dahdi_dummy: Remove real-time clock support.

This removes support for using the real-time clock as a timing source in
dahdi_dummy.  Instead, the normal kernel timers method is now more accurate
since it keeps track of how much real time has passed to determine how many
times to call dahdi_receive and dahdi_transmit.  This method was originally
suggested by bmd.

(closes issue #13930)
(closes issue #14884)
Reported by: tzafrir
Tested by: dbackeberg, ask

git-svn-id: http://svn.asterisk.org/svn/dahdi/linux/trunk@6524 a0bf4364-ded3-4de4-8d8a-66a801d63aff

1 files changed, 59 insertions, 146 deletions

diff --git a/drivers/dahdi/dahdi_dummy.c b/drivers/dahdi/dahdi_dummy.c
index f084061..97949e3 100644
--- a/drivers/dahdi/dahdi_dummy.c
+++ b/drivers/dahdi/dahdi_dummy.c
@@ -1,17 +1,16 @@
 /*
  * Dummy DAHDI Driver for DAHDI Telephony interface
  *
- * Required: usb-uhci module and kernel > 2.4.4 OR kernel > 2.6.0
+ * Required: kernel > 2.6.0
  *
  * Written by Robert Pleh <robert.pleh@hermes.si>
  * 2.6 version by Tony Hoyle
  * Unified by Mark Spencer <markster@digium.com>
- * Converted to use RTC on i386 by Tony Mountifield <tony@softins.co.uk>
  *
  * Converted to use HighResTimers on i386 by Jeffery Palmer <jeff@triggerinc.com>
  *
  * Copyright (C) 2002, Hermes Softlab
- * Copyright (C) 2004, Digium, Inc.
+ * Copyright (C) 2004-2009, Digium, Inc.
  *
  * All rights reserved.
  *
@@ -39,33 +38,9 @@
 
 #include <linux/version.h>
 
-#ifndef VERSION_CODE
-#  define VERSION_CODE(vers,rel,seq) ( ((vers)<<16) | ((rel)<<8) | (seq) )
-#endif
-
-
-#if LINUX_VERSION_CODE < VERSION_CODE(2,4,5)
-#  error "This kernel is too old: not supported by this file"
-#endif
-
-/*
- * NOTE: (only applies to kernel 2.6)
- * If using an i386 architecture without a PC real-time clock,
- * the #define USE_RTC should be commented out.
- */
-#if defined(__i386__) || defined(__x86_64__)
-#if LINUX_VERSION_CODE >= VERSION_CODE(2,6,15)
-/* The symbol hrtimer_forward is only exported as of 2.6.22: */
-#if defined(CONFIG_HIGH_RES_TIMERS) && LINUX_VERSION_CODE >= VERSION_CODE(2,6,22)
+#if defined(CONFIG_HIGH_RES_TIMERS) && \
+	LINUX_VERSION_CODE >= KERNEL_VERSION(2, 6, 22)
 #define USE_HIGHRESTIMER
-#else
-#define USE_RTC
-#endif
-#else
-#if 0
-#define USE_RTC
-#endif
-#endif
 #endif
 
 #include <linux/kernel.h>
@@ -75,19 +50,13 @@
 #include <linux/errno.h>
 #include <linux/moduleparam.h>
 
-#include <dahdi/kernel.h>
-
-#ifdef USE_HIGHRESTIMER
+#if defined(USE_HIGHRESTIMER)
 #include <linux/hrtimer.h>
-#endif
-#ifdef USE_RTC
-#include <linux/rtc.h>
+#else
+#include <linux/time.h>
 #endif
 
-#include <linux/version.h>
-#if LINUX_VERSION_CODE > KERNEL_VERSION(2,4,19)
-#define USB2420
-#endif
+#include <dahdi/kernel.h>
 
 #ifndef HAVE_HRTIMER_ACCESSORS
 #if defined(USE_HIGHRESTIMER) && \
@@ -109,10 +78,9 @@ struct dahdi_dummy {
 	struct dahdi_span span;
 	struct dahdi_chan _chan;
 	struct dahdi_chan *chan;
-	unsigned int counter;
-#ifdef USE_RTC
-	spinlock_t rtclock;
-	rtc_task_t rtc_task;
+#if !defined(USE_HIGHRESTIMER)
+	unsigned long calls_since_start;
+	struct timespec start_interval;
 #endif
 };
 
