net: phy: phy-c45: add SQI and SQI+ support for OATC14 10Base-T1S PHYs

Add support for reading Signal Quality Indicator (SQI) and enhanced SQI+
from OATC14 10Base-T1S PHYs.

- Introduce MDIO register definitions for DCQ_SQI and DCQ_SQIPLUS.
- Add `genphy_c45_oatc14_get_sqi_max()` to return the maximum supported
  SQI/SQI+ level.
- Add `genphy_c45_oatc14_get_sqi()` to return the current SQI or SQI+
  value.
- Update `include/linux/phy.h` to expose the new APIs.

SQI+ capability is read from the Advanced Diagnostic Features Capability
register (ADFCAP). If SQI+ is supported, the driver calculates the value
from the MSBs of the DCQ_SQIPLUS register; otherwise, it falls back to
basic SQI (0-7 levels). This enables ethtool to report the SQI value for
OATC14 10Base-T1S PHYs.

Open Alliance TC14 10BASE-T1S Advanced Diagnostic PHY Features
Specification ref:
https://opensig.org/wp-content/uploads/2025/06/OPEN_Alliance_10BASE-T1S_Advanced_PHY_features_for-automotive_Ethernet_V2.1b.pdf

Signed-off-by: Parthiban Veerasooran <parthiban.veerasooran@microchip.com>
Reviewed-by: Andrew Lunn <andrew@lunn.ch>
Link: https://patch.msgid.link/20251201032346.6699-2-parthiban.veerasooran@microchip.com
Signed-off-by: Jakub Kicinski <kuba@kernel.org>

1 files changed, 29 insertions, 0 deletions

diff --git a/include/linux/phy.h b/include/linux/phy.h
index 059a104223c4..fbbe028cc4b7 100644
--- a/include/linux/phy.h
+++ b/include/linux/phy.h
@@ -531,6 +531,30 @@ struct macsec_context;
 struct macsec_ops;
 
 /**
+ * struct phy_oatc14_sqi_capability - SQI capability information for OATC14
+ *                                    10Base-T1S PHY
+ * @updated: Indicates whether the SQI capability fields have been updated.
+ * @sqi_max: Maximum supported Signal Quality Indicator (SQI) level reported by
+ *           the PHY.
+ * @sqiplus_bits: Bits for SQI+ levels supported by the PHY.
+ *                0 - SQI+ is not supported
+ *                3 - SQI+ is supported, using 3 bits (8 levels)
+ *                4 - SQI+ is supported, using 4 bits (16 levels)
+ *                5 - SQI+ is supported, using 5 bits (32 levels)
+ *                6 - SQI+ is supported, using 6 bits (64 levels)
+ *                7 - SQI+ is supported, using 7 bits (128 levels)
+ *                8 - SQI+ is supported, using 8 bits (256 levels)
+ *
+ * This structure is used by the OATC14 10Base-T1S PHY driver to store the SQI
+ * and SQI+ capability information retrieved from the PHY.
+ */
+struct phy_oatc14_sqi_capability {
+	bool updated;
+	int sqi_max;
+	u8 sqiplus_bits;
+};
+
+/**
  * struct phy_device - An instance of a PHY
  *
  * @mdio: MDIO bus this PHY is on
@@ -626,6 +650,7 @@ struct macsec_ops;
  * @link_down_events: Number of times link was lost
  * @shared: Pointer to private data shared by phys in one package
  * @priv: Pointer to driver private data
+ * @oatc14_sqi_capability: SQI capability information for OATC14 10Base-T1S PHY
  *
  * interrupts currently only supports enabled or disabled,
  * but could be changed in the future to support enabling
@@ -772,6 +797,8 @@ struct phy_device {
 	/* MACsec management functions */
 	const struct macsec_ops *macsec_ops;
 #endif
+
+	struct phy_oatc14_sqi_capability oatc14_sqi_capability;
 };
 
 /* Generic phy_device::dev_flags */
@@ -2257,6 +2284,8 @@ int genphy_c45_an_config_eee_aneg(struct phy_device *phydev);
 int genphy_c45_oatc14_cable_test_start(struct phy_device *phydev);
 int genphy_c45_oatc14_cable_test_get_status(struct phy_device *phydev,
 					    bool *finished);
+int genphy_c45_oatc14_get_sqi_max(struct phy_device *phydev);
+int genphy_c45_oatc14_get_sqi(struct phy_device *phydev);
 
 /* The gen10g_* functions are the old Clause 45 stub */
 int gen10g_config_aneg(struct phy_device *phydev);