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

[Jakub Kicinski <kuba@kernel.org>]

On Wed, 19 Aug 2026 09:35:40 +0200 Kurt Kanzenbach wrote:
> >> I want to use ETF Qdisc with hardware offload, which is currently not
> >> possible on the stm32mp2.  
> >
> > Do you need multiple queues for ETF/normal traffic?
> > Or one ETF and one "normal"?
> >
> > How do you sort the traffic between the queues?  
> 
> So the stm32mp2 has two CPU cores. I've isolated CPU1 for Profinet. That
> one uses Tx/Rx queue 1 with ETF to reduce the Tx jitter. Everything else
> is routed to Tx/Rx queue 0.
> 
> Config looks like this:
> 
> #
> # Tx Assignment with SP.
> #
> # Tx Q 0 - Everything else
> # Tx Q 1 - RTC
> #
> tc qdisc replace dev ${INTERFACE} handle 100 parent root mqprio num_tc 2 \
>   map 0 0 0 0 0 0 0 1 0 0 0 0 0 0 0 0 \
>   queues 1@0 1@1 \
>   hw 1
> 
> #
> # Enable Tx launch time support for TC 1.
> #
> tc qdisc replace dev ${INTERFACE} parent 100:2 etf \
>   clockid CLOCK_TAI \
>   delta 500000 \
>   offload
> 
> On Rx incoming frames are steered via PCP field (vlan tagged).

Thanks for explaining!

> >> 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.  
> >
> > release/open is not ideal but still better than hardcoding?  
> 
> For sure it's better than hardcoding :). But, again the driver does it
> statically. Maybe there's a good reason for it. Maybe not. I'm not that
> familiar with the stmmac driver. I'll prototype something to see whether
> we can enable TBS at run time using the ETF Qdisc callback. It may take
> some time though.

I think the m in stmmac stand for 'mistake'. 
We need to start cleaning it up.