@@ -123,71 +91,21 @@ static int debug = 0;
 #ifdef USE_HIGHRESTIMER
 #define CLOCK_SRC "HRtimer"
 static struct hrtimer zaptimer;
-#elif defined(USE_RTC)
-#define CLOCK_SRC "RTC"
-static int rtc_rate = 0;
-static int current_rate = 0;
-static int taskletpending = 0;
-static struct tasklet_struct ztd_tlet;
-static void ztd_tasklet(unsigned long data);
-#else /* Linux 2.6, but no RTC or HRTIMER used */
-#define CLOCK_SRC "Linux26"
-/* 2.6 kernel timer stuff */
-static struct timer_list timer;
-#endif
-
 #define DAHDI_RATE 1000                     /* DAHDI ticks per second */
 #define DAHDI_TIME (1000000 / DAHDI_RATE)  /* DAHDI tick time in us */
 #define DAHDI_TIME_NS (DAHDI_TIME * 1000)  /* DAHDI tick time in ns */
+#else
+#define CLOCK_SRC "Linux26"
+static struct timer_list timer;
+static atomic_t shutdown;
+#define JIFFIES_INTERVAL (HZ/250) 	/* 4ms is fine for dahdi_dummy */
+#endif
 
 /* Different bits of the debug variable: */
 #define DEBUG_GENERAL (1 << 0)
 #define DEBUG_TICKS   (1 << 1)
 
-
-#ifdef USE_RTC
-static void update_rtc_rate(struct dahdi_dummy *ztd)
-{
-	if (((rtc_rate & (rtc_rate - 1)) != 0) || (rtc_rate > 8192) || (rtc_rate < 2)) {
-		printk(KERN_NOTICE "Invalid RTC rate %d specified\n", rtc_rate);
-		rtc_rate = current_rate;	/* Set default RTC rate */
-	}
-	if (!rtc_rate || (rtc_rate != current_rate)) {
-		rtc_control(&ztd->rtc_task, RTC_IRQP_SET, current_rate = (rtc_rate ? rtc_rate : 1024));	/* 1024 Hz */
-		printk(KERN_INFO "dahdi_dummy: RTC rate is %d\n", rtc_rate);
-		ztd->counter = 0;
-	}
-}
-
-static void ztd_tasklet(unsigned long data)
-{
-	if (taskletpending)
-		update_rtc_rate((struct dahdi_dummy *)ztd);
-	taskletpending = 0;
-}
-
-/* rtc_interrupt - called at 1024Hz from hook in RTC handler */
-static void dahdi_dummy_rtc_interrupt(void *private_data)
-{
-	struct dahdi_dummy *ztd = private_data;
-	unsigned long flags;
-
-	/* Is spinlock required here??? */
-	spin_lock_irqsave(&ztd->rtclock, flags);
-	ztd->counter += DAHDI_TIME;
-	while (ztd->counter >= current_rate) {
-		ztd->counter -= current_rate;
-		/* Update of RTC IRQ rate isn't possible from interrupt handler :( */
-		if (!taskletpending && (current_rate != rtc_rate)) {
-			taskletpending = 1;
-			tasklet_hi_schedule(&ztd_tlet);
-		}
-		dahdi_receive(&ztd->span);
-		dahdi_transmit(&ztd->span);
-	}
-	spin_unlock_irqrestore(&ztd->rtclock, flags);
-}
-#elif defined(USE_HIGHRESTIMER)
+#if defined(USE_HIGHRESTIMER)
 static enum hrtimer_restart dahdi_dummy_hr_int(struct hrtimer *htmr)
 {
 	unsigned long overrun;
@@ -220,17 +138,45 @@ static enum hrtimer_restart dahdi_dummy_hr_int(struct hrtimer *htmr)
 	return HRTIMER_RESTART;
 }
 #else
-/* use kernel system tick timer if PC architecture RTC is not available */
+static unsigned long timespec_diff_ms(struct timespec *t0, struct timespec *t1)
+{
+	long nanosec, sec;
+	unsigned long ms;
+	sec = (t1->tv_sec - t0->tv_sec);
+	nanosec = (t1->tv_nsec - t0->tv_nsec);
+	while (nanosec >= NSEC_PER_SEC) {
+		nanosec -= NSEC_PER_SEC;
+		++sec;
+	}
+	while (nanosec < 0) {
+		nanosec += NSEC_PER_SEC;
+		--sec;
+	}
+	ms = (sec * 1000) + (nanosec / 1000000L);
+	return ms;
+}
+
 static void dahdi_dummy_timer(unsigned long param)
 {
-	mod_timer(&timer, jiffies + 1);
+	unsigned long ms_since_start;
+	struct timespec now;
+	const unsigned long MAX_INTERVAL = 100000L;
 
