stm32c5xx_eth_driver.c

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/**
 * @file stm32c5xx_eth_driver.c
 * @brief STM32C5 Ethernet MAC driver
 *
 * @section License
 *
 * SPDX-License-Identifier: GPL-2.0-or-later
 *
 * Copyright (C) 2010-2026 Oryx Embedded SARL. All rights reserved.
 *
 * This file is part of CycloneTCP Open.
 *
 * 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.
 *
 * You should have received a copy of the GNU General Public License
 * along with this program; if not, write to the Free Software Foundation,
 * Inc., 51 Franklin Street, Fifth Floor, Boston, MA  02110-1301, USA.
 *
 * @author Oryx Embedded SARL (www.oryx-embedded.com)
 * @version 2.6.4
 **/
 
//Switch to the appropriate trace level
#define TRACE_LEVEL NIC_TRACE_LEVEL
 
//Dependencies
#include "stm32_hal.h"
#include "core/net.h"
#include "drivers/mac/stm32c5xx_eth_driver.h"
#include "debug.h"
 
//Underlying network interface
static NetInterface *nicDriverInterface;
 
//IAR EWARM compiler?
#if defined(__ICCARM__)
 
//Transmit buffer
#pragma data_alignment = ETH_BUS_DATA_WIDTH_BYTE
static uint8_t txBuffer[STM32C5XX_ETH_TX_BUFFER_COUNT][STM32C5XX_ETH_TX_BUFFER_SIZE];
//Receive buffer
#pragma data_alignment = ETH_BUS_DATA_WIDTH_BYTE
static uint8_t rxBuffer[STM32C5XX_ETH_RX_BUFFER_COUNT][STM32C5XX_ETH_RX_BUFFER_SIZE];
//Transmit DMA descriptors
#pragma data_alignment = ETH_BUS_DATA_WIDTH_BYTE
static Stm32c5xxTxDmaDesc txDmaDesc[STM32C5XX_ETH_TX_BUFFER_COUNT];
//Receive DMA descriptors
#pragma data_alignment = ETH_BUS_DATA_WIDTH_BYTE
static Stm32c5xxRxDmaDesc rxDmaDesc[STM32C5XX_ETH_RX_BUFFER_COUNT];
 
//Keil MDK-ARM or GCC compiler?
#else
 
//Transmit buffer
static uint8_t txBuffer[STM32C5XX_ETH_TX_BUFFER_COUNT][STM32C5XX_ETH_TX_BUFFER_SIZE]
   __attribute__((aligned(ETH_BUS_DATA_WIDTH_BYTE)));
//Receive buffer
static uint8_t rxBuffer[STM32C5XX_ETH_RX_BUFFER_COUNT][STM32C5XX_ETH_RX_BUFFER_SIZE]
   __attribute__((aligned(ETH_BUS_DATA_WIDTH_BYTE)));
//Transmit DMA descriptors
static Stm32c5xxTxDmaDesc txDmaDesc[STM32C5XX_ETH_TX_BUFFER_COUNT]
   __attribute__((aligned(ETH_BUS_DATA_WIDTH_BYTE)));
//Receive DMA descriptors
static Stm32c5xxRxDmaDesc rxDmaDesc[STM32C5XX_ETH_RX_BUFFER_COUNT]
   __attribute__((aligned(ETH_BUS_DATA_WIDTH_BYTE)));
 
#endif
 
//Current transmit descriptor
static uint_t txIndex;
//Current receive descriptor
static uint_t rxIndex;
 
 
/**
 * @brief STM32C5 Ethernet MAC driver
 **/
 
const NicDriver stm32c5xxEthDriver =
{
   NIC_TYPE_ETHERNET,
   ETH_MTU,
   stm32c5xxEthInit,
   stm32c5xxEthTick,
   stm32c5xxEthEnableIrq,
   stm32c5xxEthDisableIrq,
   stm32c5xxEthEventHandler,
   stm32c5xxEthSendPacket,
   stm32c5xxEthUpdateMacAddrFilter,
   stm32c5xxEthUpdateMacConfig,
   stm32c5xxEthWritePhyReg,
   stm32c5xxEthReadPhyReg,
   TRUE,
   TRUE,
   TRUE,
   FALSE
};
 
 
/**
 * @brief STM32C5 Ethernet MAC initialization
 * @param[in] interface Underlying network interface
 * @return Error code
 **/
 
error_t stm32c5xxEthInit(NetInterface *interface)
{
   error_t error;
   uint32_t temp;
 
