xref: /FreeRTOS-Plus-TCP-v3.1.0/source/portable/NetworkInterface/LPC18xx/NetworkInterface.c (revision 37bdfe577f3b728058de714e2e747d3c78803f26)

/*
 * FreeRTOS+TCP V3.1.0
 * Copyright (C) 2022 Amazon.com, Inc. or its affiliates.  All Rights Reserved.
 *
 * SPDX-License-Identifier: MIT
 *
 * Permission is hereby granted, free of charge, to any person obtaining a copy of
 * this software and associated documentation files (the "Software"), to deal in
 * the Software without restriction, including without limitation the rights to
 * use, copy, modify, merge, publish, distribute, sublicense, and/or sell copies of
 * the Software, and to permit persons to whom the Software is furnished to do so,
 * subject to the following conditions:
 *
 * The above copyright notice and this permission notice shall be included in all
 * copies or substantial portions of the Software.
 *
 * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
 * IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY, FITNESS
 * FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE AUTHORS OR
 * COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER
 * IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM, OUT OF OR IN
 * CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE SOFTWARE.
 *
 * http://aws.amazon.com/freertos
 * http://www.FreeRTOS.org
 */

/* Standard includes. */
#include <stdint.h>
#include <stdio.h>
#include <stdlib.h>

/* FreeRTOS includes. */
#include "FreeRTOS.h"
#include "task.h"
#include "queue.h"
#include "semphr.h"

/* FreeRTOS+TCP includes. */
#include "FreeRTOS_IP.h"
#include "FreeRTOS_Sockets.h"
#include "FreeRTOS_IP_Private.h"
#include "NetworkBufferManagement.h"
#include "NetworkInterface.h"

/* LPCOpen includes. */
#include "chip.h"
#include "lpc_phy.h"

/* The size of the stack allocated to the task that handles Rx packets. */
#define nwRX_TASK_STACK_SIZE    140

#ifndef PHY_LS_HIGH_CHECK_TIME_MS

/* Check if the LinkSStatus in the PHY is still high after 15 seconds of not
 * receiving packets. */
    #define PHY_LS_HIGH_CHECK_TIME_MS    15000
#endif

#ifndef PHY_LS_LOW_CHECK_TIME_MS
    /* Check if the LinkSStatus in the PHY is still low every second. */
    #define PHY_LS_LOW_CHECK_TIME_MS    1000
#endif

#ifndef configUSE_RMII
    #define configUSE_RMII    1
#endif

#ifndef configNUM_RX_DESCRIPTORS
    #error please define configNUM_RX_DESCRIPTORS in your FreeRTOSIPConfig.h
#endif

#ifndef configNUM_TX_DESCRIPTORS
    #error please define configNUM_TX_DESCRIPTORS in your FreeRTOSIPConfig.h
#endif

#ifndef NETWORK_IRQHandler
    #error NETWORK_IRQHandler must be defined to the name of the function that is installed in the interrupt vector table to handle Ethernet interrupts.
#endif

#if !defined( MAC_FF_HMC )
    /* Hash for multicast. */
    #define MAC_FF_HMC    ( 1UL << 2UL )
#endif

#ifndef iptraceEMAC_TASK_STARTING
    #define iptraceEMAC_TASK_STARTING()    do {} while( ipFALSE_BOOL )
#endif

/* Define the bits of .STATUS that indicate a reception error. */
#define nwRX_STATUS_ERROR_BITS                         \
    ( RDES_CE /* CRC Error */ |                        \
      RDES_RE /* Receive Error */ |                    \
      RDES_DE /* Descriptor Error */ |                 \
      RDES_RWT /* Receive Watchdog Timeout */ |        \
      RDES_LC /* Late Collision */ |                   \
      RDES_OE /* Overflow Error */ |                   \
      RDES_SAF /* Source Address Filter Fail */ |      \
      RDES_AFM /* Destination Address Filter Fail */ | \
      RDES_LE /* Length Error */ )

/* Define the EMAC status bits that should trigger an interrupt. */
#define nwDMA_INTERRUPT_MASK                               \
    ( DMA_IE_TIE /* Transmit interrupt enable */ |         \
      DMA_IE_TSE /* Transmit stopped enable */ |           \
      DMA_IE_OVE /* Overflow interrupt enable */ |         \
      DMA_IE_RIE /* Receive interrupt enable */ |          \
      DMA_IE_NIE /* Normal interrupt summary enable */ |   \
      DMA_IE_AIE /* Abnormal interrupt summary enable */ | \
      DMA_IE_RUE /* Receive buffer unavailable enable */ | \
      DMA_IE_UNE /* Underflow interrupt enable. */ |       \
      DMA_IE_TJE /* Transmit jabber timeout enable */ |    \
      DMA_IE_RSE /* Received stopped enable */ |           \
      DMA_IE_RWE /* Receive watchdog timeout enable */ |   \
      DMA_IE_FBE ) /* Fatal bus error enable */

/* Interrupt events to process.  Currently only the RX/TX events are processed
 * although code for other events is included to allow for possible future
 * expansion. */
#define EMAC_IF_RX_EVENT     1UL
#define EMAC_IF_TX_EVENT     2UL
#define EMAC_IF_ERR_EVENT    4UL
#define EMAC_IF_ALL_EVENT    ( EMAC_IF_RX_EVENT | EMAC_IF_TX_EVENT | EMAC_IF_ERR_EVENT )

