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    Subject[PATCH v3] Add SPI over GPIO driver
    Date
    This adds a driver that lets you drive an SPI bus over
    generic GPIO pins.

    Signed-off-by: Michael Buesch <mb@bu3sch.de>

    ---

    This driver is used in OpenWrt since quite some time, so please
    consider for inclusion in mainline.

    Simple spelling fixes since v2.

    Index: linux-next/include/linux/spi/spi_gpio.h
    ===================================================================
    --- /dev/null 1970-01-01 00:00:00.000000000 +0000
    +++ linux-next/include/linux/spi/spi_gpio.h 2008-07-20 21:40:38.000000000 +0200
    @@ -0,0 +1,73 @@
    +/*
    + * spi_gpio interface to platform code
    + *
    + * Copyright (c) 2008 Piotr Skamruk
    + * Copyright (c) 2008 Michael Buesch
    + *
    + * This program is free software; you can redistribute it and/or modify
    + * it under the terms of the GNU General Public License version 2 as
    + * published by the Free Software Foundation.
    + */
    +#ifndef _LINUX_SPI_SPI_GPIO
    +#define _LINUX_SPI_SPI_GPIO
    +
    +#include <linux/types.h>
    +#include <linux/spi/spi.h>
    +
    +
    +/**
    + * struct spi_gpio_platform_data - Data definitions for a SPI-GPIO device.
    + *
    + * This structure holds information about a GPIO-based SPI device.
    + *
    + * @pin_clk: The GPIO pin number of the CLOCK pin.
    + *
    + * @pin_miso: The GPIO pin number of the MISO pin.
    + *
    + * @pin_mosi: The GPIO pin number of the MOSI pin.
    + *
    + * @pin_cs: The GPIO pin number of the CHIPSELECT pin.
    + *
    + * @cs_activelow: If true, the chip is selected when the CS line is low.
    + *
    + * @no_spi_delay: If true, no delay is done in the lowlevel bitbanging.
    + * Note that doing no delay is not standards compliant,
    + * but it might be needed to speed up transfers on some
    + * slow embedded machines.
    + *
    + * @boardinfo_setup: This callback is called after the
    + * SPI master device was registered, but before the
    + * device is registered.
    + * @boardinfo_setup_data: Data argument passed to boardinfo_setup().
    + */
    +struct spi_gpio_platform_data {
    + unsigned int pin_clk;
    + unsigned int pin_miso;
    + unsigned int pin_mosi;
    + unsigned int pin_cs;
    + bool cs_activelow;
    + bool no_spi_delay;
    + int (*boardinfo_setup)(struct spi_board_info *bi,
    + struct spi_master *master,
    + void *data);
    + void *boardinfo_setup_data;
    +};
    +
    +/**
    + * SPI_GPIO_PLATDEV_NAME - The platform device name string.
    + *
    + * The name string that has to be used for platform_device_alloc
    + * when allocating a spi-gpio device.
    + */
    +#define SPI_GPIO_PLATDEV_NAME "spi-gpio"
    +
    +/**
    + * spi_gpio_next_id - Get another platform device ID number.
    + *
    + * This returns the next platform device ID number that has to be used
    + * for platform_device_alloc. The ID is opaque and should not be used for
    + * anything else.
    + */
    +int spi_gpio_next_id(void);
    +
    +#endif /* _LINUX_SPI_SPI_GPIO */
    Index: linux-next/drivers/spi/spi_gpio.c
    ===================================================================
    --- /dev/null 1970-01-01 00:00:00.000000000 +0000
    +++ linux-next/drivers/spi/spi_gpio.c 2008-07-20 21:40:38.000000000 +0200
    @@ -0,0 +1,251 @@
    +/*
    + * Bitbanging SPI bus driver using GPIO API
    + *
    + * Copyright (c) 2008 Piotr Skamruk
    + * Copyright (c) 2008 Michael Buesch
    + *
    + * based on spi_s3c2410_gpio.c
    + * Copyright (c) 2006 Ben Dooks
    + * Copyright (c) 2006 Simtec Electronics
    + * and on i2c-gpio.c
