x86: distangle user disabled TSC from unstable

upstream commit: 9ccc906c97e34fd91dc6aaf5b69b52d824386910

tsc_enabled is set to 0 from the command line switch "notsc" and from
the mark_tsc_unstable code. Seperate those functionalities and replace
tsc_enable with tsc_disable. This makes also the native_sched_clock()
decision when to use TSC understandable.

Preparatory patch to solve the sched_clock() issue on 32 bit.

Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Signed-off-by: Chris Wright <chrisw@sous-sol.org>

diff --git a/arch/x86/kernel/tsc_32.c b/arch/x86/kernel/tsc_32.c
index 68657d8526fb89b43d6e55eb3e316b6625549dc3..021723ccd50750d8788bb085e683fdc472394679 100644 (file)
--- a/arch/x86/kernel/tsc_32.c
+++ b/arch/x86/kernel/tsc_32.c
@@ -14,7 +14,7 @@
 
 #include "mach_timer.h"
 
-static int tsc_enabled;
+static int tsc_disabled;
 
 /*
  * On some systems the TSC frequency does not
@@ -28,8 +28,8 @@ EXPORT_SYMBOL_GPL(tsc_khz);
 static int __init tsc_setup(char *str)
 {
        printk(KERN_WARNING "notsc: Kernel compiled with CONFIG_X86_TSC, "
-                               "cannot disable TSC completely.\n");
-       mark_tsc_unstable("user disabled TSC");
+              "cannot disable TSC completely.\n");
+       tsc_disabled = 1;
        return 1;
 }
 #else
@@ -121,7 +121,7 @@ unsigned long long native_sched_clock(void)
         *   very important for it to be as fast as the platform
         *   can achive it. )
         */
-       if (unlikely(!tsc_enabled && !tsc_unstable))
+       if (unlikely(tsc_disabled))
                /* No locking but a rare wrong value is not a big deal: */
                return (jiffies_64 - INITIAL_JIFFIES) * (1000000000 / HZ);
 
@@ -310,7 +310,6 @@ void mark_tsc_unstable(char *reason)
 {
        if (!tsc_unstable) {
                tsc_unstable = 1;
-               tsc_enabled = 0;
                printk("Marking TSC unstable due to: %s.\n", reason);
                /* Can be called before registration */
                if (clocksource_tsc.mult)
@@ -324,7 +323,7 @@ EXPORT_SYMBOL_GPL(mark_tsc_unstable);
 static int __init dmi_mark_tsc_unstable(const struct dmi_system_id *d)
 {
        printk(KERN_NOTICE "%s detected: marking TSC unstable.\n",
-                      d->ident);
+              d->ident);
        tsc_unstable = 1;
        return 0;
 }
@@ -391,8 +390,11 @@ void __init tsc_init(void)
 {
        int cpu;
 
-       if (!cpu_has_tsc)
+       if (!cpu_has_tsc || tsc_disabled) {
+               /* Disable the TSC in case of !cpu_has_tsc */
+               tsc_disabled = 1;
                return;
+       }
 
        cpu_khz = calculate_cpu_khz();
        tsc_khz = cpu_khz;
@@ -429,8 +431,6 @@ void __init tsc_init(void)
        if (check_tsc_unstable()) {
                clocksource_tsc.rating = 0;
                clocksource_tsc.flags &= ~CLOCK_SOURCE_IS_CONTINUOUS;
-       } else
-               tsc_enabled = 1;
-
+       }
        clocksource_register(&clocksource_tsc);
 }