c_brownout.h"
+
+
+void brownout_hal_config(const brownout_hal_config_t *cfg)
+{
+    I2C_WRITEREG_MASK_RTC(I2C_BOD, I2C_BOD_THRESHOLD, cfg->threshold);
+    typeof(RTCCNTL.brown_out) brown_out_reg = {
+        .out2_ena = 1,
+        .int_wait = 0x002,
+        .close_flash_ena = cfg->flash_power_down,
+        .pd_rf_ena = cfg->rf_power_down,
+        .rst_wait = 0x3ff,
+        .rst_ena = cfg->reset_enabled,
+        .ena = cfg->enabled,
+    };
+    RTCCNTL.brown_out = brown_out_reg;
+}
+
+void brownout_hal_intr_enable(bool enable)
+{
+    RTCCNTL.int_ena.rtc_brown_out = enable;
+}
+
+void brownout_hal_intr_clear(void)
+{
+    RTCCNTL.int_clr.rtc_brown_out = 1;
+}

components/soc/esp32s2/i2c_brownout.h

@@ -0,0 +1,30 @@
+// Copyright 2020 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.
+
+#pragma once
+
+/**
+ * @file i2c_brownout.h
+ * @brief Register definitions for brownout detector
+ *
+ * This file lists register fields of the brownout detector, located on an internal configuration
+ * bus. These definitions are used via macros defined in i2c_rtc_clk.h.
+ */
+
+#define I2C_BOD            0x61
+#define I2C_BOD_HOSTID     1
+
+#define I2C_BOD_THRESHOLD           0x5
+#define I2C_BOD_THRESHOLD_MSB       2
+#define I2C_BOD_THRESHOLD_LSB       0

components/soc/esp32s2/include/soc/brownout_caps.h

@@ -0,0 +1,25 @@
+// Copyright 2020 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.
+
+#pragma once
+
+#ifdef __cplusplus
+extern "C" {
+#endif
+
+#define SOC_BROWNOUT_RESET_SUPPORTED 1
+
+#ifdef __cplusplus
+}
+#endif

components/soc/esp32s2/sources.cmake

@@ -1,4 +1,5 @@
 set(SOC_SRCS    "adc_periph.c"
+                "brownout_hal.c"
                 "dac_periph.c"
                 "cpu_util.c"
                 "gpio_periph.c"