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 with the use of NVMEM cells.

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 | 268 +++++++++++++++++++++++++++++++++++
 4 files changed, 275 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..10627ea2be38
--- /dev/null
+++ b/drivers/net/phy/air_an8855.c
@@ -0,0 +1,268 @@
+// SPDX-License-Identifier: GPL-2.0+
+/*
+ * Copyright (C) 2024 Christian Marangi <ansuelsmth@gmail.com>
+ */
+
+#include <linux/phy.h>
+#include <linux/module.h>
+#include <linux/bitfield.h>
+#include <linux/nvmem-consumer.h>
+
+#define AN8855_PHY_SELECT_PAGE			0x1f
+/* Mask speculation based on page up to 0x4 */
+#define   AN8855_PHY_PAGE			GENMASK(2, 0)
+#define   AN8855_PHY_PAGE_STANDARD		FIELD_PREP_CONST(AN8855_PHY_PAGE, 0x0)
+#define   AN8855_PHY_PAGE_EXTENDED_1		FIELD_PREP_CONST(AN8855_PHY_PAGE, 0x1)
+
+/* MII Registers Page 1 */
+#define AN8855_PHY_EXT_REG_14			0x14
+#define   AN8855_PHY_EN_DOWN_SHIFT		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)
+
+#define AN8855_SWITCH_EFUSE_R50O		GENMASK(30, 24)
+
+/* PHY TX PAIR DELAY SELECT Register */
+#define AN8855_PHY_TX_PAIR_DLY_SEL_GBE		0x013
+#define   AN8855_PHY_CR_DA_TX_PAIR_DELKAY_SEL_A_GBE GENMASK(14, 12)
+#define   AN8855_PHY_CR_DA_TX_PAIR_DELKAY_SEL_B_GBE GENMASK(10, 8)
+#define   AN8855_PHY_CR_DA_TX_PAIR_DELKAY_SEL_C_GBE GENMASK(6, 4)
+#define   AN8855_PHY_CR_DA_TX_PAIR_DELKAY_SEL_D_GBE GENMASK(2, 0)
+/* PHY ADC Register */
+#define AN8855_PHY_RXADC_CTRL			0x0d8
+#define   AN8855_PHY_RG_AD_SAMNPLE_PHSEL_A	BIT(12)
+#define   AN8855_PHY_RG_AD_SAMNPLE_PHSEL_B	BIT(8)
+#define   AN8855_PHY_RG_AD_SAMNPLE_PHSEL_C	BIT(4)
+#define   AN8855_PHY_RG_AD_SAMNPLE_PHSEL_D	BIT(0)
+#define AN8855_PHY_RXADC_REV_0			0x0d9
+#define   AN8855_PHY_RG_AD_RESERVE0_A		GENMASK(15, 8)
+#define   AN8855_PHY_RG_AD_RESERVE0_B		GENMASK(7, 0)
+#define AN8855_PHY_RXADC_REV_1			0x0da
+#define   AN8855_PHY_RG_AD_RESERVE0_C		GENMASK(15, 8)
+#define   AN8855_PHY_RG_AD_RESERVE0_D		GENMASK(7, 0)
+
+#define AN8855_PHY_ID				0xc0ff0410
+
+#define AN8855_PHY_FLAGS_EN_CALIBRATION		BIT(0)
+
+struct air_an8855_priv {
+	u8 calibration_data[4];
+};
+
+static const u8 dsa_r50ohm_table[] = {
+	127, 127, 127, 127, 127, 127, 127, 127, 127, 127,
+	127, 127, 127, 127, 127, 127, 127, 126, 122, 117,
+	112, 109, 104, 101,  97,  94,  90,  88,  84,  80,
+	78,  74,  72,  68,  66,  64,  61,  58,  56,  53,
+	51,  48,  47,  44,  42,  40,  38,  36,  34,  32,
+	31,  28,  27,  24,  24,  22,  20,  18,  16,  16,
+	14,  12,  11,   9
+};
+
+static int en8855_get_r50ohm_val(struct device *dev, const char *calib_name,
+				 u8 *dest)
+{
+	u32 shift_sel, val;
+	int ret;
+	int i;
+
+	ret = nvmem_cell_read_u32(dev, calib_name, &val);
+	if (ret)
+		return ret;
+
+	shift_sel = FIELD_GET(AN8855_SWITCH_EFUSE_R50O, val);
+	for (i = 0; i < ARRAY_SIZE(dsa_r50ohm_table); i++)
+		if (dsa_r50ohm_table[i] == shift_sel)
+			break;
+
+	if (i < 8 || i >= ARRAY_SIZE(dsa_r50ohm_table))
+		*dest = dsa_r50ohm_table[25];
+	else
+		*dest = dsa_r50ohm_table[i - 8];
+
+	return 0;
+}
+
+static int an8855_probe(struct phy_device *phydev)
+{
+	struct device *dev = &phydev->mdio.dev;
