crc: add crc32 driver

Makefile

@@ -122,6 +122,7 @@ LDSCRIPT= $(STARTUPLD)/STM32F411xE.ld
 # C sources that can be compiled in ARM or THUMB mode depending on the global
 # setting.
 CSRC = $(ALLCSRC)          \
+         $(SRCDIR)/crc32.c \
          $(SRCDIR)/main.c
 
 # C++ sources that can be compiled in ARM or THUMB mode depending on the global

src/crc32.c

+// This file is part of the execution-time evaluation for the qronos observer abstractions.
+// Copyright (C) 2022-2023  Tim Rheinfels  <tim.rheinfels@fau.de>
+// See https://gitlab.cs.fau.de/qronos-state-abstractions/execution-time
+//
+// 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 <https://www.gnu.org/licenses/>.
+
+///
+///  @file  crc32.c
+///
+///  @brief  Provides the implementation of the CRC driver
+///
+///  @author  Tim Rheinfels  <tim.rheinfels@fau.de>
+///
+
+#include "crc32.h"
+
+#include <string.h>
+
+#include <hal.h>
+
+// The bit-reversing was implemented based on Enix's answer on
+//   https://stackoverflow.com/questions/39646441/how-to-set-stm32-to-generate-standard-crc32
+
+///
+///  @brief  Only a remnant
+///
+///  This is a remnant of previous debugging. It's here for the artifact evaluation as removing in changes alignment in the binary thus causing some execution time measurements to be off by one cycle.
+///
+///  @todo  Remove after artifact evaluation
+///
+uint32_t processed = 0;
+
+///
+///  @brief  Wrapper for the reverse bit (rbit) instruction
+///
+///  @param[in]  in  The 32-bit word to reverse
+///
+///  @returns  Bit-wise reversed version of @p in
+///
+static inline __attribute__((always_inline)) uint32_t rbit(uint32_t in)
+{
+    uint32_t result;
+    asm("rbit %1,%0" : "=r" (result) : "r" (in));
+    return result;
+}
+
+void crc32_init(void)
+{
+
+    // Reset CRC peripheral
+    RCC->AHB1RSTR |= RCC_AHB1RSTR_CRCRST;
+    RCC->AHB1RSTR &= ~(RCC_AHB1RSTR_CRCRST);
+
+    // Enable CRC peripheral
+    RCC->AHB1ENR |= RCC_AHB1ENR_CRCEN;
+
+    crc32_reset();
+
+}
+
+void crc32_reset(void)
+{
+
+    CRC->CR |= CRC_CR_RESET;
+    while(CRC->CR &= CRC_CR_RESET);
+
+    processed = 0;
+
+}
+
+void crc32_add(uint8_t data)
+{
+
+    // Store data in the lower byte of a 32 bit word and pad with zeros
+    uint32_t edata = 0u;
+    memcpy(&edata, &data, sizeof(data));
+
+    // Append to the current checksum in reverse order (yields the default CRC32 polynomial*)
+    CRC->DR = rbit(edata);
+
+    ++processed;
+
+}
+
+uint32_t crc32_get(void)
+{
+
+    // (* after inverting the bits)
+    return ~rbit(CRC->DR);
+
+}

src/crc32.h

+// This file is part of the execution-time evaluation for the qronos observer abstractions.
+// Copyright (C) 2022-2023  Tim Rheinfels  <tim.rheinfels@fau.de>
+// See https://gitlab.cs.fau.de/qronos-state-abstractions/execution-time
+//
+// 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 <https://www.gnu.org/licenses/>.
+
+///
+///  @file  crc32.h
+///
+///  @brief  Provides the interface for the CRC driver
+///
+///  @author  Tim Rheinfels  <tim.rheinfels@fau.de>
+///
+
+#ifndef CRC32_H
+#define CRC32_H
+
+#include <stdint.h>
+
+///
+///  @brief  Initializes the CRC driver
+///
+void crc32_init(void);
+
+///
+///  @brief  Resets the currently stored checksum
+///
+void crc32_reset(void);
+
+///
+///  @brief  Adds a byte @p data to the checksum
+///
+///  @param[in]  data  Byte to add to the checksum
+///
+void crc32_add(uint8_t data);
+
+///
+///  @brief  Retrieves the currently stored checksum
+///
+///  @returns  Currently stored 32-bit checksum
+///
+uint32_t crc32_get(void);
+
+#endif // CRC32_H