From: Andi Kleen <ak@muc.de>
[Relative to the previous patch to use TSC on SMP EM64T machines]
Add an notsc option so that it can be turned off again.
This may be useful on the Summit, but will only work when there is a HPET
fallback.
Signed-off-by: Andi Kleen <ak@suse.de>
Signed-off-by: Andrew Morton <akpm@osdl.org>
---
25-akpm/arch/x86_64/kernel/time.c | 22 ++++++++++++++++++----
1 files changed, 18 insertions(+), 4 deletions(-)
diff -puN arch/x86_64/kernel/time.c~add-notsc-option-to-x86-64 arch/x86_64/kernel/time.c
--- 25/arch/x86_64/kernel/time.c~add-notsc-option-to-x86-64 Tue Oct 5 14:36:59 2004
+++ 25-akpm/arch/x86_64/kernel/time.c Tue Oct 5 14:36:59 2004
@@ -53,10 +53,10 @@ spinlock_t rtc_lock = SPIN_LOCK_UNLOCKED
spinlock_t i8253_lock = SPIN_LOCK_UNLOCKED;
static int nohpet __initdata = 0;
+static int notsc __initdata = 0;
#undef HPET_HACK_ENABLE_DANGEROUS
-
unsigned int cpu_khz; /* TSC clocks / usec, not used here */
unsigned long hpet_period; /* fsecs / HPET clock */
unsigned long hpet_tick; /* HPET clocks / interrupt */
@@ -913,10 +913,13 @@ void __init time_init_smp(void)
* Exceptions:
* IBM Summit. Will need to be special cased later.
* AMD dual core may also not need HPET. Check me.
+ *
+ * Can be turned off with "notsc".
*/
- if (vxtime.hpet_address &&
- num_online_cpus() > 1 &&
- boot_cpu_data.x86_vendor == X86_VENDOR_AMD) {
+ if (num_online_cpus() > 1 &&
+ boot_cpu_data.x86_vendor == X86_VENDOR_AMD)
+ notsc = 1;
+ if (vxtime.hpet_address && notsc) {
timetype = "HPET";
vxtime.last = hpet_readl(HPET_T0_CMP) - hpet_tick;
vxtime.mode = VXTIME_HPET;
@@ -1212,3 +1215,14 @@ static int __init nohpet_setup(char *s)
}
__setup("nohpet", nohpet_setup);
+
+
+static int __init notsc_setup(char *s)
+{
+ notsc = 1;
+ return 0;
+}
+
+__setup("notsc", notsc_setup);
+
+
_