-	ztd->counter += DAHDI_TIME;
-	while (ztd->counter >= HZ) {
-		ztd->counter -= HZ;
+	if (!atomic_read(&shutdown))
+		mod_timer(&timer, jiffies + JIFFIES_INTERVAL);
+
+	now = current_kernel_time();
+	ms_since_start = timespec_diff_ms(&ztd->start_interval, &now);
+	while (ms_since_start > ztd->calls_since_start) {
+		ztd->calls_since_start++;
 		dahdi_receive(&ztd->span);
 		dahdi_transmit(&ztd->span);
 	}
+
+	if (ms_since_start > MAX_INTERVAL) {
+		ztd->calls_since_start = 0;
+		ztd->start_interval = now;
+	}
 }
 #endif
 
@@ -257,43 +203,19 @@ static int dahdi_dummy_initialize(struct dahdi_dummy *ztd)
 
 int init_module(void)
 {
-#ifdef USE_RTC
-	int err;
-#endif
-
-	ztd = kmalloc(sizeof(struct dahdi_dummy), GFP_KERNEL);
+	ztd = kzalloc(sizeof(*ztd), GFP_KERNEL);
 	if (ztd == NULL) {
 		printk(KERN_ERR "dahdi_dummy: Unable to allocate memory\n");
 		return -ENOMEM;
 	}
 
-	memset(ztd, 0x0, sizeof(struct dahdi_dummy));
-
 	if (dahdi_dummy_initialize(ztd)) {
 		printk(KERN_ERR "dahdi_dummy: Unable to intialize DAHDI driver\n");
 		kfree(ztd);
 		return -ENODEV;
 	}
 
-	ztd->counter = 0;
-#ifdef USE_RTC
-	ztd->rtclock = SPIN_LOCK_UNLOCKED;
-	ztd->rtc_task.func = dahdi_dummy_rtc_interrupt;
-	ztd->rtc_task.private_data = ztd;
-	err = rtc_register(&ztd->rtc_task);
-	if (err < 0) {
-		printk(KERN_ERR "dahdi_dummy: Unable to register DAHDI rtc driver\n");
-		dahdi_unregister(&ztd->span);
-		kfree(ztd);
-		return err;
-	}
-	/* Set default RTC interrupt rate to 1024Hz */
-	if (!rtc_rate)
-		rtc_rate = 1024;
-	update_rtc_rate(ztd);
-	rtc_control(&ztd->rtc_task, RTC_PIE_ON, 0);
-	tasklet_init(&ztd_tlet, ztd_tasklet, 0);
-#elif defined(USE_HIGHRESTIMER)
+#if defined(USE_HIGHRESTIMER)
 	printk(KERN_DEBUG "dahdi_dummy: Trying to load High Resolution Timer\n");
 	hrtimer_init(&zaptimer, CLOCK_MONOTONIC, HRTIMER_MODE_REL);
 	printk(KERN_DEBUG "dahdi_dummy: Initialized High Resolution Timer\n");
@@ -307,7 +229,9 @@ int init_module(void)
 #else
 	init_timer(&timer);
 	timer.function = dahdi_dummy_timer;
-	timer.expires = jiffies + 1;
+	ztd->start_interval = current_kernel_time();
+	timer.expires = jiffies + JIFFIES_INTERVAL;
+	atomic_set(&shutdown, 0);
 	add_timer(&timer);
 #endif
 
@@ -319,18 +243,12 @@ int init_module(void)
 
 void cleanup_module(void)
 {
-#ifdef USE_RTC
-	if (taskletpending) {
-		tasklet_disable(&ztd_tlet);
-		tasklet_kill(&ztd_tlet);
-	}
-	rtc_control(&ztd->rtc_task, RTC_PIE_OFF, 0);
-	rtc_unregister(&ztd->rtc_task);
-#elif defined(USE_HIGHRESTIMER)
+#if defined(USE_HIGHRESTIMER)
 	/* Stop high resolution timer */
 	hrtimer_cancel(&zaptimer);
 #else
-	del_timer(&timer);
+	atomic_set(&shutdown, 1);
+	del_timer_sync(&timer);
 #endif
 	dahdi_unregister(&ztd->span);
 	kfree(ztd);
@@ -338,12 +256,7 @@ void cleanup_module(void)
 		printk(KERN_DEBUG "dahdi_dummy: cleanup() finished\n");
 }
 
-
-
 module_param(debug, int, 0600);
-#ifdef USE_RTC
-module_param(rtc_rate, int, 0600);
-#endif
 
 MODULE_DESCRIPTION("Timing-Only Driver");
 MODULE_AUTHOR("Robert Pleh <robert.pleh@hermes.si>");