using SPI with DMAC on AM3517

Please provide more details about the software you are using.

Best regards,
Miroslav

I am using AM3517 with TI SDK v05.07, Linux Kernel version 2.6.37. I have written example user space codes to run spi with spidev. 

1) I would like to set up an SPI line with baud rate greater than 4M and service interrupts when I receive some data with spi on the dma receive channel from slave and based on certain states I would like to transfer 300 bytes of data as one block in one write cycle

I read online that interrupts can be serviced only from kernel module / device drivers. How do i go about setting up interrupts for spi receive event on DMA? I know how to write simple hello world kernel modules and cross compile them for the kernel.

2) Does the spidev automatically call omap2_mcspi.c which contains DMA requests and causes  DMA to be  automatically invoked when the size of my transfer exceeds a defined threshold or is that done by /drivers/spi/spi.c?

Please find below code fragments on my implementation of read +write using spidev in user space

***********************my class SPI.ccp fragment***************************

int Spi::spiWriteRead( unsigned char *data, int length){

struct spi_ioc_transfer spi[length];
int i = 0;
int retVal = -1;

// one spi transfer for each byte

for (i = 0 ; i < length ; i++){

spi[i].tx_buf = (unsigned long)(data + i); // transmit from "data"
spi[i].rx_buf = (unsigned long)(data + i) ; // receive into "data"
spi[i].len = sizeof(*(data + i)) ;
spi[i].delay_usecs = 0 ;
spi[i].speed_hz = this->speed ;
spi[i].bits_per_word = this->bitsPerWord ;
spi[i].cs_change = 0;
}

retVal = ioctl (this->spifd, SPI_IOC_MESSAGE(length), &spi) ;

if(retVal < 0){
perror("Problem transmitting spi data..ioctl");
exit(1);
}

return retVal;

}

***************************main.cpp*************************

#include "Spi.h"

using namespace std;

int main(void)
{
Spi spi("/dev/spidev1.0", SPI_MODE_0, 5000000, 8);
//Spi spi;
int i = 6;
unsigned char data[1];
int rx_data=0;
while(i > 0)
{
data[0] = 1;
//data[1] = 'A';
//data[2] = 0;

spi.spiWriteRead(data, sizeof(data) );
rx_data = (int)data[0];
cout<<"the received data is:"<<rx_data<<endl;

i--;
}
return 0;
}

Thanks alot for your help!