int init_sdmmc_device()
{
int result;
// Set clock to 200k_hz (50Mhz system clock)
set_clock_divisor(125);
// After power on, send a bunch of clocks to initialize the chip
set_cs(1);
for (int i = 0; i < 10; i++)
spi_transfer(0xff);
set_cs(0);
// Reset the card
result = send_sd_command(SD_CMD_RESET, 0);
if (result != 1)
return -1;
// Poll until it is ready
while (1)
{
result = send_sd_command(SD_CMD_INIT, 0);
if (result == 0)
break;
if (result != 1)
return -1;
}
// Configure the block size
result = send_sd_command(SD_CMD_SET_BLOCK_LEN, BLOCK_SIZE);
if (result != 0)
return -1;
// Increase clock rate to 5 Mhz
set_clock_divisor(5);
return 0;
}
int read_sdmmc_device(unsigned int block_address, void *ptr)
{
int result;
result = send_sd_command(SD_CMD_READ_BLOCK, block_address);
if (result != 0)
return -1;
for (int i = 0; i < BLOCK_SIZE; i++)
((char*) ptr)[i] = spi_transfer(0xff);
// checksum (ignored)
spi_transfer(0xff);
spi_transfer(0xff);
return BLOCK_SIZE;
}
int read_sdmmc_device(unsigned int block_address, void *ptr)
{
int result;
int old_flags;
old_flags = disable_interrupts();
acquire_spinlock(&sd_lock);
result = send_sd_command(SD_CMD_READ_BLOCK, block_address);
if (result != 0)
return -1;
for (int i = 0; i < BLOCK_SIZE; i++)
((char*) ptr)[i] = spi_transfer(0xff);
// checksum (ignored)
spi_transfer(0xff);
spi_transfer(0xff);
release_spinlock(&sd_lock);
restore_interrupts(old_flags);
return BLOCK_SIZE;
}