pps: new client driver using GPIO

This client driver allows you to use a GPIO pin as a source for PPS
signals.  Platform data [1] are used to specify the GPIO pin number,
label, assert event edge type, and whether clear events are captured.

This driver is based on the work by Ricardo Martins who submitted an
initial implementation [2] of a PPS IRQ client driver to the linuxpps
mailing-list on Dec 3 2010.

[1] include/linux/pps-gpio.h
[2] http://ml.enneenne.com/pipermail/linuxpps/2010-December/004155.html

[akpm@linux-foundation.org: remove unneeded cast of void*]
Signed-off-by: James Nuss <jamesnuss@nanometrics.ca>
Cc: Ricardo Martins <rasm@fe.up.pt>
Acked-by: Rodolfo Giometti <giometti@linux.it>
Signed-off-by: Ricardo Martins <rasm@fe.up.pt>
Cc: Alexander Gordeev <lasaine@lvk.cs.msu.su>
Cc: Igor Plyatov <plyatov@gmail.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
diff --git a/drivers/pps/clients/Kconfig b/drivers/pps/clients/Kconfig
index 8520a7f..c2e0f1e 100644
--- a/drivers/pps/clients/Kconfig
+++ b/drivers/pps/clients/Kconfig
@@ -29,4 +29,13 @@
 	  If you say yes here you get support for a PPS source connected
 	  with the interrupt pin of your parallel port.
 
+config PPS_CLIENT_GPIO
+	tristate "PPS client using GPIO"
+	depends on PPS
+	help
+	  If you say yes here you get support for a PPS source using
+	  GPIO. To be useful you must also register a platform device
+	  specifying the GPIO pin and other options, usually in your board
+	  setup.
+
 endif
diff --git a/drivers/pps/clients/Makefile b/drivers/pps/clients/Makefile
index 4feb7e9..a461d15 100644
--- a/drivers/pps/clients/Makefile
+++ b/drivers/pps/clients/Makefile
@@ -5,5 +5,6 @@
 obj-$(CONFIG_PPS_CLIENT_KTIMER)	+= pps-ktimer.o
 obj-$(CONFIG_PPS_CLIENT_LDISC)	+= pps-ldisc.o
 obj-$(CONFIG_PPS_CLIENT_PARPORT) += pps_parport.o
+obj-$(CONFIG_PPS_CLIENT_GPIO)	+= pps-gpio.o
 
