[U-Boot] [PATCH] IXP425: Fixing timer code Part 1/1

[Stefan Althoefer]

This fixes bugs in non-interupt timer code for IXP425

Fixed udelay() implementation to be more accurate.
The timing error of udelay() was caused by
too much looping overhead. The actual timing routine
was called repeatedly for each microsecond. When
bigger slices are used, it becomes more accurate.
CONFIG_SYS_TIMER_CLK_FREQ can be set by config file
if clock speed differs from IXP425 default (66,666MHz).

Fixed get_timer() to return correct time in units
of CONFIG_SYS_HZ. The code now works for times
in execess of 64 seconds (the timer overflow
limit), assumed get_timer() is called with a period
< 64 seconds.

do_sleep() now works correctly.

Signed-off-by: Stefan Althoefer <stefan.althoefer at web.de>
---
 cpu/ixp/timer.c |   64 ++++++++++++++++++++++++++++++++++++++++++-------------
 1 files changed, 49 insertions(+), 15 deletions(-)

diff --git a/cpu/ixp/timer.c b/cpu/ixp/timer.c
index 09d8ad5..d30adbc 100644
--- a/cpu/ixp/timer.c
+++ b/cpu/ixp/timer.c
@@ -33,18 +33,28 @@
 #include <asm/arch/ixp425.h>

 #ifndef CONFIG_USE_IRQ
+
+#ifndef CONFIG_SYS_TIMER_CLK_FREQ
+#define CONFIG_SYS_TIMER_CLK_FREQ 66666666
+#endif
+
 ulong get_timer (ulong base)
 {
-       return get_timer_masked () - base;
+	return get_timer_masked () - base;
 }

-void ixp425_udelay(unsigned long usec)
+/* udelay uses timer 1 */
+
+void ixp425_udelay (unsigned long usec)
 {
 	/*
 	 * This function has a max usec, but since it is called from udelay
 	 * we should not have to worry... be happy
 	 */
-	unsigned long usecs = CONFIG_SYS_HZ/1000000L & ~IXP425_OST_RELOAD_MASK;
+	unsigned long usecs = CONFIG_SYS_TIMER_CLK_FREQ/1000000L
+		& ~IXP425_OST_RELOAD_MASK;
+
+	usecs *= usec;

 	*IXP425_OSST = IXP425_OSST_TIMER_1_PEND;
 	usecs |= IXP425_OST_ONE_SHOT | IXP425_OST_ENABLE;
@@ -54,30 +64,54 @@ void ixp425_udelay(unsigned long usec)

 void udelay (unsigned long usec)
 {
-	while (usec--) ixp425_udelay(1);
+	/* ipx425_udelay has big overhead, so call it in bigger slices */
+	while (usec>1000) {
+		ixp425_udelay (1000);
+		usec -= 1000;
+	}
+	/* and now the rest */
+	ixp425_udelay (usec);
 }

-static ulong reload_constant = 0xfffffff0;
+/* get_timer uses timer 2 */
+
+static ulong	reload_constant = 0xfffffff0;
+static int	timer_initialized = 0;
+static int	timer_accum;

 void reset_timer_masked (void)
 {
-	ulong reload = reload_constant | IXP425_OST_ONE_SHOT | IXP425_OST_ENABLE;
+	ulong reload = reload_constant | IXP425_OST_ENABLE;

-	*IXP425_OSST = IXP425_OSST_TIMER_1_PEND;
-	*IXP425_OSRT1 = reload;
+	*IXP425_OSST = IXP425_OSST_TIMER_2_PEND;
+	*IXP425_OSRT2 = reload;
 }

 ulong get_timer_masked (void)
 {
+	ulong current = *IXP425_OST2;
+	ulong this;
+
+	if (!timer_initialized) {
+		reset_timer_masked ();
+		timer_accum = 0;
+		timer_initialized = 1;
+	}
+
 	/*
-	 * Note that it is possible for this to wrap!
-	 * In this case we return max.
+	 * Timer will wrap after 64 seconds. This will
+	 * be detected if get_timer is called within
+	 * the next 64 seconds.
 	 */
-	ulong current = *IXP425_OST1;
-	if (*IXP425_OSST & IXP425_OSST_TIMER_1_PEND)
-	{
-		return reload_constant;
+	current = *IXP425_OST2;
+	if (*IXP425_OSST & IXP425_OSST_TIMER_2_PEND) {
+		*IXP425_OSST = IXP425_OSST_TIMER_2_PEND;
+		current = *IXP425_OST2;
+		timer_accum += reload_constant /
+			(CONFIG_SYS_TIMER_CLK_FREQ / CONFIG_SYS_HZ);
 	}
-	return (reload_constant - current);
+	this = (reload_constant - current) /
+		(CONFIG_SYS_TIMER_CLK_FREQ / CONFIG_SYS_HZ);
+	return (this + timer_accum);
 }
 #endif /* #ifndef CONFIG_USE_IRQ */
-- 
1.5.6