    + * Copyright (C) 2007 Atmel Corporation
    + *
    + * This program is free software; you can redistribute it and/or modify
    + * it under the terms of the GNU General Public License version 2 as
    + * published by the Free Software Foundation.
    + */
    +
    +#include <linux/kernel.h>
    +#include <linux/init.h>
    +#include <linux/delay.h>
    +#include <linux/spinlock.h>
    +#include <linux/workqueue.h>
    +#include <linux/module.h>
    +#include <linux/platform_device.h>
    +#include <linux/spi/spi.h>
    +#include <linux/spi/spi_bitbang.h>
    +#include <linux/spi/spi_gpio.h>
    +#include <linux/gpio.h>
    +#include <asm/atomic.h>
    +
    +
    +struct spi_gpio {
    + struct spi_bitbang bitbang;
    + struct spi_gpio_platform_data *info;
    + struct platform_device *pdev;
    + struct spi_board_info bi;
    +};
    +
    +
    +static inline struct spi_gpio *spidev_to_sg(struct spi_device *dev)
    +{
    + return dev->controller_data;
    +}
    +
    +static inline void setsck(struct spi_device *dev, int val)
    +{
    + struct spi_gpio *sp = spidev_to_sg(dev);
    + gpio_set_value(sp->info->pin_clk, val ? 1 : 0);
    +}
    +
    +static inline void setmosi(struct spi_device *dev, int val)
    +{
    + struct spi_gpio *sp = spidev_to_sg(dev);
    + gpio_set_value(sp->info->pin_mosi, val ? 1 : 0);
    +}
    +
    +static inline u32 getmiso(struct spi_device *dev)
    +{
    + struct spi_gpio *sp = spidev_to_sg(dev);
    + return gpio_get_value(sp->info->pin_miso) ? 1 : 0;
    +}
    +
    +static inline void do_spidelay(struct spi_device *dev, unsigned nsecs)
    +{
    + struct spi_gpio *sp = spidev_to_sg(dev);
    +
    + if (!sp->info->no_spi_delay)
    + ndelay(nsecs);
    +}
    +
    +#define spidelay(nsecs) do { \
    + /* Steal the spi_device pointer from our caller. \
    + * The bitbang-API should probably get fixed here... */ \
    + do_spidelay(spi, nsecs); \
    + } while (0)
    +
    +#define EXPAND_BITBANG_TXRX
    +#include <linux/spi/spi_bitbang.h>
    +
    +static u32 spi_gpio_txrx_mode0(struct spi_device *spi,
    + unsigned nsecs, u32 word, u8 bits)
    +{
    + return bitbang_txrx_be_cpha0(spi, nsecs, 0, word, bits);
    +}
    +
    +static u32 spi_gpio_txrx_mode1(struct spi_device *spi,
    + unsigned nsecs, u32 word, u8 bits)
    +{
    + return bitbang_txrx_be_cpha1(spi, nsecs, 0, word, bits);
    +}
    +
    +static u32 spi_gpio_txrx_mode2(struct spi_device *spi,
    + unsigned nsecs, u32 word, u8 bits)
    +{
    + return bitbang_txrx_be_cpha0(spi, nsecs, 1, word, bits);
    +}
    +
    +static u32 spi_gpio_txrx_mode3(struct spi_device *spi,
    + unsigned nsecs, u32 word, u8 bits)
    +{
    + return bitbang_txrx_be_cpha1(spi, nsecs, 1, word, bits);
    +}
    +
    +static void spi_gpio_chipselect(struct spi_device *dev, int on)
    +{
    + struct spi_gpio *sp = spidev_to_sg(dev);
    +
    + if (sp->info->cs_activelow)
    + on = !on;
    + gpio_set_value(sp->info->pin_cs, on ? 1 : 0);
    +}
    +
    +static int spi_gpio_probe(struct platform_device *pdev)
    +{
    + struct spi_master *master;
    + struct spi_gpio_platform_data *pdata;
    + struct spi_gpio *sp;
    + struct spi_device *spidev;
    + int err;
    +
    + pdata = pdev->dev.platform_data;
    + if (!pdata)
    + return -ENXIO;
    +
    + err = -ENOMEM;
    + master = spi_alloc_master(&pdev->dev, sizeof(struct spi_gpio));
    + if (!master)
    + goto err_alloc_master;
    +
    + sp = spi_master_get_devdata(master);
    + platform_set_drvdata(pdev, sp);
    + sp->info = pdata;
    +
    + err = gpio_request(pdata->pin_clk, "spi_clock");
    + if (err)
    + goto err_request_clk;
    + err = gpio_request(pdata->pin_mosi, "spi_mosi");
