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Rev 298 → Rev 299

/trunk/kernel/ethernet.c
0,0 → 1,393
/*--------------------------------------------------------------------
* TITLE: Plasma Ethernet MAC
* AUTHOR: Steve Rhoads (rhoadss@yahoo.com)
* DATE CREATED: 1/12/08
* FILENAME: ethernet.c
* PROJECT: Plasma CPU core
* COPYRIGHT: Software placed into the public domain by the author.
* Software 'as is' without warranty. Author liable for nothing.
* DESCRIPTION:
* Ethernet MAC implementation.
* Data is received from the Ethernet PHY four bits at a time.
* After 32-bits are received they are written to 0x13ff0000 + N.
* The data is received LSB first for each byte which requires the
* nibbles to be swapped.
* Transmit data is read from 0x13fe0000. Write length/4+1 to
* ETHERNET_REG to start transfer.
*--------------------------------------------------------------------*/
#include "plasma.h"
#include "rtos.h"
#include "tcpip.h"
 
#define POLYNOMIAL 0x04C11DB7 //CRC bit 33 is truncated
#define TOPBIT (1<<31)
#define BYTE_EMPTY 0xde //Data copied into receive buffer
#define COUNT_EMPTY 32 //Count to decide there isn't data
#define INDEX_MASK 0xffff //Size of receive buffer
 
//void dump(const unsigned char *data, int length);
 
static unsigned char gDestMac[]={0x5d, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff};
static unsigned int CrcTable[256];
static unsigned char reflect[256];
static unsigned char reflectNibble[256];
static OS_Semaphore_t *SemEthernet, *SemEthTransmit;
static int gIndex; //byte index into 0x13ff0000 receive buffer
static int gCheckedBefore;
 
 
//Read received data from 0x13ff0000. Data starts with 0x5d+MACaddress.
//Data is being received while processing the data. Therefore,
//all errors require waiting and then re-processing the data
//to see if the error is fixed by receiving the rest of the packet.
int EthernetReceive(unsigned char *buffer, int length)
{
int count;
int start, i, j, shift, offset;
int byte, byteNext;
unsigned long crc;
int byteCrc;
volatile unsigned char *buf = (unsigned char*)ETHERNET_RECEIVE;
int countEmpty, countOk, needWait;
 
//Find the start of a frame
countEmpty = 0;
countOk = 0;
needWait = 0;
for(i = 0; i < INDEX_MASK; ++i)
{
//Check if partial packet possibly received
if(needWait && gCheckedBefore == 0 && countOk != i && countEmpty != i)
{
gCheckedBefore = 1;
//printf("W(%d,%d,%d)", i, countOk, countEmpty);
return 0; //Wait for more data
}
 
//Detect start of frame
byte = buf[(gIndex + i) & INDEX_MASK];
if(byte == gDestMac[countOk] || (countOk && byte == 0xff))
{
if(++countOk == sizeof(gDestMac))
{
//Set bytes before 0x5d to BYTE_EMPTY
offset = i - (int)sizeof(gDestMac);
//if(offset > 3)
// printf("es%d ", offset);
for(j = 0; j <= offset; ++j)
{
buf[gIndex] = BYTE_EMPTY;
gIndex = (gIndex + 1) & INDEX_MASK;
}
break;
}
}
else
{
//if(countOk)
// printf("N%d ", countOk);
if(countOk == 3 && byte == BYTE_EMPTY)
needWait = 1;
if(byte == 0x5d)
countOk = 1;
else
countOk = 0;
}
 
//Check if remainder of buffer is empty
if(byte == BYTE_EMPTY)
{
if(++countEmpty >= COUNT_EMPTY)
{
//Set skiped bytes to BYTE_EMPTY
//if(i - COUNT_EMPTY > 3)
//{
// printf("eb%d \n", i - COUNT_EMPTY);
// //dump((char*)buf+gIndex, 0x200);
//}
for(j = 0; j <= i - COUNT_EMPTY; ++j)
{
buf[gIndex] = BYTE_EMPTY;
gIndex = (gIndex + 1) & INDEX_MASK;
}
gCheckedBefore = 0;
return 0;
}
}
else
{
if(countEmpty > 2 || (countEmpty > 0 && countEmpty == i))
needWait = 1;
countEmpty = 0;
}
}
 
