netdev - Re: [PATCH net-next] bonding: add software timestamping support

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Date:   Wed, 29 Mar 2023 21:39:13 -0700
From:   Jay Vosburgh <jay.vosburgh@...onical.com>
To:     Hangbin Liu <liuhangbin@...il.com>
cc:     netdev@...r.kernel.org, "David S . Miller" <davem@...emloft.net>,
        Jakub Kicinski <kuba@...nel.org>,
        Jonathan Toppins <jtoppins@...hat.com>,
        Paolo Abeni <pabeni@...hat.com>,
        Eric Dumazet <edumazet@...gle.com>,
        Miroslav Lichvar <mlichvar@...hat.com>,
        Richard Cochran <richardcochran@...il.com>
Subject: Re: [PATCH net-next] bonding: add software timestamping support

Hangbin Liu <liuhangbin@...il.com> wrote:

>On Tue, Mar 28, 2023 at 08:36:58PM -0700, Jay Vosburgh wrote:
>> Hangbin Liu <liuhangbin@...il.com> wrote:
>> 
>> >At present, bonding attempts to obtain the timestamp (ts) information of
>> >the active slave. However, this feature is only available for mode 1, 5,
>> >and 6. For other modes, bonding doesn't even provide support for software
>> >timestamping. To address this issue, let's call ethtool_op_get_ts_info
>> >when there is no primary active slave. This will enable the use of software
>> >timestamping for the bonding interface.
>> 
>> 	If I'm reading the patch below correctly, the actual functional
>> change here is to additionally set SOF_TIMESTAMPING_TX_SOFTWARE in
>> so_timestamping for the active-backup, balance-tlb and balance-alb modes
>
>No. In the description. I said for other modes, bonding doesn't even provide
>support for software timestamping. So this patch is to address this issue.
>i.e. add sw timestaming for all bonding modes.

	Ok, I think I follow now.  It is still adding only TX software
timestamping, as (from your example below) RX was already available.

	So, I do think the patch description is imprecise in saying,
"For other modes, bonding doesn't even provide support for software
timestamping" as this really refers to specifically TX timestamping.

	-J

>For mode 1,5,6. We will try find the active slave and get it's ts info
>directly. If there is no ops->get_ts_info, just use sw timestamping.
>
>For other modes, use sw timestamping directly.
>
>This is because some users want to use PTP over bond with other modes. e.g. LACP.
>They are satisfied with just sw timestamping as it's difficult to support hw
>timestamping for LACP bonding.
>
>Before this patch, bond mode with 0, 2, 3, 4 only has software-receive.
>
># ethtool -T bond0
>Time stamping parameters for bond0:
>Capabilities:
>        software-receive
>        software-system-clock
>PTP Hardware Clock: none
>Hardware Transmit Timestamp Modes: none
>Hardware Receive Filter Modes: none
>
># ptp4l -m -S -i bond0
>ptp4l[66296.154]: interface 'bond0' does not support requested timestamping mode
>failed to create a clock
>
>After this patch:
>
># ethtool -T bond0
>Time stamping parameters for bond0:
>Capabilities:
>        software-transmit
>        software-receive
>        software-system-clock
>PTP Hardware Clock: none
>Hardware Transmit Timestamp Modes: none
>Hardware Receive Filter Modes: none
>
># ptp4l -m -S -i bond0
>ptp4l[66952.474]: port 1: INITIALIZING to LISTENING on INIT_COMPLETE
>ptp4l[66952.474]: port 0: INITIALIZING to LISTENING on INIT_COMPLETE
>ptp4l[66952.474]: port 0: INITIALIZING to LISTENING on INIT_COMPLETE
>ptp4l[66981.681]: port 1: LISTENING to MASTER on ANNOUNCE_RECEIPT_TIMEOUT_EXPIRES
>ptp4l[66981.681]: selected local clock 007c50.fffe.70cdb6 as best master
>ptp4l[66981.682]: port 1: assuming the grand master role
>
>Thanks
>Hangbin

---
	-Jay Vosburgh, jay.vosburgh@...onical.com