[PATCH net-next] net: phy: acx00: report receive statistics

[James Hilliard <james.hilliard1@gmail.com>]

Expose receive frame and byte totals through the generic PHY statistics
interface as rx_packets and rx_bytes, alongside CRC errors in rx_errors.
Report the hardware totals directly: the packet and byte counters include
errored frames as well as successfully received traffic.

Collect the free-running 32-bit counters through phylib's
update_stats callback and accumulate wrap-safe deltas in 64-bit totals.
Read the high half on either side of the low half and retry until both
high-half reads agree.

Hardware testing confirmed that the receive-byte counter wraps at
4,000,000,000, while the receive-packet and CRC-error counters wrap at
2^32. Use the corresponding modulus for each counter so rollover does
not inflate the software totals.

Serialize collection and reporting with the package-state mutex so reads
cannot race reset or power-off, and the totals are safe on 32-bit systems.
Commit a sample only after all counter reads and page restoration succeed.
The reporting callback returns cached totals without accessing MDIO.

Take a best-effort final snapshot before soft reset and suspend. Invalidate
the hardware baseline before reset or power-off, including failed power-off
attempts, and establish a fresh baseline after configuration. Preserve the
software totals across these transitions and retain the live baseline when
resume reconfigures an already active PHY. A failed initial snapshot can be
retried by the periodic collector without preventing initialization.

Signed-off-by: James Hilliard <james.hilliard1@gmail.com>
---
 drivers/net/phy/xpowers/acx00.c | 157 +++++++++++++++++++++++++++++++++++++++-
 1 file changed, 154 insertions(+), 3 deletions(-)

diff --git a/drivers/net/phy/xpowers/acx00.c b/drivers/net/phy/xpowers/acx00.c
index d19ba6d8069a..1375784d2837 100644
--- a/drivers/net/phy/xpowers/acx00.c
+++ b/drivers/net/phy/xpowers/acx00.c
@@ -8,6 +8,7 @@
 
 #include <linux/bitfield.h>
 #include <linux/device.h>
+#include <linux/ethtool.h>
 #include <linux/module.h>
 #include <linux/mutex.h>
 #include <linux/nvmem-consumer.h>
@@ -31,6 +32,7 @@
 #define ACX00_PAGE_2				2
 #define ACX00_PAGE_6				6
 #define ACX00_PAGE_8				8
+#define ACX00_PAGE_9				9
 
 #define ACX00_PAGE0_GLOBAL_CONFIG_REG		0x13
 #define ACX00_PAGE0_XMII_RX_CLOCK_INVERT	BIT(12)
@@ -76,6 +78,29 @@
 	(ACX00_PAGE8_AUTO_CAL_TX_LEVEL_ADJUST_BYPASS | \
 	 ACX00_PAGE8_AUTO_CAL_LOW_CAL_OPAQUE_BITS)
 
+#define ACX00_PAGE9_RX_BYTES_HIGH_REG		0x19
+#define ACX00_PAGE9_RX_PACKETS_HIGH_REG		0x1b
+#define ACX00_PAGE9_RX_CRC_ERRORS_HIGH_REG	0x1d
+
+/*
+ * Hardware testing confirmed that the receive byte counter wraps at
+ * 4,000,000,000 rather than 2^32.
+ */
+#define ACX00_RX_BYTES_WRAP			4000000000ULL
+
+enum acx00_ephy_stat {
+	ACX00_STAT_RX_BYTES,
+	ACX00_STAT_RX_PACKETS,
+	ACX00_STAT_RX_CRC_ERRORS,
+	ACX00_NUM_STATS,
+};
+
+static const u8 acx00_ephy_stat_regs[ACX00_NUM_STATS] = {
+	[ACX00_STAT_RX_BYTES] = ACX00_PAGE9_RX_BYTES_HIGH_REG,
+	[ACX00_STAT_RX_PACKETS] = ACX00_PAGE9_RX_PACKETS_HIGH_REG,
+	[ACX00_STAT_RX_CRC_ERRORS] = ACX00_PAGE9_RX_CRC_ERRORS_HIGH_REG,
+};
+
 /*
  * Another integration of this exact-ID PHY documents its digital vendor
  * register map, which also matches the observed ACx00 reset values. The ACx00
@@ -86,11 +111,15 @@
 struct acx00_ephy_priv {
 	struct phy_device *phydev;
 	struct acx00_ephy_control *control;
-	/* Serializes package state and multi-register power sequences. */
+	/* Serializes package state, power sequences and statistics. */
 	struct mutex state_lock;
 	bool is_ac300;
 	bool use_low_calibration_tuning;
 	bool xmii_rx_clock_inverted;
+	bool stats_active;
+	bool stats_valid;
+	u32 stats_last[ACX00_NUM_STATS];
+	u64 stats[ACX00_NUM_STATS];
 };
 
 static int acx00_ephy_read_page(struct phy_device *phydev)
@@ -110,6 +139,105 @@ static int acx00_ephy_write_page(struct phy_device *phydev, int page)
 			   FIELD_PREP(ACX00_PAGE_SELECT_MASK, page));
 }
 