   //Debug message
   TRACE_INFO("Initializing STM32C5 Ethernet MAC...\r\n");
 
   //Save underlying network interface
   nicDriverInterface = interface;
 
   //GPIO configuration
   stm32c5xxEthInitGpio(interface);
 
   //Enable Ethernet MAC clock
   HAL_RCC_ETH1_EnableClock();
   HAL_RCC_ETH1CK_EnableClock();
   HAL_RCC_ETH1TX_EnableClock();
   HAL_RCC_ETH1RX_EnableClock();
 
   //Reset Ethernet MAC peripheral
   HAL_RCC_ETH1_Reset();
 
   //Perform a software reset
   ETH1->DMAMR |= ETH_DMAMR_SWR;
   //Wait for the reset to complete
   while((ETH1->DMAMR & ETH_DMAMR_SWR) != 0)
   {
   }
 
   //Adjust MDC clock range depending on HCLK frequency
   ETH1->MACMDIOAR = ETH_MACMDIOAR_CR_Val(5);
 
   //Valid Ethernet PHY or switch driver?
   if(interface->phyDriver != NULL)
   {
      //Ethernet PHY initialization
      error = interface->phyDriver->init(interface);
   }
   else if(interface->switchDriver != NULL)
   {
      //Ethernet switch initialization
      error = interface->switchDriver->init(interface);
   }
   else
   {
      //The interface is not properly configured
      error = ERROR_FAILURE;
   }
 
   //Any error to report?
   if(error)
   {
      return error;
   }
 
   //Use default MAC configuration
   ETH1->MACCR = ETH_MACCR_GPSLCE | ETH_MACCR_RESERVED15 | ETH_MACCR_DO;
 
   //Set the maximum packet size that can be accepted
   temp = ETH1->MACECR & ~ETH_MACECR_GPSL;
   ETH1->MACECR = temp | STM32C5XX_ETH_RX_BUFFER_SIZE;
 
   //Configure MAC address filtering
   stm32c5xxEthUpdateMacAddrFilter(interface);
 
   //Disable flow control
   ETH1->MACQTXFCR = 0;
   ETH1->MACRXFCR = 0;
 
   //Configure DMA operating mode
   ETH1->DMAMR = ETH_DMAMR_INTM_Val(0) | ETH_DMAMR_TXPR_Val(0);
   //Configure system bus mode
   ETH1->DMASBMR |= ETH_DMASBMR_AAL;
   //The DMA takes the descriptor table as contiguous
   ETH1->DMACCR = ETH_DMACCR_DSL_Val(0);
 
   //Configure TX features
   ETH1->DMACTXCR = ETH_DMACTXCR_TXPBL_Val(32);
 
   //Configure RX features
   ETH1->DMACRXCR = ETH_DMACRXCR_RXPBL_Val(32) |
      ETH_DMACRXCR_RBSZ_Val(STM32C5XX_ETH_RX_BUFFER_SIZE);
 
   //Enable store and forward mode
   ETH1->MTLTXQOMR |= ETH_MTLTXQOMR_TSF;
   ETH1->MTLRXQOMR |= ETH_MTLRXQOMR_RSF;
 
   //Initialize DMA descriptor lists
   stm32c5xxEthInitDmaDesc(interface);
 
   //Prevent interrupts from being generated when the transmit statistic
   //counters reach half their maximum value
   ETH1->MMC_TX_INTERRUPT_MASK = ETH_MMC_TX_INTERRUPT_MASK_TXLPITRCIM |
      ETH_MMC_TX_INTERRUPT_MASK_TXLPIUSCIM | ETH_MMC_TX_INTERRUPT_MASK_TXGPKTIM |
      ETH_MMC_TX_INTERRUPT_MASK_TXMCOLGPIM | ETH_MMC_TX_INTERRUPT_MASK_TXSCOLGPIM;
 
   //Prevent interrupts from being generated when the receive statistic
   //counters reach half their maximum value
   ETH1->MMC_RX_INTERRUPT_MASK = ETH_MMC_RX_INTERRUPT_MASK_RXLPITRCIM |
      ETH_MMC_RX_INTERRUPT_MASK_RXLPIUSCIM | ETH_MMC_RX_INTERRUPT_MASK_RXUCGPIM |
      ETH_MMC_RX_INTERRUPT_MASK_RXALGNERPIM | ETH_MMC_RX_INTERRUPT_MASK_RXCRCERPIM;
 
