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Date: Tue, 4 Mar 2025 17:30:21 +0000
From: Simon Horman <horms@kernel.org>
To: Kurt Kanzenbach <kurt@linutronix.de>
Cc: Tony Nguyen <anthony.l.nguyen@intel.com>,
	Przemek Kitszel <przemyslaw.kitszel@intel.com>,
	Faizal Rahim <faizal.abdul.rahim@linux.intel.com>,
	Andrew Lunn <andrew+netdev@lunn.ch>,
	"David S. Miller" <davem@davemloft.net>,
	Eric Dumazet <edumazet@google.com>,
	Jakub Kicinski <kuba@kernel.org>, Paolo Abeni <pabeni@redhat.com>,
	Sebastian Andrzej Siewior <bigeasy@linutronix.de>,
	intel-wired-lan@lists.osuosl.org, netdev@vger.kernel.org
Subject: Re: [PATCH iwl-next v3] igc: Change Tx mode for MQPRIO offloading
Message-ID: <20250304173021.GH3666230@kernel.org>
References: <20250303-igc_mqprio_tx_mode-v3-1-0efce85e6ae0@linutronix.de>
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In-Reply-To: <20250303-igc_mqprio_tx_mode-v3-1-0efce85e6ae0@linutronix.de>

On Mon, Mar 03, 2025 at 10:16:33AM +0100, Kurt Kanzenbach wrote:
> The current MQPRIO offload implementation uses the legacy TSN Tx mode. In
> this mode the hardware uses four packet buffers and considers queue
> priorities.
> 
> In order to harmonize the TAPRIO implementation with MQPRIO, switch to the
> regular TSN Tx mode. This mode also uses four packet buffers and considers
> queue priorities. In addition to the legacy mode, transmission is always
> coupled to Qbv. The driver already has mechanisms to use a dummy schedule
> of 1 second with all gates open for ETF. Simply use this for MQPRIO too.
> 
> This reduces code and makes it easier to add support for frame preemption
> later.
> 
> While at it limit the netdev_tc calls to MQPRIO only.

Hi Kurt,

Can this part be broken out into a separate patch?
It seems so to me, but perhaps I'm missing something.

The reason that I ask is that this appears to be a good portion of the
change, and doing so would make the code changes for main part of the
patch, as per the description prior to the line above, clearer IMHO.

> 
> Tested on i225 with real time application using high priority queue, iperf3
> using low priority queue and network TAP device.
> 
> Signed-off-by: Kurt Kanzenbach <kurt@linutronix.de>

...