/* If ipconfigETHERNET_DRIVER_FILTERS_FRAME_TYPES is set to 1, then the Ethernet
 * driver will filter incoming packets and only pass the stack those packets it
 * considers need processing. */
#if ( ipconfigETHERNET_DRIVER_FILTERS_FRAME_TYPES == 0 )
    #define ipCONSIDER_FRAME_FOR_PROCESSING( pucEthernetBuffer )    eProcessBuffer
#else
    #define ipCONSIDER_FRAME_FOR_PROCESSING( pucEthernetBuffer )    eConsiderFrameForProcessing( ( pucEthernetBuffer ) )
#endif

#if ( ipconfigZERO_COPY_RX_DRIVER == 0 ) || ( ipconfigZERO_COPY_TX_DRIVER == 0 )
    #warning It is adviced to enable both macros
#endif

#ifndef configPLACE_IN_SECTION_RAM
    #define configPLACE_IN_SECTION_RAM

/*
 #define configPLACE_IN_SECTION_RAM	__attribute__ ((section(".ramfunc")))
 */
#endif

/*-----------------------------------------------------------*/

/*
 * Delay function passed into the library.  The implementation uses FreeRTOS
 * calls so the scheduler must be started before the driver can be used.
 */
static void prvDelay( uint32_t ulMilliSeconds );

/*
 * Initialises the Tx and Rx descriptors respectively.
 */
static void prvSetupTxDescriptors( void );
static void prvSetupRxDescriptors( void );

/*
 * A task that processes received frames.
 */
static void prvEMACHandlerTask( void * pvParameters );

/*
 * Sets up the MAC with the results of an auto-negotiation.
 */
static BaseType_t prvSetLinkSpeed( void );

/*
 * Generates a CRC for a MAC address that is then used to generate a hash index.
 */
static uint32_t prvGenerateCRC32( const uint8_t * ucAddress );

/*
 * Generates a hash index when setting a filter to permit a MAC address.
 */
static uint32_t prvGetHashIndex( const uint8_t * ucAddress );

/*
 * Update the hash table to allow a MAC address.
 */
static void prvAddMACAddress( const uint8_t * ucMacAddress );

/*
 * Sometimes the DMA will report received data as being longer than the actual
 * received from length.  This function checks the reported length and corrects
 * if if necessary.
 */
static void prvRemoveTrailingBytes( NetworkBufferDescriptor_t * pxDescriptor );

/*-----------------------------------------------------------*/

/* Bit map of outstanding ETH interrupt events for processing.  Currently only
 * the Rx and Tx interrupt is handled, although code is included for other events
 * to enable future expansion. */
static volatile uint32_t ulISREvents;

/* A copy of PHY register 1: 'PHY_REG_01_BMSR' */
static uint32_t ulPHYLinkStatus = 0;

/* Tx descriptors and index. */
static ENET_ENHTXDESC_T xDMATxDescriptors[ configNUM_TX_DESCRIPTORS ];

/* ulNextFreeTxDescriptor is declared volatile, because it is accessed from
 * to different tasks. */
static volatile uint32_t ulNextFreeTxDescriptor;
static uint32_t ulTxDescriptorToClear;

/* Rx descriptors and index. */
static ENET_ENHRXDESC_T xDMARxDescriptors[ configNUM_RX_DESCRIPTORS ];
static uint32_t ulNextRxDescriptorToProcess;

/* The handle of the task that processes Rx packets.  The handle is required so
 * the task can be notified when new packets arrive. */
static TaskHandle_t xRxHanderTask = NULL;

#if ( ipconfigUSE_LLMNR == 1 )
    static const uint8_t xLLMNR_MACAddress[] = { '\x01', '\x00', '\x5E', '\x00', '\x00', '\xFC' };
#endif /* ipconfigUSE_LLMNR == 1 */

/* xTXDescriptorSemaphore is a counting semaphore with
 * a maximum count of ETH_TXBUFNB, which is the number of
 * DMA TX descriptors. */
static SemaphoreHandle_t xTXDescriptorSemaphore = NULL;

/*-----------------------------------------------------------*/


BaseType_t xNetworkInterfaceInitialise( void )
{
    BaseType_t xReturn = pdPASS;

    /* The interrupt will be turned on when a link is established. */
    NVIC_DisableIRQ( ETHERNET_IRQn );

    /* Disable receive and transmit DMA processes. */
    LPC_ETHERNET->DMA_OP_MODE &= ~( DMA_OM_ST | DMA_OM_SR );

    /* Disable packet reception. */
    LPC_ETHERNET->MAC_CONFIG &= ~( MAC_CFG_RE | MAC_CFG_TE );

    /* Call the LPCOpen function to initialise the hardware. */
    Chip_ENET_Init( LPC_ETHERNET );

    /* Save MAC address. */
    Chip_ENET_SetADDR( LPC_ETHERNET, ipLOCAL_MAC_ADDRESS );

    /* Clear all MAC address hash entries. */
    LPC_ETHERNET->MAC_HASHTABLE_HIGH = 0;
    LPC_ETHERNET->MAC_HASHTABLE_LOW = 0;

    #if ( ipconfigUSE_LLMNR == 1 )
        {
            prvAddMACAddress( xLLMNR_MACAddress );
        }
    #endif /* ipconfigUSE_LLMNR == 1 */

    /* Promiscuous flag (PR) and Receive All flag (RA) set to zero.  The
     * registers MAC_HASHTABLE_[LOW|HIGH] will be loaded to allow certain
     * multi-cast addresses. */
    LPC_ETHERNET->MAC_FRAME_FILTER = MAC_FF_HMC;

    #if ( configUSE_RMII == 1 )
        {
            if( lpc_phy_init( pdTRUE, prvDelay ) != SUCCESS )
            {
                xReturn = pdFAIL;
            }
        }
    #else
        {
            #warning This path has not been tested.