    + if (err)
    + goto err_request_mosi;
    + err = gpio_request(pdata->pin_miso, "spi_miso");
    + if (err)
    + goto err_request_miso;
    + err = gpio_request(pdata->pin_cs, "spi_cs");
    + if (err)
    + goto err_request_cs;
    +
    + sp->bitbang.master = spi_master_get(master);
    + sp->bitbang.master->bus_num = -1;
    + sp->bitbang.master->num_chipselect = 1;
    + sp->bitbang.chipselect = spi_gpio_chipselect;
    + sp->bitbang.txrx_word[SPI_MODE_0] = spi_gpio_txrx_mode0;
    + sp->bitbang.txrx_word[SPI_MODE_1] = spi_gpio_txrx_mode1;
    + sp->bitbang.txrx_word[SPI_MODE_2] = spi_gpio_txrx_mode2;
    + sp->bitbang.txrx_word[SPI_MODE_3] = spi_gpio_txrx_mode3;
    +
    + gpio_direction_output(pdata->pin_clk, 0);
    + gpio_direction_output(pdata->pin_mosi, 0);
    + gpio_direction_output(pdata->pin_cs,
    + pdata->cs_activelow ? 1 : 0);
    + gpio_direction_input(pdata->pin_miso);
    +
    + err = spi_bitbang_start(&sp->bitbang);
    + if (err)
    + goto err_no_bitbang;
    + err = pdata->boardinfo_setup(&sp->bi, master,
    + pdata->boardinfo_setup_data);
    + if (err)
    + goto err_bi_setup;
    + sp->bi.controller_data = sp;
    + spidev = spi_new_device(master, &sp->bi);
    + if (!spidev)
    + goto err_new_dev;
    +
    + return 0;
    +
    +err_new_dev:
    +err_bi_setup:
    + spi_bitbang_stop(&sp->bitbang);
    +err_no_bitbang:
    + spi_master_put(sp->bitbang.master);
    + gpio_free(pdata->pin_cs);
    +err_request_cs:
    + gpio_free(pdata->pin_miso);
    +err_request_miso:
    + gpio_free(pdata->pin_mosi);
    +err_request_mosi:
    + gpio_free(pdata->pin_clk);
    +err_request_clk:
    + kfree(master);
    +
    +err_alloc_master:
    + return err;
    +}
    +
    +static int __devexit spi_gpio_remove(struct platform_device *pdev)
    +{
    + struct spi_gpio *sp;
    + struct spi_gpio_platform_data *pdata;
    +
    + pdata = pdev->dev.platform_data;
    + sp = platform_get_drvdata(pdev);
    +
    + gpio_free(pdata->pin_clk);
    + gpio_free(pdata->pin_mosi);
    + gpio_free(pdata->pin_miso);
    + gpio_free(pdata->pin_cs);
    + spi_bitbang_stop(&sp->bitbang);
    + spi_master_put(sp->bitbang.master);
    +
    + return 0;
    +}
    +
    +static struct platform_driver spi_gpio_driver = {
    + .driver = {
    + .name = SPI_GPIO_PLATDEV_NAME,
    + .owner = THIS_MODULE,
    + },
    + .probe = spi_gpio_probe,
    + .remove = __devexit_p(spi_gpio_remove),
    +};
    +
    +int spi_gpio_next_id(void)
    +{
    + static atomic_t counter = ATOMIC_INIT(-1);
    +
    + return atomic_inc_return(&counter);
    +}
    +EXPORT_SYMBOL(spi_gpio_next_id);
    +
    +static int __init spi_gpio_init(void)
    +{
    + int err;
    +
    + err = platform_driver_register(&spi_gpio_driver);
    + if (err)
    + printk(KERN_ERR "spi-gpio: register failed: %d\n", err);
    +
    + return err;
    +}
    +module_init(spi_gpio_init);
    +
    +static void __exit spi_gpio_exit(void)
    +{
    + platform_driver_unregister(&spi_gpio_driver);
    +}
    +module_exit(spi_gpio_exit);
    +
    +MODULE_AUTHOR("Piot Skamruk <piotr.skamruk at gmail.com>");
    +MODULE_AUTHOR("Michael Buesch");
    +MODULE_DESCRIPTION("Platform independent GPIO bitbanging SPI driver");
    +MODULE_LICENSE("GPL v2");
    Index: linux-next/drivers/spi/Kconfig
    ===================================================================
    --- linux-next.orig/drivers/spi/Kconfig 2008-07-20 21:39:09.000000000 +0200
    +++ linux-next/drivers/spi/Kconfig 2008-07-20 21:40:38.000000000 +0200
    @@ -100,6 +100,19 @@ config SPI_BUTTERFLY
    inexpensive battery powered microcontroller evaluation board.
    This same cable can be used to flash new firmware.

