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To:     linux-wireless@vger.kernel.org, linuxwifi@intel.com
From:   Wei Liu <wei.liu1011@gmail.com>
Subject: Precise time synchronization via wifi interface (intel AX201 iwlwifi
 driver)
Message-ID: <032f07e2-2771-619b-52b4-a25c8cd10f86@gmail.com>
Date:   Thu, 5 Mar 2020 10:07:29 +0100
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Hi,

I am trying to achieve precise time synchronization via wifi interface.

I used intel AX201 card, certified with TimeSync, 802.11v, mc. So I 
assume it has the capability to do hardware time stamp when running 
applications like linux ptp (http://linuxptp.sourceforge.net/) and gptp 
(https://github.com/Avnu/gptp). However I get error that seems to 
suggest the timestamp mode is not supported.

After reading some source code, I discover that the /ptp4l/ application, 
or /gptp/, or /ethtool/ /-T/ , they all use a system call /ioctl/, which 
uses ethtool_ops call back to determine whether the hardware can do 
software/hardware timestamp.

However when searching in the driver/net/wireless/iwlwifi directory, I 
don't see anywhere /ethtool_ops/ is being implemented in the driver. So 
this most likely is why all user space tools I tried seem to determine 
the card cannot do hardware and also software (driver level) transmit 
timestamp.

Can someone tell me how I could run ptp like application to fully make 
use of the Timesync feature of intel card?

Some more details below:

root@localhost:/debug/tracing# ethtool -i wlp2s0
driver: iwlwifi
version: 5.4.6-050406-generic
firmware-version: 48.4fa0041f.0
expansion-rom-version:
bus-info: 0000:02:00.0
supports-statistics: yes
supports-test: no
supports-eeprom-access: no
supports-register-dump: no
supports-priv-flags: no

root@localhost:/debug/tracing# ethtool -T wlp2s0
Time stamping parameters for wlp2s0:
Capabilities:
         software-receive      (SOF_TIMESTAMPING_RX_SOFTWARE)
         software-system-clock (SOF_TIMESTAMPING_SOFTWARE)
PTP Hardware Clock: none
Hardware Transmit Timestamp Modes: none
Hardware Receive Filter Modes: none