From mboxrd@z Thu Jan 1 00:00:00 1970 From: "Christopher S. Hall" Subject: [PATCH v6 0/9] Patchset enabling hardware based cross-timestamps for next gen Intel platforms Date: Wed, 13 Jan 2016 04:12:20 -0800 Message-ID: <1452687149-11281-1-git-send-email-christopher.s.hall@intel.com> Mime-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit Cc: "Christopher S. Hall" , x86@kernel.org, linux-kernel@vger.kernel.org, intel-wired-lan@lists.osuosl.org, netdev@vger.kernel.org, kevin.b.stanton@intel.com To: tglx@linutronix.de, richardcochran@gmail.com, mingo@redhat.com, john.stultz@linaro.org, hpa@zytor.com, jeffrey.t.kirsher@intel.com Return-path: Sender: linux-kernel-owner@vger.kernel.org List-Id: netdev.vger.kernel.org Modern Intel hardware adds an Always Running Timer (ART) that allows the network and audio device clocks to precisely cross timestamp the device clock with the system clock. This allows a precise correlation of the device time and system time. This patchset adds interfaces to the timekeeping code allowing drivers to translate ART time to system time. Changelog: Changes from v5 to v6: * Pulled supporting code for snapshotting, correlated clocksource, and cycles to nanoseconds translation to separate patches. Added patches are marked as NEW below. There is, however, very little *actually* new code, just reorganized code * Renamed and moved clocksource change sequence to timekeeper struct (out of tk_read_base) * Renamed structs for system counter and synced device time callback to system_counterval_t and sync_device_time_cb, respectively * Changed PTP cross-timestamp callback name to getcrosststamp for consistency with the timekeeping code - corresponding function name changes in e1000e driver * Simplified PTP time calculations making use of ktime_to_* code Changes from v4 to v5: * Changes the history mechanism to interpolate system time using a single historic system time pair (monotonic raw, realtime) rather than implementing a precise history using shadow timekeeper (see v4 changes). The advantage of this approach is that the history can be arbitrarily long. This approach may also be simpler in terms of coding. The major disadvantage is that the realtime clock can be adjusted. When adjusted, the realtime clock time (when interpolating from history) is always approximate. In general, the longer the interpolation period the larger the potential error. There isn't any error interpolating the monotonic raw clock time. * This patchset also addresses objections to the previous patchsets overly complex correlated timestamp structure. This patchset splits that structure into several smaller structures. The correlated timestamp interface is renamed cross timestamp to avoid any confusion with the correlated clocksource. * The correlated clocksource is separated from the cross timestamp mechanism. * Add monotonic raw to the PTP user interface * Add e1000e driver configuration option that wraps Intel PCH specific code Changes v3 to v4: * Adds a history mechanism to accomodate slower devices. In this case the response time for timestamp reads to the Intel DSP are too slow to be accomodated by the original correlated time mechanism. The history mechanism turns shadow timekeeper into an array where the history is stored. Christopher S. Hall (9): Add cycles to nanoseconds translation (NEW) Add driver cross timestamp interface for higher precision time synchronization Add correlated clocksource relating aliased auxiliary and system clocks (NEW) Always Running Timer (ART) correlated clocksource Add timekeeping snapshot code capturing system time and counter (NEW) Add history to cross timestamp interface supporting slower devices Remove duplicated code in ktime_get_raw_and_real() Add PTP_SYS_OFFSET_PRECISE for driver crosstimestamping Adds hardware supported cross timestamp Documentation/ptp/testptp.c | 6 +- arch/x86/include/asm/cpufeature.h | 2 +- arch/x86/include/asm/tsc.h | 2 + arch/x86/kernel/tsc.c | 46 ++++++ drivers/net/ethernet/intel/Kconfig | 9 + 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 | 27 +++ include/linux/clocksource.h | 43 +++++ include/linux/pps_kernel.h | 17 +- include/linux/ptp_clock_kernel.h | 8 + include/linux/timekeeper_internal.h | 2 + include/linux/timekeeping.h | 42 +++++ include/uapi/linux/ptp_clock.h | 13 +- kernel/time/timekeeping.c | 247 +++++++++++++++++++++++++--- 16 files changed, 521 insertions(+), 40 deletions(-) -- 2.1.4