am335x gpio 模拟 spi 驱动添加

• kernel 内 make menuconfig

    //  make menuconfig
    Device Drivers  --->
        [*] SPI support  --->
              <*>   GPIO-based bitbanging SPI Master   // 这个是gpio-spi 的驱动
              <*>   User mode SPI device driver support   // 这个是生成 /dev/spidev*.*的驱动

• 在板级文件里面添加：

    //  vim arch/arm/mach-omap2/board-aplex_ECM_5416.c
    #define GPIO1_12 GPIO_TO_PIN(1, 12)
    #define GPIO1_13 GPIO_TO_PIN(1, 13)
    #define GPIO1_14 GPIO_TO_PIN(1, 14)
    #define GPIO1_15 GPIO_TO_PIN(1, 15)
    #define SPI_GPIO_BUS_NUM 3       // 设置spi 总线编号 

    static struct spi_gpio_platform_data ecm_5410_gpio_spi_data = {
        .sck = GPIO1_12,            // 指定clk 的gpio
        .mosi = GPIO1_13,         // 指定slave input
        .miso = GPIO1_14,          // 指定 slave output
        .num_chipselect = 1,      // 指定一共有几个cs
    };                                                                          

    static struct platform_device ecm_5410_gpio_spi_device = {
        .name = "spi_gpio",       // 匹配 spi-gpio.c 里面的驱动名字
        .id = SPI_GPIO_BUS_NUM,        // 配置 spi 总线编号
        .dev = {
            .platform_data = &ecm_5410_gpio_spi_data,    // 指定配置数据
        },
    };
    // 配置 pin_mux
    static struct pinmux_config ecm_5410_gpio_spi_pin_mux[] = {
        {"gpmc_ad12.gpio1_12", OMAP_MUX_MODE7 | AM33XX_PULL_ENBL | AM33XX_INPUT_EN},
        {"gpmc_ad13.gpio1_13", OMAP_MUX_MODE7 | AM33XX_PULL_ENBL | AM33XX_PULL_UP | AM33XX_INPUT_EN},
        {"gpmc_ad14.gpio1_14", OMAP_MUX_MODE7 | AM33XX_PULL_ENBL | AM33XX_INPUT_EN},
        {"gpmc_ad15.gpio1_15", OMAP_MUX_MODE7 | AM33XX_PULL_ENBL | AM33XX_INPUT_EN},
    };                                                                          

    static struct spi_board_info  am335x_spi2_slave_info[] = {
        {
            .modalias = "spidev",
            .max_speed_hz = 10000000,
            .bus_num = SPI_GPIO_BUS_NUM,
            .controller_data = (void *)GPIO1_15,       // 设置 cs 总线
            .chip_select   = 0,
            .mode = SPI_MODE_0,
        },
    };                                                                             

    static void ecm_5410_gpio_spi_init(int evm_id, int profile)
    {
        setup_pin_mux(ecm_5410_gpio_spi_pin_mux);
        // 总线设备注册，先配置到spi-gpio 的总线驱动
        platform_device_register(&ecm_5410_gpio_spi_device);
         // spi 板级信息注册，生成 /dev/spidev3.0
        spi_register_board_info(am335x_spi2_slave_info,
                    ARRAY_SIZE(am335x_spi2_slave_info));
    };                                                                          

    static struct evm_dev_cfg ECM_5412_dev_cfg[] = {
        // ... ... 加入板级初始化
        {ecm_5410_gpio_spi_init,   DEV_ON_BASEBOARD, PROFILE_ALL},
        {NULL, 0, 0},
    };