[PATCH net-next v7 4/5] net: ipqess: Add out-of-band DSA tagging support

[Maxime Chevallier <maxime.chevallier@bootlin.com>]

On the IPQ4019, there's an 5 ports switch connected to the CPU through
the IPQESS Ethernet controller. The way the DSA tag is sent-out to that
switch is through the DMA descriptor, due to how tightly it is
integrated with the switch.

We use the out-of-band tagging protocol by getting the source
port from the descriptor, push it into the skb extensions, and have the
tagger pull it to infer the destination netdev. The reverse process is
done on the TX side, where the driver pulls the tag from the skb and
builds the descriptor accordingly.

Signed-off-by: Maxime Chevallier <maxime.chevallier@bootlin.com>
---
V6->V7:
 - Added proper endianness conversion for descriptor accesses
V5->V6:
 - Fixed the CHANGEUPPER event handling
 - removed pop/push helpers
V4->V5:
 - Rework the CHANGEUPPER event handling
V3->V4:
 - No changes
V2->V3:
 - No changes
V1->V2:
 - Use the new tagger, and the dsa_oob_tag_* helpers
 
 drivers/net/ethernet/qualcomm/Kconfig         |  1 +
 drivers/net/ethernet/qualcomm/ipqess/ipqess.c | 64 ++++++++++++++++++-
 drivers/net/ethernet/qualcomm/ipqess/ipqess.h |  4 ++
 3 files changed, 68 insertions(+), 1 deletion(-)

diff --git a/drivers/net/ethernet/qualcomm/Kconfig b/drivers/net/ethernet/qualcomm/Kconfig
index 28861bca5a5b..7eda94131cb1 100644
--- a/drivers/net/ethernet/qualcomm/Kconfig
+++ b/drivers/net/ethernet/qualcomm/Kconfig
@@ -64,6 +64,7 @@ config QCOM_IPQ4019_ESS_EDMA
 	tristate "Qualcomm Atheros IPQ4019 ESS EDMA support"
 	depends on (OF && ARCH_QCOM) || COMPILE_TEST
 	select PHYLINK
+	select NET_DSA_TAG_OOB
 	help
 	  This driver supports the Qualcomm Atheros IPQ40xx built-in
 	  ESS EDMA ethernet controller.
diff --git a/drivers/net/ethernet/qualcomm/ipqess/ipqess.c b/drivers/net/ethernet/qualcomm/ipqess/ipqess.c
index df3f2ce77065..a2385d6407b3 100644
--- a/drivers/net/ethernet/qualcomm/ipqess/ipqess.c
+++ b/drivers/net/ethernet/qualcomm/ipqess/ipqess.c
@@ -9,6 +9,7 @@
 
 #include <linux/bitfield.h>
 #include <linux/clk.h>
+#include <linux/dsa/oob.h>
 #include <linux/if_vlan.h>
 #include <linux/interrupt.h>
 #include <linux/module.h>
@@ -22,6 +23,7 @@
 #include <linux/skbuff.h>
 #include <linux/vmalloc.h>
 #include <net/checksum.h>
+#include <net/dsa.h>
 #include <net/ip6_checksum.h>
 
 #include "ipqess.h"
@@ -327,6 +329,7 @@ static int ipqess_rx_poll(struct ipqess_rx_ring *rx_ring, int budget)
 	tail &= IPQESS_RFD_CONS_IDX_MASK;
 
 	while (done < budget) {
+		struct dsa_oob_tag_info *tag_info;
 		struct ipqess_rx_desc *rd;
 		struct sk_buff *skb;
 
@@ -406,6 +409,12 @@ static int ipqess_rx_poll(struct ipqess_rx_ring *rx_ring, int budget)
 			__vlan_hwaccel_put_tag(skb, htons(ETH_P_8021AD),
 					       le16_to_cpu(rd->rrd4));
 
+		if (likely(rx_ring->ess->dsa_ports)) {
+			tag_info = skb_ext_add(skb, SKB_EXT_DSA_OOB);
+			tag_info->port = FIELD_GET(IPQESS_RRD_PORT_ID_MASK,
+						   le16_to_cpu(rd->rrd1));
+		}
+
 		napi_gro_receive(&rx_ring->napi_rx, skb);
 
 		rx_ring->ess->stats.rx_packets++;
@@ -706,6 +715,23 @@ static void ipqess_rollback_tx(struct ipqess *eth,
 	tx_ring->head = start_index;
 }
 
