Re: [PATCH net v2 2/6] net: stmmac: Enable double VLAN processing only when supported

[Maxime Chevallier <maxime.chevallier@bootlin.com>]

Hi,

On 8/21/26 19:09, Ovidiu Panait wrote:
> stmmac_vlan_update() turns on double/S-VLAN processing whenever an
> 802.1ad VLAN is registered, without checking whether the MAC actually
> supports double VLAN processing. That capability is reported in
> dma_cap.dvlan.
> 
> This was found while investigating a separate bug in the double VLAN RX
> stripping path. The outer 802.1ad tags were unexpectedly stripped by the
> MAC (because the ESVL bit was set).
> 
> Check dma_cap.dvlan before enabling EDVLP/ESVL/DOVLTC bits, so that double
> VLAN processing is enabled only on supported hardware. Also, advertise
> NETIF_F_HW_VLAN_STAG_RX and NETIF_F_HW_VLAN_STAG_FILTER only when
> dma_cap.dvlan is set.
> 
> Fixes: 3cd1cfcba26e ("net: stmmac: Implement VLAN Hash Filtering in XGMAC")
> Signed-off-by: Ovidiu Panait <ovidiu.panait.rb@renesas.com>

Reviewed-by: Maxime Chevallier <maxime.chevallier@bootlin.com>

Maxime

> ---
> v2 changes:
> - Advertised NETIF_F_HW_VLAN_STAG_RX and NETIF_F_HW_VLAN_STAG_FILTER only
>   when dma_cap.dvlan is set (reported by Sashiko).
> 
>  drivers/net/ethernet/stmicro/stmmac/stmmac_main.c | 11 +++++++++--
>  1 file changed, 9 insertions(+), 2 deletions(-)
> 
> diff --git a/drivers/net/ethernet/stmicro/stmmac/stmmac_main.c b/drivers/net/ethernet/stmicro/stmmac/stmmac_main.c
> index 16fe56a1f617..880cf3fab913 100644
> --- a/drivers/net/ethernet/stmicro/stmmac/stmmac_main.c
> +++ b/drivers/net/ethernet/stmicro/stmmac/stmmac_main.c
> @@ -6820,6 +6820,9 @@ static int stmmac_vlan_update(struct stmmac_priv *priv, bool is_double)
>  	if (!netif_running(priv->dev))
>  		return 0;
>  
> +	if (!priv->dma_cap.dvlan)
> +		is_double = false;
> +
>  	return stmmac_update_vlan_hash(priv, priv->hw, hash, is_double);
>  }
>  
> @@ -7954,14 +7957,18 @@ static int __stmmac_dvr_probe(struct device *device,
>  	ndev->watchdog_timeo = msecs_to_jiffies(watchdog);
>  #ifdef STMMAC_VLAN_TAG_USED
>  	/* Both mac100 and gmac support receive VLAN tag detection */
> -	ndev->features |= NETIF_F_HW_VLAN_CTAG_RX | NETIF_F_HW_VLAN_STAG_RX;
> +	ndev->features |= NETIF_F_HW_VLAN_CTAG_RX;
> +	if (priv->dma_cap.dvlan)
> +		ndev->features |= NETIF_F_HW_VLAN_STAG_RX;
> +
>  	if (dwmac_is_xmac(priv->plat->core_type)) {
>  		ndev->hw_features |= NETIF_F_HW_VLAN_CTAG_RX;
>  		priv->hw->hw_vlan_en = true;
>  	}
>  	if (priv->dma_cap.vlhash) {
>  		ndev->features |= NETIF_F_HW_VLAN_CTAG_FILTER;
> -		ndev->features |= NETIF_F_HW_VLAN_STAG_FILTER;
> +		if (priv->dma_cap.dvlan)
> +			ndev->features |= NETIF_F_HW_VLAN_STAG_FILTER;
>  	}
>  	if (priv->dma_cap.vlins)
>  		ndev->features |= NETIF_F_HW_VLAN_CTAG_TX;