I'm trying to setup an app in Linux that uses SPI port 1. I believe the registers are all set properly, but I never get any data in on the port. What am I missing?

Here is the code:


#include <stdio.h>
#include <stdlib.h>
#include <sys/mman.h>
#include <fcntl.h>

int spi1_init(void);

int main(int argc, char *argv[])
{
spi1_init();
spi1_read(); // read data forever
}

#define ADDR_AIC 0xFFFFF000
#define ADDR_SPI1 0xF0004000

#define SPI_CR 0
#define SPI_MR 1
#define SPI_RDR 2
#define SPI_TDR 3
#define SPI_SR 4
#define SPI_IER 5
#define SPI_IDR 6
#define SPI_IMR 7
#define SPI_CSRx 12
#define SPI_WPMR 57
#define SPI_WPSR 58

#define PIOA_PER 256
#define PIOA_PDR 257
#define PIOA_PSR 258
#define PIOA_OER 260
#define PIOA_ODR 261
#define PIOA_PDSR 271
#define PIOA_ABCDSR1 284
#define PIOA_ABCDSR2 285

#define PMC_PCER 772
#define PMC_PCSR 774

int spi1_init(void)
{
unsigned long *addr;
unsigned long data;
int index;
int fd;

fd = open("/dev/mem", O_RDWR|O_SYNC);
if (fd <= 0)
return(-1);

// setup PA8, PA21, PA22, and PA23 to be SPI1
addr = (unsigned long *)mmap(0, getpagesize(), PROT_READ|PROT_WRITE, MAP_SHARED, fd, ADDR_AIC);

// setup PA8, 21, 22, and 23 for SPI
// PIOA_ABCDSR1 bits should be 1 for these pins
// PIOA_ABCDSR2 bits should be 0 for these pins
*(addr + PIOA_PDR) = 0x00E00100; // disable as PIO and enable as peripheral
*(addr + PIOA_ABCDSR1) |= 0x00E00100;
*(addr + PIOA_ABCDSR2) &= ~0x00E00100;

// make sure SPI1 is enabled in the PMC
*(addr + PMC_PCER) |= 0x00004000;

// use spi1
addr = (unsigned long *)mmap(0, getpagesize(), PROT_READ|PROT_WRITE, MAP_SHARED, fd, ADDR_SPI1);
*(addr + SPI_CR) = 0x00000080; // software reset
// after reset, the spi port is in slave mode
*(addr + SPI_CR) = 0x00000001; // enable the SPI port

return(0);
}


int spi1_read(void)
{
unsigned long *spi1Addr;
int fd;

fd = open("/dev/mem", O_RDWR|O_SYNC);
if (fd <= 0)
return(-1);

// use spi1
spi1Addr = (unsigned long *)mmap(0, getpagesize(), PROT_READ|PROT_WRITE, MAP_SHARED, fd, ADDR_SPI1);

while (1) {
if (*(spi1Addr + SPI_SR) & 0x00000100)
printf("%08lX %08lX\n", *(spi1Addr + SPI_SR), *(spi1Addr + SPI_RDR));
}

return(0);
}

I found my problem. Although the chip select registers default to the correct values, I still had to write a value to them before the device would start properly. I added the line:

*(addr + SPI_CSR0) = 0x00000000;