netdev - Re: [PATCH iwl-next v4 0/9] igc: Add support for Frame Preemption feature in IGC

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Message-ID: <87cyfmnjdh.fsf@kurt.kurt.home>
Date: Thu, 13 Feb 2025 13:01:46 +0100
From: Kurt Kanzenbach <kurt@...utronix.de>
To: "Abdul Rahim, Faizal" <faizal.abdul.rahim@...ux.intel.com>, Vladimir
 Oltean <vladimir.oltean@....com>
Cc: Tony Nguyen <anthony.l.nguyen@...el.com>, Przemek Kitszel
 <przemyslaw.kitszel@...el.com>, Andrew Lunn <andrew+netdev@...n.ch>,
 "David S . Miller" <davem@...emloft.net>, Eric Dumazet
 <edumazet@...gle.com>, Jakub Kicinski <kuba@...nel.org>, Paolo Abeni
 <pabeni@...hat.com>, Maxime Coquelin <mcoquelin.stm32@...il.com>,
 Alexandre Torgue <alexandre.torgue@...s.st.com>, Simon Horman
 <horms@...nel.org>, Russell King <linux@...linux.org.uk>, Alexei
 Starovoitov <ast@...nel.org>, Daniel Borkmann <daniel@...earbox.net>,
 Jesper Dangaard Brouer <hawk@...nel.org>, John Fastabend
 <john.fastabend@...il.com>, Furong Xu <0x1207@...il.com>, Russell King
 <rmk+kernel@...linux.org.uk>, Serge Semin <fancer.lancer@...il.com>,
 Xiaolei Wang <xiaolei.wang@...driver.com>, Suraj Jaiswal
 <quic_jsuraj@...cinc.com>, Kory Maincent <kory.maincent@...tlin.com>, Gal
 Pressman <gal@...dia.com>, Jesper Nilsson <jesper.nilsson@...s.com>,
 Andrew Halaney <ahalaney@...hat.com>, Choong Yong Liang
 <yong.liang.choong@...ux.intel.com>, Kunihiko Hayashi
 <hayashi.kunihiko@...ionext.com>, Vinicius Costa Gomes
 <vinicius.gomes@...el.com>, intel-wired-lan@...ts.osuosl.org,
 netdev@...r.kernel.org, linux-kernel@...r.kernel.org,
 linux-stm32@...md-mailman.stormreply.com,
 linux-arm-kernel@...ts.infradead.org, bpf@...r.kernel.org
Subject: Re: [PATCH iwl-next v4 0/9] igc: Add support for Frame Preemption
 feature in IGC

On Thu Feb 13 2025, Abdul Rahim, Faizal wrote:
> On 13/2/2025 6:01 am, Vladimir Oltean wrote:
>> On Mon, Feb 10, 2025 at 02:01:58AM -0500, Faizal Rahim wrote:
>>> Introduces support for the FPE feature in the IGC driver.
>>>
>>> The patches aligns with the upstream FPE API:
>>> https://patchwork.kernel.org/project/netdevbpf/cover/20230220122343.1156614-1-vladimir.oltean@nxp.com/
>>> https://patchwork.kernel.org/project/netdevbpf/cover/20230119122705.73054-1-vladimir.oltean@nxp.com/
>>>
>>> It builds upon earlier work:
>>> https://patchwork.kernel.org/project/netdevbpf/cover/20220520011538.1098888-1-vinicius.gomes@intel.com/
>>>
>>> The patch series adds the following functionalities to the IGC driver:
>>> a) Configure FPE using `ethtool --set-mm`.
>>> b) Display FPE settings via `ethtool --show-mm`.
>>> c) View FPE statistics using `ethtool --include-statistics --show-mm'.
>>> e) Enable preemptible/express queue with `fp`:
>>>     tc qdisc add ... root taprio \
>>>     fp E E P P
>> 
>> Any reason why you are only enabling the preemptible traffic classes
>> with taprio, and not with mqprio as well? I see there will have to be
>> some work harmonizing igc's existing understanding of ring priorities
>> with what Kurt did in 9f3297511dae ("igc: Add MQPRIO offload support"),
>> and I was kind of expecting to see a proposal for that as part of this.
>>
>
> I was planning to enable fpe + mqprio separately since it requires extra 
> effort to explore mqprio with preemptible rings, ring priorities, and 
> testing to ensure it works properly and there are no regressions.

Well, my idea was to move the current mqprio offload implementation from
legacy TSN Tx mode to the normal TSN Tx mode. Then, taprio and mqprio
can share the same code (with or without fpe). I have a draft patch
ready for that. What do you think about it?

Thanks,
Kurt

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