net: phy: dp83td510: add statistics support

Add support for reporting PHY statistics in the DP83TD510 driver. This
includes cumulative tracking of transmit/receive packet counts, and
error counts. Implemented functions to update and provide statistics via
ethtool, with optional polling support enabled through `PHY_POLL_STATS`.

Signed-off-by: Oleksij Rempel <o.rempel@pengutronix.de>
Signed-off-by: Paolo Abeni <pabeni@redhat.com>

drivers/net/phy/dp83td510.c

@@ -34,6 +34,29 @@
 #define DP83TD510E_CTRL_HW_RESET		BIT(15)
 #define DP83TD510E_CTRL_SW_RESET		BIT(14)
 
+/*
+ * DP83TD510E_PKT_STAT_x registers correspond to similarly named registers
+ * in the datasheet (PKT_STAT_1 through PKT_STAT_6). These registers store
+ * 32-bit or 16-bit counters for TX and RX statistics and must be read in
+ * sequence to ensure the counters are cleared correctly.
+ *
+ * - DP83TD510E_PKT_STAT_1: Contains TX packet count bits [15:0].
+ * - DP83TD510E_PKT_STAT_2: Contains TX packet count bits [31:16].
+ * - DP83TD510E_PKT_STAT_3: Contains TX error packet count.
+ * - DP83TD510E_PKT_STAT_4: Contains RX packet count bits [15:0].
+ * - DP83TD510E_PKT_STAT_5: Contains RX packet count bits [31:16].
+ * - DP83TD510E_PKT_STAT_6: Contains RX error packet count.
+ *
+ * Keeping the register names as defined in the datasheet helps maintain
+ * clarity and alignment with the documentation.
+ */
+#define DP83TD510E_PKT_STAT_1			0x12b
+#define DP83TD510E_PKT_STAT_2			0x12c
+#define DP83TD510E_PKT_STAT_3			0x12d
+#define DP83TD510E_PKT_STAT_4			0x12e
+#define DP83TD510E_PKT_STAT_5			0x12f
+#define DP83TD510E_PKT_STAT_6			0x130
+
 #define DP83TD510E_AN_STAT_1			0x60c
 #define DP83TD510E_MASTER_SLAVE_RESOL_FAIL	BIT(15)
 
@@ -58,8 +81,16 @@ static const u16 dp83td510_mse_sqi_map[] = {
 	0x0000  /* 24dB =< SNR */
 };
 
+struct dp83td510_stats {
+	u64 tx_pkt_cnt;
+	u64 tx_err_pkt_cnt;
+	u64 rx_pkt_cnt;
+	u64 rx_err_pkt_cnt;
+};
+
 struct dp83td510_priv {
 	bool alcd_test_active;
+	struct dp83td510_stats stats;
 };
 
 /* Time Domain Reflectometry (TDR) Functionality of DP83TD510 PHY
@@ -177,6 +208,85 @@ struct dp83td510_priv {
 #define DP83TD510E_ALCD_COMPLETE			BIT(15)
 #define DP83TD510E_ALCD_CABLE_LENGTH			GENMASK(10, 0)
 
+/**
+ * dp83td510_update_stats - Update the PHY statistics for the DP83TD510 PHY.
+ * @phydev: Pointer to the phy_device structure.
+ *
+ * The function reads the PHY statistics registers and updates the statistics
+ * structure.
+ *
+ * Returns: 0 on success or a negative error code on failure.
+ */
+static int dp83td510_update_stats(struct phy_device *phydev)
+{
+	struct dp83td510_priv *priv = phydev->priv;
+	u32 count;
+	int ret;
+
+	/* The DP83TD510E_PKT_STAT registers are divided into two groups:
+	 * - Group 1 (TX stats): DP83TD510E_PKT_STAT_1 to DP83TD510E_PKT_STAT_3
+	 * - Group 2 (RX stats): DP83TD510E_PKT_STAT_4 to DP83TD510E_PKT_STAT_6
+	 *
+	 * Registers in each group are cleared only after reading them in a
+	 * plain sequence (e.g., 1, 2, 3 for Group 1 or 4, 5, 6 for Group 2).
+	 * Any deviation from the sequence, such as reading 1, 2, 1, 2, 3, will
+	 * prevent the group from being cleared. Additionally, the counters
+	 * for a group are frozen as soon as the first register in that group
+	 * is accessed.
+	 */
+	ret = phy_read_mmd(phydev, MDIO_MMD_VEND2, DP83TD510E_PKT_STAT_1);
+	if (ret < 0)
+		return ret;
+	/* tx_pkt_cnt_15_0 */
+	count = ret;
+
+	ret = phy_read_mmd(phydev, MDIO_MMD_VEND2, DP83TD510E_PKT_STAT_2);
+	if (ret < 0)
+		return ret;
+	/* tx_pkt_cnt_31_16 */
+	count |= ret << 16;
+	priv->stats.tx_pkt_cnt += count;
+
+	ret = phy_read_mmd(phydev, MDIO_MMD_VEND2, DP83TD510E_PKT_STAT_3);
+	if (ret < 0)
+		return ret;
+	/* tx_err_pkt_cnt */
+	priv->stats.tx_err_pkt_cnt += ret;
+
+	ret = phy_read_mmd(phydev, MDIO_MMD_VEND2, DP83TD510E_PKT_STAT_4);
+	if (ret < 0)
+		return ret;
+	/* rx_pkt_cnt_15_0 */
+	count = ret;
+
+	ret = phy_read_mmd(phydev, MDIO_MMD_VEND2, DP83TD510E_PKT_STAT_5);
+	if (ret < 0)
+		return ret;
+	/* rx_pkt_cnt_31_16 */
+	count |= ret << 16;
+	priv->stats.rx_pkt_cnt += count;
+
+	ret = phy_read_mmd(phydev, MDIO_MMD_VEND2, DP83TD510E_PKT_STAT_6);
+	if (ret < 0)
+		return ret;
+	/* rx_err_pkt_cnt */
+	priv->stats.rx_err_pkt_cnt += ret;
+
+	return 0;
+}
+
+static void dp83td510_get_phy_stats(struct phy_device *phydev,
+				    struct ethtool_eth_phy_stats *eth_stats,
+				    struct ethtool_phy_stats *stats)
+{
+	struct dp83td510_priv *priv = phydev->priv;
+
+	stats->tx_packets = priv->stats.tx_pkt_cnt;
+	stats->tx_errors = priv->stats.tx_err_pkt_cnt;
+	stats->rx_packets = priv->stats.rx_pkt_cnt;
+	stats->rx_errors = priv->stats.rx_err_pkt_cnt;
+}
+
 static int dp83td510_config_intr(struct phy_device *phydev)
 {
 	int ret;
@@ -599,6 +709,8 @@ static struct phy_driver dp83td510_driver[] = {
 	.get_sqi_max	= dp83td510_get_sqi_max,
 	.cable_test_start = dp83td510_cable_test_start,
 	.cable_test_get_status = dp83td510_cable_test_get_status,
+	.get_phy_stats	= dp83td510_get_phy_stats,
+	.update_stats	= dp83td510_update_stats,
 
 	.suspend	= genphy_suspend,
 	.resume		= genphy_resume,