   //Disable MAC interrupts
   ETH1->MACIER = 0;
   //Enable the desired DMA interrupts
   ETH1->DMACIER = ETH_DMACIER_NIE | ETH_DMACIER_RIE | ETH_DMACIER_TIE;
 
   //Set priority grouping (4 bits for pre-emption priority, no bits for subpriority)
   NVIC_SetPriorityGrouping(STM32C5XX_ETH_IRQ_PRIORITY_GROUPING);
 
   //Configure Ethernet interrupt priority
   NVIC_SetPriority(ETH1_IRQn, NVIC_EncodePriority(STM32C5XX_ETH_IRQ_PRIORITY_GROUPING,
      STM32C5XX_ETH_IRQ_GROUP_PRIORITY, STM32C5XX_ETH_IRQ_SUB_PRIORITY));
 
   //Enable MAC transmission and reception
   ETH1->MACCR |= ETH_MACCR_TE | ETH_MACCR_RE;
 
   //Enable DMA transmission and reception
   ETH1->DMACTXCR |= ETH_DMACTXCR_ST;
   ETH1->DMACRXCR |= ETH_DMACRXCR_SR;
 
   //Accept any packets from the upper layer
   osSetEvent(&interface->nicTxEvent);
 
   //Successful initialization
   return NO_ERROR;
}
 
 
/**
 * @brief GPIO configuration
 * @param[in] interface Underlying network interface
 **/
 
__weak_func void stm32c5xxEthInitGpio(NetInterface *interface)
{
//Nucleo-C5A3ZG evaluation board?
#if defined(USE_NUCLEO_C5A3ZG)
   hal_gpio_config_t gpio_config;
 
   //Enable SBS clock
   HAL_RCC_SBS_EnableClock();
 
   //Enable GPIO clocks
   HAL_RCC_GPIOA_EnableClock();
   HAL_RCC_GPIOC_EnableClock();
   HAL_RCC_GPIOD_EnableClock();
   HAL_RCC_GPIOE_EnableClock();
   HAL_RCC_GPIOG_EnableClock();
 
   //Select RMII interface mode
   HAL_SBS_SetETHPHYInterface(ETH1, HAL_SBS_ETHPHY_ITF_RMII);
 
   //Configure RMII pins
   gpio_config.mode = HAL_GPIO_MODE_ALTERNATE;
   gpio_config.output_type = HAL_GPIO_OUTPUT_PUSHPULL;
   gpio_config.pull = HAL_GPIO_PULL_NO;
   gpio_config.speed = HAL_GPIO_SPEED_FREQ_VERY_HIGH;
 
   //Configure ETH1_RMII_REF_CLK (PA1)
   gpio_config.alternate = HAL_GPIO_AF_10;
   HAL_GPIO_Init(HAL_GPIOA, HAL_GPIO_PIN_1, &gpio_config);
 
   //Configure ETH1_MDC (PC1)
   gpio_config.alternate = HAL_GPIO_AF_10;
   HAL_GPIO_Init(HAL_GPIOC, HAL_GPIO_PIN_1, &gpio_config);
 
   //Configure ETH1_RMII_RXD0 (PC4)
   gpio_config.alternate = HAL_GPIO_AF_12;
   HAL_GPIO_Init(HAL_GPIOC, HAL_GPIO_PIN_4, &gpio_config);
 
   //Configure ETH1_RMII_RXD1 (PC5)
   gpio_config.alternate = HAL_GPIO_AF_13;
   HAL_GPIO_Init(HAL_GPIOC, HAL_GPIO_PIN_5, &gpio_config);
 
   //Configure ETH1_RMII_CRS_DV (PD1)
   gpio_config.alternate = HAL_GPIO_AF_10;
   HAL_GPIO_Init(HAL_GPIOD, HAL_GPIO_PIN_1, &gpio_config);
 
   //Configure ETH1_MDIO (PE12)
   gpio_config.alternate = HAL_GPIO_AF_10;
   HAL_GPIO_Init(HAL_GPIOE, HAL_GPIO_PIN_12, &gpio_config);
 
   //Configure RMII_TX_EN (PG11)
   gpio_config.alternate = HAL_GPIO_AF_10;
   HAL_GPIO_Init(HAL_GPIOG, HAL_GPIO_PIN_11, &gpio_config);
 
