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Date: Sun, 6 Mar 2022 09:56:52 +0100 From: Gerhard Engleder <gerhard@...leder-embedded.com> To: richardcochran@...il.com, yangbo.lu@....com, davem@...emloft.net, kuba@...nel.org Cc: mlichvar@...hat.com, vinicius.gomes@...el.com, netdev@...r.kernel.org, Gerhard Engleder <gerhard@...leder-embedded.com> Subject: [RFC PATCH net-next 0/6] ptp: Support hardware clocks with additional free running time ptp vclocks require a clock with free running time for the timecounter. Currently only a physical clock forced to free running is supported. If vclocks are used, then the physical clock cannot be synchronized anymore. The synchronized time is not available in hardware in this case. As a result, timed transmission with ETF/TAPRIO hardware support is not possible anymore. If hardware would support a free running time additionally to the physical clock, then the physical clock does not need to be forced to free running. Thus, the physical clocks can still be synchronized while vclocks are in use. The physical clock could be used to synchronize the time domain of the TSN network and trigger ETF/TAPRIO. In parallel vclocks can be used to synchronize other time domains. One year ago I thought for two time domains within a TSN network also two physical clocks are required. This would lead to new kernel interfaces for asking for the second clock, ... . But actually for a time triggered system like TSN there can be only one time domain that controls the system itself. All other time domains belong to other layers, but not to the time triggered system itself. So other time domains can be based on a free running counter if similar mechanisms to 2 step synchronisation are used. Synchronisation was tested with two time domains between two directly connected hosts. Each host run two ptp4l instances, the first used the physical clock and the second used the virtual clock. I used my FPGA based network controller as network device. ptp4l was used in combination with the virtual clock support patch set from Miroslav Lichvar. Please give me some feedback. For me it seems like a straight forward extension for ptp vclocks, but I'm new to this topic. Gerhard Engleder (6): bpf: Access hwtstamp field of hwtstamps directly ptp: Initialize skb_shared_hwtstamps ptp: Add free running time support ptp: Support time stamps based on free running time ptp: Allow vclocks without free running physical clock tsnep: Add free running time support .../net/ethernet/cavium/liquidio/lio_main.c | 1 + .../ethernet/cavium/liquidio/lio_vf_main.c | 1 + .../net/ethernet/chelsio/cxgb4/cxgb4_ptp.c | 1 + drivers/net/ethernet/engleder/tsnep_hw.h | 9 ++++-- drivers/net/ethernet/engleder/tsnep_main.c | 6 ++++ drivers/net/ethernet/engleder/tsnep_ptp.c | 28 +++++++++++++++++++ .../hisilicon/hns3/hns3pf/hclge_ptp.c | 1 + .../ethernet/mellanox/mlxsw/spectrum_ptp.c | 1 + drivers/net/ethernet/sfc/tx_common.c | 1 + drivers/ptp/ptp_clock.c | 8 +++--- drivers/ptp/ptp_ines.c | 1 + drivers/ptp/ptp_private.h | 9 ++++++ drivers/ptp/ptp_sysfs.c | 11 ++++---- drivers/ptp/ptp_vclock.c | 25 +++++++++++++---- include/linux/ptp_clock_kernel.h | 27 ++++++++++++++++++ include/linux/skbuff.h | 3 ++ net/core/filter.c | 3 +- 17 files changed, 117 insertions(+), 19 deletions(-) -- 2.20.1
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