[GitHub/mt8127/android_kernel_alcatel_ttab.git] / Documentation / spi / 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.
Commit	Line	Data
011f23a3 MW	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
a3b29245	29	#include <linux/platform_data/spi-ep93xx.h>
011f23a3 MW	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
626a96db MW	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
011f23a3 MW	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.