            if( lpc_phy_init( pdFALSE, prvDelay ) != SUCCESS )
            {
                xReturn = pdFAIL;
            }
        }
    #endif /* if ( configUSE_RMII == 1 ) */

    if( xReturn == pdPASS )
    {
        /* Guard against the task being created more than once and the
         * descriptors being initialised more than once. */
        if( xRxHanderTask == NULL )
        {
            xReturn = xTaskCreate( prvEMACHandlerTask, "EMAC", nwRX_TASK_STACK_SIZE, NULL, configMAX_PRIORITIES - 1, &xRxHanderTask );
            configASSERT( xReturn != NULL );
        }

        if( xTXDescriptorSemaphore == NULL )
        {
            /* Create a counting semaphore, with a value of 'configNUM_TX_DESCRIPTORS'
             * and a maximum of 'configNUM_TX_DESCRIPTORS'. */
            xTXDescriptorSemaphore = xSemaphoreCreateCounting( ( UBaseType_t ) configNUM_TX_DESCRIPTORS, ( UBaseType_t ) configNUM_TX_DESCRIPTORS );
            configASSERT( xTXDescriptorSemaphore != NULL );
        }

        /* Enable MAC interrupts. */
        LPC_ETHERNET->DMA_INT_EN = nwDMA_INTERRUPT_MASK;
    }

    if( xReturn != pdFAIL )
    {
        /* Auto-negotiate was already started.  Wait for it to complete. */
        xReturn = prvSetLinkSpeed();

        if( xReturn == pdPASS )
        {
            /* Initialise the descriptors. */
            prvSetupTxDescriptors();
            prvSetupRxDescriptors();

            /* Clear all interrupts. */
            LPC_ETHERNET->DMA_STAT = DMA_ST_ALL;

            /* Enable receive and transmit DMA processes. */
            LPC_ETHERNET->DMA_OP_MODE |= DMA_OM_ST | DMA_OM_SR;

            /* Set Receiver / Transmitter Enable. */
            LPC_ETHERNET->MAC_CONFIG |= MAC_CFG_RE | MAC_CFG_TE;

            /* Start receive polling. */
            LPC_ETHERNET->DMA_REC_POLL_DEMAND = 1;

            /* Enable interrupts in the NVIC. */
            NVIC_SetPriority( ETHERNET_IRQn, configMAC_INTERRUPT_PRIORITY );
            NVIC_EnableIRQ( ETHERNET_IRQn );
        }
    }

    return xReturn;
}
/*-----------------------------------------------------------*/

#define niBUFFER_1_PACKET_SIZE    1536

static __attribute__( ( section( "._ramAHB32" ) ) ) uint8_t ucNetworkPackets[ ipconfigNUM_NETWORK_BUFFER_DESCRIPTORS * niBUFFER_1_PACKET_SIZE ] __attribute__( ( aligned( 32 ) ) );

void vNetworkInterfaceAllocateRAMToBuffers( NetworkBufferDescriptor_t pxNetworkBuffers[ ipconfigNUM_NETWORK_BUFFER_DESCRIPTORS ] )
{
    uint8_t * ucRAMBuffer = ucNetworkPackets;
    uint32_t ul;

    for( ul = 0; ul < ipconfigNUM_NETWORK_BUFFER_DESCRIPTORS; ul++ )
    {
        pxNetworkBuffers[ ul ].pucEthernetBuffer = ucRAMBuffer + ipBUFFER_PADDING;
        *( ( unsigned * ) ucRAMBuffer ) = ( unsigned ) ( &( pxNetworkBuffers[ ul ] ) );
        ucRAMBuffer += niBUFFER_1_PACKET_SIZE;
    }
}
/*-----------------------------------------------------------*/

configPLACE_IN_SECTION_RAM
static void vClearTXBuffers()
{
    uint32_t ulLastDescriptor = ulNextFreeTxDescriptor;
    size_t uxCount = ( ( size_t ) configNUM_TX_DESCRIPTORS ) - uxSemaphoreGetCount( xTXDescriptorSemaphore );

    #if ( ipconfigZERO_COPY_TX_DRIVER != 0 )
        NetworkBufferDescriptor_t * pxNetworkBuffer;
        uint8_t * ucPayLoad;
    #endif

    /* This function is called after a TX-completion interrupt.
     * It will release each Network Buffer used in xNetworkInterfaceOutput().
     * 'uxCount' represents the number of descriptors given to DMA for transmission.
     * After sending a packet, the DMA will clear the 'TDES_OWN' bit. */
    while( ( uxCount > ( size_t ) 0u ) && ( ( xDMATxDescriptors[ ulTxDescriptorToClear ].CTRLSTAT & TDES_OWN ) == 0 ) )
    {
        if( ( ulTxDescriptorToClear == ulLastDescriptor ) && ( uxCount != ( size_t ) configNUM_TX_DESCRIPTORS ) )
        {
            break;
        }

        #if ( ipconfigZERO_COPY_TX_DRIVER != 0 )
            {
                ucPayLoad = ( uint8_t * ) xDMATxDescriptors[ ulTxDescriptorToClear ].B1ADD;

                if( ucPayLoad != NULL )
                {
                    /* B1ADD points to a pucEthernetBuffer of a Network Buffer descriptor. */
                    pxNetworkBuffer = pxPacketBuffer_to_NetworkBuffer( ucPayLoad );

                    configASSERT( pxNetworkBuffer != NULL );

                    vReleaseNetworkBufferAndDescriptor( pxNetworkBuffer );
                    xDMATxDescriptors[ ulTxDescriptorToClear ].B1ADD = ( uint32_t ) 0u;
                }
            }
        #endif /* ipconfigZERO_COPY_TX_DRIVER */

