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Subject[PATCH 4.14 17/75] bnxt_en: Fix TX timeout when TX ring size is set to the smallest
Date
From: Michael Chan <michael.chan@broadcom.com>

[ Upstream commit 5bed8b0704c9ecccc8f4a2c377d7c8e21090a82e ]

The smallest TX ring size we support must fit a TX SKB with MAX_SKB_FRAGS
+ 1. Because the first TX BD for a packet is always a long TX BD, we
need an extra TX BD to fit this packet. Define BNXT_MIN_TX_DESC_CNT with
this value to make this more clear. The current code uses a minimum
that is off by 1. Fix it using this constant.

The tx_wake_thresh to determine when to wake up the TX queue is half the
ring size but we must have at least BNXT_MIN_TX_DESC_CNT for the next
packet which may have maximum fragments. So the comparison of the
available TX BDs with tx_wake_thresh should be >= instead of > in the
current code. Otherwise, at the smallest ring size, we will never wake
up the TX queue and will cause TX timeout.

Fixes: c0c050c58d84 ("bnxt_en: New Broadcom ethernet driver.")
Reviewed-by: Pavan Chebbi <pavan.chebbi@broadcom.com>
Signed-off-by: Michael Chan <michael.chan@broadocm.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
Signed-off-by: Sasha Levin <sashal@kernel.org>
---
drivers/net/ethernet/broadcom/bnxt/bnxt.c | 8 ++++----
drivers/net/ethernet/broadcom/bnxt/bnxt.h | 5 +++++
drivers/net/ethernet/broadcom/bnxt/bnxt_ethtool.c | 2 +-
3 files changed, 10 insertions(+), 5 deletions(-)

diff --git a/drivers/net/ethernet/broadcom/bnxt/bnxt.c b/drivers/net/ethernet/broadcom/bnxt/bnxt.c
index c4b0c35a270c..17592aeb2618 100644
--- a/drivers/net/ethernet/broadcom/bnxt/bnxt.c
+++ b/drivers/net/ethernet/broadcom/bnxt/bnxt.c
@@ -278,7 +278,7 @@ static bool bnxt_txr_netif_try_stop_queue(struct bnxt *bp,
* netif_tx_queue_stopped().
*/
smp_mb();
- if (bnxt_tx_avail(bp, txr) > bp->tx_wake_thresh) {
+ if (bnxt_tx_avail(bp, txr) >= bp->tx_wake_thresh) {
netif_tx_wake_queue(txq);
return false;
}
@@ -609,7 +609,7 @@ static void bnxt_tx_int(struct bnxt *bp, struct bnxt_napi *bnapi, int nr_pkts)
smp_mb();

if (unlikely(netif_tx_queue_stopped(txq)) &&
- bnxt_tx_avail(bp, txr) > bp->tx_wake_thresh &&
+ bnxt_tx_avail(bp, txr) >= bp->tx_wake_thresh &&
READ_ONCE(txr->dev_state) != BNXT_DEV_STATE_CLOSING)
netif_tx_wake_queue(txq);
}
@@ -1888,7 +1888,7 @@ static int bnxt_poll_work(struct bnxt *bp, struct bnxt_napi *bnapi, int budget)
if (TX_CMP_TYPE(txcmp) == CMP_TYPE_TX_L2_CMP) {
tx_pkts++;
/* return full budget so NAPI will complete. */
- if (unlikely(tx_pkts > bp->tx_wake_thresh)) {
+ if (unlikely(tx_pkts >= bp->tx_wake_thresh)) {
rx_pkts = budget;
raw_cons = NEXT_RAW_CMP(raw_cons);
break;
@@ -2662,7 +2662,7 @@ static int bnxt_init_tx_rings(struct bnxt *bp)
u16 i;

bp->tx_wake_thresh = max_t(int, bp->tx_ring_size / 2,
- MAX_SKB_FRAGS + 1);
+ BNXT_MIN_TX_DESC_CNT);

for (i = 0; i < bp->tx_nr_rings; i++) {
struct bnxt_tx_ring_info *txr = &bp->tx_ring[i];
diff --git a/drivers/net/ethernet/broadcom/bnxt/bnxt.h b/drivers/net/ethernet/broadcom/bnxt/bnxt.h
index 5aaf7f5a23dc..ad0a69a81f10 100644
--- a/drivers/net/ethernet/broadcom/bnxt/bnxt.h
+++ b/drivers/net/ethernet/broadcom/bnxt/bnxt.h
@@ -477,6 +477,11 @@ struct rx_tpa_end_cmp_ext {
#define BNXT_MAX_RX_JUM_DESC_CNT (RX_DESC_CNT * MAX_RX_AGG_PAGES - 1)
#define BNXT_MAX_TX_DESC_CNT (TX_DESC_CNT * MAX_TX_PAGES - 1)

+/* Minimum TX BDs for a TX packet with MAX_SKB_FRAGS + 1. We need one extra
+ * BD because the first TX BD is always a long BD.
+ */
+#define BNXT_MIN_TX_DESC_CNT (MAX_SKB_FRAGS + 2)
+
#define RX_RING(x) (((x) & ~(RX_DESC_CNT - 1)) >> (BNXT_PAGE_SHIFT - 4))
#define RX_IDX(x) ((x) & (RX_DESC_CNT - 1))

diff --git a/drivers/net/ethernet/broadcom/bnxt/bnxt_ethtool.c b/drivers/net/ethernet/broadcom/bnxt/bnxt_ethtool.c
index e8544e8637db..e3123cb0fb70 100644
--- a/drivers/net/ethernet/broadcom/bnxt/bnxt_ethtool.c
+++ b/drivers/net/ethernet/broadcom/bnxt/bnxt_ethtool.c
@@ -348,7 +348,7 @@ static int bnxt_set_ringparam(struct net_device *dev,

if ((ering->rx_pending > BNXT_MAX_RX_DESC_CNT) ||
(ering->tx_pending > BNXT_MAX_TX_DESC_CNT) ||
- (ering->tx_pending <= MAX_SKB_FRAGS))
+ (ering->tx_pending < BNXT_MIN_TX_DESC_CNT))
return -EINVAL;

if (netif_running(dev))
--
2.33.0


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