Date:	Thu, 8 Jan 2009 17:11:20 +0100
From:	"Davide Rizzo" <elpa.rizzo@...il.com>
To:	"Hans J. Koch" <hjk@...utronix.de>
Cc:	linux-kernel@...r.kernel.org, gregkh@...e.de, ben-linux@...ff.org
Subject: Re: [PATCH 1/2] Driver for user access to internal timer

>> >
>> > Davide,
>> > please don't use drivers/uio/ for things that are no UIO drivers.
>> >
>> > Thanks,
>> > Hans
>>
>> I thought drivers/uoi is a better choice then driver/misc, because
>> this driver allows user to access internal hardware to generate PWM
>> signals.
>
> Yes, but you do not use the UIO framework to achieve this.
>
>> Otherwise, where do you suggest to put it ?
>
> I didn't have a deeper look at your driver. I suggest you ask the people
> who maintain the clock/timer frameworks you use. Since you seem to be
> working on an ARM platform, you should Cc: the linux-arm-kernel mailing
> list as well.
>
> Thanks,
> Hans
>
>
Moved to drivers/misc

Allows user programs to manage internal timers, through virtual files
 frequency and duty.
If pwm_one_shot is implemented, it allows also waiting for one-shot period.

Signed-off-by: Davide Rizzo <elpa-rizzo@...il.com>
---
diff -urNp linux-2.6.28/drivers/misc/Kconfig
linux-2.6.28.elpa/drivers/misc/Kconfig
--- linux-2.6.28/drivers/misc/Kconfig	2008-12-25 00:26:37.000000000 +0100
+++ linux-2.6.28.elpa/drivers/misc/Kconfig	2009-01-08 16:38:49.000000000 +0100
@@ -500,4 +500,24 @@ config SGI_GRU_DEBUG

 source "drivers/misc/c2port/Kconfig"

+config UIO_TIMER
+	tristate "General purpose timer driver"
+	default y
+	---help---
+	  This driver allows to configure and control general purpose timers
+	   from user level code.
+	  To use driver to generate one-shot interrupt-terminated delays, the
+	   function pwm_one_shot() must be implemented in low-level drivers
+	  Currently it's implemented only on Samsung S3C24xx platforms.
+
+config UIO_TIMER_ONESHOT
+	bool "Timer driver uses one-shot mode"
+	depends on PLAT_S3C
+	default y
+	---help---
+	  Enable this to allow general purpose timer driver to use timers
+	   in one-shot mode. For this to work, the function pwm_one_shot()
+	   must be implemented in low-level drivers.
+	  Currently it's implemented only on Samsung S3C24xx platforms.
+
 endif # MISC_DEVICES
diff -urNp linux-2.6.28/drivers/misc/Makefile
linux-2.6.28.elpa/drivers/misc/Makefile
--- linux-2.6.28/drivers/misc/Makefile	2008-12-25 00:26:37.000000000 +0100
+++ linux-2.6.28.elpa/drivers/misc/Makefile	2009-01-08 16:37:48.000000000 +0100
@@ -3,6 +3,7 @@
#
 obj- := misc.o	# Dummy rule to force built-in.o to be made

