626a96db11
This patch adds DMA support for the EP93xx SPI driver. By default the DMA is not enabled but it can be enabled by setting ep93xx_spi_info.use_dma to true in board configuration file. Note that the SPI driver still uses PIO for small transfers (<= 8 bytes) for performance reasons. Signed-off-by: Mika Westerberg <mika.westerberg@iki.fi> Acked-by: H Hartley Sweeten <hsweeten@visionengravers.com> Acked-by: Vinod Koul <vinod.koul@intel.com> Signed-off-by: Grant Likely <grant.likely@secretlab.ca>
106 lines
2.7 KiB
Plaintext
106 lines
2.7 KiB
Plaintext
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.
|