        /* Move onto the next descriptor, wrapping if necessary. */
        ulTxDescriptorToClear++;

        if( ulTxDescriptorToClear >= configNUM_TX_DESCRIPTORS )
        {
            ulTxDescriptorToClear = 0;
        }

        uxCount--;
        /* Tell the counting semaphore that one more TX descriptor is available. */
        xSemaphoreGive( xTXDescriptorSemaphore );
    }
}

/*-----------------------------------------------------------*/

configPLACE_IN_SECTION_RAM
BaseType_t xNetworkInterfaceOutput( NetworkBufferDescriptor_t * const pxDescriptor,
                                    BaseType_t bReleaseAfterSend )
{
    BaseType_t xReturn = pdFAIL;
    const TickType_t xBlockTimeTicks = pdMS_TO_TICKS( 50 );

    /* Attempt to obtain access to a Tx descriptor. */
    do
    {
        if( xTXDescriptorSemaphore == NULL )
        {
            break;
        }

        if( xSemaphoreTake( xTXDescriptorSemaphore, xBlockTimeTicks ) != pdPASS )
        {
            /* Time-out waiting for a free TX descriptor. */
            break;
        }

        /* If the descriptor is still owned by the DMA it can't be used. */
        if( ( xDMATxDescriptors[ ulNextFreeTxDescriptor ].CTRLSTAT & TDES_OWN ) != 0 )
        {
            /* The semaphore was taken, the TX DMA-descriptor is still not available.
             * Actually that should not occur, the 'TDES_OWN' was already confirmed low in vClearTXBuffers(). */
            xSemaphoreGive( xTXDescriptorSemaphore );
        }
        else
        {
            #if ( ipconfigZERO_COPY_TX_DRIVER != 0 )
                {
                    /* bReleaseAfterSend should always be set when using the zero
                     * copy driver. */
                    configASSERT( bReleaseAfterSend != pdFALSE );

                    /* The DMA's descriptor to point directly to the data in the
                     * network buffer descriptor.  The data is not copied. */
                    xDMATxDescriptors[ ulNextFreeTxDescriptor ].B1ADD = ( uint32_t ) pxDescriptor->pucEthernetBuffer;

                    /* The DMA descriptor will 'own' this Network Buffer,
                     * until it has been sent.  So don't release it now. */
                    bReleaseAfterSend = false;
                }
            #else /* if ( ipconfigZERO_COPY_TX_DRIVER != 0 ) */
                {
                    /* The data is copied from the network buffer descriptor into
                     * the DMA's descriptor. */
                    memcpy( ( void * ) xDMATxDescriptors[ ulNextFreeTxDescriptor ].B1ADD, ( void * ) pxDescriptor->pucEthernetBuffer, pxDescriptor->xDataLength );
                }
            #endif /* if ( ipconfigZERO_COPY_TX_DRIVER != 0 ) */

            xDMATxDescriptors[ ulNextFreeTxDescriptor ].BSIZE = ( uint32_t ) TDES_ENH_BS1( pxDescriptor->xDataLength );

            /* This descriptor is given back to the DMA. */
            xDMATxDescriptors[ ulNextFreeTxDescriptor ].CTRLSTAT |= TDES_OWN;

            /* Ensure the DMA is polling Tx descriptors. */
            LPC_ETHERNET->DMA_TRANS_POLL_DEMAND = 1;

            iptraceNETWORK_INTERFACE_TRANSMIT();

            /* Move onto the next descriptor, wrapping if necessary. */
            ulNextFreeTxDescriptor++;

            if( ulNextFreeTxDescriptor >= configNUM_TX_DESCRIPTORS )
            {
                ulNextFreeTxDescriptor = 0;
            }

            /* The Tx has been initiated. */
            xReturn = pdPASS;
        }
    } while( 0 );

    /* The buffer has been sent so can be released. */
    if( bReleaseAfterSend != pdFALSE )
    {
        vReleaseNetworkBufferAndDescriptor( pxDescriptor );
    }

    return xReturn;
}
/*-----------------------------------------------------------*/

static void prvDelay( uint32_t ulMilliSeconds )
{
    /* Ensure the scheduler was started before attempting to use the scheduler to
     * create a delay. */
    configASSERT( xTaskGetSchedulerState() == taskSCHEDULER_RUNNING );

    vTaskDelay( pdMS_TO_TICKS( ulMilliSeconds ) );
}
/*-----------------------------------------------------------*/

static void prvSetupTxDescriptors( void )
{
    BaseType_t x;

    /* Start with Tx descriptors clear. */
    memset( ( void * ) xDMATxDescriptors, 0, sizeof( xDMATxDescriptors ) );

    /* Index to the next Tx descriptor to use. */
    ulNextFreeTxDescriptor = 0ul;

    /* Index to the next Tx descriptor to clear ( after transmission ). */
    ulTxDescriptorToClear = 0ul;

    for( x = 0; x < configNUM_TX_DESCRIPTORS; x++ )
    {
        #if ( ipconfigZERO_COPY_TX_DRIVER != 0 )
            {
                /* Nothing to do, B1ADD will be set when data is ready to transmit.
                 * Currently the memset above will have set it to NULL. */
            }
        #else
            {
                /* Allocate a buffer to the Tx descriptor.  This is the most basic
                 * way of creating a driver as the data is then copied into the
                 * buffer. */
                xDMATxDescriptors[ x ].B1ADD = ( uint32_t ) pvPortMalloc( ipTOTAL_ETHERNET_FRAME_SIZE );

                /* Use an assert to check the allocation as +TCP applications will
                 * often not use a malloc() failed hook as the TCP stack will recover
                 * from allocation failures. */
                configASSERT( xDMATxDescriptors[ x ].B1ADD != 0U );
            }
        #endif /* if ( ipconfigZERO_COPY_TX_DRIVER != 0 ) */

