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

From: Jakub Kicinski <[email-masked]>
Date: Tue, 7 Oct 2025 16:26:45 -0700

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 <[email-masked]>
Fixes: 168deb7b31b2 ("eth: fbnic: Add support for XDP_TX action")
Signed-off-by: Jakub Kicinski <[email-masked]>
---
CC: [email-masked]
CC: [email-masked]
CC: [email-masked]
---
 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,
-- 
2.51.0