[PATCH 09/14] net/enetc: support stats reset for VF

[Gagandeep Singh]

The NETC SI-level hardware counters (SIROCT0, SIRFRM0, SITOCT0,
SITFRM0, SITDFCR) are read-only for a VF and cannot be directly
zeroed. No VSI-PSI command class exists for stats reset, and using
FLR/soft-reset to clear counters is not reliable due to a known
hardware erratum on some NETC platforms.

Implement stats_reset for the enetc4 VF PMD using a software
snapshot/delta approach: on stats_reset, the current HW counter
values are captured as a baseline in a new per-device
enetc4_vf_stats_saved struct. stats_get then reports the delta
(current_hw_value - saved_baseline), so counters appear to start
from zero after each reset call. Per-ring software Rx error
accumulators (ierrors) are zeroed directly on reset.

Register the stats_reset callback in both VF ops tables
(enetc4_vf_ops and enetc4_vf_ops_no_vsi_m) so the feature is
available regardless of whether the VSI messaging path is enabled.

Signed-off-by: Gagandeep Singh <g.singh at nxp.com>
---
 doc/guides/rel_notes/release_26_11.rst |  1 +
 drivers/net/enetc/enetc.h              | 17 +++++++
 drivers/net/enetc/enetc4_vf.c          | 61 +++++++++++++++++++++++---
 3 files changed, 74 insertions(+), 5 deletions(-)

diff --git a/doc/guides/rel_notes/release_26_11.rst b/doc/guides/rel_notes/release_26_11.rst
index eca0dc1dea..b88e2825a6 100644
--- a/doc/guides/rel_notes/release_26_11.rst
+++ b/doc/guides/rel_notes/release_26_11.rst
@@ -68,6 +68,7 @@ New Features
   * Added register dump support for ENETC4 PF and VF.
   * Added ring parameters support for the ENETC4 VF (rxq_info_get / txq_info_get).
   * Refreshed VF link speed on the link-up interrupt in the ENETC4 VF driver.
+  * Added stats reset for the ENETC4 VF using a software snapshot/delta approach.
 
 Removed Items
 -------------
diff --git a/drivers/net/enetc/enetc.h b/drivers/net/enetc/enetc.h
index 367d350dde..3590cf6639 100644
--- a/drivers/net/enetc/enetc.h
+++ b/drivers/net/enetc/enetc.h
@@ -105,6 +105,21 @@ struct enetc_bdr {
 	uint8_t rsc_enable;
 };
 
+/*
+ * Saved SI counter baseline for VF stats reset. Since the SI-level
+ * hardware counters (SIROCT0, SIRFRM0, SITOCT0, SITFRM0, SITDFCR)
+ * are read-only for a VF and cannot be directly zeroed, stats_reset
+ * captures the current counter values as a baseline. stats_get then
+ * reports the delta: current_hw_value - baseline.
+ */
+struct enetc4_vf_stats_saved {
+	uint64_t ipackets;
+	uint64_t opackets;
+	uint64_t ibytes;
+	uint64_t obytes;
+	uint64_t oerrors;
+};
+
 struct enetc_eth_hw {
 	struct rte_eth_dev *ndev;
 	struct enetc_hw hw;
@@ -124,6 +139,8 @@ struct enetc_eth_hw {
 	 * for PF kernel versions before 6.18.37. Set via vf_link_legacy devarg.
 	 */
 	uint8_t vf_link_legacy;
+	/* Baseline snapshot for VF stats reset (software delta approach). */
+	struct enetc4_vf_stats_saved vf_stats_saved;
 };
 
 /*
diff --git a/drivers/net/enetc/enetc4_vf.c b/drivers/net/enetc/enetc4_vf.c
index 58e38fe398..70cef39116 100644
--- a/drivers/net/enetc/enetc4_vf.c
+++ b/drivers/net/enetc/enetc4_vf.c
@@ -225,15 +225,64 @@ enetc4_vf_stats_get(struct rte_eth_dev *dev, struct rte_eth_stats *stats,
 	uint8_t i;
 
