Add support for Airoha AN8855 Internal Switch Gigabit PHY.

This is a simple PHY driver to configure and calibrate the PHY for the
AN8855 Switch.

Signed-off-by: Christian Marangi <ansuelsmth@gmail.com>
---
 MAINTAINERS                  |   1 +
 drivers/net/phy/Kconfig      |   5 +
 drivers/net/phy/Makefile     |   1 +
 drivers/net/phy/air_an8855.c | 187 +++++++++++++++++++++++++++++++++++
 4 files changed, 194 insertions(+)
 create mode 100644 drivers/net/phy/air_an8855.c

diff --git a/MAINTAINERS b/MAINTAINERS
index e3077d9feee2..cf34add2a0bb 100644
--- a/MAINTAINERS
+++ b/MAINTAINERS
@@ -726,6 +726,7 @@ S:	Maintained
 F:	Documentation/devicetree/bindings/net/dsa/airoha,an8855.yaml
 F:	drivers/net/dsa/an8855.c
 F:	drivers/net/dsa/an8855.h
+F:	drivers/net/phy/air_an8855.c
 
 AIROHA ETHERNET DRIVER
 M:	Lorenzo Bianconi <lorenzo@kernel.org>
diff --git a/drivers/net/phy/Kconfig b/drivers/net/phy/Kconfig
index ee3ea0b56d48..1d474038ea7f 100644
--- a/drivers/net/phy/Kconfig
+++ b/drivers/net/phy/Kconfig
@@ -79,6 +79,11 @@ config SFP
 
 comment "MII PHY device drivers"
 
+config AIR_AN8855_PHY
+	tristate "Airoha AN8855 Internal Gigabit PHY"
+	help
+	  Currently supports the internal Airoha AN8855 Switch PHY.
+
 config AIR_EN8811H_PHY
 	tristate "Airoha EN8811H 2.5 Gigabit PHY"
 	help
diff --git a/drivers/net/phy/Makefile b/drivers/net/phy/Makefile
index 90f886844381..baba7894785b 100644
--- a/drivers/net/phy/Makefile
+++ b/drivers/net/phy/Makefile
@@ -35,6 +35,7 @@ obj-y				+= $(sfp-obj-y) $(sfp-obj-m)
 
