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Mika Westerberg011f23a2010-05-06 04:47:04 +00001Cirrus 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 <mach/ep93xx_spi.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
Mika Westerberg626a96d2011-05-29 13:10:06 +030091The 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
Mika Westerberg011f23a2010-05-06 04:47:04 +0000101Thanks 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.