SPI and uClinux

1. Add a SPI device (Actual SPI device driver), in my case it is altera spi

static struct resource spi_master_resource = {
     = {
           .start = SPI_MASTER_BASE,
           .end = SPI_MASTER_END,
           .flags = IORESOURCE_MEM,
           },
     = {
           .start = SPI_MASTER_IRQ,
           .end = SPI_MASTER_IRQ,
           .flags = IORESOURCE_IRQ,
           },
};
static struct platform_device spi_master_device = {
    .name = "spi_altera",
    .id = 0,        /* Bus number */
    .num_resources = ARRAY_SIZE(spi_master_resource),
    .resource = spi_master_resource,
};

2. Add spi board info. The id in SPI device and bus_num in spi board info shall match. you can add multiple entries if you have many.

static struct spi_board_info nios2_spi_devices = {
     /* the modalias must be the same as spi device driver name */
     .modalias = "spidev",    /* Name of spi_driver for this device */
     .max_speed_hz = 4000000,    /* max spi clock (SCK) speed in HZ */
     .bus_num = 0,                /* bus number */
     .chip_select = 4,
     .mode = SPI_CPOL | SPI_CPHA,
     },

3. Add a device in device table

/dev/spimas        c    640     0       0       153       0       0       0       -

4. If all these things are done, still spi does show up, debug your spi device probe (not spidev), it may be returning due to not supported mode bits