 obj-$(CONFIG_ADIN_PHY)		+= adin.o
 obj-$(CONFIG_ADIN1100_PHY)	+= adin1100.o
+obj-$(CONFIG_AIR_AN8855_PHY)   += air_an8855.o
 obj-$(CONFIG_AIR_EN8811H_PHY)   += air_en8811h.o
 obj-$(CONFIG_AMD_PHY)		+= amd.o
 obj-$(CONFIG_AMCC_QT2025_PHY)	+= qt2025.o
diff --git a/drivers/net/phy/air_an8855.c b/drivers/net/phy/air_an8855.c
new file mode 100644
index 000000000000..d40b0b17a2e4
--- /dev/null
+++ b/drivers/net/phy/air_an8855.c
@@ -0,0 +1,187 @@
+// SPDX-License-Identifier: GPL-2.0+
+
+#include <linux/phy.h>
+#include <linux/module.h>
+#include <linux/bitfield.h>
+
+#define AN8855_PHY_PAGE_CTRL			0x1f
+#define   AN8855_PHY_NORMAL_PAGE		0x0
+#define   AN8855_PHY_EXT_PAGE			0x1
+
+#define AN8855_PHY_EXT_REG_14			0x14
+#define   AN8855_PHY_EN_DOWN_SHFIT		BIT(4)
+
+/* R50 Calibration regs in MDIO_MMD_VEND1 */
+#define AN8855_PHY_R500HM_RSEL_TX_AB		0x174
+#define AN8855_PHY_R50OHM_RSEL_TX_A_EN		BIT(15)
+#define AN8855_PHY_R50OHM_RSEL_TX_A		GENMASK(14, 8)
+#define AN8855_PHY_R50OHM_RSEL_TX_B_EN		BIT(7)
+#define AN8855_PHY_R50OHM_RSEL_TX_B		GENMASK(6, 0)
+#define AN8855_PHY_R500HM_RSEL_TX_CD		0x175
+#define AN8855_PHY_R50OHM_RSEL_TX_C_EN		BIT(15)
+#define AN8855_PHY_R50OHM_RSEL_TX_C		GENMASK(14, 8)
+#define AN8855_PHY_R50OHM_RSEL_TX_D_EN		BIT(7)
+#define AN8855_PHY_R50OHM_RSEL_TX_D		GENMASK(6, 0)
+
+/* PHY TX PAIR DELAY SELECT Register */
+#define PHY_TX_PAIR_DLY_SEL_GBE			0x013
+/* PHY ADC Register */
+#define PHY_RXADC_CTRL				0x0d8
+#define PHY_RXADC_REV_0				0x0d9
+#define PHY_RXADC_REV_1				0x0da
+
+#define AN8855_PHY_ID			0xc0ff0410
+
+static int an8855_config_init(struct phy_device *phydev)
+{
+	u8 calibration_data[4];
+	int ret;
+
+	memcpy(calibration_data, &phydev->dev_flags, sizeof(u32));
+
+	/* Enable HW auto downshift */
+	ret = phy_write(phydev, AN8855_PHY_PAGE_CTRL, AN8855_PHY_EXT_PAGE);
+	if (ret)
+		return ret;
+	ret = phy_set_bits(phydev, AN8855_PHY_EXT_REG_14,
+			   AN8855_PHY_EN_DOWN_SHFIT);
+	if (ret)
+		return ret;
+	ret = phy_write(phydev, AN8855_PHY_PAGE_CTRL, AN8855_PHY_NORMAL_PAGE);
+	if (ret)
+		return ret;
+
+	/* Enable Asymmetric Pause Capability */
+	ret = phy_set_bits(phydev, MII_ADVERTISE, ADVERTISE_PAUSE_ASYM);
+	if (ret)
+		return ret;
+
+	/* Disable EEE */
+	ret = phy_write_mmd(phydev, MDIO_MMD_AN, MDIO_AN_EEE_ADV, 0);
+	if (ret)
+		return ret;
+
+	/* Apply calibration values, if needed. */
+	if (phydev->dev_flags) {
+		ret = phy_modify_mmd(phydev, MDIO_MMD_VEND1, AN8855_PHY_R500HM_RSEL_TX_AB,
+				     AN8855_PHY_R50OHM_RSEL_TX_A | AN8855_PHY_R50OHM_RSEL_TX_B,
+				     FIELD_PREP(AN8855_PHY_R50OHM_RSEL_TX_A, calibration_data[0]) |
+				     FIELD_PREP(AN8855_PHY_R50OHM_RSEL_TX_B, calibration_data[1]));
+		if (ret)
+			return ret;
+		ret = phy_modify_mmd(phydev, MDIO_MMD_VEND1, AN8855_PHY_R500HM_RSEL_TX_CD,
+				     AN8855_PHY_R50OHM_RSEL_TX_C | AN8855_PHY_R50OHM_RSEL_TX_D,
+				     FIELD_PREP(AN8855_PHY_R50OHM_RSEL_TX_C, calibration_data[2]) |