//Found start of frame. Now find end of frame and check CRC.
start = gIndex;
gIndex = (gIndex + 1) & INDEX_MASK; //skip 0x5d byte
crc = 0xffffffff;
for(count = 0; count < length; )
{
byte = buf[gIndex];
gIndex = (gIndex + 1) & INDEX_MASK;
 
byte = ((byte << 4) & 0xf0) | (byte >> 4); //swap nibbles
buffer[count++] = (unsigned char)byte;
byte = reflect[byte] ^ (crc >> 24); //calculate CRC32
crc = CrcTable[byte] ^ (crc << 8);
if(count >= 60)
{
//Check if CRC matches to detect end of frame
byteCrc = reflectNibble[crc >> 24];
byteNext = buf[gIndex];
if(byteCrc == byteNext)
{
for(i = 1; i < 4; ++i)
{
shift = 24 - (i << 3);
byteCrc = reflectNibble[(crc >> shift) & 0xff];
byteNext = buf[(gIndex + i) & 0xffff];
if(byteCrc != byteNext)
{
//printf("nope %d %d 0x%x 0x%x\n", count, i, byteCrc, byteNext);
i = 99;
}
}
if(i == 4)
{
//Found end of frame -- set used bytes to BYTE_EMPTY
//printf("Found it! %d\n", count);
gIndex = (gIndex + 4) & INDEX_MASK;
for(i = 0; i < count+5; ++i)
buf[(start + i) & INDEX_MASK] = BYTE_EMPTY;
while(gIndex & 3)
{
buf[gIndex] = BYTE_EMPTY;
gIndex = (gIndex + 1) & INDEX_MASK;
}
gCheckedBefore = 0;
return count;
}
}
}
}
gIndex = start;
if(gCheckedBefore)
{
//printf("CRC failure\n");
buf[gIndex] = BYTE_EMPTY;
}
gCheckedBefore = 1;
return 0; //wait for more data
}
 
 
//Copy transmit data to 0x13fe0000 with preamble and CRC32
void EthernetTransmit(unsigned char *buffer, int length)
{
int i, byte, shift;
unsigned long crc;
volatile unsigned char *buf = (unsigned char*)ETHERNET_TRANSMIT;
 
OS_SemaphorePend(SemEthTransmit, OS_WAIT_FOREVER);
 
//Wait for previous transfer to complete
for(i = 0; i < 10000; ++i)
{
if(MemoryRead(IRQ_STATUS) & IRQ_ETHERNET_TRANSMIT)
break;
}
//if(i > 100)
// printf("wait=%d ", i);
 
Led(2);
while(length < 60 || (length & 3) != 0)
buffer[length++] = 0;
 
//Start of Ethernet frame
for(i = 0; i < 7; ++i)
buf[i] = 0x55;
buf[7] = 0x5d;
 
//Calculate CRC32
crc = 0xffffffff;
for(i = 0; i < length; ++i)
{
byte = buffer[i];
buf[i + 8] = (unsigned char)((byte << 4) | (byte >> 4)); //swap nibbles
byte = reflect[byte] ^ (crc >> 24); //calculate CRC32
crc = CrcTable[byte] ^ (crc << 8);
}
 
//Output CRC32
for(i = 0; i < 4; ++i)
{
shift = 24 - (i << 3);
byte = reflectNibble[(crc >> shift) & 0xff];
buf[length + 8 + i] = (unsigned char)byte;
}
 
//Start transfer
length = (length + 12 + 4) >> 2;
MemoryWrite(ETHERNET_REG, length);
Led(0);
 
OS_SemaphorePost(SemEthTransmit);
}
 
 
void EthernetThread(void *arg)
{
int length;
int rc;
unsigned int ticks, ticksLast=0;
IPFrame *ethFrame=NULL;
(void)arg;
 
for(;;)
{
OS_InterruptMaskSet(IRQ_ETHERNET_RECEIVE);
OS_SemaphorePend(SemEthernet, 50); //wait for interrupt
 
