[AVR32] Change system timer from count-compare to Timer/Counter 0

Due to limitation of the count-compare system timer (not able to
count when CPU is in sleep), the system timer had to be changed to
use a peripheral timer/counter.

The old COUNT-COMPARE code is still present in time.c as weak
functions. The new timer is added to the architecture directory.

This patch sets up TC0 as system timer The new timer has been tested
on AT32AP7000/ATSTK1000 at 100 Hz, 250 Hz, 300 Hz and 1000 Hz.

For more details about the timer/counter see the datasheet for
AT32AP700x available at

http://www.atmel.com/dyn/products/product_card.asp?part_id=3903

Signed-off-by: Hans-Christian Egtvedt <hcegtvedt@atmel.com>
Signed-off-by: Haavard Skinnemoen <hskinnemoen@atmel.com>

1 files changed, 77 insertions, 73 deletions

diff --git a/arch/avr32/kernel/time.c b/arch/avr32/kernel/time.c
index c10833f2ee0..7014a3571ec 100644
--- a/arch/avr32/kernel/time.c
+++ b/arch/avr32/kernel/time.c
@@ -1,5 +1,5 @@
 /*
- * Copyright (C) 2004-2006 Atmel Corporation
+ * Copyright (C) 2004-2007 Atmel Corporation
  *
  * Based on MIPS implementation arch/mips/kernel/time.c
  *   Copyright 2001 MontaVista Software Inc.
@@ -20,18 +20,25 @@
 #include <linux/init.h>
 #include <linux/profile.h>
 #include <linux/sysdev.h>
+#include <linux/err.h>
 
 #include <asm/div64.h>
 #include <asm/sysreg.h>
 #include <asm/io.h>
 #include <asm/sections.h>
 
-static cycle_t read_cycle_count(void)
+/* how many counter cycles in a jiffy? */
+static u32 cycles_per_jiffy;
+
+/* the count value for the next timer interrupt */
+static u32 expirelo;
+
+cycle_t __weak read_cycle_count(void)
 {
 	return (cycle_t)sysreg_read(COUNT);
 }
 
-static struct clocksource clocksource_avr32 = {
+struct clocksource __weak clocksource_avr32 = {
 	.name		= "avr32",
 	.rating		= 350,
 	.read		= read_cycle_count,
@@ -40,12 +47,20 @@ static struct clocksource clocksource_avr32 = {
 	.flags		= CLOCK_SOURCE_IS_CONTINUOUS,
 };
 
+irqreturn_t __weak timer_interrupt(int irq, void *dev_id);
+
+struct irqaction timer_irqaction = {
+	.handler	= timer_interrupt,
+	.flags		= IRQF_DISABLED,
+	.name		= "timer",
+};
+
 /*
  * By default we provide the null RTC ops
  */
 static unsigned long null_rtc_get_time(void)
 {
-	return mktime(2004, 1, 1, 0, 0, 0);
+	return mktime(2007, 1, 1, 0, 0, 0);
 }
 
 static int null_rtc_set_time(unsigned long sec)
@@ -56,23 +71,14 @@ static int null_rtc_set_time(unsigned long sec)
 static unsigned long (*rtc_get_time)(void) = null_rtc_get_time;
 static int (*rtc_set_time)(unsigned long) = null_rtc_set_time;
 
-/* how many counter cycles in a jiffy? */
-static unsigned long cycles_per_jiffy;
-
-/* cycle counter value at the previous timer interrupt */
-static unsigned int timerhi, timerlo;
-
-/* the count value for the next timer interrupt */
-static unsigned int expirelo;
-
 static void avr32_timer_ack(void)
 {
-	unsigned int count;
+	u32 count;
 
 	/* Ack this timer interrupt and set the next one */
 	expirelo += cycles_per_jiffy;
+	/* setting COMPARE to 0 stops the COUNT-COMPARE */
 	if (expirelo == 0) {
-		printk(KERN_DEBUG "expirelo == 0\n");
 		sysreg_write(COMPARE, expirelo + 1);
 	} else {
 		sysreg_write(COMPARE, expirelo);
@@ -86,27 +92,56 @@ static void avr32_timer_ack(void)
 	}
 }
 
-static unsigned int avr32_hpt_read(void)
+int __weak avr32_hpt_init(void)
 {
-	return sysreg_read(COUNT);
+	int ret;
+	unsigned long mult, shift, count_hz;
+
+	count_hz = clk_get_rate(boot_cpu_data.clk);
+	shift = clocksource_avr32.shift;
+	mult = clocksource_hz2mult(count_hz, shift);
+	clocksource_avr32.mult = mult;
+
+	{
+		u64 tmp;
+
+		tmp = TICK_NSEC;
+		tmp <<= shift;
+		tmp += mult / 2;
+		do_div(tmp, mult);
+
+		cycles_per_jiffy = tmp;
+	}
+
+	ret = setup_irq(0, &timer_irqaction);
+	if (ret) {
+		pr_debug("timer: could not request IRQ 0: %d\n", ret);
+		return -ENODEV;
+	}
+
+	printk(KERN_INFO "timer: AT32AP COUNT-COMPARE at irq 0, "
+			"%lu.%03lu MHz\n",
+			((count_hz + 500) / 1000) / 1000,
+			((count_hz + 500) / 1000) % 1000);
+
+	return 0;
 }
 
