Subject: Re: [PATCH net-next] net: stmmac: fix .ndo_fix_features()

From: Jakub Kicinski <[email-masked]>
Date: Tue, 24 Feb 2026 17:30:37 -0800

On Mon, 23 Feb 2026 11:24:51 +0000 Russell King (Oracle) wrote:
> netdev features documentation requires that .ndo_fix_features() is
> stateless: it shouldn't modify driver state. Yet, stmmac_fix_features()
> does exactly that, changing whether GSO frames are processed by the
> driver.
> 
> Move this code to stmmac_set_features() instead, which is the correct
> place for it. We don't need to check whether TSO is supported; this
> is already handled via the setup of netdev->hw_features, and we are
> guaranteed that if netdev->hw_features indicates that a feature is
> not supported, .ndo_set_features() won't be called with it set.

No lies detected, but is this enough? The whole TSO enablement 
looks quite wobbly (as you mentioned in another email IIRC). 

Only stmmac_hw_setup() actually calls stmmac_enable_tso(). 
And stmmac_set_features() does not call stmmac_hw_setup().

IDK what the cost of having TSO enabled is for this IP, it's 
entirely possible that there is no cost. So maybe we should set
the TSO feature in features but not in hw_features which will
make it "fixed" to be always enabled? And not bother with handling 
the changes?

> Signed-off-by: Russell King (Oracle) <[email-masked]>
> ---
>  drivers/net/ethernet/stmicro/stmmac/stmmac_main.c | 10 ++--------
>  1 file changed, 2 insertions(+), 8 deletions(-)
> 
> diff --git a/drivers/net/ethernet/stmicro/stmmac/stmmac_main.c b/drivers/net/ethernet/stmicro/stmmac/stmmac_main.c
> index 82375d34ad57..a2a0985e8c37 100644
> --- a/drivers/net/ethernet/stmicro/stmmac/stmmac_main.c
> +++ b/drivers/net/ethernet/stmicro/stmmac/stmmac_main.c
> @@ -6105,14 +6105,6 @@ static netdev_features_t stmmac_fix_features(struct net_device *dev,
>  	if (priv->plat->bugged_jumbo && (dev->mtu > ETH_DATA_LEN))
>  		features &= ~NETIF_F_CSUM_MASK;
>  
> -	/* Disable tso if asked by ethtool */
> -	if ((priv->plat->flags & STMMAC_FLAG_TSO_EN) && (priv->dma_cap.tsoen)) {
> -		if (features & NETIF_F_TSO)
> -			priv->tso = true;
> -		else
> -			priv->tso = false;
> -	}
> -
>  	return features;
>  }
>  
> @@ -6144,6 +6136,8 @@ static int stmmac_set_features(struct net_device *netdev,
>  	else
>  		priv->hw->hw_vlan_en = false;
>  
> +	priv->tso = !!(features & NETIF_F_TSO);

extra nit, I think you're inserting this in the middle of a section of
code handling vlan config.

>  	phylink_rx_clk_stop_block(priv->phylink);
>  	stmmac_set_hw_vlan_mode(priv, priv->hw);
>  	phylink_rx_clk_stop_unblock(priv->phylink);
-- 
pw-bot: cr