[PATCH net-next v3 2/2] net: stmmac: align real_num_tx_queues to mqprio configuration

[Lorenzo Bianconi]

stmmac_hw_setup() unconditionally sets the number of real TX queues to
plat->tx_queues_to_use on every device open. When a tc-mqprio qdisc is
offloaded the driver reduces netif_set_real_num_tx_queues() to the number
of queues enabled by the offload, but the next device open reverts it to
plat->tx_queues_to_use while the netdev TC map is still the one programmed
by the qdisc, leaving the two inconsistent.

Track the number of TX queues enabled by the current qdisc configuration
in the per-qdisc state (priv->xmit_qdisc.num_tx_queues) and use it in
stmmac_hw_setup(). The field defaults to plat->tx_queues_to_use at probe
time and when the mqprio qdisc is destroyed, meaning no offload is active
and the number of real TX queues must match the number of queues the
driver allocated, and it is updated to the offloaded queue count on a
successful mqprio setup.

Refuse to lower the number of TX queues below the count required by the
active mqprio offload in stmmac_reinit_queues(), otherwise
netif_set_real_num_tx_queues() would leave real_num_tx_queues
inconsistent with the netdev TC map.

Fixes: 195e4f409a40 ("net: stmmac: support fp parameter of tc-mqprio")
Signed-off-by: Lorenzo Bianconi <lorenzo.bianconi at oss.qualcomm.com>
---
 drivers/net/ethernet/stmicro/stmmac/stmmac.h      |  2 ++
 drivers/net/ethernet/stmicro/stmmac/stmmac_main.c | 12 +++++++++++-
 drivers/net/ethernet/stmicro/stmmac/stmmac_tc.c   |  6 ++++++
 3 files changed, 19 insertions(+), 1 deletion(-)

diff --git a/drivers/net/ethernet/stmicro/stmmac/stmmac.h b/drivers/net/ethernet/stmicro/stmmac/stmmac.h
index f1bdb65d0fe6..40eab899027b 100644
--- a/drivers/net/ethernet/stmicro/stmmac/stmmac.h
+++ b/drivers/net/ethernet/stmicro/stmmac/stmmac.h
@@ -301,8 +301,10 @@ struct stmmac_priv {
 	struct stmmac_est *est;
 
 	struct {
+		bool enabled;
 		u32 prio[MTL_MAX_TX_QUEUES];
 		bool prio_offload;
+		u32 num_tx_queues;
 		u8 algo;
 	} xmit_qdisc;
 
diff --git a/drivers/net/ethernet/stmicro/stmmac/stmmac_main.c b/drivers/net/ethernet/stmicro/stmmac/stmmac_main.c
index 27e4e86e3c8b..1c25d1c129d4 100644
--- a/drivers/net/ethernet/stmicro/stmmac/stmmac_main.c
+++ b/drivers/net/ethernet/stmicro/stmmac/stmmac_main.c
@@ -3772,7 +3772,7 @@ static int stmmac_hw_setup(struct net_device *dev)
 
 	/* Configure real RX and TX queues */
 	netif_set_real_num_rx_queues(dev, priv->plat->rx_queues_to_use);
-	netif_set_real_num_tx_queues(dev, priv->plat->tx_queues_to_use);
+	netif_set_real_num_tx_queues(dev, priv->xmit_qdisc.num_tx_queues);
 
 	/* Start the ball rolling... */
 	stmmac_start_all_dma(priv);
@@ -7676,6 +7676,10 @@ int stmmac_reinit_queues(struct net_device *dev, u8 rx_cnt, u8 tx_cnt)
 	struct stmmac_priv *priv = netdev_priv(dev);
 	int ret = 0, i;
 
+	if (priv->xmit_qdisc.enabled &&
+	    tx_cnt < priv->xmit_qdisc.num_tx_queues)
+		return -EINVAL;
+
 	if (netif_running(dev))
 		stmmac_release(dev);
 
@@ -7683,6 +7687,9 @@ int stmmac_reinit_queues(struct net_device *dev, u8 rx_cnt, u8 tx_cnt)
 
 	priv->plat->rx_queues_to_use = rx_cnt;
 	priv->plat->tx_queues_to_use = tx_cnt;
+	if (!priv->xmit_qdisc.enabled)
+		priv->xmit_qdisc.num_tx_queues = tx_cnt;
+
 	if (!netif_is_rxfh_configured(dev))
 		for (i = 0; i < ARRAY_SIZE(priv->rss.table); i++)
 			priv->rss.table[i] = ethtool_rxfh_indir_default(i,
@@ -8003,6 +8010,9 @@ static int __stmmac_dvr_probe(struct device *device,
 	ndev->xdp_features = NETDEV_XDP_ACT_BASIC | NETDEV_XDP_ACT_REDIRECT |
 			     NETDEV_XDP_ACT_XSK_ZEROCOPY;
 
+	/* Default qdisc num_tx_queues */
+	priv->xmit_qdisc.num_tx_queues = priv->plat->tx_queues_to_use;
+
 	ret = stmmac_tc_init(priv, priv);
 	if (!ret) {
 		ndev->hw_features |= NETIF_F_HW_TC;
diff --git a/drivers/net/ethernet/stmicro/stmmac/stmmac_tc.c b/drivers/net/ethernet/stmicro/stmmac/stmmac_tc.c
index 07cf4582ed76..8bdc411e902f 100644
--- a/drivers/net/ethernet/stmicro/stmmac/stmmac_tc.c
+++ b/drivers/net/ethernet/stmicro/stmmac/stmmac_tc.c
@@ -1290,6 +1290,9 @@ static int stmmac_reset_tc_mqprio(struct net_device *ndev,
 		priv->xmit_qdisc.prio_offload = false;
 	}
 
+	priv->xmit_qdisc.num_tx_queues = priv->plat->tx_queues_to_use;
+	priv->xmit_qdisc.enabled = false;
+
 	netdev_reset_tc(ndev);
 	netif_set_real_num_tx_queues(ndev, priv->plat->tx_queues_to_use);
 
@@ -1438,6 +1441,9 @@ static int tc_setup_dwmac510_mqprio(struct stmmac_priv *priv,
 	if (mode == TC_MQPRIO_MODE_CHANNEL)
 		tc_mqprio_config_queue_prio(priv, qopt);
 
+	priv->xmit_qdisc.num_tx_queues = num_tx_queues;
+	priv->xmit_qdisc.enabled = true;
+
 	return 0;
 
 error_reset_num_tx_queues:

-- 
2.55.0