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.
106