feat(core): introduce IWDG driver

[no changelog]

Author: TychoVrahe

core/SConscript.bootloader

@@ -24,6 +24,7 @@ FEATURES_WANTED = [
     "secure_domain",
     "tropic",
     "usb",
+    "iwdg",
     ]
 
 if TREZOR_MODEL in ('T3W1', ):

core/embed/sec/iwdg/inc/sec/iwdg.h

@@ -0,0 +1,37 @@
+/*
+ * This file is part of the Trezor project, https://trezor.io/
+ *
+ * Copyright (c) SatoshiLabs
+ *
+ * This program is free software: you can redistribute it and/or modify
+ * it under the terms of the GNU General Public License as published by
+ * the Free Software Foundation, either version 3 of the License, or
+ * (at your option) any later version.
+ *
+ * This program is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+ * GNU General Public License for more details.
+ *
+ * You should have received a copy of the GNU General Public License
+ * along with this program.  If not, see <http://www.gnu.org/licenses/>.
+ */
+
+#pragma once
+
+#include <trezor_types.h>
+
+#define IWDG_MAX_TIME (60 * 60 * 4)  // 4 hours
+
+/**
+ * @brief Start the Independent Watchdog, to enforce reset after specified time
+ * elapsed.
+ *
+ * The IWDG is clocked from LSI, which is expected to be set to 250 Hz.
+ * The IWDG prescaler is set to 1024, which means that the watchdog
+ * will tick every 4.096 s. The time is floored to the nearest multiple of 4.096
+ * s.
+ *
+ * @param time_s Watchdog timeout in seconds. Time is ceiled to IWDG_MAX_TIME.
+ */
+void iwdg_start(uint32_t time_s);

core/embed/sec/iwdg/stm32/iwdg.c

@@ -0,0 +1,49 @@
+/*
+ * This file is part of the Trezor project, https://trezor.io/
+ *
+ * Copyright (c) SatoshiLabs
+ *
+ * This program is free software: you can redistribute it and/or modify
+ * it under the terms of the GNU General Public License as published by
+ * the Free Software Foundation, either version 3 of the License, or
+ * (at your option) any later version.
+ *
+ * This program is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+ * GNU General Public License for more details.
+ *
+ * You should have received a copy of the GNU General Public License
+ * along with this program.  If not, see <http://www.gnu.org/licenses/>.
+ */
+#ifdef SECURE_MODE
+
+#include <trezor_bsp.h>
+#include <trezor_rtl.h>
+
+#include <sec/iwdg.h>
+
+_Static_assert(LSI_VALUE == 250, "LSI_VALUE must be defined to 250 Hz");
+
+void iwdg_start(uint32_t time_s) {
+  if (time_s > IWDG_MAX_TIME) {
+    // Limit the maximum watchdog timeout to 4 hours
+    time_s = IWDG_MAX_TIME;
+  }
+
+  // Set the reload value based on the desired time in seconds
+  uint32_t reload_value = ((time_s * LSI_VALUE) / 1024) - 1;
+
+  IWDG_HandleTypeDef hiwdg = {0};
+
+  hiwdg.Instance = IWDG;
+  hiwdg.Init.Prescaler = IWDG_PRESCALER_1024;
+  hiwdg.Init.Reload = reload_value;
+  hiwdg.Init.Window = 0xFFF;
+  hiwdg.Init.EWI = 0;
+
+  // Configure the IWDG
+  HAL_IWDG_Init(&hiwdg);
+}
+
+#endif

core/embed/sys/bsp/stm32u5/stm32u5xx_hal_conf.h

@@ -60,7 +60,7 @@ extern "C" {
 #define HAL_HASH_MODULE_ENABLED
 /*#define HAL_HRTIM_MODULE_ENABLED */
 /*#define HAL_IRDA_MODULE_ENABLED */
-/*#define HAL_IWDG_MODULE_ENABLED */
+#define HAL_IWDG_MODULE_ENABLED
 #define HAL_I2C_MODULE_ENABLED
 /*#define HAL_I2S_MODULE_ENABLED */
 #define HAL_LPTIM_MODULE_ENABLED

core/embed/sys/startup/stm32u5/startup_init.c

@@ -91,7 +91,15 @@ void lsi_init(void) {
 
   uint32_t bdcr_temp = RCC->BDCR;
 
-  if (RCC_LSI_DIV1 != (bdcr_temp & RCC_BDCR_LSIPREDIV)) {
+#if LSI_VALUE == 32000
+  uint32_t lsi_div = RCC_LSI_DIV1;
+#elif LSI_VALUE == 250
+  uint32_t lsi_div = RCC_LSI_DIV128;
+#else
+#error Unsupported LSI frequency
+#endif
+
+  if (lsi_div != (bdcr_temp & RCC_BDCR_LSIPREDIV)) {
     if (((bdcr_temp & RCC_BDCR_LSIRDY) == RCC_BDCR_LSIRDY) &&
         ((bdcr_temp & RCC_BDCR_LSION) != RCC_BDCR_LSION)) {
       // If LSIRDY is set while LSION is not enabled, LSIPREDIV can't be updated
@@ -110,7 +118,7 @@ void lsi_init(void) {
     }
 
     // Set LSI division factor
-    MODIFY_REG(RCC->BDCR, RCC_BDCR_LSIPREDIV, 0);
+    MODIFY_REG(RCC->BDCR, RCC_BDCR_LSIPREDIV, lsi_div);
   }
 
   // Enable the Internal Low Speed oscillator (LSI)
@@ -254,7 +262,9 @@ void SystemInit(void) {
 
 #ifdef USE_LSE
   lse_init();
-#else
+#endif
+
+#if defined(USE_LSI) || !defined(USE_LSE)
   lsi_init();
 #endif
 

core/embed/sys/trustzone/stm32u5/trustzone.c

@@ -517,6 +517,10 @@ void tz_init(void) {
   HAL_GTZC_TZSC_ConfigPeriphAttributes(
       GTZC_PERIPH_SAES, GTZC_TZSC_PERIPH_SEC | GTZC_TZSC_PERIPH_PRIV);
 
+  // Set IWDG as secure & privileged
+  HAL_GTZC_TZSC_ConfigPeriphAttributes(
+      GTZC_PERIPH_IWDG, GTZC_TZSC_PERIPH_SEC | GTZC_TZSC_PERIPH_PRIV);
+
   // Set all interrupts as non-secure
   for (int i = 0; i < 512; i++) {
     NVIC_SetTargetState(i);