net: Add the possibility to support a selected hwtstamp in netdevice

Introduce the description of a hwtstamp provider, mainly defined with a
the hwtstamp source and the phydev pointer.

Add a hwtstamp provider description within the netdev structure to
allow saving the hwtstamp we want to use. This prepares for future
support of an ethtool netlink command to select the desired hwtstamp
provider. By default, the old API that does not support hwtstamp
selectability is used, meaning the hwtstamp provider pointer is unset.

Signed-off-by: Kory Maincent <[e-mail]>
Signed-off-by: David S. Miller <[e-mail]>

drivers/net/phy/phy_device.c

···
 #include <linux/phy_link_topology.h>
 #include <linux/pse-pd/pse.h>
 #include <linux/property.h>
+#include <linux/ptp_clock_kernel.h>
 #include <linux/rtnetlink.h>
 #include <linux/sfp.h>
 #include <linux/skbuff.h>
···
 
 	phy_suspend(phydev);
 	if (dev) {
+		struct hwtstamp_provider *hwprov;
+
+		hwprov = rtnl_dereference(dev->hwprov);
+		/* Disable timestamp if it is the one selected */
+		if (hwprov && hwprov->phydev == phydev) {
+			rcu_assign_pointer(dev->hwprov, NULL);
+			kfree_rcu(hwprov, rcu_head);
+		}
+
 		phydev->attached_dev->phydev = NULL;
 		phydev->attached_dev = NULL;
 		phy_link_topo_del_phy(dev, phydev);

include/linux/net_tstamp.h

···
 };
 
 /**
+ * struct hwtstamp_provider_desc - hwtstamp provider description
+ *
+ * @index: index of the hwtstamp provider.
+ * @qualifier: hwtstamp provider qualifier.
+ */
+struct hwtstamp_provider_desc {
+	int index;
+	enum hwtstamp_provider_qualifier qualifier;
+};
+
+/**
+ * struct hwtstamp_provider - hwtstamp provider object
+ *
+ * @rcu_head: RCU callback used to free the struct.
+ * @source: source of the hwtstamp provider.
+ * @phydev: pointer of the phydev source in case a PTP coming from phylib
+ * @desc: hwtstamp provider description.
+ */
+
+struct hwtstamp_provider {
+	struct rcu_head rcu_head;
+	enum hwtstamp_source source;
+	struct phy_device *phydev;
+	struct hwtstamp_provider_desc desc;
+};
+
+/**
  * struct kernel_hwtstamp_config - Kernel copy of struct hwtstamp_config
  *
  * @flags: see struct hwtstamp_config
···
  *	copied the ioctl request back to user space
  * @source: indication whether timestamps should come from the netdev or from
  *	an attached phylib PHY
+ * @qualifier: qualifier of the hwtstamp provider
  *
  * Prefer using this structure for in-kernel processing of hardware
  * timestamping configuration, over the inextensible struct hwtstamp_config
···
 	struct ifreq *ifr;
 	bool copied_to_user;
 	enum hwtstamp_source source;
+	enum hwtstamp_provider_qualifier qualifier;
 };
 
 static inline void hwtstamp_config_to_kernel(struct kernel_hwtstamp_config *kernel_cfg,

include/linux/netdevice.h

···
 struct xdp_md;
 struct ethtool_netdev_state;
 struct phy_link_topology;
+struct hwtstamp_provider;
 
 typedef u32 xdp_features_t;
 
···
  *
  *	@neighbours:	List heads pointing to this device's neighbours'
  *			dev_list, one per address-family.
+ *	@hwprov: Tracks which PTP performs hardware packet time stamping.
  *
  *	FIXME: cleanup struct net_device such that network protocol info
  *	moves out.
···
 #endif
 
 	struct hlist_head neighbours[NEIGH_NR_TABLES];
+
+	struct hwtstamp_provider __rcu	*hwprov;
 
 	u8			priv[] ____cacheline_aligned
 				       __counted_by(priv_len);

include/uapi/linux/net_tstamp.h

···
 #include <linux/types.h>
 #include <linux/socket.h>   /* for SO_TIMESTAMPING */
 
+/*
+ * Possible type of hwtstamp provider. Mainly "precise" the default one
+ * is for IEEE 1588 quality and "approx" is for NICs DMA point.
+ */
+enum hwtstamp_provider_qualifier {
+	HWTSTAMP_PROVIDER_QUALIFIER_PRECISE,
+	HWTSTAMP_PROVIDER_QUALIFIER_APPROX,
+
+	HWTSTAMP_PROVIDER_QUALIFIER_CNT,
+};
+
 /* SO_TIMESTAMPING flags */
 enum {
 	SOF_TIMESTAMPING_TX_HARDWARE = (1<<0),

net/core/dev_ioctl.c

···
 #include <linux/rtnetlink.h>
 #include <linux/net_tstamp.h>
 #include <linux/phylib_stubs.h>
+#include <linux/ptp_clock_kernel.h>
 #include <linux/wireless.h>
 #include <linux/if_bridge.h>
 #include <net/dsa_stubs.h>
···
 int dev_get_hwtstamp_phylib(struct net_device *dev,
 			    struct kernel_hwtstamp_config *cfg)
 {
+	struct hwtstamp_provider *hwprov;
+
+	hwprov = rtnl_dereference(dev->hwprov);
+	if (hwprov) {
+		cfg->qualifier = hwprov->desc.qualifier;
+		if (hwprov->source == HWTSTAMP_SOURCE_PHYLIB &&
+		    hwprov->phydev)
+			return phy_hwtstamp_get(hwprov->phydev, cfg);
+
+		if (hwprov->source == HWTSTAMP_SOURCE_NETDEV)
+			return dev->netdev_ops->ndo_hwtstamp_get(dev, cfg);
+
+		return -EOPNOTSUPP;
+	}
+
 	if (phy_is_default_hwtstamp(dev->phydev))
 		return phy_hwtstamp_get(dev->phydev, cfg);
 
