netdev - Re: [PATCH net v2 1/9] eth: fbnic: fix missing programming of the default descriptor

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Message-ID: <affd8ea3-58c8-463b-8cdb-a8f2b9c61d77@intel.com>
Date: Wed, 8 Oct 2025 16:28:15 -0700
From: Jacob Keller <jacob.e.keller@...el.com>
To: Jakub Kicinski <kuba@...nel.org>, <davem@...emloft.net>
CC: <netdev@...r.kernel.org>, <edumazet@...gle.com>, <pabeni@...hat.com>,
	<andrew+netdev@...n.ch>, <horms@...nel.org>, <bpf@...r.kernel.org>,
	<alexanderduyck@...com>, <mohsin.bashr@...il.com>
Subject: Re: [PATCH net v2 1/9] eth: fbnic: fix missing programming of the
 default descriptor



On 10/7/2025 4:26 PM, Jakub Kicinski wrote:
> XDP_TX typically uses no offloads. To optimize XDP we added a "default
> descriptor" feature to the chip, which allows us to send XDP frames with
> just the buffer descriptors (DMA address + length). All the metadata
> descriptors are derived from the queue config.
> 
> Commit under Fixes missed adding setting the defaults up when transplanting
> the code from the prototype driver. Importantly after reset the "request
> completion" bit is not set. Packets still get sent but there's no
> completion, so ring is not cleaned up. We can send one ring's worth
> of packets and then will start dropping all frames that got the XDP_TX
> action from the XDP prog.
> 
> Reviewed-by: Simon Horman <horms@...nel.org>
> Fixes: 168deb7b31b2 ("eth: fbnic: Add support for XDP_TX action")
> Signed-off-by: Jakub Kicinski <kuba@...nel.org>
> ---
> CC: alexanderduyck@...com
> CC: jacob.e.keller@...el.com
> CC: mohsin.bashr@...il.com
> ---

Reviewed-by: Jacob Keller <jacob.e.keller@...el.com>

>  drivers/net/ethernet/meta/fbnic/fbnic_mac.c | 8 ++++++++
>  1 file changed, 8 insertions(+)
> 
> diff --git a/drivers/net/ethernet/meta/fbnic/fbnic_mac.c b/drivers/net/ethernet/meta/fbnic/fbnic_mac.c
> index 8f998d26b9a3..2a84bd1d7e26 100644
> --- a/drivers/net/ethernet/meta/fbnic/fbnic_mac.c
> +++ b/drivers/net/ethernet/meta/fbnic/fbnic_mac.c
> @@ -83,8 +83,16 @@ static void fbnic_mac_init_axi(struct fbnic_dev *fbd)
>  
>  static void fbnic_mac_init_qm(struct fbnic_dev *fbd)
>  {
> +	u64 default_meta = FIELD_PREP(FBNIC_TWD_L2_HLEN_MASK, ETH_HLEN) |
> +			   FBNIC_TWD_FLAG_REQ_COMPLETION;
>  	u32 clock_freq;
>  
> +	/* Configure default TWQ Metadata descriptor */
> +	wr32(fbd, FBNIC_QM_TWQ_DEFAULT_META_L,
> +	     lower_32_bits(default_meta));
> +	wr32(fbd, FBNIC_QM_TWQ_DEFAULT_META_H,
> +	     upper_32_bits(default_meta));
> +
>  	/* Configure TSO behavior */
>  	wr32(fbd, FBNIC_QM_TQS_CTL0,
>  	     FIELD_PREP(FBNIC_QM_TQS_CTL0_LSO_TS_MASK,



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