ep93xx_spi

Cirrus EP93xx SPI controller driver HOWTO
=========================================

ep93xx_spi driver brings SPI master support for EP93xx SPI controller.  Chip
selects are implemented with GPIO lines.

NOTE: If possible, don't use SFRMOUT (SFRM1) signal as a chip select. It will
not work correctly (it cannot be controlled by software). Use GPIO lines
instead.

Sample configuration
====================

Typically driver configuration is done in platform board files (the files under
arch/arm/mach-ep93xx/*.c). In this example we configure MMC over SPI through
this driver on TS-7260 board. You can adapt the code to suit your needs.

This example uses EGPIO9 as SD/MMC card chip select (this is wired in DIO1
header on the board).

You need to select CONFIG_MMC_SPI to use mmc_spi driver.

arch/arm/mach-ep93xx/ts72xx.c:

...
#include <linux/gpio.h>
#include <linux/spi/spi.h>

#include <linux/platform_data/spi-ep93xx.h>

/* this is our GPIO line used for chip select */
#define MMC_CHIP_SELECT_GPIO EP93XX_GPIO_LINE_EGPIO9

static int ts72xx_mmc_spi_setup(struct spi_device *spi)
{
	int err;

	err = gpio_request(MMC_CHIP_SELECT_GPIO, spi->modalias);
	if (err)
		return err;

	gpio_direction_output(MMC_CHIP_SELECT_GPIO, 1);

	return 0;
}

static void ts72xx_mmc_spi_cleanup(struct spi_device *spi)
{
	gpio_set_value(MMC_CHIP_SELECT_GPIO, 1);
	gpio_direction_input(MMC_CHIP_SELECT_GPIO);
	gpio_free(MMC_CHIP_SELECT_GPIO);
}

static void ts72xx_mmc_spi_cs_control(struct spi_device *spi, int value)
{
	gpio_set_value(MMC_CHIP_SELECT_GPIO, value);
}

static struct ep93xx_spi_chip_ops ts72xx_mmc_spi_ops = {
	.setup		= ts72xx_mmc_spi_setup,
	.cleanup	= ts72xx_mmc_spi_cleanup,
	.cs_control	= ts72xx_mmc_spi_cs_control,
};

static struct spi_board_info ts72xx_spi_devices[] __initdata = {
	{
		.modalias		= "mmc_spi",
		.controller_data	= &ts72xx_mmc_spi_ops,
		/*
		 * We use 10 MHz even though the maximum is 7.4 MHz. The driver
		 * will limit it automatically to max. frequency.
		 */
		.max_speed_hz		= 10 * 1000 * 1000,
		.bus_num		= 0,
		.chip_select		= 0,
		.mode			= SPI_MODE_0,
	},
};

static struct ep93xx_spi_info ts72xx_spi_info = {
	.num_chipselect	= ARRAY_SIZE(ts72xx_spi_devices),
};

static void __init ts72xx_init_machine(void)
{
	...
	ep93xx_register_spi(&ts72xx_spi_info, ts72xx_spi_devices,
			    ARRAY_SIZE(ts72xx_spi_devices));
}

The driver can use DMA for the transfers also. In this case ts72xx_spi_info
becomes:

static struct ep93xx_spi_info ts72xx_spi_info = {
	.num_chipselect	= ARRAY_SIZE(ts72xx_spi_devices),
	.use_dma	= true;
};

Note that CONFIG_EP93XX_DMA should be enabled as well.

Thanks to
=========
Martin Guy, H. Hartley Sweeten and others who helped me during development of
the driver. Simplemachines.it donated me a Sim.One board which I used testing
the driver on EP9307.