Re: [PATCH net-next] net: stmmac: stm32: Set TSO/TBS Tx queues default settings

Kurt Kanzenbach <[email protected]> Tue, 18 Aug 2026 08:57:08 +0200

Newsgroups	gmane.linux.network,gmane.linux.ports.arm.kernel
Message-ID	<[email protected]>

On Mon Aug 17 2026, Jakub Kicinski wrote:
> On Wed, 12 Aug 2026 08:28:57 +0200 Kurt Kanzenbach wrote:
>> TSO and TBS cannot coexist. Use the first queue with TSO and the rest for
>> TBS. Tx queues with TBS can support etf qdisc hw offload. This is done
>> similar to dwmac-imx and dwmac-intel.
>
> Can you explain your use case?

I want to use ETF Qdisc with hardware offload, which is currently not
possible on the stm32mp2.

> And how many queues the device has in total?

The stm32mp2 has four Tx and two Rx queues.

>
> You say "TSO and TBS cannot coexist" but can any queue on your
> platform be configured to support either feature?

I think so. The data sheet says: "Do not enable time-based scheduling for
channels on which the TSO feature is enabled.". But, I didn't find any
limitations on what queue/channel can enable TBS.

> If yes why are we configuring this statically instead of making
> appropriate configuration based on qdisc or some other uAPI knob?

It seems like a static configuration in the driver today. I basically
followed the same convention as dwmac-imx, dwmac-intel, dwmac-mediatek
and dwmac-qcom-ethqos. Only dwmac-socfpga does it differently.

Tx Launch Time requires a different DMA descriptor layout. Currently
tc_setup_etf() just returns -EINVAL if the DMA configuration is not
setup appropriately. I guess a dynamic configuration requires to change
the DMA config and perform a full release/open cycle.

Thanks,
Kurt

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