cpu/esp_common: port periph/hwrng to ESP-IDF random API

cpu/esp32/include/periph_cpu.h

@@ -407,7 +407,7 @@ typedef struct {
 /**
  * @brief   The address of the register for accessing the hardware RNG.
  */
-#define RNG_DATA_REG_ADDR   (0x3ff75144)
+#define RNG_DATA_REG_ADDR   (WDEV_RND_REG)
 /** @} */
 
 /**

cpu/esp32/periph/hwrng.c

@@ -0,0 +1,65 @@
+/*
+ * Copyright (C) 2019 Gunar Schorcht
+ *
+ * This file is subject to the terms and conditions of the GNU Lesser
+ * General Public License v2.1. See the file LICENSE in the top level
+ * directory for more details.
+ */
+
+/**
+ * @ingroup     cpu_esp32
+ * @ingroup     drivers_periph_hwrng
+ * @{
+ *
+ * @file
+ * @brief       Low-level random number generator driver implementation for ESP32x SoCs
+ *
+ * @author      Gunar Schorcht <gunar@schorcht.net>
+ *
+ * @}
+ */
+
+#include "cpu.h"
+#include "periph_conf.h"
+#include "periph/hwrng.h"
+
+#include "bootloader_random.h"
+#include "esp_random.h"
+#include "soc/wdev_reg.h"
+
+#define RNG_DATA_REG (*(volatile uint32_t *)RNG_DATA_REG_ADDR)
+
+void hwrng_init(void)
+{
+    if (!IS_USED(MODULE_WIFI_ANY)) {
+        /*
+         * The hardware RNG generates random numbers uses the noise in the
+         * RF system of the WiFi or the BT interface as entropy source.
+         * If both are disabled, the random number generator just returns
+         * pseudo-random numbers.
+         * However, the bootloader use an internal non-RF entropy source,
+         * the internal reference voltage noise. This can be re-enabled
+         * after startup as entropy source for applications that don't
+         * use the WiFi or the BT interface.
+         */
+        bootloader_random_enable();
+    }
+}
+
+/**
+ * The RNG implementation of the ESP-IDF also uses the hardware RNG register
+ * RNG_DATA_REG (WDEV_RND_REG) for random number generation, which adds 2 bits
+ * of entropy at each APB clock cycle when WiFi or BT are enabled. However,
+ * it ensures that the random numbers are not read faster than generated
+ * in hardware by including some busy waiting. We therefore use this
+ * implementation here.
+ */
+void hwrng_read(void *buf, unsigned int num)
+{
+    esp_fill_random(buf, num);
+}
+
+uint32_t hwrand(void)
+{
+    return esp_random();
+}

cpu/esp8266/periph/hwrng.c

@@ -7,12 +7,12 @@
  */
 
 /**
- * @ingroup     cpu_esp_common
+ * @ingroup     cpu_esp8266
  * @ingroup     drivers_periph_hwrng
  * @{
  *
  * @file
- * @brief       Low-level random number generator driver implementation for ESP SoCs
+ * @brief       Low-level random number generator driver implementation for ESP8266 SoCs
  *
  * @author      Gunar Schorcht <gunar@schorcht.net>
  *