        /* Buffers hold an entire frame so all buffers are both the start and
         * end of a frame. */
        /* TDES_ENH_TCH     Second Address Chained. */
        /* TDES_ENH_CIC(n)  Checksum Insertion Control, tried but it does not work for the LPC18xx... */
        /* TDES_ENH_FS      First Segment. */
        /* TDES_ENH_LS      Last Segment. */
        /* TDES_ENH_IC      Interrupt on Completion. */
        xDMATxDescriptors[ x ].CTRLSTAT = TDES_ENH_TCH | TDES_ENH_CIC( 3 ) | TDES_ENH_FS | TDES_ENH_LS | TDES_ENH_IC;
        xDMATxDescriptors[ x ].B2ADD = ( uint32_t ) &xDMATxDescriptors[ x + 1 ];
    }

    xDMATxDescriptors[ configNUM_TX_DESCRIPTORS - 1 ].CTRLSTAT |= TDES_ENH_TER;
    xDMATxDescriptors[ configNUM_TX_DESCRIPTORS - 1 ].B2ADD = ( uint32_t ) &xDMATxDescriptors[ 0 ];

    /* Point the DMA to the base of the descriptor list. */
    LPC_ETHERNET->DMA_TRANS_DES_ADDR = ( uint32_t ) xDMATxDescriptors;
}
/*-----------------------------------------------------------*/

static void prvSetupRxDescriptors( void )
{
    BaseType_t x;

    #if ( ipconfigZERO_COPY_RX_DRIVER != 0 )
        NetworkBufferDescriptor_t * pxNetworkBuffer;
    #endif

    /* Index to the next Rx descriptor to use. */
    ulNextRxDescriptorToProcess = 0;

    /* Clear RX descriptor list. */
    memset( ( void * ) xDMARxDescriptors, 0, sizeof( xDMARxDescriptors ) );

    for( x = 0; x < configNUM_RX_DESCRIPTORS; x++ )
    {
        /* Allocate a buffer of the largest	possible frame size as it is not
         * known what size received frames will be. */

        #if ( ipconfigZERO_COPY_RX_DRIVER != 0 )
            {
                pxNetworkBuffer = pxGetNetworkBufferWithDescriptor( ipTOTAL_ETHERNET_FRAME_SIZE, 0 );

                /* During start-up there should be enough Network Buffers available,
                 * so it is safe to use configASSERT().
                 * In case this assert fails, please check: configNUM_RX_DESCRIPTORS,
                 * ipconfigNUM_NETWORK_BUFFER_DESCRIPTORS, and in case BufferAllocation_2.c
                 * is included, check the amount of available heap. */
                configASSERT( pxNetworkBuffer != NULL );

                /* Pass the actual buffer to DMA. */
                xDMARxDescriptors[ x ].B1ADD = ( uint32_t ) pxNetworkBuffer->pucEthernetBuffer;
            }
        #else
            {
                /* All DMA descriptors are populated with permanent memory blocks.
                 * Their contents will be copy to Network Buffers. */
                xDMARxDescriptors[ x ].B1ADD = ( uint32_t ) pvPortMalloc( ipTOTAL_ETHERNET_FRAME_SIZE );
            }
        #endif /* ipconfigZERO_COPY_RX_DRIVER */

        /* Use an assert to check the allocation as +TCP applications will often
         * not use a malloc failed hook as the TCP stack will recover from
         * allocation failures. */
        configASSERT( xDMARxDescriptors[ x ].B1ADD != 0U );

        xDMARxDescriptors[ x ].B2ADD = ( uint32_t ) &( xDMARxDescriptors[ x + 1 ] );
        xDMARxDescriptors[ x ].CTRL = ( uint32_t ) RDES_ENH_BS1( ipTOTAL_ETHERNET_FRAME_SIZE ) | RDES_ENH_RCH;

        /* The descriptor is available for use by the DMA. */
        xDMARxDescriptors[ x ].STATUS = RDES_OWN;
    }

    /* RDES_ENH_RER  Receive End of Ring. */
    xDMARxDescriptors[ ( configNUM_RX_DESCRIPTORS - 1 ) ].CTRL |= RDES_ENH_RER;
    xDMARxDescriptors[ configNUM_RX_DESCRIPTORS - 1 ].B2ADD = ( uint32_t ) &( xDMARxDescriptors[ 0 ] );

    /* Point the DMA to the base of the descriptor list. */
    LPC_ETHERNET->DMA_REC_DES_ADDR = ( uint32_t ) xDMARxDescriptors;
}
/*-----------------------------------------------------------*/
configPLACE_IN_SECTION_RAM
static void prvRemoveTrailingBytes( NetworkBufferDescriptor_t * pxDescriptor )
{
    size_t xExpectedLength;
    IPPacket_t * pxIPPacket;

    pxIPPacket = ( IPPacket_t * ) pxDescriptor->pucEthernetBuffer;
    /* Look at the actual length of the packet, translate it to a host-endian notation. */
    xExpectedLength = sizeof( EthernetHeader_t ) + ( size_t ) FreeRTOS_htons( pxIPPacket->xIPHeader.usLength );

    if( xExpectedLength == ( pxDescriptor->xDataLength + 4 ) )
    {
        pxDescriptor->xDataLength -= 4;
    }
    else
    {
        if( pxDescriptor->xDataLength > xExpectedLength )
        {
            pxDescriptor->xDataLength = ( size_t ) xExpectedLength;
        }
    }
}
/*-----------------------------------------------------------*/
configPLACE_IN_SECTION_RAM
BaseType_t xGetPhyLinkStatus( void )
{
    BaseType_t xReturn;

    if( ( ulPHYLinkStatus & PHY_LINK_CONNECTED ) == 0 )
    {
        xReturn = pdFALSE;
    }
    else
    {
        xReturn = pdTRUE;
    }

    return xReturn;
}
/*-----------------------------------------------------------*/

uint32_t ulDataAvailable;

configPLACE_IN_SECTION_RAM
static BaseType_t prvNetworkInterfaceInput()
{
    BaseType_t xResult = pdFALSE;
    uint32_t ulStatus;
    eFrameProcessingResult_t eResult;
    const TickType_t xDescriptorWaitTime = pdMS_TO_TICKS( 250 );
    const UBaseType_t uxMinimumBuffersRemaining = 3UL;
    uint16_t usLength;
    NetworkBufferDescriptor_t * pxDescriptor;

