106 lines
2.8 KiB
Plaintext
106 lines
2.8 KiB
Plaintext
Cirrus EP93xx SPI controller driver HOWTO
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=========================================
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ep93xx_spi driver brings SPI master support for EP93xx SPI controller. Chip
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selects are implemented with GPIO lines.
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NOTE: If possible, don't use SFRMOUT (SFRM1) signal as a chip select. It will
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not work correctly (it cannot be controlled by software). Use GPIO lines
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instead.
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Sample configuration
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====================
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Typically driver configuration is done in platform board files (the files under
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arch/arm/mach-ep93xx/*.c). In this example we configure MMC over SPI through
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this driver on TS-7260 board. You can adapt the code to suit your needs.
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This example uses EGPIO9 as SD/MMC card chip select (this is wired in DIO1
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header on the board).
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You need to select CONFIG_MMC_SPI to use mmc_spi driver.
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arch/arm/mach-ep93xx/ts72xx.c:
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...
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#include <linux/gpio.h>
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#include <linux/spi/spi.h>
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#include <linux/platform_data/spi-ep93xx.h>
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/* this is our GPIO line used for chip select */
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#define MMC_CHIP_SELECT_GPIO EP93XX_GPIO_LINE_EGPIO9
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static int ts72xx_mmc_spi_setup(struct spi_device *spi)
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{
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int err;
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err = gpio_request(MMC_CHIP_SELECT_GPIO, spi->modalias);
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if (err)
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return err;
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gpio_direction_output(MMC_CHIP_SELECT_GPIO, 1);
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return 0;
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}
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static void ts72xx_mmc_spi_cleanup(struct spi_device *spi)
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{
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gpio_set_value(MMC_CHIP_SELECT_GPIO, 1);
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gpio_direction_input(MMC_CHIP_SELECT_GPIO);
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gpio_free(MMC_CHIP_SELECT_GPIO);
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}
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static void ts72xx_mmc_spi_cs_control(struct spi_device *spi, int value)
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{
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gpio_set_value(MMC_CHIP_SELECT_GPIO, value);
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}
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static struct ep93xx_spi_chip_ops ts72xx_mmc_spi_ops = {
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.setup = ts72xx_mmc_spi_setup,
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.cleanup = ts72xx_mmc_spi_cleanup,
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.cs_control = ts72xx_mmc_spi_cs_control,
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};
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static struct spi_board_info ts72xx_spi_devices[] __initdata = {
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{
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.modalias = "mmc_spi",
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.controller_data = &ts72xx_mmc_spi_ops,
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/*
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* We use 10 MHz even though the maximum is 7.4 MHz. The driver
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* will limit it automatically to max. frequency.
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*/
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.max_speed_hz = 10 * 1000 * 1000,
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.bus_num = 0,
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.chip_select = 0,
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.mode = SPI_MODE_0,
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},
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};
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static struct ep93xx_spi_info ts72xx_spi_info = {
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.num_chipselect = ARRAY_SIZE(ts72xx_spi_devices),
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};
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static void __init ts72xx_init_machine(void)
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{
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...
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ep93xx_register_spi(&ts72xx_spi_info, ts72xx_spi_devices,
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ARRAY_SIZE(ts72xx_spi_devices));
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}
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The driver can use DMA for the transfers also. In this case ts72xx_spi_info
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becomes:
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static struct ep93xx_spi_info ts72xx_spi_info = {
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.num_chipselect = ARRAY_SIZE(ts72xx_spi_devices),
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.use_dma = true;
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};
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Note that CONFIG_EP93XX_DMA should be enabled as well.
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Thanks to
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=========
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Martin Guy, H. Hartley Sweeten and others who helped me during development of
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the driver. Simplemachines.it donated me a Sim.One board which I used testing
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the driver on EP9307.
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