netdev - Re: [PATCH v1 0/4] Add support for DMA timestamp for non-PTP packets

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Date:   Tue, 27 Sep 2022 17:27:27 +0200
From:   Andrew Lunn <andrew@...n.ch>
To:     Muhammad Husaini Zulkifli <muhammad.husaini.zulkifli@...el.com>
Cc:     intel-wired-lan@...osl.org, netdev@...r.kernel.org,
        davem@...emloft.net, kuba@...nel.org, edumazet@...gle.com,
        vinicius.gomes@...el.com, aravindhan.gunasekaran@...el.com,
        noor.azura.ahmad.tarmizi@...el.com
Subject: Re: [PATCH v1 0/4] Add support for DMA timestamp for non-PTP packets

On Tue, Sep 27, 2022 at 09:06:52PM +0800, Muhammad Husaini Zulkifli wrote:
> The HW TX timestamps created by the NIC via socket options can be
> requested using the current network timestamps generation capability of
> SOF_TIMESTAMPING_TX_HARDWARE. The most common users of this socket flag
> is PTP, however other packet applications that require tx timestamps might
> also ask for it.
> 
> The problem is that, when there is a lot of traffic, there is a high chance
> that the timestamps for a PTP packet will be lost if both PTP and Non-PTP
> packets use the same SOF TIMESTAMPING TX HARDWARE causing the tx timeout.
> 
> DMA timestamps through socket options are not currently available to
> the user. Because if the user wants to, they can configure the hwtstamp
> config option to use the new introduced DMA Time Stamp flag through the
> setsockopt().
> 
> With these additional socket options, users can continue to utilise
> HW timestamps for PTP while specifying non-PTP packets to use DMA
> timestamps if the NIC can support them.

Although this is not actually for PTP, you probably should Cc: the PTP
maintainer for patches like this.

	   Andrew