gve: Add initial PTP device support

If the device supports reading of the nic clock, add support
to initialize and register the PTP clock.

Signed-off-by: Ziwei Xiao <ziweixiao@google.com>
Reviewed-by: Willem de Bruijn <willemb@google.com>
Signed-off-by: Harshitha Ramamurthy <hramamurthy@google.com>
Link: https://patch.msgid.link/20250614000754.164827-4-hramamurthy@google.com
Signed-off-by: Jakub Kicinski <kuba@kernel.org>

drivers/net/ethernet/google/Kconfig

@@ -18,6 +18,7 @@ if NET_VENDOR_GOOGLE
 config GVE
 	tristate "Google Virtual NIC (gVNIC) support"
 	depends on (PCI_MSI && (X86 || CPU_LITTLE_ENDIAN))
+	depends on PTP_1588_CLOCK_OPTIONAL
 	select PAGE_POOL
 	help
 	  This driver supports Google Virtual NIC (gVNIC)"

drivers/net/ethernet/google/gve/Makefile

@@ -1,5 +1,7 @@
 # Makefile for the Google virtual Ethernet (gve) driver
 
 obj-$(CONFIG_GVE) += gve.o
-gve-objs := gve_main.o gve_tx.o gve_tx_dqo.o gve_rx.o gve_rx_dqo.o gve_ethtool.o gve_adminq.o gve_utils.o gve_flow_rule.o \
+gve-y := gve_main.o gve_tx.o gve_tx_dqo.o gve_rx.o gve_rx_dqo.o gve_ethtool.o gve_adminq.o gve_utils.o gve_flow_rule.o \
 	    gve_buffer_mgmt_dqo.o
+
+gve-$(CONFIG_PTP_1588_CLOCK) += gve_ptp.o

drivers/net/ethernet/google/gve/gve.h

@@ -12,6 +12,7 @@
 #include <linux/ethtool_netlink.h>
 #include <linux/netdevice.h>
 #include <linux/pci.h>
+#include <linux/ptp_clock_kernel.h>
 #include <linux/u64_stats_sync.h>
 #include <net/page_pool/helpers.h>
 #include <net/xdp.h>
@@ -750,6 +751,12 @@ struct gve_rss_config {
 	u32 *hash_lut;
 };
 
+struct gve_ptp {
+	struct ptp_clock_info info;
+	struct ptp_clock *clock;
+	struct gve_priv *priv;
+};
+
 struct gve_priv {
 	struct net_device *dev;
 	struct gve_tx_ring *tx; /* array of tx_cfg.num_queues */
@@ -874,6 +881,7 @@ struct gve_priv {
 
 	/* True if the device supports reading the nic clock */
 	bool nic_timestamp_supported;
+	struct gve_ptp *ptp;
 };
 
 enum gve_service_task_flags_bit {

drivers/net/ethernet/google/gve/gve_ptp.c

@@ -0,0 +1,59 @@
+// SPDX-License-Identifier: (GPL-2.0 OR MIT)
+/* Google virtual Ethernet (gve) driver
+ *
+ * Copyright (C) 2025 Google LLC
+ */
+
+#include "gve.h"
+
+static const struct ptp_clock_info gve_ptp_caps = {
+	.owner          = THIS_MODULE,
+	.name		= "gve clock",
+};
+
+static int __maybe_unused gve_ptp_init(struct gve_priv *priv)
+{
+	struct gve_ptp *ptp;
+	int err;
+
+	if (!priv->nic_timestamp_supported) {
+		dev_dbg(&priv->pdev->dev, "Device does not support PTP\n");
+		return -EOPNOTSUPP;
+	}
+
+	priv->ptp = kzalloc(sizeof(*priv->ptp), GFP_KERNEL);
+	if (!priv->ptp)
+		return -ENOMEM;
+
+	ptp = priv->ptp;
+	ptp->info = gve_ptp_caps;
+	ptp->clock = ptp_clock_register(&ptp->info, &priv->pdev->dev);
+
+	if (IS_ERR(ptp->clock)) {
+		dev_err(&priv->pdev->dev, "PTP clock registration failed\n");
+		err  = PTR_ERR(ptp->clock);
+		goto free_ptp;
+	}
+
+	ptp->priv = priv;
+	return 0;
+
+free_ptp:
+	kfree(ptp);
+	priv->ptp = NULL;
+	return err;
+}
+
+static void __maybe_unused gve_ptp_release(struct gve_priv *priv)
+{
+	struct gve_ptp *ptp = priv->ptp;
+
+	if (!ptp)
+		return;
+
+	if (ptp->clock)
+		ptp_clock_unregister(ptp->clock);
+
+	kfree(ptp);
+	priv->ptp = NULL;
+}