x86: merge sched_clock handling

Move the basic global variable definitions and sched_clock handling in the
common "tsc.c" file.

 - Unify notsc kernel command line handling for 32 bit and 64bit.
 - Functional changes for 64bit.
        - "tsc_disabled" is updated if "notsc" is passed at boottime.
        - Fallback to jiffies for sched_clock, incase notsc is passed on
	  commandline.

Signed-off-by: Alok N Kataria <akataria@vmware.com>
Signed-off-by: Dan Hecht <dhecht@vmware.com>
Cc: Dan Hecht <dhecht@vmware.com>
Signed-off-by: Ingo Molnar <mingo@elte.hu>

1 files changed, 86 insertions, 0 deletions

diff --git a/arch/x86/kernel/tsc.c b/arch/x86/kernel/tsc.c
new file mode 100644
index 000000000000..5d0be778fadd
--- /dev/null
+++ b/arch/x86/kernel/tsc.c
@@ -0,0 +1,86 @@
+#include <linux/sched.h>
+#include <linux/init.h>
+#include <linux/module.h>
+#include <linux/timer.h>
+
+unsigned int cpu_khz;           /* TSC clocks / usec, not used here */
+EXPORT_SYMBOL(cpu_khz);
+unsigned int tsc_khz;
+EXPORT_SYMBOL(tsc_khz);
+
+/*
+ * TSC can be unstable due to cpufreq or due to unsynced TSCs
+ */
+int tsc_unstable;
+
+/* native_sched_clock() is called before tsc_init(), so
+   we must start with the TSC soft disabled to prevent
+   erroneous rdtsc usage on !cpu_has_tsc processors */
+int tsc_disabled = -1;
+
+/*
+ * Scheduler clock - returns current time in nanosec units.
+ */
+u64 native_sched_clock(void)
+{
+        u64 this_offset;
+
+        /*
+         * Fall back to jiffies if there's no TSC available:
+         * ( But note that we still use it if the TSC is marked
+         *   unstable. We do this because unlike Time Of Day,
+         *   the scheduler clock tolerates small errors and it's
+         *   very important for it to be as fast as the platform
+         *   can achive it. )
+         */
+        if (unlikely(tsc_disabled)) {
+                /* No locking but a rare wrong value is not a big deal: */
+                return (jiffies_64 - INITIAL_JIFFIES) * (1000000000 / HZ);
+        }
+
+        /* read the Time Stamp Counter: */
+        rdtscll(this_offset);
+
+        /* return the value in ns */
+        return cycles_2_ns(this_offset);
+}
+
+/* We need to define a real function for sched_clock, to override the
+   weak default version */
+#ifdef CONFIG_PARAVIRT
+unsigned long long sched_clock(void)
+{
+        return paravirt_sched_clock();
+}
+#else
+unsigned long long
+sched_clock(void) __attribute__((alias("native_sched_clock")));
+#endif
+
+int check_tsc_unstable(void)
+{
+        return tsc_unstable;
+}
+EXPORT_SYMBOL_GPL(check_tsc_unstable);
+
+#ifdef CONFIG_X86_TSC
+int __init notsc_setup(char *str)
+{
+        printk(KERN_WARNING "notsc: Kernel compiled with CONFIG_X86_TSC, "
+                        "cannot disable TSC completely.\n");
+        tsc_disabled = 1;
+        return 1;
+}
+#else
+/*
+ * disable flag for tsc. Takes effect by clearing the TSC cpu flag
+ * in cpu/common.c
+ */
+int __init notsc_setup(char *str)
+{
+        setup_clear_cpu_cap(X86_FEATURE_TSC);
+        return 1;
+}
+#endif
+
+__setup("notsc", notsc_setup);