 /*
  * Taken from MIPS c0_hpt_timer_init().
  *
- * Why is it so complicated, and what is "count"?  My assumption is
- * that `count' specifies the "reference cycle", i.e. the cycle since
- * reset that should mean "zero". The reason COUNT is written twice is
- * probably to make sure we don't get any timer interrupts while we
- * are messing with the counter.
+ * The reason COUNT is written twice is probably to make sure we don't get any
+ * timer interrupts while we are messing with the counter.
  */
-static void avr32_hpt_init(unsigned int count)
+int __weak avr32_hpt_start(void)
 {
-	count = sysreg_read(COUNT) - count;
+	u32 count = sysreg_read(COUNT);
 	expirelo = (count / cycles_per_jiffy + 1) * cycles_per_jiffy;
 	sysreg_write(COUNT, expirelo - cycles_per_jiffy);
 	sysreg_write(COMPARE, expirelo);
 	sysreg_write(COUNT, count);
+
+	return 0;
 }
 
 /*
@@ -115,26 +150,18 @@ static void avr32_hpt_init(unsigned int count)
  *
  * In UP mode, it is invoked from the (global) timer_interrupt.
  */
-static void local_timer_interrupt(int irq, void *dev_id)
+void local_timer_interrupt(int irq, void *dev_id)
 {
 	if (current->pid)
 		profile_tick(CPU_PROFILING);
 	update_process_times(user_mode(get_irq_regs()));
 }
 
-static irqreturn_t
-timer_interrupt(int irq, void *dev_id)
+irqreturn_t __weak timer_interrupt(int irq, void *dev_id)
 {
-	unsigned int count;
-
 	/* ack timer interrupt and try to set next interrupt */
-	count = avr32_hpt_read();
 	avr32_timer_ack();
 
-	/* Update timerhi/timerlo for intra-jiffy calibration */
-	timerhi += count < timerlo;	/* Wrap around */
-	timerlo = count;
-
 	/*
 	 * Call the generic timer interrupt handler
 	 */
@@ -153,60 +180,37 @@ timer_interrupt(int irq, void *dev_id)
 	return IRQ_HANDLED;
 }
 
-static struct irqaction timer_irqaction = {
-	.handler	= timer_interrupt,
-	.flags		= IRQF_DISABLED,
-	.name		= "timer",
-};
-
 void __init time_init(void)
 {
-	unsigned long mult, shift, count_hz;
 	int ret;
 
+	/*
+	 * Make sure we don't get any COMPARE interrupts before we can
+	 * handle them.
+	 */
+	sysreg_write(COMPARE, 0);
+
 	xtime.tv_sec = rtc_get_time();
 	xtime.tv_nsec = 0;
 
 	set_normalized_timespec(&wall_to_monotonic,
 				-xtime.tv_sec, -xtime.tv_nsec);
 
-	printk("Before time_init: count=%08lx, compare=%08lx\n",
-	       (unsigned long)sysreg_read(COUNT),
-	       (unsigned long)sysreg_read(COMPARE));
-
-	count_hz = clk_get_rate(boot_cpu_data.clk);
-	shift = clocksource_avr32.shift;
-	mult = clocksource_hz2mult(count_hz, shift);
-	clocksource_avr32.mult = mult;
-
-	printk("Cycle counter: mult=%lu, shift=%lu\n", mult, shift);
-
-	{
-		u64 tmp;
-
-		tmp = TICK_NSEC;
-		tmp <<= shift;
-		tmp += mult / 2;
-		do_div(tmp, mult);
-
-		cycles_per_jiffy = tmp;
+	ret = avr32_hpt_init();
+	if (ret) {
+		pr_debug("timer: failed setup: %d\n", ret);
+		return;
 	}
 
-	/* This sets up the high precision timer for the first interrupt. */
-	avr32_hpt_init(avr32_hpt_read());
-
-	printk("After time_init: count=%08lx, compare=%08lx\n",
-	       (unsigned long)sysreg_read(COUNT),
-	       (unsigned long)sysreg_read(COMPARE));
-
 	ret = clocksource_register(&clocksource_avr32);
 	if (ret)
-		printk(KERN_ERR
-		       "timer: could not register clocksource: %d\n", ret);
+		pr_debug("timer: could not register clocksource: %d\n", ret);
 
-	ret = setup_irq(0, &timer_irqaction);
-	if (ret)
-		printk("timer: could not request IRQ 0: %d\n", ret);
+	ret = avr32_hpt_start();
+	if (ret) {
+		pr_debug("timer: failed starting: %d\n", ret);
+		return;
+	}
 }
 
 static struct sysdev_class timer_class = {