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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 <mach/ep93xx_spi.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.
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