Merge branch 'for-upstream' of git://openrisc.net/jonas/linux

[pandora-kernel.git] / arch / x86 / vdso / vclock_gettime.c

diff --git a/arch/x86/vdso/vclock_gettime.c b/arch/x86/vdso/vclock_gettime.c
index a724905..6bc0e72 100644 (file)
--- a/arch/x86/vdso/vclock_gettime.c
+++ b/arch/x86/vdso/vclock_gettime.c
@@ -6,7 +6,6 @@
  *
  * The code should have no internal unresolved relocations.
  * Check with readelf after changing.
- * Also alternative() doesn't work.
  */
 
 /* Disable profiling for userspace code: */
@@ -17,6 +16,7 @@
 #include <linux/time.h>
 #include <linux/string.h>
 #include <asm/vsyscall.h>
+#include <asm/fixmap.h>
 #include <asm/vgtod.h>
 #include <asm/timex.h>
 #include <asm/hpet.h>
@@ -25,6 +25,43 @@
 
 #define gtod (&VVAR(vsyscall_gtod_data))
 
+notrace static cycle_t vread_tsc(void)
+{
+       cycle_t ret;
+       u64 last;
+
+       /*
+        * Empirically, a fence (of type that depends on the CPU)
+        * before rdtsc is enough to ensure that rdtsc is ordered
+        * with respect to loads.  The various CPU manuals are unclear
+        * as to whether rdtsc can be reordered with later loads,
+        * but no one has ever seen it happen.
+        */
+       rdtsc_barrier();
+       ret = (cycle_t)vget_cycles();
+
+       last = VVAR(vsyscall_gtod_data).clock.cycle_last;
+
+       if (likely(ret >= last))
+               return ret;
+
+       /*
+        * GCC likes to generate cmov here, but this branch is extremely
+        * predictable (it's just a funciton of time and the likely is
+        * very likely) and there's a data dependence, so force GCC
+        * to generate a branch instead.  I don't barrier() because
+        * we don't actually need a barrier, and if this function
+        * ever gets inlined it will generate worse code.
+        */
+       asm volatile ("");
+       return last;
+}
+
+static notrace cycle_t vread_hpet(void)
+{
+       return readl((const void __iomem *)fix_to_virt(VSYSCALL_HPET) + 0xf0);
+}
+
 notrace static long vdso_fallback_gettime(long clock, struct timespec *ts)
 {
        long ret;
@@ -36,9 +73,12 @@ notrace static long vdso_fallback_gettime(long clock, struct timespec *ts)
 notrace static inline long vgetns(void)
 {
        long v;
-       cycles_t (*vread)(void);
-       vread = gtod->clock.vread;
-       v = (vread() - gtod->clock.cycle_last) & gtod->clock.mask;
+       cycles_t cycles;
+       if (gtod->clock.vclock_mode == VCLOCK_TSC)
+               cycles = vread_tsc();
+       else
+               cycles = vread_hpet();
+       v = (cycles - gtod->clock.cycle_last) & gtod->clock.mask;
        return (v * gtod->clock.mult) >> gtod->clock.shift;
 }
 
@@ -116,21 +156,21 @@ notrace static noinline int do_monotonic_coarse(struct timespec *ts)
 
 notrace int __vdso_clock_gettime(clockid_t clock, struct timespec *ts)
 {
-       if (likely(gtod->sysctl_enabled))
-               switch (clock) {
-               case CLOCK_REALTIME:
-                       if (likely(gtod->clock.vread))
-                               return do_realtime(ts);
-                       break;
-               case CLOCK_MONOTONIC:
-                       if (likely(gtod->clock.vread))
-                               return do_monotonic(ts);
-                       break;
-               case CLOCK_REALTIME_COARSE:
-                       return do_realtime_coarse(ts);
-               case CLOCK_MONOTONIC_COARSE:
-                       return do_monotonic_coarse(ts);
-               }
+       switch (clock) {
+       case CLOCK_REALTIME:
+               if (likely(gtod->clock.vclock_mode != VCLOCK_NONE))
+                       return do_realtime(ts);
+               break;
+       case CLOCK_MONOTONIC:
+               if (likely(gtod->clock.vclock_mode != VCLOCK_NONE))
+                       return do_monotonic(ts);
+               break;
+       case CLOCK_REALTIME_COARSE:
+               return do_realtime_coarse(ts);
+       case CLOCK_MONOTONIC_COARSE:
+               return do_monotonic_coarse(ts);
+       }
+
        return vdso_fallback_gettime(clock, ts);
 }
 int clock_gettime(clockid_t, struct timespec *)
@@ -139,7 +179,7 @@ int clock_gettime(clockid_t, struct timespec *)
 notrace int __vdso_gettimeofday(struct timeval *tv, struct timezone *tz)
 {
        long ret;
-       if (likely(gtod->sysctl_enabled && gtod->clock.vread)) {
+       if (likely(gtod->clock.vclock_mode != VCLOCK_NONE)) {
                if (likely(tv != NULL)) {
                        BUILD_BUG_ON(offsetof(struct timeval, tv_usec) !=
                                     offsetof(struct timespec, tv_nsec) ||
@@ -161,27 +201,14 @@ notrace int __vdso_gettimeofday(struct timeval *tv, struct timezone *tz)
 int gettimeofday(struct timeval *, struct timezone *)
        __attribute__((weak, alias("__vdso_gettimeofday")));
 
-/* This will break when the xtime seconds get inaccurate, but that is
- * unlikely */
-
-static __always_inline long time_syscall(long *t)
-{
-       long secs;
-       asm volatile("syscall"
-                    : "=a" (secs)
-                    : "0" (__NR_time), "D" (t) : "cc", "r11", "cx", "memory");
-       return secs;
-}
-
+/*
+ * This will break when the xtime seconds get inaccurate, but that is
+ * unlikely
+ */
 notrace time_t __vdso_time(time_t *t)
 {
-       time_t result;
-
-       if (unlikely(!VVAR(vsyscall_gtod_data).sysctl_enabled))
-               return time_syscall(t);
-
        /* This is atomic on x86_64 so we don't need any locks. */
-       result = ACCESS_ONCE(VVAR(vsyscall_gtod_data).wall_time_sec);
+       time_t result = ACCESS_ONCE(VVAR(vsyscall_gtod_data).wall_time_sec);
 
        if (t)
                *t = result;