gve: Add support to query the nic clock

Query the nic clock and store the results. The timestamp delivered
in descriptors has a wraparound time of ~4 seconds so 250ms is chosen
as the sync cadence to provide a balance between performance, and
drift potential when we do start associating host time and nic time.

Leverage PTP's aux_work to query the nic clock periodically.

Signed-off-by: Kevin Yang <yyd@google.com>
Signed-off-by: John Fraker <jfraker@google.com>
Signed-off-by: Tim Hostetler <thostet@google.com>
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/20250614000754.164827-6-hramamurthy@google.com
Signed-off-by: Jakub Kicinski <kuba@kernel.org>

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

@@ -882,6 +882,9 @@ struct gve_priv {
 	/* True if the device supports reading the nic clock */
 	bool nic_timestamp_supported;
 	struct gve_ptp *ptp;
+	struct gve_nic_ts_report *nic_ts_report;
+	dma_addr_t nic_ts_report_bus;
+	u64 last_sync_nic_counter; /* Clock counter from last NIC TS report */
 };
 
 enum gve_service_task_flags_bit {
@@ -1261,6 +1264,24 @@ int gve_del_flow_rule(struct gve_priv *priv, struct ethtool_rxnfc *cmd);
 int gve_flow_rules_reset(struct gve_priv *priv);
 /* RSS config */
 int gve_init_rss_config(struct gve_priv *priv, u16 num_queues);
+/* PTP and timestamping */
+#if IS_ENABLED(CONFIG_PTP_1588_CLOCK)
+int gve_clock_nic_ts_read(struct gve_priv *priv);
+int gve_init_clock(struct gve_priv *priv);
+void gve_teardown_clock(struct gve_priv *priv);
+#else /* CONFIG_PTP_1588_CLOCK */
+static inline int gve_clock_nic_ts_read(struct gve_priv *priv)
+{
+	return -EOPNOTSUPP;
+}
+
+static inline int gve_init_clock(struct gve_priv *priv)
+{
+	return 0;
+}
+
+static inline void gve_teardown_clock(struct gve_priv *priv) { }
+#endif /* CONFIG_PTP_1588_CLOCK */
 /* report stats handling */
 void gve_handle_report_stats(struct gve_priv *priv);
 /* exported by ethtool.c */

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

@@ -619,9 +619,12 @@ static int gve_setup_device_resources(struct gve_priv *priv)
 	err = gve_alloc_counter_array(priv);
 	if (err)
 		goto abort_with_rss_config_cache;
-	err = gve_alloc_notify_blocks(priv);
+	err = gve_init_clock(priv);
 	if (err)
 		goto abort_with_counter;
+	err = gve_alloc_notify_blocks(priv);
+	if (err)
+		goto abort_with_clock;
 	err = gve_alloc_stats_report(priv);
 	if (err)
 		goto abort_with_ntfy_blocks;
@@ -674,6 +677,8 @@ static int gve_setup_device_resources(struct gve_priv *priv)
 	gve_free_stats_report(priv);
 abort_with_ntfy_blocks:
 	gve_free_notify_blocks(priv);
+abort_with_clock:
+	gve_teardown_clock(priv);
 abort_with_counter:
 	gve_free_counter_array(priv);
 abort_with_rss_config_cache:

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

@@ -5,13 +5,52 @@
  */
 
 #include "gve.h"
+#include "gve_adminq.h"
+
+/* Interval to schedule a nic timestamp calibration, 250ms. */
+#define GVE_NIC_TS_SYNC_INTERVAL_MS 250
+
+/* Read the nic timestamp from hardware via the admin queue. */
+int gve_clock_nic_ts_read(struct gve_priv *priv)
+{
+	u64 nic_raw;
+	int err;
+
+	err = gve_adminq_report_nic_ts(priv, priv->nic_ts_report_bus);
+	if (err)
+		return err;
+
+	nic_raw = be64_to_cpu(priv->nic_ts_report->nic_timestamp);
+	WRITE_ONCE(priv->last_sync_nic_counter, nic_raw);
+
+	return 0;
+}
+
+static long gve_ptp_do_aux_work(struct ptp_clock_info *info)
+{
+	const struct gve_ptp *ptp = container_of(info, struct gve_ptp, info);
+	struct gve_priv *priv = ptp->priv;
+	int err;
+
+	if (gve_get_reset_in_progress(priv) || !gve_get_admin_queue_ok(priv))
+		goto out;
+
+	err = gve_clock_nic_ts_read(priv);
+	if (err && net_ratelimit())
+		dev_err(&priv->pdev->dev,
+			"%s read err %d\n", __func__, err);
+
+out:
+	return msecs_to_jiffies(GVE_NIC_TS_SYNC_INTERVAL_MS);
+}
 
 static const struct ptp_clock_info gve_ptp_caps = {
 	.owner          = THIS_MODULE,
 	.name		= "gve clock",
+	.do_aux_work	= gve_ptp_do_aux_work,
 };
 
-static int __maybe_unused gve_ptp_init(struct gve_priv *priv)
+static int gve_ptp_init(struct gve_priv *priv)
 {
 	struct gve_ptp *ptp;
 	int err;
@@ -44,7 +83,7 @@ static int __maybe_unused gve_ptp_init(struct gve_priv *priv)
 	return err;
 }
 
-static void __maybe_unused gve_ptp_release(struct gve_priv *priv)
+static void gve_ptp_release(struct gve_priv *priv)
 {
 	struct gve_ptp *ptp = priv->ptp;
 
@@ -57,3 +96,44 @@ static void __maybe_unused gve_ptp_release(struct gve_priv *priv)
 	kfree(ptp);
 	priv->ptp = NULL;
 }
+
+int gve_init_clock(struct gve_priv *priv)
+{
+	int err;
+
+	if (!priv->nic_timestamp_supported)
+		return 0;
+
+	err = gve_ptp_init(priv);
+	if (err)
+		return err;
+
+	priv->nic_ts_report =
+		dma_alloc_coherent(&priv->pdev->dev,
+				   sizeof(struct gve_nic_ts_report),
+				   &priv->nic_ts_report_bus,
+				   GFP_KERNEL);
+	if (!priv->nic_ts_report) {
+		dev_err(&priv->pdev->dev, "%s dma alloc error\n", __func__);
+		err = -ENOMEM;
+		goto release_ptp;
+	}
+
+	return 0;
+
+release_ptp:
+	gve_ptp_release(priv);
+	return err;
+}
+
+void gve_teardown_clock(struct gve_priv *priv)
+{
+	gve_ptp_release(priv);
+
+	if (priv->nic_ts_report) {
+		dma_free_coherent(&priv->pdev->dev,
+				  sizeof(struct gve_nic_ts_report),
+				  priv->nic_ts_report, priv->nic_ts_report_bus);
+		priv->nic_ts_report = NULL;
+	}
+}