[PATCH 3/3] spi: psdev: add passive serial driver

[Michael Grzeschik <m.grzeschik@xxxxxxxxxxxxxx>]

This patch introduces the psdev driver. It is used to communicate to an
Altera passive serial connected FPGA by writing into an character
device.

It simply initates the protocol on open and clocks the data into the
FPGA by using the underlying SPI bus on write. The used SPI bus can also
be an bitbang SPI bus. On close it will check for the response of the
FPGA and tells if the write process was successful.

Signed-off-by: Michael Grzeschik <m.grzeschik@xxxxxxxxxxxxxx>
---
 drivers/spi/Kconfig    |   9 +
 drivers/spi/Makefile   |   1 +
 drivers/spi/spipsdev.c | 520 +++++++++++++++++++++++++++++++++++++++++++++++++
 3 files changed, 530 insertions(+)
 create mode 100644 drivers/spi/spipsdev.c

diff --git a/drivers/spi/Kconfig b/drivers/spi/Kconfig
index 581ee2a..ab6d438 100644
--- a/drivers/spi/Kconfig
+++ b/drivers/spi/Kconfig
@@ -208,6 +208,15 @@ config SPI_GPIO
 	  GPIO operations, you should be able to leverage that for better
 	  speed with a custom version of this driver; see the source code.
 
+config SPI_PASSIVE_SERIAL
+	tristate "GPIO-based bitbanging SPI Altera Passive Serial"
+	depends on GPIOLIB
+	select SPI_BITBANG
+	help
+	  This driver uses GPIOs to communicate by alteras passive serial
+	  protocol. It creates an character device, that can be used to
+	  simply cat RBF Firmware images into the FPGA.
+
 config SPI_IMX
 	tristate "Freescale i.MX SPI controllers"
 	depends on ARCH_MXC || COMPILE_TEST
diff --git a/drivers/spi/Makefile b/drivers/spi/Makefile
index 95af48d..296b1dd 100644
--- a/drivers/spi/Makefile
+++ b/drivers/spi/Makefile
@@ -8,6 +8,7 @@ ccflags-$(CONFIG_SPI_DEBUG) := -DDEBUG
 # config declarations into driver model code
 obj-$(CONFIG_SPI_MASTER)		+= spi.o
 obj-$(CONFIG_SPI_SPIDEV)		+= spidev.o
+obj-$(CONFIG_SPI_PASSIVE_SERIAL)	+= spipsdev.o
 