   //Configure ETH1_RMII_TXD1 (PG12)
   gpio_config.alternate = HAL_GPIO_AF_10;
   HAL_GPIO_Init(HAL_GPIOG, HAL_GPIO_PIN_12, &gpio_config);
 
   //Configure ETH1_RMII_TXD0 (PG13)
   gpio_config.alternate = HAL_GPIO_AF_10;
   HAL_GPIO_Init(HAL_GPIOG, HAL_GPIO_PIN_13, &gpio_config);
 
   //Select ETH1 clock source
   HAL_RCC_ETH1_SetKernelClkSource(HAL_RCC_ETH1_CLK_SRC_HSE);
   //Select ETH1REF clock source
   HAL_RCC_ETH1REF_SetKernelClkSource(HAL_RCC_ETH1REF_CLK_SRC_RMII);
#endif
}
 
 
/**
 * @brief Initialize DMA descriptor lists
 * @param[in] interface Underlying network interface
 **/
 
void stm32c5xxEthInitDmaDesc(NetInterface *interface)
{
   uint_t i;
 
   //Initialize TX DMA descriptor list
   for(i = 0; i < STM32C5XX_ETH_TX_BUFFER_COUNT; i++)
   {
      //The descriptor is initially owned by the application
      txDmaDesc[i].tdes0 = 0;
      txDmaDesc[i].tdes1 = 0;
      txDmaDesc[i].tdes2 = 0;
      txDmaDesc[i].tdes3 = 0;
   }
 
   //Initialize TX descriptor index
   txIndex = 0;
 
   //Initialize RX DMA descriptor list
   for(i = 0; i < STM32C5XX_ETH_RX_BUFFER_COUNT; i++)
   {
      //The descriptor is initially owned by the DMA
      rxDmaDesc[i].rdes0 = (uint32_t) rxBuffer[i];
      rxDmaDesc[i].rdes1 = 0;
      rxDmaDesc[i].rdes2 = 0;
      rxDmaDesc[i].rdes3 = ETH_RDES3_OWN | ETH_RDES3_IOC | ETH_RDES3_BUF1V;
   }
 
   //Initialize RX descriptor index
   rxIndex = 0;
 
   //Start location of the TX descriptor list
   ETH1->DMACTXDLAR = (uint32_t) &txDmaDesc[0];
   //Length of the transmit descriptor ring
   ETH1->DMACTXRLR = STM32C5XX_ETH_TX_BUFFER_COUNT - 1;
 
   //Start location of the RX descriptor list
   ETH1->DMACRXDLAR = (uint32_t) &rxDmaDesc[0];
   //Length of the receive descriptor ring
   ETH1->DMACRXRLR = STM32C5XX_ETH_RX_BUFFER_COUNT - 1;
}
 
 
/**
 * @brief STM32C5 Ethernet MAC timer handler
 *
 * This routine is periodically called by the TCP/IP stack to handle periodic
 * operations such as polling the link state
 *
 * @param[in] interface Underlying network interface
 **/
 
void stm32c5xxEthTick(NetInterface *interface)
{
   //Valid Ethernet PHY or switch driver?
   if(interface->phyDriver != NULL)
   {
      //Handle periodic operations
      interface->phyDriver->tick(interface);
   }
   else if(interface->switchDriver != NULL)
   {
      //Handle periodic operations
      interface->switchDriver->tick(interface);
   }
   else
   {
      //Just for sanity
   }
}
 
 
/**
 * @brief Enable interrupts
 * @param[in] interface Underlying network interface
 **/
 
void stm32c5xxEthEnableIrq(NetInterface *interface)
{
   //Enable Ethernet MAC interrupts
   NVIC_EnableIRQ(ETH1_IRQn);
 
   //Valid Ethernet PHY or switch driver?
   if(interface->phyDriver != NULL)
   {
      //Enable Ethernet PHY interrupts
      interface->phyDriver->enableIrq(interface);
   }
   else if(interface->switchDriver != NULL)
   {
      //Enable Ethernet switch interrupts
      interface->switchDriver->enableIrq(interface);
   }
   else
   {
      //Just for sanity
   }
}
 
 
/**
 * @brief Disable interrupts
 * @param[in] interface Underlying network interface
 **/
 
void stm32c5xxEthDisableIrq(NetInterface *interface)
{
   //Disable Ethernet MAC interrupts
   NVIC_DisableIRQ(ETH1_IRQn);
 