//Process all received packets
for(;;)
{
if(ethFrame == NULL)
ethFrame = IPFrameGet(FRAME_COUNT_RCV);
if(ethFrame == NULL)
break;
MemoryRead(ETHERNET_REG); //clear receive interrupt
length = EthernetReceive(ethFrame->packet, PACKET_SIZE);
if(length == 0)
break;
Led(1);
rc = IPProcessEthernetPacket(ethFrame, length);
Led(0);
if(rc)
ethFrame = NULL;
}
 
ticks = OS_ThreadTime();
if(ticks - ticksLast > 50)
{
IPTick();
ticksLast = ticks;
}
}
}
 
 
void EthernetIsr(void *arg)
{
(void)arg;
OS_InterruptMaskClear(IRQ_ETHERNET_TRANSMIT | IRQ_ETHERNET_RECEIVE);
OS_SemaphorePost(SemEthernet);
}
 
 
/******************* CRC32 calculations **********************
* The CRC32 code is modified from Michale Barr's article in
* Embedded Systems Programming January 2000.
* A CRC is really modulo-2 binary division. Substraction means XOR. */
static unsigned int Reflect(unsigned int value, int bits)
{
unsigned int num=0;
int i;
for(i = 0; i < bits; ++i)
{
num = (num << 1) | (value & 1);
value >>= 1;
}
return num;
}
 
 
static void CrcInit(void)
{
unsigned int remainder;
int dividend, bit, i;
 
//Compute the remainder of each possible dividend
for(dividend = 0; dividend < 256; ++dividend)
{
//Start with the dividend followed by zeros
remainder = dividend << 24;
//Perform modulo-2 division, a bit at a time
for(bit = 8; bit > 0; --bit)
{
//Try to divide the current data bit
if(remainder & TOPBIT)
remainder = (remainder << 1) ^ POLYNOMIAL;
else
remainder = remainder << 1;
}
CrcTable[dividend] = remainder;
}
for(i = 0; i < 256; ++i)
{
reflect[i] = (unsigned char)Reflect(i, 8);
reflectNibble[i] = (unsigned char)((Reflect((i >> 4) ^ 0xf, 4) << 4) |
Reflect(i ^ 0xf, 4));
}
}
 
 
static void SpinWait(int clocks)
{
int value = *(volatile int*)COUNTER_REG + clocks;
while(*(volatile int*)COUNTER_REG - value < 0)
;
}
 
 
void EthernetInit(unsigned char MacAddress[6])
{
//Format of SMI data: 0101 A4:A0 R4:R0 00 D15:D0
unsigned long data=0x5f800100; //SMI R0 = 10Mbps full duplex
//unsigned long data=0x5f800000; //SMI R0 = 10Mbps half duplex
int i, value;
volatile unsigned char *buf = (unsigned char*)ETHERNET_RECEIVE;
 
CrcInit();
for(i = 0; i < 6; ++i)
{
value = MacAddress[i];
gDestMac[i+1] = (unsigned char)((value >> 4) | (value << 4));
}
 
//Configure Ethernet PHY for 10Mbps full duplex via SMI interface
MemoryWrite(GPIO0_OUT, ETHERNET_MDIO | ETHERNET_MDIO_WE | ETHERENT_MDC);
for(i = 0; i < 34; ++i)
{
MemoryWrite(GPIO0_OUT, ETHERENT_MDC); //clock high
SpinWait(10);
MemoryWrite(GPIO0_CLEAR, ETHERENT_MDC); //clock low
SpinWait(10);
}
for(i = 31; i >= 0; --i)
{
value = (data >> i) & 1;
if(value)
MemoryWrite(GPIO0_OUT, ETHERNET_MDIO);
else
MemoryWrite(GPIO0_CLEAR, ETHERNET_MDIO);
MemoryWrite(GPIO0_OUT, ETHERENT_MDC); //clock high
SpinWait(10);
MemoryWrite(GPIO0_CLEAR, ETHERENT_MDC); //clock low
SpinWait(10);
}
MemoryWrite(GPIO0_CLEAR, ETHERNET_MDIO_WE | ETHERNET_ENABLE);
 
//Clear receive buffer
for(i = 0; i <= INDEX_MASK; ++i)
buf[i] = BYTE_EMPTY;
 
//Start receive DMA
MemoryWrite(GPIO0_OUT, ETHERNET_ENABLE);
 
//Setup interrupts for receiving data
SemEthernet = OS_SemaphoreCreate("eth", 0);
SemEthTransmit = OS_SemaphoreCreate("ethT", 1);
OS_ThreadCreate("eth", EthernetThread, NULL, 240, 0);
OS_InterruptRegister(IRQ_ETHERNET_RECEIVE, EthernetIsr);
}

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