6th generation Intel platforms will have an Always Running
Timer (ART) that always runs when the system is powered and
is available to both the CPU and various on-board devices.
Initially, those devices include audio and network. The
ART will give these devices the capability of precisely
cross timestamping their local device clock with the system
clock. The ART is precisely related to the TSC by a ratio
read from CPUID leaf 0x15.
A device (such as the network controller) produces cross timestamps in
terms of the ART and the local device clock. The ART value on its
own isn't useful.
The first two patches enable translation of ART to system time.
The first patch adds the correlated clocksource concept which is
an auxiliary clock directly relate-able to a clock registered as
a clocksource. The second patch adds the Intel specific ART
correlated clocksource.
The last two patches modify the PTP character driver to call a
cross timestamp function (getsynctime()) in the driver when
available and perform the cross timestamp in the e1000e driver.
The patches taken together enable sub-microsecond cross timestamps
between the system clock and network device clock
Changelog since v2:
Split out x86 architecture specific code from common timekeeping code
additions
Split ART initialization between early TSC initialization and TSC
frequency refinement. Now, cpu_has_art can be used in
driver initialization code
Added e1000e PTP init code that detects presence of ART/spt disabling
cross timestamp if they're not available
Added additional commenting in TSC/ART init code, minor renaming of
functions and variables for greater clarity
Fixed a few formatting problems in e1000e driver patch
Christopher Hall (2):
Add support for driver cross-timestamp to PTP_SYS_OFFSET ioctl
Enabling hardware supported PTP system/device crosstimestamping
Christopher S. Hall (2):
Add correlated clocksource deriving system time from an auxiliary
clocksource
Added ART correlated clocksource and ART CPU feature
Documentation/ptp/testptp.c | 6 +-
arch/x86/include/asm/cpufeature.h | 3 +-
arch/x86/include/asm/tsc.h | 2 +
arch/x86/kernel/tsc.c | 54 ++++++++++++++++++
drivers/net/ethernet/intel/e1000e/defines.h | 5 ++
drivers/net/ethernet/intel/e1000e/ptp.c | 88 +++++++++++++++++++++++++++++
drivers/net/ethernet/intel/e1000e/regs.h | 4 ++
drivers/ptp/ptp_chardev.c | 29 +++++++---
include/linux/clocksource.h | 33 +++++++++++
include/linux/ptp_clock_kernel.h | 7 +++
include/linux/timekeeping.h | 4 ++
include/uapi/linux/ptp_clock.h | 4 +-
kernel/time/timekeeping.c | 65 +++++++++++++++++++++
13 files changed, 292 insertions(+), 12 deletions(-)
--
2.1.4
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