how to use "GPIO-based bitbanging spi master"?

lightrain · **Joined:** Fri Feb 17, 2012 9:14 am **Posts:** 1

I configure kernel 2.6.30 as below: make menuconfig [Device Drivers -> SPI support]

Code:

          --- SPI support                           
                *** SPI Master Controller Drivers ***
          < >   Atmel SPI Controller                 
          -*-   Utilities for Bitbanging SPI masters 
          <*>   GPIO-based bitbanging SPI Master     
                *** SPI Protocol Masters ***         
          < >   User mode SPI device driver support  
          < >   Infineon TLE62X0 (for power switching)

then add something to /arch/arm/mach-at91/board-sam9260ek.c

Code:

.....
static struct spi_board_info ek_spi_gpio_devices[] = {
   {   /* ATT7022 */
      .modalias   = "acsample",
      .chip_select   = 0,
      .max_speed_hz   = 15 * 1000 * 1000,
      .mode      = SPI_MODE_0,
      .controller_data = (void*) AT91_PIN_PB27,
   },

};

......

extern void __init at91_add_device_spi_gpio(struct spi_board_info *devices, int nr_devices);

static void __init ek_board_init(void)
{

    .....
    //at91_add_device_spi(ek_spi_devices, ARRAY_SIZE(ek_spi_devices));
    at91_add_device_spi_gpio( ek_spi_gpio_devices, ARRAY_SIZE(ek_spi_gpio_devices) );
    .....
}

add code to /arch/arm/mach-at91/at91sam9260_devices.c

Code:

.....
static struct spi_gpio_platform_data pacsdata = {
   .sck      = AT91_PIN_PB23,
   .mosi      = AT91_PIN_PB26,
   .miso      = AT91_PIN_PB22,
   .num_chipselect = 1,
};

static struct platform_device at91sam9260_acsample_device = {
   .name         = "spi_gpio",
   .id         = 0,
   .dev.platform_data   = &pacsdata,
};

void __init at91_add_device_spi_gpio(struct spi_board_info *devices, int nr_devices)
{
   unsigned long cs_pin;
   int ret;
   
   at91_sys_write( AT91_PMC_PCER, (1<<AT91SAM9260_ID_PIOB) );
   
   at91_set_GPIO_periph(AT91_PIN_PB23, 1);      /* SCK */
   at91_set_multi_drive(AT91_PIN_PB23, 1);

   at91_set_GPIO_periph(AT91_PIN_PB26, 1);      /* MOSI */
   at91_set_multi_drive(AT91_PIN_PB26, 1);

   at91_set_GPIO_periph(AT91_PIN_PB22, 1);      /* MISO */
   at91_set_multi_drive(AT91_PIN_PB22, 1);
   
   at91_set_GPIO_periph(AT91_PIN_PB27, 1);      /* CS */
   at91_set_multi_drive(AT91_PIN_PB27, 1);

   ret = spi_register_board_info(devices, nr_devices);
   ret = platform_device_register(&at91sam9260_acsample_device);
}
.........

then "make uImage", and boot it.

I can found file "spi_gpio.0" in "/sys/devices/platform/", but found nothing about spi device in "/dev".

I want to use the bitbanging spi master device to read/write ATT7022, Can anyone give me some advices or examples? I am a linux newer.

Code:

/ # cat /sys/devices/platform/spi_gpio.0/spi0.0/modalias 
acsample

blue_z · **Posted:** Mon Mar 05, 2012 12:29 am

lightrain wrote:

I can found file "spi_gpio.0" in "/sys/devices/platform/", but found nothing about spi device in "/dev".

I want to use the bitbanging spi master device to read/write ATT7022, Can anyone give me some advices or examples?

You won't find a "spi" device in /dev, because the SPI is not a device node; SPI is an interface path to a target device. Your target device apparently is an ATT7022 (whatever that is).

You need to write a SPI target device driver for your ATT7022. That driver will utilize the (bit-banging) SPI master driver to access and control the ATT7022. There are several SPI target devices in the Linux source tree to use as examples.

Regards

how to use "GPIO-based bitbanging spi master"?

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