 ccflags-$(CONFIG_PPS_DEBUG) := -DDEBUG
diff --git a/drivers/pps/clients/pps-gpio.c b/drivers/pps/clients/pps-gpio.c
new file mode 100644
index 0000000..6550555
--- /dev/null
+++ b/drivers/pps/clients/pps-gpio.c
@@ -0,0 +1,227 @@
+/*
+ * pps-gpio.c -- PPS client driver using GPIO
+ *
+ *
+ * Copyright (C) 2010 Ricardo Martins <rasm@fe.up.pt>
+ * Copyright (C) 2011 James Nuss <jamesnuss@nanometrics.ca>
+ *
+ *   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.
+ *
+ *   You should have received a copy of the GNU General Public License
+ *   along with this program; if not, write to the Free Software
+ *   Foundation, Inc., 675 Mass Ave, Cambridge, MA 02139, USA.
+ */
+
+#define PPS_GPIO_NAME "pps-gpio"
+#define pr_fmt(fmt) PPS_GPIO_NAME ": " fmt
+
+#include <linux/init.h>
+#include <linux/kernel.h>
+#include <linux/interrupt.h>
+#include <linux/module.h>
+#include <linux/platform_device.h>
+#include <linux/slab.h>
+#include <linux/pps_kernel.h>
+#include <linux/pps-gpio.h>
+#include <linux/gpio.h>
+#include <linux/list.h>
+
+/* Info for each registered platform device */
+struct pps_gpio_device_data {
+	int irq;			/* IRQ used as PPS source */
+	struct pps_device *pps;		/* PPS source device */
+	struct pps_source_info info;	/* PPS source information */
+	const struct pps_gpio_platform_data *pdata;
+};
+
+/*
+ * Report the PPS event
+ */
+
+static irqreturn_t pps_gpio_irq_handler(int irq, void *data)
+{
+	const struct pps_gpio_device_data *info;
+	struct pps_event_time ts;
+	int rising_edge;
+
+	/* Get the time stamp first */
+	pps_get_ts(&ts);
+
+	info = data;
+
+	rising_edge = gpio_get_value(info->pdata->gpio_pin);
+	if ((rising_edge && !info->pdata->assert_falling_edge) ||
+			(!rising_edge && info->pdata->assert_falling_edge))
+		pps_event(info->pps, &ts, PPS_CAPTUREASSERT, NULL);
+	else if (info->pdata->capture_clear &&
+			((rising_edge && info->pdata->assert_falling_edge) ||
+			 (!rising_edge && !info->pdata->assert_falling_edge)))
+		pps_event(info->pps, &ts, PPS_CAPTURECLEAR, NULL);
+
+	return IRQ_HANDLED;
+}
+
+static int pps_gpio_setup(struct platform_device *pdev)
+{
+	int ret;
+	const struct pps_gpio_platform_data *pdata = pdev->dev.platform_data;
+
+	ret = gpio_request(pdata->gpio_pin, pdata->gpio_label);
+	if (ret) {
+		pr_warning("failed to request GPIO %u\n", pdata->gpio_pin);
+		return -EINVAL;
+	}
+
+	ret = gpio_direction_input(pdata->gpio_pin);
+	if (ret) {
+		pr_warning("failed to set pin direction\n");
+		gpio_free(pdata->gpio_pin);
+		return -EINVAL;
+	}
+
+	return 0;
+}
+
+static unsigned long
+get_irqf_trigger_flags(const struct pps_gpio_platform_data *pdata)
+{
+	unsigned long flags = pdata->assert_falling_edge ?
+		IRQF_TRIGGER_FALLING : IRQF_TRIGGER_RISING;
+
+	if (pdata->capture_clear) {
+		flags |= ((flags & IRQF_TRIGGER_RISING) ?
+				IRQF_TRIGGER_FALLING : IRQF_TRIGGER_RISING);
+	}
+
+	return flags;
+}
+
+static int pps_gpio_probe(struct platform_device *pdev)
+{
+	struct pps_gpio_device_data *data;
+	int irq;
+	int ret;
+	int err;
+	int pps_default_params;
+	const struct pps_gpio_platform_data *pdata = pdev->dev.platform_data;
+
+
+	/* GPIO setup */
+	ret = pps_gpio_setup(pdev);
+	if (ret)
+		return -EINVAL;
+
+	/* IRQ setup */
+	irq = gpio_to_irq(pdata->gpio_pin);
+	if (irq < 0) {
+		pr_err("failed to map GPIO to IRQ: %d\n", irq);
+		err = -EINVAL;
+		goto return_error;
+	}
+
+	/* allocate space for device info */