   //Valid Ethernet PHY or switch driver?
   if(interface->phyDriver != NULL)
   {
      //Disable Ethernet PHY interrupts
      interface->phyDriver->disableIrq(interface);
   }
   else if(interface->switchDriver != NULL)
   {
      //Disable Ethernet switch interrupts
      interface->switchDriver->disableIrq(interface);
   }
   else
   {
      //Just for sanity
   }
}
 
 
/**
 * @brief STM32C5 Ethernet MAC interrupt service routine
 **/
 
void ETH1_IRQHandler(void)
{
   bool_t flag;
   uint32_t status;
 
   //Interrupt service routine prologue
   osEnterIsr();
 
   //This flag will be set if a higher priority task must be woken
   flag = FALSE;
 
   //Read DMA status register
   status = ETH1->DMACSR;
 
   //Packet transmitted?
   if((status & ETH_DMACSR_TI) != 0)
   {
      //Clear TI interrupt flag
      ETH1->DMACSR = ETH_DMACSR_TI;
 
      //Check whether the TX buffer is available for writing
      if((txDmaDesc[txIndex].tdes3 & ETH_TDES3_OWN) == 0)
      {
         //Notify the TCP/IP stack that the transmitter is ready to send
         flag |= osSetEventFromIsr(&nicDriverInterface->nicTxEvent);
      }
   }
 
   //Packet received?
   if((status & ETH_DMACSR_RI) != 0)
   {
      //Clear RI interrupt flag
      ETH1->DMACSR = ETH_DMACSR_RI;
 
      //Set event flag
      nicDriverInterface->nicEvent = TRUE;
      //Notify the TCP/IP stack of the event
      flag |= osSetEventFromIsr(&nicDriverInterface->netContext->event);
   }
 
   //Clear NIS interrupt flag
   ETH1->DMACSR = ETH_DMACSR_NIS;
 
   //Interrupt service routine epilogue
   osExitIsr(flag);
}
 
 
/**
 * @brief STM32C5 Ethernet MAC event handler
 * @param[in] interface Underlying network interface
 **/
 
void stm32c5xxEthEventHandler(NetInterface *interface)
{
   error_t error;
 
   //Process all pending packets
   do
   {
      //Read incoming packet
      error = stm32c5xxEthReceivePacket(interface);
 
      //No more data in the receive buffer?
   } while(error != ERROR_BUFFER_EMPTY);
}
 
 
/**
 * @brief Send a packet
 * @param[in] interface Underlying network interface
 * @param[in] buffer Multi-part buffer containing the data to send
 * @param[in] offset Offset to the first data byte
 * @param[in] ancillary Additional options passed to the stack along with
 *   the packet
 * @return Error code
 **/
 
error_t stm32c5xxEthSendPacket(NetInterface *interface,
   const NetBuffer *buffer, size_t offset, NetTxAncillary *ancillary)
{
   size_t length;
 
   //Retrieve the length of the packet
   length = netBufferGetLength(buffer) - offset;
 
   //Check the frame length
   if(length > STM32C5XX_ETH_TX_BUFFER_SIZE)
   {
      //The transmitter can accept another packet
      osSetEvent(&interface->nicTxEvent);
      //Report an error
      return ERROR_INVALID_LENGTH;
   }
 
   //Make sure the current buffer is available for writing
   if((txDmaDesc[txIndex].tdes3 & ETH_TDES3_OWN) != 0)
   {
      return ERROR_FAILURE;
   }
 
   //Copy user data to the transmit buffer
   netBufferRead(txBuffer[txIndex], buffer, offset, length);
 
   //Set the start address of the buffer
   txDmaDesc[txIndex].tdes0 = (uint32_t) txBuffer[txIndex];
   //Write the number of bytes to send
   txDmaDesc[txIndex].tdes2 = ETH_TDES2_IOC | (length & ETH_TDES2_B1L);
   //Give the ownership of the descriptor to the DMA
   txDmaDesc[txIndex].tdes3 = ETH_TDES3_OWN | ETH_TDES3_FD | ETH_TDES3_LD;
 
   //Data synchronization barrier
   __DSB();
 
   //Clear TBU flag to resume processing
   ETH1->DMACSR = ETH_DMACSR_TBU;
   //Instruct the DMA to poll the transmit descriptor list
   ETH1->DMACTXDTPR = 0;
 
