Comme=
nt # 19
on bug 10778=
4
from Sylvain BERTRAND
Breaking commit is a merge commit from upstream mainline:
--------
commit 13e091b6dd0e78a518a7d8756607d3acb8215768
Merge: eac341194426 1088c6eef261
Author: Linus Torvalds <torvalds@linux-foundation.org>
Date: Mon Aug 13 18:28:19 2018 -0700
Merge branch 'x86-timers-for-linus' of
git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip
Pull x86 timer updates from Thomas Gleixner:
"Early TSC based time stamping to allow better boot time analysis.
This comes with a general cleanup of the TSC calibration code which
grew warts and duct taping over the years and removes 250 lines of
code. Initiated and mostly implemented by Pavel with help from various
folks"
* 'x86-timers-for-linus' of
git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip: (37 commits)
x86/kvmclock: Mark kvm_get_preset_lpj() as __init
x86/tsc: Consolidate init code
sched/clock: Disable interrupts when calling generic_sched_clock_init=
()
timekeeping: Prevent false warning when persistent clock is not avail=
able
sched/clock: Close a hole in sched_clock_init()
x86/tsc: Make use of tsc_calibrate_cpu_early()
x86/tsc: Split native_calibrate_cpu() into early and late parts
sched/clock: Use static key for sched_clock_running
sched/clock: Enable sched clock early
sched/clock: Move sched clock initialization and merge with generic c=
lock
x86/tsc: Use TSC as sched clock early
x86/tsc: Initialize cyc2ns when tsc frequency is determined
x86/tsc: Calibrate tsc only once
ARM/time: Remove read_boot_clock64()
s390/time: Remove read_boot_clock64()
timekeeping: Default boot time offset to local_clock()
timekeeping: Replace read_boot_clock64() with
read_persistent_wall_and_boot_offset()
s390/time: Add read_persistent_wall_and_boot_offset()
x86/xen/time: Output xen sched_clock time from 0
x86/xen/time: Initialize pv xen time in init_hypervisor_platform()
...
--------
If I revert this merge commit on amd-staging-drm-next branch, my displayport
monitor works again.
In the 1088c6eef261 branch, the one merged in mainline, displayport program=
ming
stopped working on the following commit:
--------
commit e2a9ca29b5edc89da2fddeae30e1070b272395c5
Author: Pavel Tatashin <pasha.tatashin@oracle.com>
Date: Thu Jul 19 16:55:39 2018 -0400
x86/tsc: Initialize cyc2ns when tsc frequency is determined
cyc2ns converts tsc to nanoseconds, and it is handled in a per-cpu data
structure.
Currently, the setup code for c2ns data for every possible CPU goes thr=
ough
the same sequence of calculations as for the boot CPU, but is based on =
the
same tsc frequency as the boot CPU, and thus this is not necessary.
Initialize the boot cpu when tsc frequency is determined. Copy the
calculated data from the boot CPU to the other CPUs in tsc_init().
In addition do the following:
- Remove unnecessary zeroing of c2ns data by removing cyc2ns_data_init=
()
- Split set_cyc2ns_scale() into two functions, so set_cyc2ns_scale() c=
an
be
called when system is up, and wraps around __set_cyc2ns_scale() that=
can
be called directly when system is booting but avoids saving restoring
IRQs and going and waking up from idle.
----
I did not check if this issue was known from upstream yet.