+obj-$(CONFIG_UIO_TIMER) += timer.o
 obj-$(CONFIG_IBM_ASM)		+= ibmasm/
 obj-$(CONFIG_HDPU_FEATURES)	+= hdpuftrs/
 obj-$(CONFIG_ASUS_LAPTOP)	+= asus-laptop.o
diff -urNp linux-2.6.28/drivers/misc/timer.c
linux-2.6.28.elpa/drivers/misc/timer.c
--- linux-2.6.28/drivers/misc/timer.c	1970-01-01 01:00:00.000000000 +0100
+++ linux-2.6.28.elpa/drivers/misc/timer.c	2009-01-08 12:22:37.000000000 +0100
@@ -0,0 +1,302 @@
+/*
+ drivers/misc/timer.c
+
+ Written Jan 2009 by Davide Rizzo <elpa-rizzo@...il.com>
+
+ This driver allows user to access internal timers
+ You can use any timer to generate a fixed frequency signal, or to wait for a
+ defined short time (if hardware can do it).
+ To generate a PWM signal, you have to write the frequency value in Hz into the
+ virtual file "freq". After that you can program the duty cycle in the virtual
+ file "duty", in 1/1000 units (500 = 50%).
+ To wait for a time, you have to write the number of microseconds in virtual
+ file "wait". Reading from same file will complete when timer will expire.
+
+ 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.
+*/
+
+#include <linux/platform_device.h>
+#include <linux/err.h>
+#include <linux/pwm.h>
+
+struct timer_info {
+	int id;
+	struct pwm_device *pwm;
+	unsigned long period_ns, duty_ns;
+	struct mutex mtx;
+#ifdef CONFIG_UIO_TIMER_ONESHOT
+	int flag;
+	wait_queue_head_t wq;
+#endif	/* CONFIG_UIO_TIMER_ONESHOT */
+};
+
+#ifdef CONFIG_UIO_TIMER_ONESHOT
+static void expired(struct pwm_device *pwm, void *arg)
+{
+	struct timer_info *info = dev_get_drvdata((struct device *)arg);
+
+	info->flag = 1;
+
+	wake_up_interruptible(&info->wq);
+}
+
+/* Delay is in usec */
+static ssize_t wait_store(struct device *dev, struct device_attribute *attr,
+	const char *buffer, size_t count)
+{
+	struct timer_info *info = dev_get_drvdata(dev);
+	unsigned long delay;
+	int err = strict_strtoul(buffer, 10, &delay);
+
+	if (err)
+		return err;
+
+	mutex_lock(&info->mtx);
+
+	info->flag = 0;
+	pwm_one_shot(info->pwm, delay * 1000, expired, dev);
+
+	mutex_unlock(&info->mtx);
+
+	return count;
+}
+
+/* Waits for delay */
+static ssize_t wait_show(struct device *dev, struct device_attribute *attr,
+	char *buffer)
+{
+	struct timer_info *info = dev_get_drvdata(dev);
+	int ret;
+
+	mutex_lock(&info->mtx);
+
+	/* !=0 if interrupted by some other signal */
+	ret = wait_event_interruptible(info->wq, info->flag);
+
+	mutex_unlock(&info->mtx);
+
+	snprintf(buffer, PAGE_SIZE - 1, "%d\n", ret);
+	return strlen(buffer);
+}
+#endif	/* CONFIG_UIO_TIMER_ONESHOT */
+
+#define NS_IN_HZ (1000000000UL)
+
+/* Freq is in Hz */
+static ssize_t freq_store(struct device *dev, struct device_attribute *attr,
+	const char *buffer, size_t count)
+{
+	struct timer_info *info = dev_get_drvdata(dev);
+	unsigned long output_freq;
+	int err = strict_strtoul(buffer, 10, &output_freq);
+	if (err)
+		return err;
+
+	mutex_lock(&info->mtx);
+
+	if (output_freq == 0) { /* Stop timer */
+		pwm_disable(info->pwm);
+		info->period_ns = 0;
+		info->duty_ns = 0;
+	} else {
+		unsigned long new_period = NS_IN_HZ / output_freq;
+		if (info->period_ns == 0)
+			info->duty_ns = new_period / 2;
+		else {
+			unsigned long long ll = (unsigned long long)new_period *
+				info->duty_ns ;
+			do_div(ll, info->period_ns);
+			info->duty_ns = ll;
+		}
+		info->period_ns = new_period;
+		pwm_config(info->pwm, info->duty_ns, info->period_ns);
+		pwm_enable(info->pwm);
+	}
+
+	mutex_unlock(&info->mtx);
+
+	return count;
+}
+
+/* Freq is in Hz */
+static ssize_t freq_show(struct device *dev, struct device_attribute *attr,
+	char *buffer)
+{
+	struct timer_info *info = dev_get_drvdata(dev);
+	if (info->period_ns)
+		snprintf(buffer, PAGE_SIZE - 1, "%ld\n", NS_IN_HZ /
+			info->period_ns);
+	else
+		strlcpy(buffer, "0\n", PAGE_SIZE);
+	return strlen(buffer);
+}
+
+/* Duty is in 1/1000 units */
+static ssize_t duty_store(struct device *dev, struct device_attribute *attr,
+	const char *buffer, size_t count)
+{
