[PATCH v2 net-next] net: phy: mediatek: support MT7530 PHYs on EN71221 MCM

[Caleb James DeLisle <cjd@cjdns.fr>]

The EcoNet EN751221 multi-chip module implementation of the MT7530
requires some additional configuration of the PHYs on startup.
The reason for this is not known, but it is possible that it has
to do with the fact that the EN751221 MCM implementation of the
MT7530 runs at an abnormal PLL frequency (362.5Mhz).

Detect whether the MT7530 PHY is attached to the MDIO bus of an
EcoNet EN751221 switch and if so, apply the necessary register
updates. Additionally, never attempt to configure an MT7530
identified PHY which does not have gigabit support because the same
ID is used for another (FE) PHY.

Of note: MDIO_AN_EEE_ADV must be zero at startup or else link will
fail to connect. Setting MDIO_AN_EEE_ADV to 6 after link is brought
up will make EEE work when cable is next plugged in, but link fails
to downgrade to 100mb if gigabit is not possible, leaving a
"connected" (nonfunctional) gigabit link.

Co-developed-by: Matheus Sampaio Queiroga <srherobrine20@gmail.com>
Signed-off-by: Matheus Sampaio Queiroga <srherobrine20@gmail.com>
Signed-off-by: Caleb James DeLisle <cjd@cjdns.fr>
---
 drivers/net/phy/mediatek/mtk-ge.c | 61 +++++++++++++++++++++++++++++++
 1 file changed, 61 insertions(+)

diff --git a/drivers/net/phy/mediatek/mtk-ge.c b/drivers/net/phy/mediatek/mtk-ge.c
index 73d9b72f9d9e..42b06c40d703 100644
--- a/drivers/net/phy/mediatek/mtk-ge.c
+++ b/drivers/net/phy/mediatek/mtk-ge.c
@@ -1,4 +1,5 @@
 // SPDX-License-Identifier: GPL-2.0+
+#include <linux/of.h>
 #include <linux/bitfield.h>
 #include <linux/module.h>
 #include <linux/phy.h>
@@ -62,8 +63,68 @@ static void mtk_gephy_config_init(struct phy_device *phydev)
 		       FIELD_PREP(MTK_MCC_NEARECHO_OFFSET_MASK, 0x3));
 }
 
+static bool mt7530_phy_is_en751221_companion(struct phy_device *phydev)
+{
+	struct device *parent = phydev->mdio.bus->parent;
+
+	return parent && parent->of_node &&
+	       of_device_is_compatible(parent->of_node, "econet,en751221");
+}
+
+/*
+ * The EcoNet reference implementation applies additional tuning to
+ * the PHYs of the multi-chip module MT7530.
+ */
+static int mt7530_phy_en751221_config_init(struct phy_device *phydev)
+{
+	int ret;
+
+	ret = genphy_soft_reset(phydev);
+	if (ret)
+		return ret;
+
+	/* Clause 22 local data. */
+	ret = phy_write(phydev, MII_CTRL1000, 0x1e00);
+	if (ret < 0)
+		return ret;
+
+	ret = phy_write_paged(phydev, MTK_PHY_PAGE_EXTENDED_1, 0x14, 0x3a04);
+	if (ret < 0)
+		return ret;
+
+	/* Clause 45 global/local data from mt7530GePhyCfgLoad(E3.0). */
+	ret = phy_write_mmd(phydev, MDIO_MMD_VEND2, 0x0417, 0x7775);
+	if (ret < 0)
+		return ret;
+
+	ret = phy_write_mmd(phydev, MDIO_MMD_VEND1, 0x00a6, 0x0350);
+	if (ret < 0)
+		return ret;
+
+	ret = phy_write_mmd(phydev, MDIO_MMD_VEND1, 0x0012, 0xd210);
+	if (ret < 0)
+		return ret;
+
+	/* Vendor profile disables 100/1000BASE-T EEE advertisement. */
+	ret = phy_write_mmd(phydev, MDIO_MMD_AN, 0x003c, 0x0000);
+	if (ret < 0)
+		return ret;
+
+	phydev_info(phydev, "EN751221 companion MT7530 E3.0 PHY profile loaded\n");
+
+	return 0;
+}
+
 static int mt7530_phy_config_init(struct phy_device *phydev)
 {
+	int ret;
+
+	if (mt7530_phy_is_en751221_companion(phydev)) {
+		ret = mt7530_phy_en751221_config_init(phydev);
+		if (ret)
+			return ret;
+	}
+
 	mtk_gephy_config_init(phydev);
 
 	/* Increase post_update_timer */
-- 
2.39.5