 # SPI master controller drivers (bus)
 obj-$(CONFIG_SPI_ALTERA)		+= spi-altera.o
diff --git a/drivers/spi/spipsdev.c b/drivers/spi/spipsdev.c
new file mode 100644
index 0000000..bda89b2
--- /dev/null
+++ b/drivers/spi/spipsdev.c
@@ -0,0 +1,520 @@
+/*
+ * Passive Serial Programming Driver
+ *
+ * Copyright (C) 2014 Michael Grzeschik <mgr@xxxxxxxxxxxxxx>
+ *
+ * This program is free software; you can redistribute it and/or modify
+ * it under the terms of the GNU General Public License as published by
+ * the Free Software Foundation; either version 2 of the License, or
+ * (at your option) any later version.
+ *
+ * This program is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+ * GNU General Public License for more details.
+ *
+ */
+
+#include <linux/init.h>
+#include <linux/module.h>
+#include <linux/ioctl.h>
+#include <linux/fs.h>
+#include <linux/device.h>
+#include <linux/gpio.h>
+#include <linux/delay.h>
+#include <linux/err.h>
+#include <linux/list.h>
+#include <linux/errno.h>
+#include <linux/mutex.h>
+#include <linux/slab.h>
+#include <linux/compat.h>
+#include <linux/of.h>
+#include <linux/of_gpio.h>
+#include <linux/of_device.h>
+
+#include <linux/spi/spi.h>
+
+#include <linux/uaccess.h>
+
+#define N_PS_MINORS		32
+
+unsigned int major;
+static DECLARE_BITMAP(minors, N_PS_MINORS);
+
+struct psdev_data {
+	dev_t			devt;
+	spinlock_t		spi_lock;
+	struct spi_device	*spi;
+	struct list_head	device_entry;
+	bool			open;
+
+	struct mutex		buf_lock;
+	u8			*buffer;
+
+	/* gpios for ps protocol */
+	unsigned		nconfig_gpio;
+	unsigned		confd_gpio;
+	unsigned		nstat_gpio;
+};
+
+static LIST_HEAD(device_list);
+static DEFINE_MUTEX(minor_lock);
+
+static unsigned bufsiz = 4096;
+module_param(bufsiz, uint, S_IRUGO);
+MODULE_PARM_DESC(bufsiz, "data bytes in biggest supported SPI message");
+
+/*
+ * We can't use the standard synchronous wrappers for file I/O; we
+ * need to protect against async removal of the underlying spi_device.
+ */
+static void psdev_complete(void *arg)
+{
+	if (arg)
+		complete(arg);
+}
+
+static ssize_t psdev_sync(struct psdev_data *psdev, struct spi_message *message)
+{
+	DECLARE_COMPLETION_ONSTACK(done);
+	int status;
+
+	message->complete = psdev_complete;
+	message->context = &done;
+
+	spin_lock_irq(&psdev->spi_lock);
+	if (psdev->spi == NULL)
+		status = -ESHUTDOWN;
+	else
+		status = spi_async(psdev->spi, message);
+	spin_unlock_irq(&psdev->spi_lock);
+
+	if (status == 0) {
+		unsigned long time_left = msecs_to_jiffies(100);
+
+		time_left = wait_for_completion_timeout(&done, time_left);
+		if (!time_left) {
+			message->context = NULL;
+			return -ETIMEDOUT;
+		}
+		status = message->status;
+		if (status == 0)
+			status = message->actual_length;
+	}
+	return status;
+}
+
+static inline ssize_t psdev_sync_write(struct psdev_data *psdev, size_t len)
+{
+	struct spi_transfer t = {
+		.tx_buf		= psdev->buffer,
+		.len		= len,
+	};
+	struct spi_message m;
+
+	spi_message_init(&m);
+	spi_message_add_tail(&t, &m);
+	return psdev_sync(psdev, &m);
+}
+
+/* Write-only message with current device setup */
+static ssize_t psdev_write(struct file *filp, const char __user *buf,
+		size_t count, loff_t *f_pos)
+{
+	struct psdev_data *psdev;
+	ssize_t	status = 0;
+	unsigned long missing;
+
+	if (count > bufsiz)
+		return -EMSGSIZE;
+
+	psdev = filp->private_data;
+
+	mutex_lock(&psdev->buf_lock);
+	missing = copy_from_user(psdev->buffer, buf, count);
+	if (missing == 0)
+		status = psdev_sync_write(psdev, count);
+	else
+		status = -EFAULT;
+	mutex_unlock(&psdev->buf_lock);
+
+	return status;
+}
+
+static int psdev_start(struct psdev_data *psdev)
+{
+	struct device *dev = &psdev->spi->dev;
+	unsigned long timeout;
+	int ret = -ENXIO;
+
+	dev_dbg(dev, "Initiating programming\n");
+
+	/* initiate an FPGA programming */
+	gpio_set_value(psdev->nconfig_gpio, 0);
+
+	/*
+	 * after about 2 µs the FPGA must acknowledge with
+	 * STATUS and CONFIG DONE lines at low level
+	 */
+	timeout = jiffies + usecs_to_jiffies(2);
+	do {
+		if ((gpio_get_value(psdev->nstat_gpio) == 0) &&
+		    (gpio_get_value(psdev->confd_gpio) == 0)) {
+			ret = 0;
+			break;
+		}
+		ndelay(100);
+
