[IA64] ia64: simplify and fix udelay()

[safe/jmp/linux-2.6] / arch / ia64 / kernel / time.c

diff --git a/arch/ia64/kernel/time.c b/arch/ia64/kernel/time.c
index a094ec4..307d01e 100644 (file)
--- a/arch/ia64/kernel/time.c
+++ b/arch/ia64/kernel/time.c
@@ -250,32 +250,27 @@ time_init (void)
        set_normalized_timespec(&wall_to_monotonic, -xtime.tv_sec, -xtime.tv_nsec);
 }
 
-#define SMALLUSECS 100
-
-void
-udelay (unsigned long usecs)
+/*
+ * Generic udelay assumes that if preemption is allowed and the thread
+ * migrates to another CPU, that the ITC values are synchronized across
+ * all CPUs.
+ */
+static void
+ia64_itc_udelay (unsigned long usecs)
 {
-       unsigned long start;
-       unsigned long cycles;
-       unsigned long smallusecs;
+       unsigned long start = ia64_get_itc();
+       unsigned long end = start + usecs*local_cpu_data->cyc_per_usec;
 
-       /*
-        * Execute the non-preemptible delay loop (because the ITC might
-        * not be synchronized between CPUS) in relatively short time
-        * chunks, allowing preemption between the chunks.
-        */
-       while (usecs > 0) {
-               smallusecs = (usecs > SMALLUSECS) ? SMALLUSECS : usecs;
-               preempt_disable();
-               cycles = smallusecs*local_cpu_data->cyc_per_usec;
-               start = ia64_get_itc();
+       while (time_before(ia64_get_itc(), end))
+               cpu_relax();
+}
 
-               while (ia64_get_itc() - start < cycles)
-                       cpu_relax();
+void (*ia64_udelay)(unsigned long usecs) = &ia64_itc_udelay;
 
-               preempt_enable();
-               usecs -= smallusecs;
-       }
+void
+udelay (unsigned long usecs)
+{
+       (*ia64_udelay)(usecs);
 }
 EXPORT_SYMBOL(udelay);