Documentation/spi/ep93xx_spi

   1 Cirrus EP93xx SPI controller driver HOWTO
   2 =========================================
   3
   4 ep93xx_spi driver brings SPI master support for EP93xx SPI controller.  Chip
   5 selects are implemented with GPIO lines.
   6
   7 NOTE: If possible, don't use SFRMOUT (SFRM1) signal as a chip select. It will
   8 not work correctly (it cannot be controlled by software). Use GPIO lines
   9 instead.
  10
  11 Sample configuration
  12 ====================
  13
  14 Typically driver configuration is done in platform board files (the files under
  15 arch/arm/mach-ep93xx/*.c). In this example we configure MMC over SPI through
  16 this driver on TS-7260 board. You can adapt the code to suit your needs.
  17
  18 This example uses EGPIO9 as SD/MMC card chip select (this is wired in DIO1
  19 header on the board).
  20
  21 You need to select CONFIG_MMC_SPI to use mmc_spi driver.
  22
  23 arch/arm/mach-ep93xx/ts72xx.c:
  24
  25 ...
  26 #include <linux/gpio.h>
  27 #include <linux/spi/spi.h>
  28
  29 #include <linux/platform_data/spi-ep93xx.h>
  30
  31 /* this is our GPIO line used for chip select */
  32 #define MMC_CHIP_SELECT_GPIO EP93XX_GPIO_LINE_EGPIO9
  33
  34 static int ts72xx_mmc_spi_setup(struct spi_device *spi)
  35 {
  36         int err;
  37
  38         err = gpio_request(MMC_CHIP_SELECT_GPIO, spi->modalias);
  39         if (err)
  40                 return err;
  41
  42         gpio_direction_output(MMC_CHIP_SELECT_GPIO, 1);
  43
  44         return 0;
  45 }
  46
  47 static void ts72xx_mmc_spi_cleanup(struct spi_device *spi)
  48 {
  49         gpio_set_value(MMC_CHIP_SELECT_GPIO, 1);
  50         gpio_direction_input(MMC_CHIP_SELECT_GPIO);
  51         gpio_free(MMC_CHIP_SELECT_GPIO);
  52 }
  53
  54 static void ts72xx_mmc_spi_cs_control(struct spi_device *spi, int value)
  55 {
  56         gpio_set_value(MMC_CHIP_SELECT_GPIO, value);
  57 }
  58
  59 static struct ep93xx_spi_chip_ops ts72xx_mmc_spi_ops = {
  60         .setup          = ts72xx_mmc_spi_setup,
  61         .cleanup        = ts72xx_mmc_spi_cleanup,
  62         .cs_control     = ts72xx_mmc_spi_cs_control,
  63 };
  64
  65 static struct spi_board_info ts72xx_spi_devices[] __initdata = {
  66         {
  67                 .modalias               = "mmc_spi",
  68                 .controller_data        = &ts72xx_mmc_spi_ops,
  69                 /*
  70                  * We use 10 MHz even though the maximum is 7.4 MHz. The driver
  71                  * will limit it automatically to max. frequency.
  72                  */
  73                 .max_speed_hz           = 10 * 1000 * 1000,
  74                 .bus_num                = 0,
  75                 .chip_select            = 0,
  76                 .mode                   = SPI_MODE_0,
  77         },
  78 };
  79
  80 static struct ep93xx_spi_info ts72xx_spi_info = {
  81         .num_chipselect = ARRAY_SIZE(ts72xx_spi_devices),
  82 };
  83
  84 static void __init ts72xx_init_machine(void)
  85 {
  86         ...
  87         ep93xx_register_spi(&ts72xx_spi_info, ts72xx_spi_devices,
  88                             ARRAY_SIZE(ts72xx_spi_devices));
  89 }
  90
  91 The driver can use DMA for the transfers also. In this case ts72xx_spi_info
  92 becomes:
  93
  94 static struct ep93xx_spi_info ts72xx_spi_info = {
  95         .num_chipselect = ARRAY_SIZE(ts72xx_spi_devices),
  96         .use_dma        = true;
  97 };
  98
  99 Note that CONFIG_EP93XX_DMA should be enabled as well.
 100
 101 Thanks to
 102 =========
 103 Martin Guy, H. Hartley Sweeten and others who helped me during development of
 104 the driver. Simplemachines.it donated me a Sim.One board which I used testing
 105 the driver on EP9307.