 	PMD_INIT_FUNC_TRACE();
-	stats->ipackets = enetc4_rd(enetc_hw, ENETC4_SIRFRM0);
-	stats->opackets = enetc4_rd(enetc_hw, ENETC4_SITFRM0);
-	stats->ibytes = enetc4_rd(enetc_hw, ENETC4_SIROCT0);
-	stats->obytes = enetc4_rd(enetc_hw, ENETC4_SITOCT0);
-	stats->oerrors = enetc4_rd(enetc_hw, ENETC4_SITDFCR);
+
+	/*
+	 * The SI-level counters are read-only for a VF; they cannot be
+	 * zeroed directly. Instead, stats_reset captures a baseline
+	 * snapshot, and stats_get reports the delta so that the reported
+	 * values appear to start from zero after each reset call.
+	 */
+	stats->ipackets = enetc4_rd(enetc_hw, ENETC4_SIRFRM0) -
+			  hw->vf_stats_saved.ipackets;
+	stats->opackets = enetc4_rd(enetc_hw, ENETC4_SITFRM0) -
+			  hw->vf_stats_saved.opackets;
+	stats->ibytes   = enetc4_rd(enetc_hw, ENETC4_SIROCT0) -
+			  hw->vf_stats_saved.ibytes;
+	stats->obytes   = enetc4_rd(enetc_hw, ENETC4_SITOCT0) -
+			  hw->vf_stats_saved.obytes;
+	stats->oerrors  = enetc4_rd(enetc_hw, ENETC4_SITDFCR) -
+			  hw->vf_stats_saved.oerrors;
+
 	for (i = 0; i < dev->data->nb_rx_queues; i++) {
 		rx_ring = dev->data->rx_queues[i];
 		stats->ierrors += rx_ring->ierrors;
 	}
+
+	return 0;
+}
+
+/*
+ * Reset VF statistics by capturing a new baseline snapshot of the
+ * SI-level hardware counters. Because those counters are read-only
+ * for a VF (hardware erratum prevents reliable clear via FLR/soft
+ * reset too), the driver uses a software delta approach: every
+ * stats_get call reports current_hw_value - saved_baseline.
+ */
+static int
+enetc4_vf_stats_reset(struct rte_eth_dev *dev)
+{
+	struct enetc_eth_hw *hw =
+		ENETC_DEV_PRIVATE_TO_HW(dev->data->dev_private);
+	struct enetc_hw *enetc_hw = &hw->hw;
+	struct enetc_bdr *rx_ring;
+	uint8_t i;
+
+	PMD_INIT_FUNC_TRACE();
+
+	/* Snapshot current HW SI counter values as the new zero baseline. */
+	hw->vf_stats_saved.ipackets = enetc4_rd(enetc_hw, ENETC4_SIRFRM0);
+	hw->vf_stats_saved.opackets = enetc4_rd(enetc_hw, ENETC4_SITFRM0);
+	hw->vf_stats_saved.ibytes   = enetc4_rd(enetc_hw, ENETC4_SIROCT0);
+	hw->vf_stats_saved.obytes   = enetc4_rd(enetc_hw, ENETC4_SITOCT0);
+	hw->vf_stats_saved.oerrors  = enetc4_rd(enetc_hw, ENETC4_SITDFCR);
+
+	/* Reset the per-ring software Rx error accumulators. */
+	for (i = 0; i < dev->data->nb_rx_queues; i++) {
+		rx_ring = dev->data->rx_queues[i];
+		if (rx_ring)
+			rx_ring->ierrors = 0;
+	}
+
 	return 0;
 }
 
@@ -1514,6 +1563,7 @@ static const struct eth_dev_ops enetc4_vf_ops_no_vsi_m = {
 	.dev_stop             = enetc4_vf_dev_stop,
 	.dev_close            = enetc4_dev_close,
 	.stats_get            = enetc4_vf_stats_get,
+	.stats_reset          = enetc4_vf_stats_reset,
 	.dev_infos_get        = enetc4_vf_dev_infos_get,
 	.fw_version_get       = enetc4_vf_fw_version_get,
 	.get_reg              = enetc4_vf_get_regs,
@@ -1538,6 +1588,7 @@ static const struct eth_dev_ops enetc4_vf_ops = {
 	.dev_stop             = enetc4_vf_dev_stop,
 	.dev_close            = enetc4_dev_close,
 	.stats_get            = enetc4_vf_stats_get,
+	.stats_reset          = enetc4_vf_stats_reset,
 	.dev_infos_get        = enetc4_vf_dev_infos_get,
 	.get_reg              = enetc4_vf_get_regs,
 	.mtu_set              = enetc4_vf_mtu_set,