bnxt_en: Fix TX timeout when TX ring size is set to the smallest

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: 93658deae41f ("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>

diff --git a/drivers/net/ethernet/broadcom/bnxt/bnxt.c b/drivers/net/ethernet/broadcom/bnxt/bnxt.c
index 037767b370d54fbfce7b0c322a6b8badde56aebe..62f84cc91e4d10b504b439f93c11c453930077d7 100644 (file)
--- a/drivers/net/ethernet/broadcom/bnxt/bnxt.c
+++ b/drivers/net/ethernet/broadcom/bnxt/bnxt.c
@@ -391,7 +391,7 @@ 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;
        }
@@ -764,7 +764,7 @@ next_tx_int:
        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);
 }
@@ -2416,7 +2416,7 @@ static int __bnxt_poll_work(struct bnxt *bp, struct bnxt_cp_ring_info *cpr,
                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);
                                if (budget)
@@ -3640,7 +3640,7 @@ 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 ec046e7a2484d28b83c24306f5323de9fab694c1..19fe6478e9b4bc40f7e391cb318efe04c8140d46 100644 (file)
--- a/drivers/net/ethernet/broadcom/bnxt/bnxt.h
+++ b/drivers/net/ethernet/broadcom/bnxt/bnxt.h
@@ -629,6 +629,11 @@ struct nqe_cn {
 #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 b056e3c29bbda42d9695ac404fae306faae0a1d9..7260910e75fb2a62eb74fcdc3aa08b64a9638737 100644 (file)
--- a/drivers/net/ethernet/broadcom/bnxt/bnxt_ethtool.c
+++ b/drivers/net/ethernet/broadcom/bnxt/bnxt_ethtool.c
@@ -798,7 +798,7 @@ 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))