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Subject[PATCH v4 0/2] reduce TSC deadline frequency errors
Date
The v3 series can be found at

http://lkml.kernel.org/g/20160713130344.8319-1-nicstange@gmail.com

Applicable to linux-next-20160708 (in case you wonder why I turned back
from the 20160712 given in v3 to 20160708 again: mysteriously, 20160712
doesn't boot neither w/ nor w/o this series anymore).

The individual patches don't depend on each other.

Changes to v3:
As Paolo Bonzini pointed out in reply to v3, for the values of 2, 4 and
8 of TSC_DIVISOR, the 64 bit division
(u32)(((u64)tsc_khz * 1000) / TSC_DIVISOR)
can be safely turned into a 32 bit division by changing associativity:
tsc_khz * (1000 / TSC_DIVISOR)

In doing so, it suggests itself to squash former [1/3] ("arch, x86, tsc
deadline clockevent dev: reduce frequency roundoff error") and
[2/3] ("arch, x86, tsc deadline clockevent dev: reduce TSC_DIVISOR to 2")
into a single patch. Furthermore, reducing TSC_DIVISOR down to 2 becomes
unnessecary -- setting it to 8 suffices already.

Thus,
- [1/2] ("arch, x86, tsc deadline clockevent dev: eliminate frequency
roundoff error")
Former [1/3] and [2/3] squashed together. Don't reduce TSC_DIVISOR
to 2 but to 8 only. Change associativity in order to get rid of the
64 bit division. Adapt the commit message accordingly.
- [2/2] ("arch, x86, tsc: inform TSC deadline clockevent device about
recalibration")
Former [3/3]. Likewise change associativity in order to get rid of
the 64 bit division here, too.

Changes to v2:
- [3/3] ("arch, x86, tsc: inform TSC deadline clockevent device about
recalibration")
Use clockevents_update_freq() rather than clockevents_config().

- Former [4/4] ("kernel/time/clockevents: compensate for monotonic
clock's dynamic frequency")
Split off, not a member of this series anymore.

Changes to v1:
- [1/3] ("arch, x86, tsc deadline clockevent dev: reduce frequency
roundoff error")
No changes to the patch. Note that the v1 mail could not be delivered
to the author of the TSC_DIVISOR introducing commit 279f1461432c
("x86: apic: Use tsc deadline for oneshot when available"),
Suresh Siddha <suresh.b.siddha@intel.com>, so I had to remove him
from the CC list.

- [2/3] ("arch, x86, tsc deadline clockevent dev: reduce TSC_DIVISOR
to 2")
Likewise.

- [3/3] ("arch, x86, tsc: inform TSC deadline clockevent device about
recalibration")
Silence the kbuild test robot on ARCH=i386 by wrapping the new call
to lapic_update_tsc_freq() from arch/x86/kernel/tsc.c in an
#ifdef CONFIG_X86_LOCAL_APIC.

Nicolai Stange (2):
arch, x86, tsc deadline clockevent dev: eliminate frequency roundoff
error
arch, x86, tsc: inform TSC deadline clockevent device about
recalibration

arch/x86/include/asm/apic.h | 1 +
arch/x86/kernel/apic/apic.c | 28 ++++++++++++++++++++++++++--
arch/x86/kernel/tsc.c | 6 ++++++
3 files changed, 33 insertions(+), 2 deletions(-)

--
2.9.0

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