openwrt/target/linux/ar71xx/patches-2.6.26/902-mips_clocksource_init_war.patch

--- a/arch/mips/kernel/cevt-r4k.c
+++ b/arch/mips/kernel/cevt-r4k.c
@@ -13,6 +13,22 @@
 #include <asm/smtc_ipi.h>
 #include <asm/time.h>
 
+/*
+ * Compare interrupt can be routed and latched outside the core,
+ * so a single execution hazard barrier may not be enough to give
+ * it time to clear as seen in the Cause register.  4 time the
+ * pipeline depth seems reasonably conservative, and empirically
+ * works better in configurations with high CPU/bus clock ratios.
+ */
+
+#define compare_change_hazard() \
+	do { \
+		irq_disable_hazard(); \
+		irq_disable_hazard(); \
+		irq_disable_hazard(); \
+		irq_disable_hazard(); \
+	} while (0)
+
 static int mips_next_event(unsigned long delta,
                            struct clock_event_device *evt)
 {
@@ -28,6 +44,7 @@ static int mips_next_event(unsigned long
 	cnt = read_c0_count();
 	cnt += delta;
 	write_c0_compare(cnt);
+	compare_change_hazard();
 	res = ((int)(read_c0_count() - cnt) > 0) ? -ETIME : 0;
 #ifdef CONFIG_MIPS_MT_SMTC
 	evpe(vpflags);
@@ -187,7 +204,7 @@ static int c0_compare_int_usable(void)
 	 */
 	if (c0_compare_int_pending()) {
 		write_c0_compare(read_c0_count());
-		irq_disable_hazard();
+		compare_change_hazard();
 		if (c0_compare_int_pending())
 			return 0;
 	}
@@ -196,7 +213,7 @@ static int c0_compare_int_usable(void)
 		cnt = read_c0_count();
 		cnt += delta;
 		write_c0_compare(cnt);
-		irq_disable_hazard();
+		compare_change_hazard();
 		if ((int)(read_c0_count() - cnt) < 0)
 		    break;
 		/* increase delta if the timer was already expired */
@@ -205,11 +222,12 @@ static int c0_compare_int_usable(void)
 	while ((int)(read_c0_count() - cnt) <= 0)
 		;	/* Wait for expiry  */
 
+	compare_change_hazard();
 	if (!c0_compare_int_pending())
 		return 0;
 
 	write_c0_compare(read_c0_count());
-	irq_disable_hazard();
+	compare_change_hazard();
 	if (c0_compare_int_pending())
 		return 0;