[PATCH v2 5/6] net/gve: support read clock ethdev op

[Mark Blasko <blasko@google.com>]

Implement the read_clock operation in eth_dev_ops. The function calls
the AdminQ command to fetch the current NIC timestamp synchronously,
updates the cached timestamp used for reconstruction, and returns the
full 64-bit value.

Signed-off-by: Mark Blasko <blasko@google.com>
Reviewed-by: Joshua Washington <joshwash@google.com>
Reviewed-by: Jasper Tran O'Leary <jtranoleary@google.com>
---
v2:
    - Scoped read_clock ethdev operation strictly to DQO queues.
---
 drivers/net/gve/gve_ethdev.c | 28 ++++++++++++++++++++++++++++
 1 file changed, 28 insertions(+)

diff --git a/drivers/net/gve/gve_ethdev.c b/drivers/net/gve/gve_ethdev.c
index ee21fb3ec4..c600062faf 100644
--- a/drivers/net/gve/gve_ethdev.c
+++ b/drivers/net/gve/gve_ethdev.c
@@ -1271,6 +1271,34 @@ gve_flow_ops_get(struct rte_eth_dev *dev, const struct rte_flow_ops **ops)
 	return 0;
 }
 
+static int
+gve_read_clock(struct rte_eth_dev *dev, uint64_t *clock)
+{
+	struct gve_priv *priv = dev->data->dev_private;
+	uint64_t ts;
+	int err;
+
+	if (!priv->nic_timestamp_supported)
+		return -EOPNOTSUPP;
+
+	if (!priv->nic_ts_report_mz)
+		return -EIO;
+
+	err = gve_adminq_report_nic_timestamp(priv, priv->nic_ts_report_mz->iova);
+	if (err != 0)
+		return err;
+
+	ts = be64_to_cpu(priv->nic_ts_report->nic_timestamp);
+	*clock = ts;
+
+	/* Update the cached value */
+	rte_atomic_store_explicit(&priv->last_read_nic_timestamp, ts, rte_memory_order_relaxed);
+	rte_atomic_store_explicit(&priv->nic_ts_read_fails, 0, rte_memory_order_relaxed);
+	rte_atomic_store_explicit(&priv->nic_ts_stale, 0, rte_memory_order_release);
+
+	return 0;
+}
+
 static const struct eth_dev_ops gve_eth_dev_ops = {
 	.dev_configure        = gve_dev_configure,
 	.dev_start            = gve_dev_start,
-- 
2.54.0.563.g4f69b47b94-goog