From 4975e2b3f1d37bba04f262784cef0d5b7e0a30a4 Mon Sep 17 00:00:00 2001
From: Maxime Chevallier <maxime.chevallier@bootlin.com>
Date: Fri, 4 Nov 2022 18:41:50 +0100
Subject: [PATCH] net: ipqess: Add out-of-band DSA tagging support

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>
---
 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(-)

--- a/drivers/net/ethernet/qualcomm/Kconfig
+++ b/drivers/net/ethernet/qualcomm/Kconfig
@@ -65,6 +65,7 @@ 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.
--- 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_
 	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_
 			__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 ip
 	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
 	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 ipqes
 	.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 platf
 		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);
 
--- 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;