+	} while (time_before(jiffies, timeout));
+
+	if (ret != 0) {
+		dev_err(dev, "FPGA does not acknowledge the programming initiation\n");
+		if (gpio_get_value(psdev->nstat_gpio))
+			dev_err(dev, "STATUS is still high!\n");
+		if (gpio_get_value(psdev->confd_gpio))
+			dev_err(dev, "CONFIG DONE is still high!\n");
+
+		return ret;
+	}
+
+	/* arm the FPGA to await its new firmware */
+	gpio_set_value(psdev->nconfig_gpio, 1);
+
+	ret = -ENXIO;
+	timeout = jiffies + usecs_to_jiffies(1600);
+	do {
+		if (gpio_get_value(psdev->nstat_gpio) == 0) {
+			ret = 0;
+			break;
+		}
+		udelay(10);
+
+	} while (time_before(jiffies, timeout));
+
+	if (ret != 0) {
+		dev_err(dev, "FPGA does not acknowledge the programming start\n");
+		return ret;
+	}
+
+	dev_dbg(dev, "Initiating passed\n");
+
+	/* at the end, wait at least 2 µs prior beginning writing data */
+	udelay(2);
+
+	return 0;
+}
+
+static int psdev_open(struct inode *inode, struct file *filp)
+{
+	struct psdev_data *psdev, *tmp;
+	struct device *dev;
+	int status = -ENXIO;
+
+	list_for_each_entry_safe(psdev, tmp, &device_list, device_entry) {
+		if (psdev->devt == inode->i_rdev) {
+			status = 0;
+			break;
+		}
+	}
+
+	if (psdev->open) {
+		status = -EBUSY;
+		goto out;
+	}
+
+	dev = &psdev->spi->dev;
+
+	if (status == 0) {
+		if (!psdev->buffer) {
+			psdev->buffer = kmalloc(bufsiz, GFP_KERNEL);
+			if (!psdev->buffer) {
+				dev_dbg(dev, "open/ENOMEM\n");
+				status = -ENOMEM;
+			}
+		}
+		if (status == 0) {
+			filp->private_data = psdev;
+			nonseekable_open(inode, filp);
+		}
+	} else
+		pr_debug("psdev: nothing for minor %d\n", iminor(inode));
+
+	psdev_start(psdev);
+
+	psdev->open = 1;
+
+ out:
+
+	return status;
+}
+
+static int psdev_release(struct inode *inode, struct file *filp)
+{
+	struct psdev_data *psdev;
+	unsigned long timeout;
+	struct device *dev;
+	int status = -ENXIO;
+
+	psdev = filp->private_data;
+	filp->private_data = NULL;
+
+	dev = &psdev->spi->dev;
+
+	/*
+	 * when programming was successfully,
+	 * both status lines should be at high level
+	 */
+	timeout = jiffies + usecs_to_jiffies(1000);
+	do {
+		if ((gpio_get_value(psdev->nstat_gpio)) &&
+		    (gpio_get_value(psdev->confd_gpio))) {
+			status = 0;
+			break;
+		}
+		udelay(10);
+
+	} while (time_before(jiffies, timeout));
+
+	if (status != 0) {
+		dev_err(dev, "FPGA does not acknowledge the programming initiation\n");
+		if (gpio_get_value(psdev->nstat_gpio) == 0)
+			dev_err(dev, "STATUS is still low!\n");
+		if (gpio_get_value(psdev->confd_gpio) == 0)
+			dev_err(dev, "CONFIG DONE is still low!\n");
+	}
+
+	kfree(psdev->buffer);
+	psdev->buffer = NULL;
+
+	psdev->open = 0;
+
+	return status;
+}
+
+static const struct file_operations psdev_fops = {
+	.owner =	THIS_MODULE,
+	.write =	psdev_write,
+	.open =		psdev_open,
+	.release =	psdev_release,
+	.llseek =	no_llseek,
+};
+
+static struct class *psdev_class;
+
+/*-------------------------------------------------------------------------*/
+#ifdef CONFIG_OF
+
+static const struct of_device_id psdev_dt_ids[] = {
+	{ .compatible = "altr,passive-serial" },
+	{},
+};
+
+MODULE_DEVICE_TABLE(of, psdev_dt_ids);
+
+static int psdev_probe_dt(struct psdev_data *psdev)
+{
+	int ret = 0;
+	struct device *dev = &psdev->spi->dev;
+	struct device_node *np = dev->of_node;
+	const struct of_device_id *of_id =
+			of_match_device(psdev_dt_ids, &psdev->spi->dev);
+
+	if (!of_id)
+		return -EINVAL;
+
+	ret = of_get_named_gpio(np, "gpio-nstatus", 0);
+	if (ret < 0) {
+		dev_err(dev, "gpio-nstatus property not found\n");
+		goto error;
+	}
+	psdev->nstat_gpio = ret;
+
+	ret = of_get_named_gpio(np, "gpio-confdone", 0);
+	if (ret < 0) {
+		dev_err(dev, "gpio-confdone property not found\n");
+		goto error;
+	}
+	psdev->confd_gpio = ret;
+
+	ret = of_get_named_gpio(np, "gpio-nconfig", 0);
+	if (ret < 0) {
+		dev_err(dev, "gpio-nconfig property not found\n");
+		goto error;
+	}
+	psdev->nconfig_gpio = ret;
+
+	ret = devm_gpio_request_one(dev, psdev->nconfig_gpio,
+			GPIOF_OUT_INIT_HIGH, "nconfig");
+	if (ret) {
+		dev_err(dev, "unable to get nconfig gpio\n");
+		goto error;
+	}
+
+	ret = devm_gpio_request_one(dev, psdev->nstat_gpio,