    #if ( ipconfigZERO_COPY_RX_DRIVER != 0 )
        NetworkBufferDescriptor_t * pxNewDescriptor;
    #endif /* ipconfigZERO_COPY_RX_DRIVER */
    #if ( ipconfigUSE_LINKED_RX_MESSAGES == 0 )
        IPStackEvent_t xRxEvent = { eNetworkRxEvent, NULL };
    #endif

    /* Process each descriptor that is not still in use by the DMA. */
    ulStatus = xDMARxDescriptors[ ulNextRxDescriptorToProcess ].STATUS;

    if( ( ulStatus & RDES_OWN ) == 0 )
    {
        /* Check packet for errors */
        if( ( ulStatus & nwRX_STATUS_ERROR_BITS ) != 0 )
        {
            /* There is some reception error. */
            intCount[ 3 ]++;
            /* Clear error bits. */
            ulStatus &= ~( ( uint32_t ) nwRX_STATUS_ERROR_BITS );
        }
        else
        {
            xResult++;

            eResult = ipCONSIDER_FRAME_FOR_PROCESSING( ( const uint8_t * const ) ( xDMARxDescriptors[ ulNextRxDescriptorToProcess ].B1ADD ) );

            if( eResult == eProcessBuffer )
            {
                if( ( ulPHYLinkStatus & PHY_LINK_CONNECTED ) == 0 )
                {
                    ulPHYLinkStatus |= PHY_LINK_CONNECTED;
                    FreeRTOS_printf( ( "prvEMACHandlerTask: PHY LS now %d (message received)\n", ( ulPHYLinkStatus & PHY_LINK_CONNECTED ) != 0 ) );
                }

                #if ( ipconfigZERO_COPY_RX_DRIVER != 0 )
                    if( uxGetNumberOfFreeNetworkBuffers() > uxMinimumBuffersRemaining )
                    {
                        pxNewDescriptor = pxGetNetworkBufferWithDescriptor( ipTOTAL_ETHERNET_FRAME_SIZE, xDescriptorWaitTime );
                    }
                    else
                    {
                        /* Too risky to allocate a new Network Buffer. */
                        pxNewDescriptor = NULL;
                    }

                    if( pxNewDescriptor != NULL )
                #else /* if ( ipconfigZERO_COPY_RX_DRIVER != 0 ) */
                    if( uxGetNumberOfFreeNetworkBuffers() > uxMinimumBuffersRemaining )
                #endif /* ipconfigZERO_COPY_RX_DRIVER */
                {
                    #if ( ipconfigZERO_COPY_RX_DRIVER != 0 )
                        const uint8_t * pucBuffer;
                    #endif

                    /* Get the actual length. */
                    usLength = RDES_FLMSK( ulStatus );

                    #if ( ipconfigZERO_COPY_RX_DRIVER != 0 )
                        {
                            /* Replace the character buffer 'B1ADD'. */
                            pucBuffer = ( const uint8_t * const ) ( xDMARxDescriptors[ ulNextRxDescriptorToProcess ].B1ADD );
                            xDMARxDescriptors[ ulNextRxDescriptorToProcess ].B1ADD = ( uint32_t ) pxNewDescriptor->pucEthernetBuffer;

                            /* 'B1ADD' contained the address of a 'pucEthernetBuffer' that
                             * belongs to a Network Buffer.  Find the original Network Buffer. */
                            pxDescriptor = pxPacketBuffer_to_NetworkBuffer( pucBuffer );

                            /* This zero-copy driver makes sure that every 'xDMARxDescriptors' contains
                             * a reference to a Network Buffer at any time.
                             * In case it runs out of Network Buffers, a DMA buffer won't be replaced,
                             * and the received messages is dropped. */
                            configASSERT( pxDescriptor != NULL );
                        }
                    #else /* if ( ipconfigZERO_COPY_RX_DRIVER != 0 ) */
                        {
                            /* Create a buffer of exactly the required length. */
                            pxDescriptor = pxGetNetworkBufferWithDescriptor( usLength, xDescriptorWaitTime );
                        }
                    #endif /* ipconfigZERO_COPY_RX_DRIVER */

                    if( pxDescriptor != NULL )
                    {
                        pxDescriptor->xDataLength = ( size_t ) usLength;
                        #if ( ipconfigZERO_COPY_RX_DRIVER == 0 )
                            {
                                /* Copy the data into the allocated buffer. */
                                memcpy( ( void * ) pxDescriptor->pucEthernetBuffer, ( void * ) xDMARxDescriptors[ ulNextRxDescriptorToProcess ].B1ADD, usLength );
                            }
                        #endif /* ipconfigZERO_COPY_RX_DRIVER */

                        /* It is possible that more data was copied than
                         * actually makes up the frame.  If this is the case
                         * adjust the length to remove any trailing bytes. */
                        prvRemoveTrailingBytes( pxDescriptor );

                        /* Pass the data to the TCP/IP task for processing. */
                        xRxEvent.pvData = ( void * ) pxDescriptor;