+	struct device_node *node = dev->of_node;
+	struct air_an8855_priv *priv;
+	int ret;
+
+	/* If we don't have a node, skip get calib */
+	if (!node)
+		return 0;
+
+	priv = devm_kzalloc(dev, sizeof(*priv), GFP_KERNEL);
+	if (!priv)
+		return -ENOMEM;
+
+	ret = en8855_get_r50ohm_val(dev, "tx_a", &priv->calibration_data[0]);
+	if (ret)
+		return ret;
+
+	ret = en8855_get_r50ohm_val(dev, "tx_b", &priv->calibration_data[1]);
+	if (ret)
+		return ret;
+
+	ret = en8855_get_r50ohm_val(dev, "tx_c", &priv->calibration_data[2]);
+	if (ret)
+		return ret;
+
+	ret = en8855_get_r50ohm_val(dev, "tx_d", &priv->calibration_data[3]);
+	if (ret)
+		return ret;
+
+	phydev->priv = priv;
+
+	return 0;
+}
+
+static int an8855_get_downshift(struct phy_device *phydev, u8 *data)
+{
+	int val;
+
+	val = phy_read_paged(phydev, AN8855_PHY_PAGE_EXTENDED_1, AN8855_PHY_EXT_REG_14);
+	if (val < 0)
+		return val;
+
+	*data = val & AN8855_PHY_EN_DOWN_SHIFT ? DOWNSHIFT_DEV_DEFAULT_COUNT :
+						 DOWNSHIFT_DEV_DISABLE;
+
+	return 0;
+}
+
+static int an8855_set_downshift(struct phy_device *phydev, u8 cnt)
+{
+	u16 ds = cnt != DOWNSHIFT_DEV_DISABLE ? AN8855_PHY_EN_DOWN_SHIFT : 0;
+
+	return phy_modify_paged(phydev, AN8855_PHY_PAGE_EXTENDED_1,
+				AN8855_PHY_EXT_REG_14, AN8855_PHY_EN_DOWN_SHIFT,
+				ds);
+}
+
+static int an8855_config_init(struct phy_device *phydev)
+{
+	struct air_an8855_priv *priv = phydev->priv;
+	int ret;
+
+	/* Enable HW auto downshift */
+	ret = an8855_set_downshift(phydev, DOWNSHIFT_DEV_DEFAULT_COUNT);
+	if (ret)
+		return ret;
+
+	/* Apply calibration values, if needed.
+	 * AN8855_PHY_FLAGS_EN_CALIBRATION signal this.
+	 */
+	if (priv && phydev->dev_flags & AN8855_PHY_FLAGS_EN_CALIBRATION) {
+		u8 *calibration_data = priv->calibration_data;
+
+		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 reduce signal noise */
+	ret = phy_write_mmd(phydev, MDIO_MMD_VEND1, AN8855_PHY_TX_PAIR_DLY_SEL_GBE,
+			    FIELD_PREP(AN8855_PHY_CR_DA_TX_PAIR_DELKAY_SEL_A_GBE, 0x4) |
+			    FIELD_PREP(AN8855_PHY_CR_DA_TX_PAIR_DELKAY_SEL_C_GBE, 0x4));
+	if (ret)
+		return ret;
+	ret = phy_write_mmd(phydev, MDIO_MMD_VEND1, AN8855_PHY_RXADC_CTRL,
+			    AN8855_PHY_RG_AD_SAMNPLE_PHSEL_A |
+			    AN8855_PHY_RG_AD_SAMNPLE_PHSEL_C);
+	if (ret)
+		return ret;
+	ret = phy_write_mmd(phydev, MDIO_MMD_VEND1, AN8855_PHY_RXADC_REV_0,
+			    FIELD_PREP(AN8855_PHY_RG_AD_RESERVE0_A, 0x1));
+	if (ret)
+		return ret;
+	ret = phy_write_mmd(phydev, MDIO_MMD_VEND1, AN8855_PHY_RXADC_REV_1,
+			    FIELD_PREP(AN8855_PHY_RG_AD_RESERVE0_C, 0x1));
+	if (ret)
+		return ret;
+
+	return 0;
+}
+
+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 int an8855_read_page(struct phy_device *phydev)
+{
+	return __phy_read(phydev, AN8855_PHY_SELECT_PAGE);
+}
+
+static int an8855_write_page(struct phy_device *phydev, int page)
+{
+	return __phy_write(phydev, AN8855_PHY_SELECT_PAGE, page);
+}
+
+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,
+	.probe			= an8855_probe,
+	.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,
+	.read_page		= an8855_read_page,
+	.write_page		= an8855_write_page,
+}, };
+
+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