+			GPIOF_DIR_IN,  "nstat");
+	if (ret) {
+		dev_err(dev, "unable to get nstat gpio\n");
+		goto error;
+	}
+
+	ret = devm_gpio_request_one(dev, psdev->confd_gpio,
+			GPIOF_DIR_IN, "confd");
+	if (ret) {
+		dev_err(dev, "unable to get confd gpio\n");
+		goto error;
+	}
+
+ error:
+	return ret;
+}
+#else
+static inline int spi_gpio_probe_dt(struct platform_device *pdev)
+{
+	return -EINVAL;
+}
+#endif
+
+static int psdev_probe(struct spi_device *spi)
+{
+	struct psdev_data *psdev;
+	unsigned long minor;
+	int status = 0;
+
+	/* Allocate driver data */
+	psdev = devm_kzalloc(&spi->dev, sizeof(*psdev), GFP_KERNEL);
+	if (!psdev)
+		return -ENOMEM;
+
+	/* Initialize the driver data */
+	psdev->spi = spi;
+	spin_lock_init(&psdev->spi_lock);
+	mutex_init(&psdev->buf_lock);
+
+	INIT_LIST_HEAD(&psdev->device_entry);
+	/* If we can allocate a minor number, hook up this device.
+	 * Reusing minors is fine so long as udev or mdev is working.
+	 */
+	mutex_lock(&minor_lock);
+	minor = find_first_zero_bit(minors, N_PS_MINORS);
+	if (minor < N_PS_MINORS) {
+		struct device *dev;
+
+		psdev->devt = MKDEV(major, minor);
+		dev = device_create(psdev_class, &spi->dev, psdev->devt,
+				    psdev, "psdev%lu", minor);
+		status = PTR_ERR_OR_ZERO(dev);
+		if (status) {
+			mutex_unlock(&minor_lock);
+			return -ENODEV;
+		}
+	} else {
+		mutex_unlock(&minor_lock);
+		dev_dbg(&spi->dev, "no minor number available!\n");
+		return -ENODEV;
+	}
+	set_bit(minor, minors);
+	mutex_unlock(&minor_lock);
+
+	list_add(&psdev->device_entry, &device_list);
+
+	spi->mode |= SPI_LSB_FIRST | SPI_NO_CS;
+	spi_setup(spi);
+
+	status = psdev_probe_dt(psdev);
+	if (status)
+		goto error;
+
+	spi_set_drvdata(spi, psdev);
+
+	return status;
+
+ error:
+	mutex_lock(&minor_lock);
+	clear_bit(MINOR(psdev->devt), minors);
+	mutex_unlock(&minor_lock);
+
+	list_del(&psdev->device_entry);
+	device_destroy(psdev_class, psdev->devt);
+
+	return status;
+}
+
+static int psdev_remove(struct spi_device *spi)
+{
+	struct psdev_data *psdev = spi_get_drvdata(spi);
+
+	/* make sure ops on existing fds can abort cleanly */
+	spin_lock_irq(&psdev->spi_lock);
+	psdev->spi = NULL;
+	spin_unlock_irq(&psdev->spi_lock);
+
+	/* prevent new opens */
+	list_del(&psdev->device_entry);
+	device_destroy(psdev_class, psdev->devt);
+	mutex_lock(&minor_lock);
+	clear_bit(MINOR(psdev->devt), minors);
+	mutex_unlock(&minor_lock);
+
+	return 0;
+}
+
+static struct spi_driver psdev_spi_driver = {
+	.driver = {
+		.name =		"psdev",
+		.owner =	THIS_MODULE,
+		.of_match_table = of_match_ptr(psdev_dt_ids),
+	},
+	.probe =	psdev_probe,
+	.remove =	psdev_remove,
+
+	/* NOTE:  suspend/resume methods are not necessary here.
+	 * We don't do anything except pass the requests to/from
+	 * the underlying controller.  The refrigerator handles
+	 * most issues; the controller driver handles the rest.
+	 */
+};
+
+/*-------------------------------------------------------------------------*/
+
+static int __init psdev_init(void)
+{
+	int status;
+
+	/* Claim our 256 reserved device numbers.  Then register a class
+	 * that will key udev/mdev to add/remove /dev nodes.  Last, register
+	 * the driver which manages those device numbers.
+	 */
+	BUILD_BUG_ON(N_PS_MINORS > 256);
+	status = register_chrdev(0, "psdev", &psdev_fops);
+	if (status < 0)
+		return status;
+
+	major = status;
+
+	psdev_class = class_create(THIS_MODULE, "psdev");
+	if (IS_ERR(psdev_class)) {
+		unregister_chrdev(major, psdev_spi_driver.driver.name);
+		return PTR_ERR(psdev_class);
+	}
+
+	status = spi_register_driver(&psdev_spi_driver);
+	if (status < 0) {
+		class_destroy(psdev_class);
+		unregister_chrdev(major, psdev_spi_driver.driver.name);
+	}
+	return status;
+}
+module_init(psdev_init);
+
+static void __exit psdev_exit(void)
+{
+	spi_unregister_driver(&psdev_spi_driver);
+	class_destroy(psdev_class);
+	unregister_chrdev(major, psdev_spi_driver.driver.name);
+}
+module_exit(psdev_exit);
+
+MODULE_AUTHOR("Michael Grzeschik, <mgrzeschik@xxxxxxx>");
+MODULE_DESCRIPTION("User mode SPI Passive Serial interface");
+MODULE_LICENSE("GPL");
+MODULE_ALIAS("spi:psdev");
-- 
1.9.0

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