[PATCH net-next v4 08/10] net: airoha: Do not stop GDM port if it is shared

[Lorenzo Bianconi <lorenzo@kernel.org>]

Theoretically, in the current codebase, two independent net_devices can
be connected to the same GDM port so we need to check the GDM port is not
used by any other running net_device before setting the forward
configuration to FE_PSE_PORT_DROP.

Tested-by: Xuegang Lu <xuegang.lu@airoha.com>
Signed-off-by: Lorenzo Bianconi <lorenzo@kernel.org>
---
 drivers/net/ethernet/airoha/airoha_eth.c | 36 +++++++++++++++++++++++++-------
 drivers/net/ethernet/airoha/airoha_eth.h |  2 ++
 2 files changed, 30 insertions(+), 8 deletions(-)

diff --git a/drivers/net/ethernet/airoha/airoha_eth.c b/drivers/net/ethernet/airoha/airoha_eth.c
index 0253919714e0..1c4927c1aeb0 100644
--- a/drivers/net/ethernet/airoha/airoha_eth.c
+++ b/drivers/net/ethernet/airoha/airoha_eth.c
@@ -1714,8 +1714,8 @@ static int airoha_dev_open(struct net_device *netdev)
 	int err, len = ETH_HLEN + netdev->mtu + ETH_FCS_LEN;
 	struct airoha_gdm_dev *dev = netdev_priv(netdev);
 	struct airoha_gdm_port *port = dev->port;
+	u32 cur_len, pse_port = FE_PSE_PORT_PPE1;
 	struct airoha_qdma *qdma = dev->qdma;
-	u32 pse_port = FE_PSE_PORT_PPE1;
 
 	netif_tx_start_all_queues(netdev);
 	err = airoha_set_vip_for_gdm_port(dev, true);
@@ -1729,10 +1729,14 @@ static int airoha_dev_open(struct net_device *netdev)
 		airoha_fe_clear(qdma->eth, REG_GDM_INGRESS_CFG(port->id),
 				GDM_STAG_EN_MASK);
 
-	airoha_fe_rmw(qdma->eth, REG_GDM_LEN_CFG(port->id),
-		      GDM_SHORT_LEN_MASK | GDM_LONG_LEN_MASK,
-		      FIELD_PREP(GDM_SHORT_LEN_MASK, 60) |
-		      FIELD_PREP(GDM_LONG_LEN_MASK, len));
+	cur_len = airoha_fe_get(qdma->eth, REG_GDM_LEN_CFG(port->id),
+				GDM_LONG_LEN_MASK);
+	if (!atomic_read(&port->users) || len > cur_len)
+		airoha_fe_rmw(qdma->eth, REG_GDM_LEN_CFG(port->id),
+			      GDM_SHORT_LEN_MASK | GDM_LONG_LEN_MASK,
+			      FIELD_PREP(GDM_SHORT_LEN_MASK, 60) |
+			      FIELD_PREP(GDM_LONG_LEN_MASK, len));
+	atomic_inc(&port->users);
 
 	airoha_qdma_set(qdma, REG_QDMA_GLOBAL_CFG,
 			GLOBAL_CFG_TX_DMA_EN_MASK |
@@ -1762,8 +1766,12 @@ static int airoha_dev_stop(struct net_device *netdev)
 	for (i = 0; i < netdev->num_tx_queues; i++)
 		netdev_tx_reset_subqueue(netdev, i);
 
-	airoha_set_gdm_port_fwd_cfg(qdma->eth, REG_GDM_FWD_CFG(port->id),
-				    FE_PSE_PORT_DROP);
+	if (atomic_dec_and_test(&port->users)) {
+		airoha_set_vip_for_gdm_port(dev, false);
+		airoha_set_gdm_port_fwd_cfg(qdma->eth,
+					    REG_GDM_FWD_CFG(port->id),
+					    FE_PSE_PORT_DROP);
+	}
 
 	if (atomic_dec_and_test(&qdma->users)) {
 		airoha_qdma_clear(qdma, REG_QDMA_GLOBAL_CFG,
@@ -1915,10 +1923,22 @@ static void airoha_dev_get_stats64(struct net_device *netdev,
 static int airoha_dev_change_mtu(struct net_device *netdev, int mtu)
 {
 	struct airoha_gdm_dev *dev = netdev_priv(netdev);
+	u32 cur_len, len = ETH_HLEN + mtu + ETH_FCS_LEN;
 	struct airoha_gdm_port *port = dev->port;
-	u32 len = ETH_HLEN + mtu + ETH_FCS_LEN;
 	struct airoha_eth *eth = dev->eth;
 
+	cur_len = airoha_fe_get(eth, REG_GDM_LEN_CFG(port->id),
+				GDM_LONG_LEN_MASK);
+	if (len < cur_len) {
+		u8 port_refcnt = atomic_read(&port->users);
+
+		/* We can decrease the device MTU just if the GDM port is
+		 * not shared or if the other device is not running.
+		 */
+		if (port_refcnt > 1 || (port_refcnt && !netif_running(netdev)))
+			return -EBUSY;
+	}
+
 	airoha_fe_rmw(eth, REG_GDM_LEN_CFG(port->id),
 		      GDM_LONG_LEN_MASK,
 		      FIELD_PREP(GDM_LONG_LEN_MASK, len));
diff --git a/drivers/net/ethernet/airoha/airoha_eth.h b/drivers/net/ethernet/airoha/airoha_eth.h
index 207c75152fde..3a313ac439e7 100644
--- a/drivers/net/ethernet/airoha/airoha_eth.h
+++ b/drivers/net/ethernet/airoha/airoha_eth.h
@@ -553,6 +553,8 @@ struct airoha_gdm_port {
 	struct airoha_gdm_dev *devs[AIROHA_MAX_NUM_GDM_DEVS];
 	int id;
 
+	atomic_t users;
+
 	struct airoha_hw_stats stats;
 
 	struct metadata_dst *dsa_meta[AIROHA_MAX_DSA_PORTS];

-- 
2.54.0