+	struct timer_info *info = dev_get_drvdata(dev);
+	unsigned long duty;
+	int err = strict_strtoul(buffer, 10, &duty);
+	if (err)
+		return err;
+	if (duty > 1000)
+		return -ERANGE;
+
+	mutex_lock(&info->mtx);
+
+	if ((info->period_ns == 0) || (duty == 0)) { /* Stop timer */
+		info->duty_ns = 0;
+		pwm_disable(info->pwm);
+	} else {
+		unsigned long long ll = (unsigned long long)duty *
+			info->period_ns;
+		do_div(ll, 1000);
+		info->duty_ns = ll;
+		pwm_config(info->pwm, info->duty_ns, info->period_ns);
+		pwm_enable(info->pwm);
+	}
+
+	mutex_unlock(&info->mtx);
+
+	return count;
+}
+
+/* Duty is in 1/1000 units */
+static ssize_t duty_show(struct device *dev, struct device_attribute *attr,
+	char *buffer)
+{
+	struct timer_info *info = dev_get_drvdata(dev);
+
+	mutex_lock(&info->mtx);
+
+	if (info->period_ns) {
+		volatile unsigned long long ll = info->duty_ns * 1000;
+		do_div(ll, info->period_ns);
+		snprintf(buffer, PAGE_SIZE - 1, "%ld\n", (long int)ll);
+	} else
+		strlcpy(buffer, "0\n", PAGE_SIZE);
+
+	mutex_unlock(&info->mtx);
+
+	return strlen(buffer);
+}
+
+#ifdef CONFIG_UIO_TIMER_ONESHOT
+static DEVICE_ATTR(wait, S_IRUGO | S_IWUSR, wait_show, wait_store);
+#endif	/* CONFIG_UIO_TIMER_ONESHOT */
+static DEVICE_ATTR(frequency, S_IRUGO | S_IWUSR, freq_show, freq_store);
+static DEVICE_ATTR(duty, S_IRUGO | S_IWUSR, duty_show, duty_store);
+
+static int timer_probe(struct platform_device *pdev)
+{
+	struct timer_info *info;
+	int err;
+	info = kzalloc(sizeof(*info), GFP_KERNEL);
+	if (!info) {
+		dev_err(&pdev->dev, "out of kernel memory\n");
+		err = -ENOMEM;
+		goto fail_malloc;
+	}
+	platform_set_drvdata(pdev, info);
+	mutex_init(&info->mtx);
+	info->pwm = pwm_request(pdev->id, "timer driver");
+	if (IS_ERR(info->pwm)) {
+		err = PTR_ERR(info->pwm);
+		goto fail_req;
+	}
+#ifdef CONFIG_UIO_TIMER_ONESHOT
+	init_waitqueue_head(&info->wq);
+	info->flag = 1;
+	err = device_create_file(&pdev->dev, &dev_attr_wait);
+	if (err) {
+		dev_err(&pdev->dev, "Unable to create wait virtual file\n");
+		goto fail_wait;
+	}
+#endif	/* CONFIG_UIO_TIMER_ONESHOT */
+	err = device_create_file(&pdev->dev, &dev_attr_frequency);
+	if (err) {
+		dev_err(&pdev->dev, "Unable to create freq virtual file\n");
+		goto fail_freq;
+	}
+	err = device_create_file(&pdev->dev, &dev_attr_duty);
+	if (err) {
+		dev_err(&pdev->dev, "Unable to create duty virtual file\n");
+		goto fail_duty;
+	}
+	dev_notice(&pdev->dev, "timer %d device driver loaded OK\n", pdev->id);
+	return 0;
+
+fail_duty:
+	device_remove_file(&pdev->dev, &dev_attr_frequency);
+fail_freq:
+#ifdef CONFIG_UIO_TIMER_ONESHOT
+	device_remove_file(&pdev->dev, &dev_attr_wait);
+fail_wait:
+#endif	/* CONFIG_UIO_TIMER_ONESHOT */
+	pwm_free(info->pwm);
+fail_req:
+	platform_set_drvdata(pdev, NULL);
+	kfree(info);
+fail_malloc:
+	return err;
+}
+
+static int timer_remove(struct platform_device *pdev)
+{
+	struct timer_info *info = platform_get_drvdata(pdev);
+
+	mutex_lock(&info->mtx);
+
+	device_remove_file(&pdev->dev, &dev_attr_duty);
+	device_remove_file(&pdev->dev, &dev_attr_frequency);
+#ifdef CONFIG_UIO_TIMER_ONESHOT
+	device_remove_file(&pdev->dev, &dev_attr_wait);
+#endif	/* CONFIG_UIO_TIMER_ONESHOT */
+	pwm_free(info->pwm);
+	platform_set_drvdata(pdev, NULL);
+
+	mutex_unlock(&info->mtx);
+
+	kfree(info);
+	return 0;
+}
+
+static struct platform_driver timer_driver = {
+	.probe  = timer_probe,
+	.remove = timer_remove,
+	.driver = {
+		.name = "timer",
+		.owner = THIS_MODULE,
+	},
+};
+
+static int __init timer_init_module(void)
+{
+	return platform_driver_register(&timer_driver);
+}
+
+static void __exit timer_cleanup_module(void)
+{
+	platform_driver_unregister(&timer_driver);
+}
+
+module_init(timer_init_module);
+module_exit(timer_cleanup_module);
+
+MODULE_AUTHOR("Davide Rizzo <elpa-rizzo@...il.com>");
+MODULE_DESCRIPTION("Timers driver");
+MODULE_SUPPORTED_DEVICE("timers");
+MODULE_LICENSE("GPL");
--
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