+static void ipqess_process_dsa_tag_sh(struct ipqess *ess, struct sk_buff *skb,
+				      u32 *word3)
+{
+	struct dsa_oob_tag_info *tag_info;
+
+	if (unlikely(!ess->dsa_ports))
+		return;
+
+	tag_info = skb_ext_find(skb, SKB_EXT_DSA_OOB);
+	if (!tag_info)
+		return;
+
+	*word3 |= tag_info->port << IPQESS_TPD_PORT_BITMAP_SHIFT;
+	*word3 |= BIT(IPQESS_TPD_FROM_CPU_SHIFT);
+	*word3 |= 0x3e << IPQESS_TPD_PORT_BITMAP_SHIFT;
+}
+
 static int ipqess_tx_map_and_fill(struct ipqess_tx_ring *tx_ring,
 				  struct sk_buff *skb)
 {
@@ -716,6 +742,8 @@ static int ipqess_tx_map_and_fill(struct ipqess_tx_ring *tx_ring,
 	u16 len;
 	int i;
 
+	ipqess_process_dsa_tag_sh(tx_ring->ess, skb, &word3);
+
 	if (skb_is_gso(skb)) {
 		if (skb_shinfo(skb)->gso_type & SKB_GSO_TCPV4) {
 			lso_word1 |= IPQESS_TPD_IPV4_EN;
@@ -917,6 +945,33 @@ static const struct net_device_ops ipqess_axi_netdev_ops = {
 	.ndo_tx_timeout		= ipqess_tx_timeout,
 };
 
+static int ipqess_netdevice_event(struct notifier_block *nb,
+				  unsigned long event, void *ptr)
+{
+	struct ipqess *ess = container_of(nb, struct ipqess, netdev_notifier);
+	struct net_device *dev = netdev_notifier_info_to_dev(ptr);
+	struct netdev_notifier_changeupper_info *info;
+
+	if (dev != ess->netdev)
+		return NOTIFY_DONE;
+
+	switch (event) {
+	case NETDEV_CHANGEUPPER:
+		info = ptr;
+
+		if (!dsa_slave_dev_check(info->upper_dev))
+			return NOTIFY_DONE;
+
+		if (info->linking)
+			ess->dsa_ports++;
+		else
+			ess->dsa_ports--;
+
+		return NOTIFY_DONE;
+	}
+	return NOTIFY_OK;
+}
+
 static void ipqess_hw_stop(struct ipqess *ess)
 {
 	int i;
@@ -1184,12 +1239,19 @@ static int ipqess_axi_probe(struct platform_device *pdev)
 		netif_napi_add(netdev, &ess->rx_ring[i].napi_rx, ipqess_rx_napi);
 	}
 
-	err = register_netdev(netdev);
+	ess->netdev_notifier.notifier_call = ipqess_netdevice_event;
+	err = register_netdevice_notifier(&ess->netdev_notifier);
 	if (err)
 		goto err_hw_stop;
 
+	err = register_netdev(netdev);
+	if (err)
+		goto err_notifier_unregister;
+
 	return 0;
 
+err_notifier_unregister:
+	unregister_netdevice_notifier(&ess->netdev_notifier);
 err_hw_stop:
 	ipqess_hw_stop(ess);
 
diff --git a/drivers/net/ethernet/qualcomm/ipqess/ipqess.h b/drivers/net/ethernet/qualcomm/ipqess/ipqess.h
index dae17f3a23e4..5999a3b26235 100644
--- a/drivers/net/ethernet/qualcomm/ipqess/ipqess.h
+++ b/drivers/net/ethernet/qualcomm/ipqess/ipqess.h
@@ -171,6 +171,10 @@ struct ipqess {
 	struct platform_device *pdev;
 	struct phylink *phylink;
 	struct phylink_config phylink_config;
+
+	struct notifier_block netdev_notifier;
+	int dsa_ports;
+
 	struct ipqess_tx_ring tx_ring[IPQESS_NETDEV_QUEUES];
 
 	struct ipqess_statistics ipqess_stats;
-- 
2.37.3