[PATCH v2 2/2] pps: new client driver using GPIO

[James Nuss]

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 <rasm@xxxxxxxx> 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

Signed-off-by: James Nuss <jamesnuss@xxxxxxxxxxxxxx>
CC: Ricardo Martins <rasm@xxxxxxxx>
---
 drivers/pps/clients/Kconfig    |    9 ++
 drivers/pps/clients/Makefile   |    1 +
 drivers/pps/clients/pps-gpio.c |  218 ++++++++++++++++++++++++++++++++++++++++
 include/linux/pps-gpio.h       |   32 ++++++
 4 files changed, 260 insertions(+), 0 deletions(-)
 create mode 100644 drivers/pps/clients/pps-gpio.c
 create mode 100644 include/linux/pps-gpio.h

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 @@ config PPS_CLIENT_PARPORT
 	  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..fe9d913
--- /dev/null
+++ b/drivers/pps/clients/pps-gpio.c
@@ -0,0 +1,218 @@
+/*
+ * pps-gpio.c -- PPS client driver using GPIO
+ *
+ *
+ * Copyright (C) 2010 Ricardo Martins <rasm@xxxxxxxx>
+ * Copyright (C) 2011 James Nuss <jamesnuss@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.
+ *
+ *   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 pr_fmt(fmt) KBUILD_MODNAME ": " 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>
+
+#define PPS_GPIO_NAME		"pps-gpio"
+#define PPS_GPIO_VERSION	"1.0.0"
+
+/* 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 = (const struct pps_gpio_device_data *)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 -1;
+	}
+
+	ret = gpio_direction_input(pdata->gpio_pin);
+	if (ret) {
+		pr_warning("failed to set pin direction\n");
+		return -1;
+	}
+
+	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 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);
+		return -EINVAL;
+	}
+
+	/* allocate space for device info */
+	data = kzalloc(sizeof(struct pps_gpio_device_data), GFP_KERNEL);
+	if (data == NULL)
+		return -ENOMEM;
+
+	/* 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);
+		return -EINVAL;
+	}
+
+	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);
+		return -EINVAL;
+	}
+
+	platform_set_drvdata(pdev, data);
+	dev_info(data->pps->dev, "Registered IRQ %d as PPS source\n", irq);
+
+	return 0;
+}
+
+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@xxxxxxxx>");
+MODULE_AUTHOR("James Nuss <jamesnuss@xxxxxxxxxxxxxx>");
+MODULE_DESCRIPTION("Use GPIO pin as PPS source");
+MODULE_LICENSE("GPL");
+MODULE_VERSION(PPS_GPIO_VERSION);
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@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.
+ *
+ *   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
-- 
1.7.1

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