This adds a driver that lets you drive an SPI bus over
generic GPIO pins.
Signed-off-by: Michael Buesch <[email protected]>
---
This driver is used in OpenWrt since quite some time, so please
consider for inclusion in mainline.
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 2008-07-14 20:52:48.000000000 +0200
@@ -0,0 +1,53 @@
+/*
+ * spi_gpio interface to platform code
+ *
+ * Copyright (c) 2008 Piotr Skamruk
+ *
+ * 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;
+};
+
+#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 2008-07-14 21:03:40.000000000 +0200
@@ -0,0 +1,242 @@
+/*
+ * 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>
+
+
+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",
+ .owner = THIS_MODULE,
+ },
+ .probe = spi_gpio_probe,
+ .remove = __devexit_p(spi_gpio_remove),
+};
+
+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 2008-07-14 20:52:44.000000000 +0200
+++ linux-next/drivers/spi/Kconfig 2008-07-14 20:52:48.000000000 +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 2008-07-14 20:52:44.000000000 +0200
+++ linux-next/drivers/spi/Makefile 2008-07-14 20:52:48.000000000 +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
--
Greetings Michael.
On Mon, 14 Jul 2008 21:09:12 +0200
Michael Buesch <[email protected]> wrote:
> +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)
A macro which requires that its caller have a particular local variable
is a bit nasty. Could we plan to add the spi_device* to spidelay()
please?
On Mon, 2008-07-14 at 21:09 +0200, Michael Buesch wrote:
> This adds a driver that lets you drive an SPI bus over
> generic GPIO pins.
Right, this is where spi-gpio is, please disregard my question in the
mmc-spi-gpio thing thread, it was domestic blindness after all :-)
Looks good overall. I'm not sure that it need pretend to be
hotpluggable though (i.e. the board info can be hardwired so there's no
need for the board setup callback). I guess this is to integrate with
your "dynamically create an mmc over spi over gpio" thinggy in the other
thread. As I said there, I'd prefer that this platform device is
treated like other platform devices and any dynamicness be introduced at
in a more generic way.
What problem are you solving (or whole in board support are you
plugging) in this dynamic plugging of MMCs?
Thanks,
--Ben.
On Monday 14 July 2008 22:43:45 Andrew Morton wrote:
> On Mon, 14 Jul 2008 21:09:12 +0200
> Michael Buesch <[email protected]> wrote:
>
> > +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)
>
> A macro which requires that its caller have a particular local variable
> is a bit nasty. Could we plan to add the spi_device* to spidelay()
> please?
Yeah right. I was planning to fix this later on _after_ this was merged.
This makes the merge easier with less patch cross-dependencies.
--
Greetings Michael.
On Tuesday 15 July 2008 07:30:51 Ben Nizette wrote:
> Looks good overall. I'm not sure that it need pretend to be
> hotpluggable though
Because the hardware _is_ hotpluggable.
> (i.e. the board info can be hardwired so there's no
> need for the board setup callback).
I'm not sure why we should limit ourselves so much by compiling
dynamic and completely individual information, like the bus
wireing into the kernel.
This _has_ to be dynamic, as the wireing is _completely_ random and
different for every machine. This is selfmade hardware. ;)
> What problem are you solving (or whole in board support are you
> plugging) in this dynamic plugging of MMCs?
This is to support running MMCs/SDs on GPIO pins.
Which board or card provides the GPIO pins doesn't matter. It doesn't
matter, as it's completely abstracted. You can even run 10 or more
of the cards at the same time, if you have enough GPIO pins.
Of course, this is mostly useful for embedded systems only.
But it is not bound to any specific type of hardware. The hardware just
has to implement generic GPIO for its GPIO pins.
--
Greetings Michael.