Add independent watchdog reference implementation for STM32

targets/TARGET_STM/TARGET_STM32F4/watchdog.c

@@ -0,0 +1,116 @@
+#include "watchdog_api.h"
+
+#include "reset_reason_api.h"
+
+#include "device.h"
+
+
+// Platform specific watchdog definitions
+#define LPO_CLOCK_FREQUENCY 40000
+#define MAX_PRESCALER       256
+#define MAX_TIMEOUT         0xFFF
+
+// Number of decrements in the timeout register per millisecond
+#define TICKS_PER_MS (LPO_CLOCK_FREQUENCY / 1000)
+// Maximum timeout that can be specified in milliseconds
+#define MAX_TIMEOUT_MS ((MAX_TIMEOUT / TICKS_PER_MS) * MAX_PRESCALER)
+// Maximum supported watchdog timeout for given prescaler value
+#define CALCULATE_MAX_TIMEOUT_MS(scale) \
+   ((MAX_TIMEOUT / TICKS_PER_MS) * scale)
+
+
+static uint32_t calculate_prescaler_value(const uint32_t timeout_ms)
+{
+    if (timeout_ms > MAX_TIMEOUT_MS) {
+        return 0;
+    }
+
+    for (uint32_t scale = 0; scale < 7; ++scale) {
+        const uint32_t prescaler = (4U << scale);
+
+        if (timeout_ms < CALCULATE_MAX_TIMEOUT_MS(prescaler)) {
+            return scale;
+        }
+    }
+
+    return 0;
+}
+
+
+watchdog_status_t hal_watchdog_init(const watchdog_config_t *config)
+{
+    // Validate the input parameters
+    if (config == NULL) {
+        return WATCHDOG_STATUS_INVALID_ARGUMENT;
+    }
+
+    if (config->timeout_ms > MAX_TIMEOUT_MS) {
+        return WATCHDOG_STATUS_INVALID_ARGUMENT;
+    }
+
+    if (config->window_ms > MAX_TIMEOUT_MS) {
+        return WATCHDOG_STATUS_INVALID_ARGUMENT;
+    }
+
+    if (config->window_ms > config->timeout_ms) {
+        return WATCHDOG_STATUS_INVALID_ARGUMENT;
+    }
+
+    if (config->enable_sleep == false) {
+        return WATCHDOG_STATUS_NOT_SUPPORTED;
+    }
+
+
+    const uint32_t prescaler = calculate_prescaler_value(config->timeout_ms);
+
+    if (prescaler == 0) {
+        return WATCHDOG_STATUS_INVALID_ARGUMENT;
+    }
+
+    // Enable write access to Prescaler(IWDG_PR) and Reload(IWDG_RLR) registers
+    IWDG->KR  = 0x5555;
+
+    // Set the prescaler and timeout values
+    IWDG->RLR = (TICKS_PER_MS * config->timeout_ms) / (4U << prescaler);
+    IWDG->PR  = prescaler;
+
+    // Reload the Watchdog Counter.
+    IWDG->KR = 0xAAAA;
+    // Enable the Independent Watchdog.
+    IWDG->KR = 0xCCCC;
+
+    return WATCHDOG_STATUS_OK;
+}
+
+
+void hal_watchdog_kick(void)
+{
+    IWDG->KR = 0xAAAA;
+}
+
+
+watchdog_status_t hal_watchdog_stop(void)
+{
+    return WATCHDOG_STATUS_NOT_SUPPORTED;
+}
+
+
+uint32_t hal_watchdog_get_reload_value(void)
+{
+    const uint32_t timeout   = (IWDG->RLR & 0xFFF);
+    const uint32_t prescaler = (4U << (IWDG->PR & 0x7));
+
+    return ((timeout / TICKS_PER_MS) * prescaler);
+}
+
+
+bool hal_watchdog_caused_last_reset(void)
+{
+    return (hal_reset_reason_get() == RESET_REASON_WATCHDOG);
+}
+
+
+uint32_t hal_watchdog_get_max_timeout(void)
+{
+    return MAX_TIMEOUT_MS;
+}

targets/targets.json

@@ -1904,7 +1904,8 @@
             "SPI",
             "SPISLAVE",
             "SPI_ASYNCH",
-            "STDIO_MESSAGES"
+            "STDIO_MESSAGES",
+            "WATCHDOG"
         ]
     },
     "MIMXRT1050_EVK": {