Add the rt linux 4.1.3-rt3 as base

[kvmfornfv.git] / kernel / Documentation / spi / ep93xx_spi

diff --git a/kernel/Documentation/spi/ep93xx_spi b/kernel/Documentation/spi/ep93xx_spi
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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 <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.