   //Increment index and wrap around if necessary
   if(++txIndex >= STM32C5XX_ETH_TX_BUFFER_COUNT)
   {
      txIndex = 0;
   }
 
   //Check whether the next buffer is available for writing
   if((txDmaDesc[txIndex].tdes3 & ETH_TDES3_OWN) == 0)
   {
      //The transmitter can accept another packet
      osSetEvent(&interface->nicTxEvent);
   }
 
   //Data successfully written
   return NO_ERROR;
}
 
 
/**
 * @brief Receive a packet
 * @param[in] interface Underlying network interface
 * @return Error code
 **/
 
error_t stm32c5xxEthReceivePacket(NetInterface *interface)
{
   error_t error;
   size_t n;
   uint32_t status;
   NetRxAncillary ancillary;
 
   //Current buffer available for reading?
   if((rxDmaDesc[rxIndex].rdes3 & ETH_RDES3_OWN) == 0)
   {
      //FD and LD flags should be set
      if((rxDmaDesc[rxIndex].rdes3 & ETH_RDES3_FD) != 0 &&
         (rxDmaDesc[rxIndex].rdes3 & ETH_RDES3_LD) != 0)
      {
         //Check error bits
         status = rxDmaDesc[rxIndex].rdes3 & (ETH_RDES3_CE | ETH_RDES3_GP |
            ETH_RDES3_RWT | ETH_RDES3_OE | ETH_RDES3_RE | ETH_RDES3_DE);
 
         //The dribble bit error is valid only in the MII mode
         if((SBS->PMCR & SBS_PMCR_ETH1_SEL_PHY) != HAL_SBS_ETHPHY_ITF_GMII_MII)
         {
            status &= ~ETH_RDES3_DE;
         }
 
         //Make sure no error occurred
         if(status == 0)
         {
            //Retrieve the length of the frame
            n = rxDmaDesc[rxIndex].rdes3 & ETH_RDES3_PL;
            //Limit the number of data to read
            n = MIN(n, STM32C5XX_ETH_RX_BUFFER_SIZE);
 
            //Additional options can be passed to the stack along with the packet
            ancillary = NET_DEFAULT_RX_ANCILLARY;
 
            //Pass the packet to the upper layer
            nicProcessPacket(interface, rxBuffer[rxIndex], n, &ancillary);
 
            //Valid packet received
            error = NO_ERROR;
         }
         else
         {
            //The received packet contains an error
            error = ERROR_INVALID_PACKET;
         }
      }
      else
      {
         //The packet is not valid
         error = ERROR_INVALID_PACKET;
      }
 
      //Set the start address of the buffer
      rxDmaDesc[rxIndex].rdes0 = (uint32_t) rxBuffer[rxIndex];
      //Give the ownership of the descriptor back to the DMA
      rxDmaDesc[rxIndex].rdes3 = ETH_RDES3_OWN | ETH_RDES3_IOC | ETH_RDES3_BUF1V;
 
      //Increment index and wrap around if necessary
      if(++rxIndex >= STM32C5XX_ETH_RX_BUFFER_COUNT)
      {
         rxIndex = 0;
      }
   }
   else
   {
      //No more data in the receive buffer
      error = ERROR_BUFFER_EMPTY;
   }
 
   //Clear RBU flag to resume processing
   ETH1->DMACSR = ETH_DMACSR_RBU;
   //Instruct the DMA to poll the receive descriptor list
   ETH1->DMACRXDTPR = 0;
 
   //Return status code
   return error;
}
 
 
/**
 * @brief Configure MAC address filtering
 * @param[in] interface Underlying network interface
 * @return Error code
 **/
 
error_t stm32c5xxEthUpdateMacAddrFilter(NetInterface *interface)
{
   uint_t i;
   uint_t j;
   uint_t k;
   uint32_t crc;
   uint32_t hashTable[2];
   MacAddr unicastMacAddr[3];
   MacFilterEntry *entry;
 
   //Debug message
   TRACE_DEBUG("Updating MAC filter...\r\n");
 
   //Promiscuous mode?
   if(interface->promiscuous)
   {
      //Pass all incoming frames regardless of their destination address
      ETH1->MACPFR = ETH_MACPFR_PR;
   }
   else
   {
      //Set the MAC address of the station
      ETH1->MACA0LR = interface->macAddr.w[0] | (interface->macAddr.w[1] << 16);
      ETH1->MACA0HR = interface->macAddr.w[2];
 