                        if( xSendEventStructToIPTask( &xRxEvent, xDescriptorWaitTime ) == pdFALSE )
                        {
                            /* Could not send the descriptor into the TCP/IP
                             * stack, it must be released. */
                            vReleaseNetworkBufferAndDescriptor( pxDescriptor );
                        }
                        else
                        {
                            iptraceNETWORK_INTERFACE_RECEIVE();

                            /* The data that was available at the top of this
                             *  loop has been sent, so is no longer available. */
                            ulDataAvailable = pdFALSE;
                        }
                    }
                }
            }
            else
            {
                /* The packet is discarded as uninteresting. */
                ulDataAvailable = pdFALSE;
            }

            /* Got here because received data was sent to the IP task or the
             * data contained an error and was discarded.  Give the descriptor
             * back to the DMA. */
            xDMARxDescriptors[ ulNextRxDescriptorToProcess ].STATUS = ulStatus | RDES_OWN;

            /* Move onto the next descriptor. */
            ulNextRxDescriptorToProcess++;

            if( ulNextRxDescriptorToProcess >= configNUM_RX_DESCRIPTORS )
            {
                ulNextRxDescriptorToProcess = 0;
            }

            ulStatus = xDMARxDescriptors[ ulNextRxDescriptorToProcess ].STATUS;
        } /* if( ( ulStatus & nwRX_STATUS_ERROR_BITS ) != 0 ) */
    }     /* if( ( ulStatus & RDES_OWN ) == 0 ) */

    /* Restart receive polling. */
    LPC_ETHERNET->DMA_REC_POLL_DEMAND = 1;

    return xResult;
}
/*-----------------------------------------------------------*/

configPLACE_IN_SECTION_RAM
void NETWORK_IRQHandler( void )
{
    BaseType_t xHigherPriorityTaskWoken = pdFALSE;
    uint32_t ulDMAStatus;
    const uint32_t ulRxInterruptMask =
        DMA_ST_RI | /* Receive interrupt */
        DMA_ST_RU;  /* Receive buffer unavailable */
    const uint32_t ulTxInterruptMask =
        DMA_ST_TI | /* Transmit interrupt */
        DMA_ST_TPS; /* Transmit process stopped */

    configASSERT( xRxHanderTask );

    /* Get pending interrupts. */
    ulDMAStatus = LPC_ETHERNET->DMA_STAT;

    /* RX group interrupt(s). */
    if( ( ulDMAStatus & ulRxInterruptMask ) != 0x00 )
    {
        /* Remember that an RX event has happened. */
        ulISREvents |= EMAC_IF_RX_EVENT;
        vTaskNotifyGiveFromISR( xRxHanderTask, &xHigherPriorityTaskWoken );
        intCount[ 0 ]++;
    }

    /* TX group interrupt(s). */
    if( ( ulDMAStatus & ulTxInterruptMask ) != 0x00 )
    {
        /* Remember that a TX event has happened. */
        ulISREvents |= EMAC_IF_TX_EVENT;
        vTaskNotifyGiveFromISR( xRxHanderTask, &xHigherPriorityTaskWoken );
        intCount[ 1 ]++;
    }

    /* Test for 'Abnormal interrupt summary'. */
    if( ( ulDMAStatus & DMA_ST_AIE ) != 0x00 )
    {
        /* The trace macro must be written such that it can be called from
         * an interrupt. */
        iptraceETHERNET_RX_EVENT_LOST();
    }

    /* Clear pending interrupts */
    LPC_ETHERNET->DMA_STAT = ulDMAStatus;

    /* Context switch needed? */
    portYIELD_FROM_ISR( xHigherPriorityTaskWoken );
}
/*-----------------------------------------------------------*/

static BaseType_t prvSetLinkSpeed( void )
{
    BaseType_t xReturn = pdFAIL;
    TickType_t xTimeOnEntering;
    uint32_t ulPhyStatus;
    const TickType_t xAutoNegotiateDelay = pdMS_TO_TICKS( 5000UL );

    /* Ensure polling does not starve lower priority tasks by temporarily
     * setting the priority of this task to that of the idle task. */
    vTaskPrioritySet( NULL, tskIDLE_PRIORITY );

    xTimeOnEntering = xTaskGetTickCount();

    do
    {
        ulPhyStatus = lpcPHYStsPoll();

        if( ( ulPhyStatus & PHY_LINK_CONNECTED ) != 0x00 )
        {
            /* Set interface speed and duplex. */
            if( ( ulPhyStatus & PHY_LINK_SPEED100 ) != 0x00 )
            {
                Chip_ENET_SetSpeed( LPC_ETHERNET, 1 );
            }
            else
            {
                Chip_ENET_SetSpeed( LPC_ETHERNET, 0 );
            }

            if( ( ulPhyStatus & PHY_LINK_FULLDUPLX ) != 0x00 )
            {
                Chip_ENET_SetDuplex( LPC_ETHERNET, true );
            }
            else
            {
                Chip_ENET_SetDuplex( LPC_ETHERNET, false );
            }

            xReturn = pdPASS;
            break;
        }
    } while( ( xTaskGetTickCount() - xTimeOnEntering ) < xAutoNegotiateDelay );

    /* Reset the priority of this task back to its original value. */
    vTaskPrioritySet( NULL, ipconfigIP_TASK_PRIORITY );

    return xReturn;
}
/*-----------------------------------------------------------*/

static uint32_t prvGenerateCRC32( const uint8_t * ucAddress )
{
    unsigned int j;
    const uint32_t Polynomial = 0xEDB88320;
    uint32_t crc = ~0ul;
    const uint8_t * pucCurrent = ( const uint8_t * ) ucAddress;
    const uint8_t * pucLast = pucCurrent + 6;

