1Cirrus EP93xx SPI controller driver HOWTO
  2=========================================
  3
  4ep93xx_spi driver brings SPI master support for EP93xx SPI controller.  Chip
  5selects are implemented with GPIO lines.
  6
  7NOTE: If possible, don't use SFRMOUT (SFRM1) signal as a chip select. It will
  8not work correctly (it cannot be controlled by software). Use GPIO lines
  9instead.
 10
 11Sample configuration
 12====================
 13
 14Typically driver configuration is done in platform board files (the files under
 15arch/arm/mach-ep93xx/*.c). In this example we configure MMC over SPI through
 16this driver on TS-7260 board. You can adapt the code to suit your needs.
 17
 18This example uses EGPIO9 as SD/MMC card chip select (this is wired in DIO1
 19header on the board).
 20
 21You need to select CONFIG_MMC_SPI to use mmc_spi driver.
 22
 23arch/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
 34static 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
 47static 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
 54static void ts72xx_mmc_spi_cs_control(struct spi_device *spi, int value)
 55{
 56	gpio_set_value(MMC_CHIP_SELECT_GPIO, value);
 57}
 58
 59static 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
 65static 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
 80static struct ep93xx_spi_info ts72xx_spi_info = {
 81	.num_chipselect	= ARRAY_SIZE(ts72xx_spi_devices),
 82};
 83
 84static 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
 91The driver can use DMA for the transfers also. In this case ts72xx_spi_info
 92becomes:
 93
 94static struct ep93xx_spi_info ts72xx_spi_info = {
 95	.num_chipselect	= ARRAY_SIZE(ts72xx_spi_devices),
 96	.use_dma	= true;
 97};
 98
 99Note that CONFIG_EP93XX_DMA should be enabled as well.
100
101Thanks to
102=========
103Martin Guy, H. Hartley Sweeten and others who helped me during development of
104the driver. Simplemachines.it donated me a Sim.One board which I used testing
105the driver on EP9307.