···
 			    struct netlink_ext_ack *extack)
 {
 	const struct net_device_ops *ops = dev->netdev_ops;
-	bool phy_ts = phy_is_default_hwtstamp(dev->phydev);
 	struct kernel_hwtstamp_config old_cfg = {};
+	struct hwtstamp_provider *hwprov;
+	struct phy_device *phydev;
 	bool changed = false;
+	bool phy_ts;
 	int err;
+
+	hwprov = rtnl_dereference(dev->hwprov);
+	if (hwprov) {
+		if (hwprov->source == HWTSTAMP_SOURCE_PHYLIB &&
+		    hwprov->phydev) {
+			phy_ts = true;
+			phydev = hwprov->phydev;
+		} else if (hwprov->source == HWTSTAMP_SOURCE_NETDEV) {
+			phy_ts = false;
+		} else {
+			return -EOPNOTSUPP;
+		}
+
+		cfg->qualifier = hwprov->desc.qualifier;
+	} else {
+		phy_ts = phy_is_default_hwtstamp(dev->phydev);
+		if (phy_ts)
+			phydev = dev->phydev;
+	}
 
 	cfg->source = phy_ts ? HWTSTAMP_SOURCE_PHYLIB : HWTSTAMP_SOURCE_NETDEV;
 
···
 		changed = kernel_hwtstamp_config_changed(&old_cfg, cfg);
 
 	if (phy_ts) {
-		err = phy_hwtstamp_set(dev->phydev, cfg, extack);
+		err = phy_hwtstamp_set(phydev, cfg, extack);
 		if (err) {
 			if (changed)
 				ops->ndo_hwtstamp_set(dev, &old_cfg, NULL);

net/core/timestamping.c

···
 #include <linux/ptp_classify.h>
 #include <linux/skbuff.h>
 #include <linux/export.h>
+#include <linux/ptp_clock_kernel.h>
 
 static unsigned int classify(const struct sk_buff *skb)
 {
···
 
 void skb_clone_tx_timestamp(struct sk_buff *skb)
 {
+	struct hwtstamp_provider *hwprov;
 	struct mii_timestamper *mii_ts;
+	struct phy_device *phydev;
 	struct sk_buff *clone;
 	unsigned int type;
 
-	if (!skb->sk || !skb->dev ||
-	    !phy_is_default_hwtstamp(skb->dev->phydev))
+	if (!skb->sk || !skb->dev)
 		return;
+
+	rcu_read_lock();
+	hwprov = rcu_dereference(skb->dev->hwprov);
+	if (hwprov) {
+		if (hwprov->source != HWTSTAMP_SOURCE_PHYLIB ||
+		    !hwprov->phydev) {
+			rcu_read_unlock();
+			return;
+		}
+
+		phydev = hwprov->phydev;
+	} else {
+		phydev = skb->dev->phydev;
+		if (!phy_is_default_hwtstamp(phydev)) {
+			rcu_read_unlock();
+			return;
+		}
+	}
+	rcu_read_unlock();
 
 	type = classify(skb);
 	if (type == PTP_CLASS_NONE)
 		return;
 
-	mii_ts = skb->dev->phydev->mii_ts;
+	mii_ts = phydev->mii_ts;
 	if (likely(mii_ts->txtstamp)) {
 		clone = skb_clone_sk(skb);
 		if (!clone)
···
 
 bool skb_defer_rx_timestamp(struct sk_buff *skb)
 {
+	struct hwtstamp_provider *hwprov;
 	struct mii_timestamper *mii_ts;
+	struct phy_device *phydev;
 	unsigned int type;
 
-	if (!skb->dev || !phy_is_default_hwtstamp(skb->dev->phydev))
+	if (!skb->dev)
 		return false;
+
+	rcu_read_lock();
+	hwprov = rcu_dereference(skb->dev->hwprov);
+	if (hwprov) {
+		if (hwprov->source != HWTSTAMP_SOURCE_PHYLIB ||
+		    !hwprov->phydev) {
+			rcu_read_unlock();
+			return false;
+		}
+
+		phydev = hwprov->phydev;
+	} else {
+		phydev = skb->dev->phydev;
+		if (!phy_is_default_hwtstamp(phydev)) {
+			rcu_read_unlock();
+			return false;
+		}
+	}
+	rcu_read_unlock();
 
 	if (skb_headroom(skb) < ETH_HLEN)
 		return false;
···
 	if (type == PTP_CLASS_NONE)
 		return false;
 
-	mii_ts = skb->dev->phydev->mii_ts;
+	mii_ts = phydev->mii_ts;
 	if (likely(mii_ts->rxtstamp))
 		return mii_ts->rxtstamp(mii_ts, skb, type);