      //The MAC supports 3 additional addresses for unicast perfect filtering
      unicastMacAddr[0] = MAC_UNSPECIFIED_ADDR;
      unicastMacAddr[1] = MAC_UNSPECIFIED_ADDR;
      unicastMacAddr[2] = MAC_UNSPECIFIED_ADDR;
 
      //The hash table is used for multicast address filtering
      hashTable[0] = 0;
      hashTable[1] = 0;
 
      //The MAC address filter contains the list of MAC addresses to accept
      //when receiving an Ethernet frame
      for(i = 0, j = 0; i < MAC_ADDR_FILTER_SIZE; i++)
      {
         //Point to the current entry
         entry = &interface->macAddrFilter[i];
 
         //Valid entry?
         if(entry->refCount > 0)
         {
            //Multicast address?
            if(macIsMulticastAddr(&entry->addr))
            {
               //Compute CRC over the current MAC address
               crc = stm32c5xxEthCalcCrc(&entry->addr, sizeof(MacAddr));
 
               //The upper 6 bits in the CRC register are used to index the
               //contents of the hash table
               k = (crc >> 26) & 0x3F;
 
               //Update hash table contents
               hashTable[k / 32] |= (1 << (k % 32));
            }
            else
            {
               //Up to 3 additional MAC addresses can be specified
               if(j < 3)
               {
                  //Save the unicast address
                  unicastMacAddr[j++] = entry->addr;
               }
            }
         }
      }
 
      //Configure the first unicast address filter
      if(j >= 1)
      {
         //When the AE bit is set, the entry is used for perfect filtering
         ETH1->MACA1LR = unicastMacAddr[0].w[0] | (unicastMacAddr[0].w[1] << 16);
         ETH1->MACA1HR = unicastMacAddr[0].w[2] | ETH_MACA1HR_AE;
      }
      else
      {
         //When the AE bit is cleared, the entry is ignored
         ETH1->MACA1LR = 0;
         ETH1->MACA1HR = 0;
      }
 
      //Configure the second unicast address filter
      if(j >= 2)
      {
         //When the AE bit is set, the entry is used for perfect filtering
         ETH1->MACA2LR = unicastMacAddr[1].w[0] | (unicastMacAddr[1].w[1] << 16);
         ETH1->MACA2HR = unicastMacAddr[1].w[2] | ETH_MACA2HR_AE;
      }
      else
      {
         //When the AE bit is cleared, the entry is ignored
         ETH1->MACA2LR = 0;
         ETH1->MACA2HR = 0;
      }
 
      //Configure the third unicast address filter
      if(j >= 3)
      {
         //When the AE bit is set, the entry is used for perfect filtering
         ETH1->MACA3LR = unicastMacAddr[2].w[0] | (unicastMacAddr[2].w[1] << 16);
         ETH1->MACA3HR = unicastMacAddr[2].w[2] | ETH_MACA3HR_AE;
      }
      else
      {
         //When the AE bit is cleared, the entry is ignored
         ETH1->MACA3LR = 0;
         ETH1->MACA3HR = 0;
      }
 
      //Check whether frames with a multicast destination address should be
      //accepted
      if(interface->acceptAllMulticast)
      {
         //Configure the receive filter
         ETH1->MACPFR = ETH_MACPFR_HPF | ETH_MACPFR_PM;
      }
      else
      {
         //Configure the receive filter
         ETH1->MACPFR = ETH_MACPFR_HPF | ETH_MACPFR_HMC;
 
         //Configure the multicast hash table
         ETH1->MACHT0R = hashTable[0];
         ETH1->MACHT1R = hashTable[1];
 
         //Debug message
         TRACE_DEBUG("  MACHT0R = 0x%08" PRIX32 "\r\n", ETH1->MACHT0R);
         TRACE_DEBUG("  MACHT1R = 0x%08" PRIX32 "\r\n", ETH1->MACHT1R);
      }
   }
 
   //Successful processing
   return NO_ERROR;
}
 
 
/**
 * @brief Adjust MAC configuration parameters for proper operation
 * @param[in] interface Underlying network interface
 * @return Error code
 **/
 
error_t stm32c5xxEthUpdateMacConfig(NetInterface *interface)
{
   uint32_t config;
 
   //Read current MAC configuration
   config = ETH1->MACCR;
 
   //10BASE-T or 100BASE-TX operation mode?
   if(interface->linkSpeed == NIC_LINK_SPEED_100MBPS)
   {
      config |= ETH_MACCR_FES;
   }
   else
   {
      config &= ~ETH_MACCR_FES;
   }
 