+				     FIELD_PREP(AN8855_PHY_R50OHM_RSEL_TX_D, calibration_data[3]));
+		if (ret)
+			return ret;
+	}
+
+	/* Apply values to decude signal noise */
+	ret = phy_write_mmd(phydev, MDIO_MMD_VEND1, PHY_TX_PAIR_DLY_SEL_GBE, 0x4040);
+	if (ret)
+		return ret;
+	ret = phy_write_mmd(phydev, MDIO_MMD_VEND1, PHY_RXADC_CTRL, 0x1010);
+	if (ret)
+		return ret;
+	ret = phy_write_mmd(phydev, MDIO_MMD_VEND1, PHY_RXADC_REV_0, 0x100);
+	if (ret)
+		return ret;
+	ret = phy_write_mmd(phydev, MDIO_MMD_VEND1, PHY_RXADC_REV_1, 0x100);
+	if (ret)
+		return ret;
+
+	return 0;
+}
+
+static int an8855_get_downshift(struct phy_device *phydev, u8 *data)
+{
+	int val;
+	int ret;
+
+	ret = phy_write(phydev, AN8855_PHY_PAGE_CTRL, AN8855_PHY_EXT_PAGE);
+	if (ret)
+		return ret;
+
+	val = phy_read(phydev, AN8855_PHY_EXT_REG_14);
+	*data = val & AN8855_PHY_EXT_REG_14 ? DOWNSHIFT_DEV_DEFAULT_COUNT :
+					      DOWNSHIFT_DEV_DISABLE;
+
+	ret = phy_write(phydev, AN8855_PHY_PAGE_CTRL, AN8855_PHY_NORMAL_PAGE);
+	if (ret)
+		return ret;
+
+	return 0;
+}
+
+static int an8855_set_downshift(struct phy_device *phydev, u8 cnt)
+{
+	int ret;
+
+	ret = phy_write(phydev, AN8855_PHY_PAGE_CTRL, AN8855_PHY_EXT_PAGE);
+	if (ret)
+		return ret;
+
+	if (cnt != DOWNSHIFT_DEV_DISABLE) {
+		ret = phy_set_bits(phydev, AN8855_PHY_EXT_REG_14,
+				   AN8855_PHY_EN_DOWN_SHFIT);
+		if (ret)
+			return ret;
+	} else {
+		ret = phy_clear_bits(phydev, AN8855_PHY_EXT_REG_14,
+				     AN8855_PHY_EN_DOWN_SHFIT);
+		if (ret)
+			return ret;
+	}
+
+	return phy_write(phydev, AN8855_PHY_PAGE_CTRL, AN8855_PHY_NORMAL_PAGE);
+}
+
+static int an8855_get_tunable(struct phy_device *phydev,
+			      struct ethtool_tunable *tuna, void *data)
+{
+	switch (tuna->id) {
+	case ETHTOOL_PHY_DOWNSHIFT:
+		return an8855_get_downshift(phydev, data);
+	default:
+		return -EOPNOTSUPP;
+	}
+}
+
+static int an8855_set_tunable(struct phy_device *phydev,
+			      struct ethtool_tunable *tuna, const void *data)
+{
+	switch (tuna->id) {
+	case ETHTOOL_PHY_DOWNSHIFT:
+		return an8855_set_downshift(phydev, *(const u8 *)data);
+	default:
+		return -EOPNOTSUPP;
+	}
+}
+
+static struct phy_driver An8855_driver[] = {
+{
+	PHY_ID_MATCH_EXACT(AN8855_PHY_ID),
+	.name			= "Airoha AN8855 internal PHY",
+	/* PHY_GBIT_FEATURES */
+	.flags			= PHY_IS_INTERNAL,
+	.config_init		= an8855_config_init,
+	.soft_reset		= genphy_soft_reset,
+	.get_tunable		= an8855_get_tunable,
+	.set_tunable		= an8855_set_tunable,
+	.suspend		= genphy_suspend,
+	.resume			= genphy_resume,
+}, };
+
+module_phy_driver(An8855_driver);
+
+static struct mdio_device_id __maybe_unused An8855_tbl[] = {
+	{ PHY_ID_MATCH_EXACT(AN8855_PHY_ID) },
+	{ }
+};
+
+MODULE_DEVICE_TABLE(mdio, An8855_tbl);
+
+MODULE_DESCRIPTION("Airoha AN8855 PHY driver");
+MODULE_AUTHOR("Christian Marangi <ansuelsmth@gmail.com>");
+MODULE_LICENSE("GPL");
-- 
2.45.2