[PATCH 5.13 053/127] bnxt: make sure xmit_more + errors does not miss doorbells

Sasha Levin
2021-08-24T16:59:40Z

From: Jakub Kicinski <kuba@kernel.org>

[ Upstream commit e8d8c5d80f5e9d4586c68061b62c642752289095 ]

skbs are freed on error and not put on the ring. We may, however,
be in a situation where we're freeing the last skb of a batch,
and there is a doorbell ring pending because of xmit_more() being
true earlier. Make sure we ring the door bell in such situations.

Since errors are rare don't pay attention to xmit_more() and just
always flush the pending frames.

The busy case should be safe to be left alone because it can
only happen if start_xmit races with completions and they
both enable the queue. In that case the kick can't be pending.

Noticed while reading the code.

Fixes: 4d172f21cefe ("bnxt_en: Implement xmit_more.")
Reviewed-by: Michael Chan <michael.chan@broadcom.com>
Reviewed-by: Edwin Peer <edwin.peer@broadcom.com>
Signed-off-by: Jakub Kicinski <kuba@kernel.org>
Signed-off-by: Sasha Levin <sashal@kernel.org>
---
drivers/net/ethernet/broadcom/bnxt/bnxt.c | 39 +++++++++++++++--------
drivers/net/ethernet/broadcom/bnxt/bnxt.h | 1 +
2 files changed, 27 insertions(+), 13 deletions(-)

diff --git a/drivers/net/ethernet/broadcom/bnxt/bnxt.c b/drivers/net/ethernet/broadcom/bnxt/bnxt.c
index 17ee5c436069..ea67c8c07a8b 100644
--- a/drivers/net/ethernet/broadcom/bnxt/bnxt.c
+++ b/drivers/net/ethernet/broadcom/bnxt/bnxt.c
@@ -69,7 +69,8 @@
#include "bnxt_debugfs.h"

#define BNXT_TX_TIMEOUT (5 * HZ)
-#define BNXT_DEF_MSG_ENABLE (NETIF_MSG_DRV | NETIF_MSG_HW)
+#define BNXT_DEF_MSG_ENABLE (NETIF_MSG_DRV | NETIF_MSG_HW | \
+ NETIF_MSG_TX_ERR)

MODULE_LICENSE("GPL");
MODULE_DESCRIPTION("Broadcom BCM573xx network driver");
@@ -362,6 +363,13 @@ static u16 bnxt_xmit_get_cfa_action(struct sk_buff *skb)
return md_dst->u.port_info.port_id;
}

+static void bnxt_txr_db_kick(struct bnxt *bp, struct bnxt_tx_ring_info *txr,
+ u16 prod)
+{
+ bnxt_db_write(bp, &txr->tx_db, prod);
+ txr->kick_pending = 0;
+}
+
static bool bnxt_txr_netif_try_stop_queue(struct bnxt *bp,
struct bnxt_tx_ring_info *txr,
struct netdev_queue *txq)
@@ -410,6 +418,10 @@ static netdev_tx_t bnxt_start_xmit(struct sk_buff *skb, struct net_device *dev)

free_size = bnxt_tx_avail(bp, txr);
if (unlikely(free_size < skb_shinfo(skb)->nr_frags + 2)) {
+ /* We must have raced with NAPI cleanup */
+ if (net_ratelimit() && txr->kick_pending)
+ netif_warn(bp, tx_err, dev,
+ "bnxt: ring busy w/ flush pending!\n");
if (bnxt_txr_netif_try_stop_queue(bp, txr, txq))
return NETDEV_TX_BUSY;
}
@@ -518,21 +530,16 @@ static netdev_tx_t bnxt_start_xmit(struct sk_buff *skb, struct net_device *dev)
normal_tx:
if (length < BNXT_MIN_PKT_SIZE) {
pad = BNXT_MIN_PKT_SIZE - length;
- if (skb_pad(skb, pad)) {
+ if (skb_pad(skb, pad))
/* SKB already freed. */
- tx_buf->skb = NULL;
- return NETDEV_TX_OK;
- }
+ goto tx_kick_pending;
length = BNXT_MIN_PKT_SIZE;
}

mapping = dma_map_single(&pdev->dev, skb->data, len, DMA_TO_DEVICE);

- if (unlikely(dma_mapping_error(&pdev->dev, mapping))) {
- dev_kfree_skb_any(skb);
- tx_buf->skb = NULL;
- return NETDEV_TX_OK;
- }
+ if (unlikely(dma_mapping_error(&pdev->dev, mapping)))
+ goto tx_free;

dma_unmap_addr_set(tx_buf, mapping, mapping);
flags = (len << TX_BD_LEN_SHIFT) | TX_BD_TYPE_LONG_TX_BD |
@@ -617,13 +624,15 @@ normal_tx:
txr->tx_prod = prod;

if (!netdev_xmit_more() || netif_xmit_stopped(txq))
- bnxt_db_write(bp, &txr->tx_db, prod);
+ bnxt_txr_db_kick(bp, txr, prod);
+ else
+ txr->kick_pending = 1;

tx_done:

if (unlikely(bnxt_tx_avail(bp, txr) <= MAX_SKB_FRAGS + 1)) {
if (netdev_xmit_more() && !tx_buf->is_push)
- bnxt_db_write(bp, &txr->tx_db, prod);
+ bnxt_txr_db_kick(bp, txr, prod);

bnxt_txr_netif_try_stop_queue(bp, txr, txq);
}
@@ -635,7 +644,6 @@ tx_dma_error:
/* start back at beginning and unmap skb */
prod = txr->tx_prod;
tx_buf = &txr->tx_buf_ring[prod];
- tx_buf->skb = NULL;
dma_unmap_single(&pdev->dev, dma_unmap_addr(tx_buf, mapping),
skb_headlen(skb), PCI_DMA_TODEVICE);
prod = NEXT_TX(prod);
@@ -649,7 +657,12 @@ tx_dma_error:
PCI_DMA_TODEVICE);
}

+tx_free:
dev_kfree_skb_any(skb);
+tx_kick_pending:
+ if (txr->kick_pending)
+ bnxt_txr_db_kick(bp, txr, txr->tx_prod);
+ txr->tx_buf_ring[txr->tx_prod].skb = NULL;
return NETDEV_TX_OK;
}

diff --git a/drivers/net/ethernet/broadcom/bnxt/bnxt.h b/drivers/net/ethernet/broadcom/bnxt/bnxt.h
index 30e47ea343f9..e2f38aaa474b 100644
--- a/drivers/net/ethernet/broadcom/bnxt/bnxt.h
+++ b/drivers/net/ethernet/broadcom/bnxt/bnxt.h
@@ -783,6 +783,7 @@ struct bnxt_tx_ring_info {
u16 tx_prod;
u16 tx_cons;
u16 txq_index;
+ u8 kick_pending;
struct bnxt_db_info tx_db;

struct tx_bd *tx_desc_ring[MAX_TX_PAGES];
--
2.30.2