+	data = kzalloc(sizeof(struct pps_gpio_device_data), GFP_KERNEL);
+	if (data == NULL) {
+		err = -ENOMEM;
+		goto return_error;
+	}
+
+	/* initialize PPS specific parts of the bookkeeping data structure. */
+	data->info.mode = PPS_CAPTUREASSERT | PPS_OFFSETASSERT |
+		PPS_ECHOASSERT | PPS_CANWAIT | PPS_TSFMT_TSPEC;
+	if (pdata->capture_clear)
+		data->info.mode |= PPS_CAPTURECLEAR | PPS_OFFSETCLEAR |
+			PPS_ECHOCLEAR;
+	data->info.owner = THIS_MODULE;
+	snprintf(data->info.name, PPS_MAX_NAME_LEN - 1, "%s.%d",
+		 pdev->name, pdev->id);
+
+	/* register PPS source */
+	pps_default_params = PPS_CAPTUREASSERT | PPS_OFFSETASSERT;
+	if (pdata->capture_clear)
+		pps_default_params |= PPS_CAPTURECLEAR | PPS_OFFSETCLEAR;
+	data->pps = pps_register_source(&data->info, pps_default_params);
+	if (data->pps == NULL) {
+		kfree(data);
+		pr_err("failed to register IRQ %d as PPS source\n", irq);
+		err = -EINVAL;
+		goto return_error;
+	}
+
+	data->irq = irq;
+	data->pdata = pdata;
+
+	/* register IRQ interrupt handler */
+	ret = request_irq(irq, pps_gpio_irq_handler,
+			get_irqf_trigger_flags(pdata), data->info.name, data);
+	if (ret) {
+		pps_unregister_source(data->pps);
+		kfree(data);
+		pr_err("failed to acquire IRQ %d\n", irq);
+		err = -EINVAL;
+		goto return_error;
+	}
+
+	platform_set_drvdata(pdev, data);
+	dev_info(data->pps->dev, "Registered IRQ %d as PPS source\n", irq);
+
+	return 0;
+
+return_error:
+	gpio_free(pdata->gpio_pin);
+	return err;
+}
+
+static int pps_gpio_remove(struct platform_device *pdev)
+{
+	struct pps_gpio_device_data *data = platform_get_drvdata(pdev);
+	const struct pps_gpio_platform_data *pdata = data->pdata;
+
+	platform_set_drvdata(pdev, NULL);
+	free_irq(data->irq, data);
+	gpio_free(pdata->gpio_pin);
+	pps_unregister_source(data->pps);
+	pr_info("removed IRQ %d as PPS source\n", data->irq);
+	kfree(data);
+	return 0;
+}
+
+static struct platform_driver pps_gpio_driver = {
+	.probe		= pps_gpio_probe,
+	.remove		=  __devexit_p(pps_gpio_remove),
+	.driver		= {
+		.name	= PPS_GPIO_NAME,
+		.owner	= THIS_MODULE
+	},
+};
+
+static int __init pps_gpio_init(void)
+{
+	int ret = platform_driver_register(&pps_gpio_driver);
+	if (ret < 0)
+		pr_err("failed to register platform driver\n");
+	return ret;
+}
+
+static void __exit pps_gpio_exit(void)
+{
+	platform_driver_unregister(&pps_gpio_driver);
+	pr_debug("unregistered platform driver\n");
+}
+
+module_init(pps_gpio_init);
+module_exit(pps_gpio_exit);
+
+MODULE_AUTHOR("Ricardo Martins <rasm@fe.up.pt>");
+MODULE_AUTHOR("James Nuss <jamesnuss@nanometrics.ca>");
+MODULE_DESCRIPTION("Use GPIO pin as PPS source");
+MODULE_LICENSE("GPL");
+MODULE_VERSION("1.0.0");
diff --git a/include/linux/pps-gpio.h b/include/linux/pps-gpio.h
new file mode 100644
index 0000000..0035abe
--- /dev/null
+++ b/include/linux/pps-gpio.h
@@ -0,0 +1,32 @@
+/*
+ * pps-gpio.h -- PPS client for GPIOs
+ *
+ *
+ * Copyright (C) 2011 James Nuss <jamesnuss@nanometrics.ca>
+ *
+ *   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.
+ *
+ *   You should have received a copy of the GNU General Public License
+ *   along with this program; if not, write to the Free Software
+ *   Foundation, Inc., 675 Mass Ave, Cambridge, MA 02139, USA.
+ */
+
+#ifndef _PPS_GPIO_H
+#define _PPS_GPIO_H
+
+struct pps_gpio_platform_data {
+	bool assert_falling_edge;
+	bool capture_clear;
+	unsigned int gpio_pin;
+	const char *gpio_label;
+};
+
+#endif