    +config SPI_GPIO
    + tristate "GPIO API based bitbanging SPI controller"
    + depends on SPI_MASTER && GENERIC_GPIO
    + select SPI_BITBANG
    + help
    + This is a platform driver that can be used for bitbanging
    + an SPI bus over GPIO pins.
    + Select this if you have any SPI device that is connected via
    + GPIO pins.
    + The module will be called spi_gpio.
    +
    + If unsure, say N.
    +
    config SPI_IMX
    tristate "Freescale iMX SPI controller"
    depends on SPI_MASTER && ARCH_IMX && EXPERIMENTAL
    Index: linux-next/drivers/spi/Makefile
    ===================================================================
    --- linux-next.orig/drivers/spi/Makefile 2008-07-20 21:39:09.000000000 +0200
    +++ linux-next/drivers/spi/Makefile 2008-07-20 21:40:38.000000000 +0200
    @@ -16,6 +16,7 @@ obj-$(CONFIG_SPI_BFIN) += spi_bfin5xx.
    obj-$(CONFIG_SPI_BITBANG) += spi_bitbang.o
    obj-$(CONFIG_SPI_AU1550) += au1550_spi.o
    obj-$(CONFIG_SPI_BUTTERFLY) += spi_butterfly.o
    +obj-$(CONFIG_SPI_GPIO) += spi_gpio.o
    obj-$(CONFIG_SPI_IMX) += spi_imx.o
    obj-$(CONFIG_SPI_LM70_LLP) += spi_lm70llp.o
    obj-$(CONFIG_SPI_PXA2XX) += pxa2xx_spi.o
    Index: linux-next/MAINTAINERS
    ===================================================================
    --- linux-next.orig/MAINTAINERS 2008-07-20 21:39:45.000000000 +0200
    +++ linux-next/MAINTAINERS 2008-07-20 21:40:38.000000000 +0200
    @@ -3884,6 +3884,11 @@ L: cbe-oss-dev@ozlabs.org
    W: http://www.ibm.com/developerworks/power/cell/
    S: Supported

    +SPI GPIO MASTER DRIVER
    +P: Michael Buesch
    +M: mb@bu3sch.de
    +S: Maintained
    +
    STABLE BRANCH:
    P: Greg Kroah-Hartman
    M: greg@kroah.com

    --
    Greetings Michael.


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