openwrt-xburst/target/linux/ifxmips/patches-2.6.30/010-mips_clocksource_init_war.patch

Index: linux-2.6.30.5/arch/mips/kernel/cevt-r4k.c
===================================================================
--- linux-2.6.30.5.orig/arch/mips/kernel/cevt-r4k.c	2009-08-16 23:19:38.000000000 +0200
+++ linux-2.6.30.5/arch/mips/kernel/cevt-r4k.c	2009-09-02 18:26:26.000000000 +0200
@@ -21,6 +21,22 @@
 
 #ifndef CONFIG_MIPS_MT_SMTC
 
+/*
+ * 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)
 {
@@ -30,6 +46,7 @@
 	cnt = read_c0_count();
 	cnt += delta;
 	write_c0_compare(cnt);
+	compare_change_hazard();
 	res = ((int)(read_c0_count() - cnt) > 0) ? -ETIME : 0;
 	return res;
 }