   //Half-duplex or full-duplex mode?
   if(interface->duplexMode == NIC_FULL_DUPLEX_MODE)
   {
      config |= ETH_MACCR_DM;
   }
   else
   {
      config &= ~ETH_MACCR_DM;
   }
 
   //Update MAC configuration register
   ETH1->MACCR = config;
 
   //Successful processing
   return NO_ERROR;
}
 
 
/**
 * @brief Write PHY register
 * @param[in] opcode Access type (2 bits)
 * @param[in] phyAddr PHY address (5 bits)
 * @param[in] regAddr Register address (5 bits)
 * @param[in] data Register value
 **/
 
void stm32c5xxEthWritePhyReg(uint8_t opcode, uint8_t phyAddr,
   uint8_t regAddr, uint16_t data)
{
   uint32_t temp;
 
   //Valid opcode?
   if(opcode == SMI_OPCODE_WRITE)
   {
      //Take care not to alter MDC clock configuration
      temp = ETH1->MACMDIOAR & ETH_MACMDIOAR_CR;
      //Set up a write operation
      temp |= ETH_MACMDIOAR_GOC_Val(1) | ETH_MACMDIOAR_MB;
      //PHY address
      temp |= (phyAddr << 21) & ETH_MACMDIOAR_PA;
      //Register address
      temp |= (regAddr << 16) & ETH_MACMDIOAR_RDA;
 
      //Data to be written in the PHY register
      ETH1->MACMDIODR = data & ETH_MACMDIODR_MD;
 
      //Start a write operation
      ETH1->MACMDIOAR = temp;
      //Wait for the write to complete
      while((ETH1->MACMDIOAR & ETH_MACMDIOAR_MB) != 0)
      {
      }
   }
   else
   {
      //The MAC peripheral only supports standard Clause 22 opcodes
   }
}
 
 
/**
 * @brief Read PHY register
 * @param[in] opcode Access type (2 bits)
 * @param[in] phyAddr PHY address (5 bits)
 * @param[in] regAddr Register address (5 bits)
 * @return Register value
 **/
 
uint16_t stm32c5xxEthReadPhyReg(uint8_t opcode, uint8_t phyAddr,
   uint8_t regAddr)
{
   uint16_t data;
   uint32_t temp;
 
   //Valid opcode?
   if(opcode == SMI_OPCODE_READ)
   {
      //Take care not to alter MDC clock configuration
      temp = ETH1->MACMDIOAR & ETH_MACMDIOAR_CR;
      //Set up a read operation
      temp |= ETH_MACMDIOAR_GOC_Val(3) | ETH_MACMDIOAR_MB;
      //PHY address
      temp |= (phyAddr << 21) & ETH_MACMDIOAR_PA;
      //Register address
      temp |= (regAddr << 16) & ETH_MACMDIOAR_RDA;
 
      //Start a read operation
      ETH1->MACMDIOAR = temp;
      //Wait for the read to complete
      while((ETH1->MACMDIOAR & ETH_MACMDIOAR_MB) != 0)
      {
      }
 
      //Get register value
      data = ETH1->MACMDIODR & ETH_MACMDIODR_MD;
   }
   else
   {
      //The MAC peripheral only supports standard Clause 22 opcodes
      data = 0;
   }
 
   //Return the value of the PHY register
   return data;
}
 
 
/**
 * @brief CRC calculation
 * @param[in] data Pointer to the data over which to calculate the CRC
 * @param[in] length Number of bytes to process
 * @return Resulting CRC value
 **/
 
uint32_t stm32c5xxEthCalcCrc(const void *data, size_t length)
{
   uint_t i;
   uint_t j;
   uint32_t crc;
   const uint8_t *p;
 
   //Point to the data over which to calculate the CRC
   p = (uint8_t *) data;
   //CRC preset value
   crc = 0xFFFFFFFF;
 
   //Loop through data
   for(i = 0; i < length; i++)
   {
      //The message is processed bit by bit
      for(j = 0; j < 8; j++)
      {
         //Update CRC value
         if((((crc >> 31) ^ (p[i] >> j)) & 0x01) != 0)
         {
            crc = (crc << 1) ^ 0x04C11DB7;
         }
         else
         {
            crc = crc << 1;
         }
      }
   }
 
   //Return CRC value
   return ~crc;
}