+static int acx00_ephy_read_counter(struct phy_device *phydev, u8 reg, u32 *count)
+{
+	int high, low, check;
+
+	/* The free-running counter can carry while its two halves are read. */
+	do {
+		high = __phy_read(phydev, reg);
+		if (high < 0)
+			return high;
+		low = __phy_read(phydev, reg + 1);
+		if (low < 0)
+			return low;
+		check = __phy_read(phydev, reg);
+		if (check < 0)
+			return check;
+	} while (high != check);
+
+	*count = (u32)high << 16 | low;
+	return 0;
+}
+
+static int __acx00_ephy_update_stats(struct phy_device *phydev)
+{
+	struct acx00_ephy_priv *priv = phydev->priv;
+	u32 counts[ACX00_NUM_STATS];
+	int oldpage;
+	int ret;
+	int i;
+
+	lockdep_assert_held(&priv->state_lock);
+
+	if (!priv->stats_active)
+		return 0;
+
+	oldpage = phy_select_page(phydev, ACX00_PAGE_9);
+	if (oldpage < 0)
+		return phy_restore_page(phydev, oldpage, oldpage);
+
+	for (i = 0; i < ACX00_NUM_STATS; i++) {
+		ret = acx00_ephy_read_counter(phydev, acx00_ephy_stat_regs[i],
+					      &counts[i]);
+		if (ret)
+			break;
+	}
+	ret = phy_restore_page(phydev, oldpage, ret);
+	if (ret)
+		return ret;
+
+	for (i = 0; i < ACX00_NUM_STATS; i++) {
+		u64 count = counts[i];
+
+		if (priv->stats_valid) {
+			if (count < priv->stats_last[i])
+				count += i == ACX00_STAT_RX_BYTES ?
+					ACX00_RX_BYTES_WRAP : BIT_ULL(32);
+			priv->stats[i] += count - priv->stats_last[i];
+		}
+		priv->stats_last[i] = counts[i];
+	}
+	priv->stats_valid = true;
+
+	return 0;
+}
+
+static int acx00_ephy_update_stats(struct phy_device *phydev)
+{
+	struct acx00_ephy_priv *priv = phydev->priv;
+	int ret;
+
+	mutex_lock(&priv->state_lock);
+	ret = __acx00_ephy_update_stats(phydev);
+	mutex_unlock(&priv->state_lock);
+
+	return ret;
+}
+
+static void acx00_ephy_get_phy_stats(struct phy_device *phydev,
+				     struct ethtool_eth_phy_stats *eth_stats,
+				     struct ethtool_phy_stats *stats)
+{
+	struct acx00_ephy_priv *priv = phydev->priv;
+
+	mutex_lock(&priv->state_lock);
+	stats->rx_packets = priv->stats[ACX00_STAT_RX_PACKETS];
+	stats->rx_bytes = priv->stats[ACX00_STAT_RX_BYTES];
+	stats->rx_errors = priv->stats[ACX00_STAT_RX_CRC_ERRORS];
+	mutex_unlock(&priv->state_lock);
+}
+
+static void acx00_ephy_snapshot_stats(struct phy_device *phydev)
+{
+	int ret;
+
+	/* Statistics collection must not prevent reset or power management. */
+	ret = __acx00_ephy_update_stats(phydev);
+	if (ret)
+		phydev_dbg(phydev, "failed to snapshot statistics: %pe\n", ERR_PTR(ret));
+}
+
 static int acx00_ephy_control_power_on(struct acx00_ephy_priv *priv)
 {
 	lockdep_assert_held(&priv->state_lock);
@@ -122,6 +250,10 @@ static int acx00_ephy_control_power_off(struct acx00_ephy_priv *priv)
 {
 	lockdep_assert_held(&priv->state_lock);
 
+	/* Even a failed power-off can have reset the hardware counter. */
+	priv->stats_active = false;
+	priv->stats_valid = false;
+
 	return priv->control->power_off(priv->control);
 }
 
@@ -350,6 +482,10 @@ static int acx00_ephy_soft_reset(struct phy_device *phydev)
 
 	mutex_lock(&priv->state_lock);
 
+	acx00_ephy_snapshot_stats(phydev);
+	priv->stats_active = false;
+	priv->stats_valid = false;
+
 	ret = acx00_ephy_set_interface(phydev);
 	if (ret)
 		goto out_power_off;
@@ -475,10 +611,21 @@ static int __acx00_ephy_config_init(struct phy_device *phydev)
 
 	/* Restore the standard EEE policy retained by phylib across resets. */
 	ret = genphy_c45_an_config_eee_aneg(phydev);
-	if (ret <= 0)
+	if (ret < 0)
 		return ret;
+	if (ret > 0) {
+		ret = genphy_restart_aneg(phydev);
+		if (ret)
+			return ret;
+	}
 
-	return genphy_restart_aneg(phydev);
+	if (!priv->stats_active) {
+		/* Establish a new baseline after reset, retaining the software total. */
+		priv->stats_active = true;
+		acx00_ephy_snapshot_stats(phydev);
+	}
+
+	return 0;
 }
 
 static int acx00_ephy_config_init(struct phy_device *phydev)
@@ -550,6 +697,8 @@ static int acx00_ephy_suspend(struct phy_device *phydev)
 	mutex_lock(&phydev->lock);
 	mutex_lock(&priv->state_lock);
 
+	acx00_ephy_snapshot_stats(phydev);
+
 	ret = genphy_suspend(phydev);
 	if (ret)
 		goto out_unlock;
@@ -616,6 +765,8 @@ static struct phy_driver acx00_ephy_driver[] = {
 		.soft_reset = acx00_ephy_soft_reset,
 		.config_init = acx00_ephy_config_init,
 		.disable_autonomous_eee = acx00_ephy_disable_autonomous_eee,
+		.get_phy_stats = acx00_ephy_get_phy_stats,
+		.update_stats = acx00_ephy_update_stats,
 		.suspend = acx00_ephy_suspend,
 		.resume = acx00_ephy_resume,
 	},

---
base-commit: 734bef548a96e8774d6eef5dfa2026c6edc4e80b
change-id: 20261024-submit-acx00-phy-stats-v1-d838f77444e8

Best regards,
--  
James Hilliard <james.hilliard1@gmail.com>