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Subject[tip:x86/timers] x86/tsc: Use TSC as sched clock early
Commit-ID:  4763f03d3d186ce8a1125844790152d76804ad60
Gitweb: https://git.kernel.org/tip/4763f03d3d186ce8a1125844790152d76804ad60
Author: Pavel Tatashin <pasha.tatashin@oracle.com>
AuthorDate: Thu, 19 Jul 2018 16:55:40 -0400
Committer: Thomas Gleixner <tglx@linutronix.de>
CommitDate: Fri, 20 Jul 2018 00:02:42 +0200

x86/tsc: Use TSC as sched clock early

All prerequesites for enabling TSC as sched clock early in the boot
process are available now:

- Early attempt of TSC calibration

- Early availablity of static branch patching

If TSC frequency can be established in the early calibration, enable the
static key which switches sched clock to use TSC.

[ tglx: Massaged changelog ]

Signed-off-by: Pavel Tatashin <pasha.tatashin@oracle.com>
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Cc: steven.sistare@oracle.com
Cc: daniel.m.jordan@oracle.com
Cc: linux@armlinux.org.uk
Cc: schwidefsky@de.ibm.com
Cc: heiko.carstens@de.ibm.com
Cc: john.stultz@linaro.org
Cc: sboyd@codeaurora.org
Cc: hpa@zytor.com
Cc: douly.fnst@cn.fujitsu.com
Cc: peterz@infradead.org
Cc: prarit@redhat.com
Cc: feng.tang@intel.com
Cc: pmladek@suse.com
Cc: gnomes@lxorguk.ukuu.org.uk
Cc: linux-s390@vger.kernel.org
Cc: boris.ostrovsky@oracle.com
Cc: jgross@suse.com
Cc: pbonzini@redhat.com
Link: https://lkml.kernel.org/r/20180719205545.16512-22-pasha.tatashin@oracle.com

---
arch/x86/kernel/tsc.c | 1 +
1 file changed, 1 insertion(+)

diff --git a/arch/x86/kernel/tsc.c b/arch/x86/kernel/tsc.c
index 7ea0718a4c75..9277ae9b68b3 100644
--- a/arch/x86/kernel/tsc.c
+++ b/arch/x86/kernel/tsc.c
@@ -1408,6 +1408,7 @@ void __init tsc_early_init(void)
/* Sanitize TSC ADJUST before cyc2ns gets initialized */
tsc_store_and_check_tsc_adjust(true);
cyc2ns_init_boot_cpu();
+ static_branch_enable(&__use_tsc);
}

void __init tsc_init(void)
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