From a52d94acbfd617ae567a5efc1626e9b88703a0dd Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?Niccol=C3=B2=20Betto?= <niccolo.betto@skywarder.eu>
Date: Mon, 19 Aug 2024 12:36:09 +0000
Subject: [PATCH] Add a backup SRAM driver for STM32F2/F4/F7 boards
---
miosix/arch/common/drivers/stm32_bsram.cpp | 150 +++++++++++++++++++++
miosix/arch/common/drivers/stm32_bsram.h | 93 +++++++++++++
2 files changed, 243 insertions(+)
create mode 100644 miosix/arch/common/drivers/stm32_bsram.cpp
create mode 100644 miosix/arch/common/drivers/stm32_bsram.h
diff --git a/miosix/arch/common/drivers/stm32_bsram.cpp b/miosix/arch/common/drivers/stm32_bsram.cpp
new file mode 100644
index 00000000..114a8a8e
--- /dev/null
+++ b/miosix/arch/common/drivers/stm32_bsram.cpp
@@ -0,0 +1,150 @@
+/***************************************************************************
+ * Copyright (C) 2024 by Niccolò Betto *
+ * *
+ * 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 2 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. *
+ * *
+ * As a special exception, if other files instantiate templates or use *
+ * macros or inline functions from this file, or you compile this file *
+ * and link it with other works to produce a work based on this file, *
+ * this file does not by itself cause the resulting work to be covered *
+ * by the GNU General Public License. However the source code for this *
+ * file must still be made available in accordance with the GNU General *
+ * Public License. This exception does not invalidate any other reasons *
+ * why a work based on this file might be covered by the GNU General *
+ * Public License. *
+ * *
+ * You should have received a copy of the GNU General Public License *
+ * along with this program; if not, see <http://www.gnu.org/licenses/> *
+ ***************************************************************************/
+
+#include "stm32_bsram.h"
+
+#include <miosix.h>
+
+#include <cstring>
+
+namespace miosix
+{
+
+static ResetReason lastReset = ResetReason::UNKNOWN;
+
+static ResetReason readResetRegister()
+{
+ uint32_t resetReg = RCC->CSR;
+
+ // Clear the reset flag
+ RCC->CSR |= RCC_CSR_RMVF;
+
+ if (resetReg & RCC_CSR_LPWRRSTF)
+ {
+ return ResetReason::LOW_POWER;
+ }
+ else if (resetReg & RCC_CSR_WWDGRSTF)
+ {
+ return ResetReason::WINDOW_WATCHDOG;
+ }
+#ifdef _ARCH_CORTEXM7_STM32F7
+ else if (resetReg & RCC_CSR_IWDGRSTF)
+#else
+ else if (resetReg & RCC_CSR_WDGRSTF)
+#endif
+ {
+ return ResetReason::INDEPENDENT_WATCHDOG;
+ }
+ else if (resetReg & RCC_CSR_SFTRSTF)
+ {
+ return ResetReason::SOFTWARE;
+ }
+ else if (resetReg & RCC_CSR_PORRSTF)
+ {
+ return ResetReason::POWER_ON;
+ }
+#ifdef _ARCH_CORTEXM7_STM32F7
+ else if (resetReg & RCC_CSR_PINRSTF)
+#else
+ else if (resetReg & RCC_CSR_PADRSTF)
+#endif
+ {
+ return ResetReason::PIN;
+ }
+ else
+ {
+ return ResetReason::UNKNOWN;
+ }
+}
+
+ResetReason lastResetReason() { return lastReset; }
+
+namespace BSRAM
+{
+
+void init()
+{
+ // Enable PWR clock
+ RCC->APB1ENR |= RCC_APB1ENR_PWREN;
+
+ // Enable write on BSRAM since we need it to write on the PWR peripheral
+ enableWrite();
+
+ // Enable backup SRAM Clock
+ RCC->AHB1ENR |= RCC_AHB1ENR_BKPSRAMEN;
+
+ // Enable the backup regulator and wait for it to be ready
+#ifdef _ARCH_CORTEXM7_STM32F7
+ PWR->CSR1 |= PWR_CSR1_BRE;
+ while (!(PWR->CSR1 & (PWR_CSR1_BRR)))
+ ;
+#else
+ PWR->CSR |= PWR_CSR_BRE;
+ while (!(PWR->CSR & (PWR_CSR_BRR)))
+ ;
+#endif
+
+ // Retrieve last reset reason
+ lastReset = readResetRegister();
+
+ // Disable write on BSRAM since we don't need to write on the peripheral for
+ // now. It will be necessary to re-enable the write on the backup SRAM
+ // around a PRESERVED variable to effectively change its value.
