[dpdk-dev] mlx5 & pdump: convert HW timestamps to nanoseconds

[Slava Ovsiienko]

> -----Original Message-----
> From: PATRICK KEROULAS <patrick.keroulas at radio-canada.ca>
> Sent: Friday, June 5, 2020 3:10
> To: Slava Ovsiienko <viacheslavo at mellanox.com>
> Cc: dev at dpdk.org; Vivien Didelot <vivien.didelot at gmail.com>; Shahaf
> Shuler <shahafs at mellanox.com>; Raslan Darawsheh
> <rasland at mellanox.com>; Matan Azrad <matan at mellanox.com>
> Subject: Re: [dpdk-dev] mlx5 & pdump: convert HW timestamps to
> nanoseconds
> 
> On Wed, Jun 3, 2020 at 3:48 AM Slava Ovsiienko
> <viacheslavo at mellanox.com> wrote:
> >
> > > From: PATRICK KEROULAS <patrick.keroulas at radio-canada.ca>
> > > * rdma-code, libibverbs-dev: 28.0
> > > * NIC Part Number:      MCX516A-CDA_Ax
> > > * ConnectX-5 Ex EN
> > > * FW: 16.25.1020
> >
> > It looks like outdated firmware, please:
> > - update the firmware - at least 16.27.2008 is GA. I would recommend
> > to install OFED - it updates the FW
> > - make sure the UCTX_EN option in FW configuration is set to "true"
> 
> Hello Slava,
> 
> I managed to query device_frequency_khz by simply setting UCTX_EN=1,
> convert the mbuf->timestamp to nsec and write a pcap. However, the
> accuracy is quite disappointing, compared to libvma or even SW TS.
> 
> The freq value looks constant (=78125kHz). Correct me if I'm wrong, a ptp
> client is supposed to continuously adjust some kind of VCO on the NIC. And

AFAIK, it is not the case for ConnectX-5, no clock adjustment, just some free running counter.
ConnectX6DX  will provide an option of adjustable nanosecond UTC in timestamps.

> even setting a crazy value through /dev/ptp interface manually doesn't affect
> device_frequency_khz. Please could you clarify?
> 
> This leads me back to mlx5dv_clock_info->nsec. If this is a valid method, I
> think the only missing piece is to access it from the secondary process, which
> implies to share ibv_context.
> 
> Best Regards,
> 
> PK