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Subject[PATCH v6 0/4] Early boot time stamps for x86
v5 - v6
- Added a new patch:
time: sync read_boot_clock64() with persistent clock
Which fixes missing __init macro, and enabled time discrepancy
fix that was noted by Thomas Gleixner
- Split "x86/time: read_boot_clock64() implementation" into a
separate patch
v4 - v5 - Fix compiler warnings on systems with stable clocks.
v3 - v4
- Fixed tsc_early_fini() call to be in the 2nd patch as reported
by Dou Liyang
- Improved comment before __use_sched_clock_early to explain why
we need both booleans.
- Simplified valid_clock logic in read_boot_clock64().

v2 - v3
- Addressed comment from Thomas Gleixner
- Timestamps are available a little later in boot but still much
earlier than in mainline. This significantly simplified this
v1 - v2
In patch "x86/tsc: tsc early":
- added tsc_adjusted_early()
- fixed 32-bit compile error use do_div()

Adding early boot time stamps support for x86 machines.
SPARC patches for early boot time stamps are already integrated into
mainline linux.

Sample output


For more exaples how early time stamps are used, see this work:

As seen above, currently timestamps are available from around the time when
"Security Framework" is initialized. But, 26s already passed until we
reached to this point.
Pavel Tatashin (2):
sched/clock: interface to allow timestamps early in boot
x86/tsc: use tsc early

Pavel Tatashin (4):
sched/clock: interface to allow timestamps early in boot
time: sync read_boot_clock64() with persistent clock
x86/time: read_boot_clock64() implementation
x86/tsc: use tsc early

arch/arm/kernel/time.c | 2 +-
arch/s390/kernel/time.c | 2 +-
arch/x86/include/asm/tsc.h | 4 +++
arch/x86/kernel/setup.c | 10 +++++--
arch/x86/kernel/time.c | 31 ++++++++++++++++++++++
arch/x86/kernel/tsc.c | 47 +++++++++++++++++++++++++++++++++
include/linux/sched/clock.h | 4 +++
include/linux/timekeeping.h | 10 +++----
kernel/sched/clock.c | 63 ++++++++++++++++++++++++++++++++++++++++++++-
kernel/time/timekeeping.c | 8 ++++--
10 files changed, 169 insertions(+), 12 deletions(-)


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