+ disableWrite();
+}
+
+void disableWrite()
+{
+ // Ensure all memory instructions complete before disabling write
+ __DMB();
+
+ // Enable backup domain write protection
+#ifdef _ARCH_CORTEXM7_STM32F7
+ PWR->CR1 &= ~PWR_CR1_DBP;
+#else
+ PWR->CR &= ~PWR_CR_DBP;
+#endif
+
+ // Ensure write is disabled when exiting this function
+ __DMB();
+}
+
+void enableWrite()
+{
+ // Disable backup domain write protection
+#ifdef _ARCH_CORTEXM7_STM32F7
+ PWR->CR1 |= PWR_CR1_DBP;
+#else
+ PWR->CR |= PWR_CR_DBP;
+#endif
+
+ // Ensure writes to the control registers complete before returning
+ __DMB();
+}
+
+} // namespace BSRAM
+} // namespace miosix
diff --git a/miosix/arch/common/drivers/stm32_bsram.h b/miosix/arch/common/drivers/stm32_bsram.h
new file mode 100644
index 00000000..0d018460
--- /dev/null
+++ b/miosix/arch/common/drivers/stm32_bsram.h
@@ -0,0 +1,93 @@
+/***************************************************************************
+ * Copyright (C) 2024 by Niccolò Betto *
+ * *
+ * 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 2 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. *
+ * *
+ * As a special exception, if other files instantiate templates or use *
+ * macros or inline functions from this file, or you compile this file *
+ * and link it with other works to produce a work based on this file, *
+ * this file does not by itself cause the resulting work to be covered *
+ * by the GNU General Public License. However the source code for this *
+ * file must still be made available in accordance with the GNU General *
+ * Public License. This exception does not invalidate any other reasons *
+ * why a work based on this file might be covered by the GNU General *
+ * Public License. *
+ * *
+ * 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
+
+namespace miosix
+{
+
+/**
+ * Enumeration of possible causes of an STM32 reset.
+ */
+enum class ResetReason
+{
+ UNKNOWN = 0,
+ LOW_POWER,
+ WINDOW_WATCHDOG,
+ INDEPENDENT_WATCHDOG,
+ SOFTWARE,
+ POWER_ON,
+ PIN,
+};
+
+/**
+ * Returns the cause of the last reset of the microcontroller.
+ */
+ResetReason lastResetReason();
+
+/**
+ * Driver for the STM32F2/F4/F7 backup SRAM.
+ */
+namespace BSRAM
+{
+
+/**
+ * Initialize the backup SRAM and populate the last reset reason variable.
+ */
+void init();
+
+/**
+ * Disable writing to the backup SRAM.
+ */
+void disableWrite();
+
+/**
+ * Enable writing to the backup SRAM.
+ */
+void enableWrite();
+
+/**
+ * @brief This class is a RAII lock for disabling write protection on backup
+ * SRAM. This call avoids the error of not re-enabling write protection since it
+ * is done automatically.
+ */
+class EnableWriteLock
+{
+public:
+ EnableWriteLock() { enableWrite(); }
+
+ ~EnableWriteLock() { disableWrite(); }
+
+ ///< Delete copy/move constructors/operators.
+ EnableWriteLock(const EnableWriteLock& l) = delete;
+ EnableWriteLock(const EnableWriteLock&& l) = delete;
+ EnableWriteLock& operator=(const EnableWriteLock& l) = delete;
+ EnableWriteLock& operator=(const EnableWriteLock&& l) = delete;
+};
+
+} // namespace BSRAM
+} // namespace miosix
--
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