[PATCH v12 10/15] net/enetc: support stats reset for VF

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 <[email protected]>
Acked-by: Hemant Agrawal <[email protected]>
---
 doc/guides/rel_notes/release_26_11.rst |  1 +
 drivers/net/enetc/base/enetc4_hw.h     | 22 ++++++++++
 drivers/net/enetc/enetc.h              | 17 +++++++
 drivers/net/enetc/enetc4_vf.c          | 61 +++++++++++++++++++++++---
 4 files changed, 96 insertions(+), 5 deletions(-)

diff --git a/doc/guides/rel_notes/release_26_11.rst b/doc/guides/rel_notes/release_26_11.rst
index 1765adc1bc..a42577c681 100644
--- a/doc/guides/rel_notes/release_26_11.rst
+++ b/doc/guides/rel_notes/release_26_11.rst
@@ -70,6 +70,7 @@ 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/base/enetc4_hw.h b/drivers/net/enetc/base/enetc4_hw.h
index 70af9118a3..060dc03991 100644
--- a/drivers/net/enetc/base/enetc4_hw.h
+++ b/drivers/net/enetc/base/enetc4_hw.h
@@ -8,6 +8,7 @@
 #ifndef _ENETC4_HW_H_
 #define _ENETC4_HW_H_
 #include <rte_io.h>
+#include "enetc_hw.h"
 
 #define BIT(x)		((uint64_t)1 << ((x)))
 
@@ -277,6 +278,27 @@ struct enetc_rx_bd_ext {
 #define enetc4_wr_reg(reg, val)  rte_write32((val), (void *)(reg))
 
 #define enetc4_rd(hw, off)	 enetc4_rd_reg((size_t)(hw)->reg + (off))
+static inline uint64_t
+enetc4_rd64(struct enetc_hw *hw, uint32_t off)
+{
+	size_t base = (size_t)hw->reg + off;
+	uint32_t lo, hi, hi_check;
+
+	/*
+	 * A 64-bit statistics counter is read as two 32-bit accesses, so
+	 * the low word can carry into the high word between the two reads
+	 * and produce a value that is off by 2^32. Read the high word,
+	 * then the low word, then re-read the high word; if the high word
+	 * changed a carry happened during the sequence, so retry.
+	 */
+	do {
+		hi = enetc4_rd_reg(base + 4);
+		lo = enetc4_rd_reg(base);
+		hi_check = enetc4_rd_reg(base + 4);
+	} while (hi != hi_check);
+
+	return (uint64_t)hi << 32 | lo;
+}
 #define enetc4_wr(hw, off, val)  enetc4_wr_reg((size_t)(hw)->reg + (off), val)
 /* port register accessors - PF only */
 #define enetc4_port_rd(hw, off)  enetc4_rd_reg((size_t)(hw)->port + (off))
diff --git a/drivers/net/enetc/enetc.h b/drivers/net/enetc/enetc.h
index 62a8690f10..ae7fecbed2 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;
@@ -125,6 +140,8 @@ struct enetc_eth_hw {
 	 */
 	uint8_t vf_link_legacy;
 	pthread_mutex_t vsi_lock; /* serializes all VSI-PSI mailbox transactions */
+	/* 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 6dd3bc1f0b..a6e9f6b859 100644
--- a/drivers/net/enetc/enetc4_vf.c
+++ b/drivers/net/enetc/enetc4_vf.c
@@ -224,15 +224,64 @@ 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_rd64(enetc_hw, ENETC4_SIRFRM0) -
+			  hw->vf_stats_saved.ipackets;
+	stats->opackets = enetc4_rd64(enetc_hw, ENETC4_SITFRM0) -
+			  hw->vf_stats_saved.opackets;
+	stats->ibytes   = enetc4_rd64(enetc_hw, ENETC4_SIROCT0) -
+			  hw->vf_stats_saved.ibytes;
+	stats->obytes   = enetc4_rd64(enetc_hw, ENETC4_SITOCT0) -
+			  hw->vf_stats_saved.obytes;
+	stats->oerrors  = (uint32_t)enetc4_rd(enetc_hw, ENETC4_SITDFCR) -
+			  (uint32_t)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_rd64(enetc_hw, ENETC4_SIRFRM0);
+	hw->vf_stats_saved.opackets = enetc4_rd64(enetc_hw, ENETC4_SITFRM0);
+	hw->vf_stats_saved.ibytes   = enetc4_rd64(enetc_hw, ENETC4_SIROCT0);
+	hw->vf_stats_saved.obytes   = enetc4_rd64(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;
 }
 
@@ -1553,6 +1602,7 @@ 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,
 	.get_reg              = enetc4_vf_get_regs,
 	.mtu_set              = enetc4_vf_mtu_set,
@@ -1576,6 +1626,7 @@ 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,
 	.fw_version_get       = enetc4_vf_fw_version_get,
 	.get_reg              = enetc4_vf_get_regs,
-- 
2.25.1