    /* Calculate  normal CRC32 */
    while( pucCurrent < pucLast )
    {
        crc ^= *( pucCurrent++ );

        for( j = 0; j < 8; j++ )
        {
            if( ( crc & 1 ) != 0 )
            {
                crc = ( crc >> 1 ) ^ Polynomial;
            }
            else
            {
                crc >>= 1;
            }
        }
    }

    return ~crc;
}
/*-----------------------------------------------------------*/

static uint32_t prvGetHashIndex( const uint8_t * ucAddress )
{
    uint32_t ulCrc = prvGenerateCRC32( ucAddress );
    uint32_t ulIndex = 0ul;
    BaseType_t xCount = 6;

    /* Take the lowest 6 bits of the CRC32 and reverse them */
    while( xCount-- )
    {
        ulIndex <<= 1;
        ulIndex |= ( ulCrc & 1 );
        ulCrc >>= 1;
    }

    /* This is the has value of 'ucAddress' */
    return ulIndex;
}
/*-----------------------------------------------------------*/

static void prvAddMACAddress( const uint8_t * ucMacAddress )
{
    BaseType_t xIndex;

    xIndex = prvGetHashIndex( ucMacAddress );

    if( xIndex >= 32 )
    {
        LPC_ETHERNET->MAC_HASHTABLE_HIGH |= ( 1u << ( xIndex - 32 ) );
    }
    else
    {
        LPC_ETHERNET->MAC_HASHTABLE_LOW |= ( 1u << xIndex );
    }
}
/*-----------------------------------------------------------*/

configPLACE_IN_SECTION_RAM
static void prvEMACHandlerTask( void * pvParameters )
{
    TimeOut_t xPhyTime;
    TickType_t xPhyRemTime;
    UBaseType_t uxLastMinBufferCount = 0;
    UBaseType_t uxCurrentCount;
    BaseType_t xResult = 0;
    uint32_t ulStatus;
    const TickType_t xBlockTime = pdMS_TO_TICKS( 5000ul );

    /* Remove compiler warning about unused parameter. */
    ( void ) pvParameters;

    /* A possibility to set some additional task properties. */
    iptraceEMAC_TASK_STARTING();

    vTaskSetTimeOutState( &xPhyTime );
    xPhyRemTime = pdMS_TO_TICKS( PHY_LS_LOW_CHECK_TIME_MS );

    for( ; ; )
    {
        uxCurrentCount = uxGetMinimumFreeNetworkBuffers();

        if( uxLastMinBufferCount != uxCurrentCount )
        {
            /* The logging produced below may be helpful
             * while tuning +TCP: see how many buffers are in use. */
            uxLastMinBufferCount = uxCurrentCount;
            FreeRTOS_printf( ( "Network buffers: %lu lowest %lu\n",
                               uxGetNumberOfFreeNetworkBuffers(), uxCurrentCount ) );
        }

        #if ( ipconfigCHECK_IP_QUEUE_SPACE != 0 )
            {
                static UBaseType_t uxLastMinQueueSpace = 0;

                uxCurrentCount = uxGetMinimumIPQueueSpace();

                if( uxLastMinQueueSpace != uxCurrentCount )
                {
                    /* The logging produced below may be helpful
                     * while tuning +TCP: see how many buffers are in use. */
                    uxLastMinQueueSpace = uxCurrentCount;
                    FreeRTOS_printf( ( "Queue space: lowest %lu\n", uxCurrentCount ) );
                }
            }
        #endif /* ipconfigCHECK_IP_QUEUE_SPACE */

        ulTaskNotifyTake( pdTRUE, xBlockTime );

        xResult = ( BaseType_t ) 0;

        if( ( ulISREvents & EMAC_IF_TX_EVENT ) != 0 )
        {
            /* Code to release TX buffers if zero-copy is used. */
            ulISREvents &= ~EMAC_IF_TX_EVENT;
            {
                /* Check if DMA packets have been delivered. */
                vClearTXBuffers();
            }
        }

        if( ( ulISREvents & EMAC_IF_RX_EVENT ) != 0 )
        {
            ulISREvents &= ~EMAC_IF_RX_EVENT;

            xResult = prvNetworkInterfaceInput();

            if( xResult > 0 )
            {
                while( prvNetworkInterfaceInput() > 0 )
                {
                }
            }
        }

        if( xResult > 0 )
        {
            /* A packet was received. No need to check for the PHY status now,
             * but set a timer to check it later on. */
            vTaskSetTimeOutState( &xPhyTime );
            xPhyRemTime = pdMS_TO_TICKS( PHY_LS_HIGH_CHECK_TIME_MS );
            xResult = 0;
        }
        else if( xTaskCheckForTimeOut( &xPhyTime, &xPhyRemTime ) != pdFALSE )
        {
            ulStatus = lpcPHYStsPoll();

            if( ( ulPHYLinkStatus & PHY_LINK_CONNECTED ) != ( ulStatus & PHY_LINK_CONNECTED ) )
            {
                ulPHYLinkStatus = ulStatus;
                FreeRTOS_printf( ( "prvEMACHandlerTask: PHY LS now %d (polled PHY)\n", ( ulPHYLinkStatus & PHY_LINK_CONNECTED ) != 0 ) );
            }

            vTaskSetTimeOutState( &xPhyTime );

            if( ( ulPHYLinkStatus & PHY_LINK_CONNECTED ) != 0 )
            {
                xPhyRemTime = pdMS_TO_TICKS( PHY_LS_HIGH_CHECK_TIME_MS );
            }
            else
            {
                xPhyRemTime = pdMS_TO_TICKS( PHY_LS_LOW_CHECK_TIME_MS );
            }
        }
    }
}
/*-----------------------------------------------------------*/