kernel: net: phy: realtek: improve RealTek 2.5G PHY driver

 * use interface mode switching only when operating in C45 mode
   Linux prevents switching the interface mode when using C22 MDIO,
   hence use rate-adapter mode in case the PHY controlled via C22.

 * use phy_read_paged where appropriate

 * use existing generic inline functions to handle 10GbE advertisements
   instead of redundantly defining register macros in realtek.c which
   are not actually vendor-specific.

 * make sure 10GbE advertisement is valid, preventing false-positive
   warning "Downshift occurred from negotiated speed 2.5Gbps to actual
   speed 1Gbps, check cabling!" with some link-partners using 1G mode.

 * Support Link Down Power Saving Mode (ALDPS)

Signed-off-by: Daniel Golle <daniel@makrotopia.org>

1 files changed, 100 insertions, 0 deletions

diff --git a/target/linux/generic/pending-5.15/729-net-phy-realtek-introduce-rtl822x_probe.patch b/target/linux/generic/pending-5.15/729-net-phy-realtek-introduce-rtl822x_probe.patch
new file mode 100644
index 0000000000..ae4a7dfa60
--- /dev/null
+++ b/target/linux/generic/pending-5.15/729-net-phy-realtek-introduce-rtl822x_probe.patch
@@ -0,0 +1,100 @@
+From 9155098547fb1172d4fa536f3f6bc9d42f59d08c Mon Sep 17 00:00:00 2001
+From: Daniel Golle <daniel@makrotopia.org>
+Date: Sat, 22 Apr 2023 03:26:01 +0100
+Subject: [PATCH] net: phy: realtek: setup ALDPS on RTL822x
+
+Setup Link Down Power Saving Mode according the DTS property
+just like for RTL821x 1GE PHYs.
+
+Signed-off-by: Daniel Golle <daniel@makrotopia.org>
+---
+ drivers/net/phy/realtek.c | 11 +++++++++++
+ 1 file changed, 11 insertions(+)
+
+--- a/drivers/net/phy/realtek.c
++++ b/drivers/net/phy/realtek.c
+@@ -62,6 +62,10 @@
+ #define RTL8221B_SERDES_OPTION_MODE_2500BASEX		2
+ #define RTL8221B_SERDES_OPTION_MODE_HISGMII		3
+ 
++#define RTL8221B_PHYCR1				0xa430
++#define RTL8221B_PHYCR1_ALDPS_EN		BIT(2)
++#define RTL8221B_PHYCR1_ALDPS_XTAL_OFF_EN	BIT(12)
++
+ #define RTL8366RB_POWER_SAVE			0x15
+ #define RTL8366RB_POWER_SAVE_ON			BIT(12)
+ 
+@@ -736,6 +741,25 @@ static int rtl8226_match_phy_device(stru
+ 	       rtlgen_supports_2_5gbps(phydev);
+ }
+ 
++static int rtl822x_probe(struct phy_device *phydev)
++{
++	struct device *dev = &phydev->mdio.dev;
++	int val;
++
++	val = phy_read_mmd(phydev, RTL8221B_MMD_SERDES_CTRL, RTL8221B_PHYCR1);
++	if (val < 0)
++		return val;
++
++	if (of_property_read_bool(dev->of_node, "realtek,aldps-enable"))
++		val |= RTL8221B_PHYCR1_ALDPS_EN | RTL8221B_PHYCR1_ALDPS_XTAL_OFF_EN;
++	else
++		val &= ~(RTL8221B_PHYCR1_ALDPS_EN | RTL8221B_PHYCR1_ALDPS_XTAL_OFF_EN);
++
++	phy_write_mmd(phydev, RTL8221B_MMD_SERDES_CTRL, RTL8221B_PHYCR1, val);
++
++	return 0;
++}
++
+ static int rtlgen_resume(struct phy_device *phydev)
+ {
+ 	int ret = genphy_resume(phydev);
+@@ -1009,6 +1030,7 @@ static struct phy_driver realtek_drvs[]
+ 		.match_phy_device = rtl8226_match_phy_device,
+ 		.get_features	= rtl822x_get_features,
+ 		.config_aneg	= rtl822x_config_aneg,
++		.probe          = rtl822x_probe,
+ 		.read_status	= rtl822x_read_status,
+ 		.suspend	= genphy_suspend,
+ 		.resume		= rtlgen_resume,
+@@ -1022,6 +1044,7 @@ static struct phy_driver realtek_drvs[]
+ 		.name		= "RTL8226B_RTL8221B 2.5Gbps PHY",
+ 		.get_features	= rtl822x_get_features,
+ 		.config_aneg	= rtl822x_config_aneg,
++		.probe          = rtl822x_probe,
+ 		.read_status	= rtl822x_read_status,
+ 		.suspend	= genphy_suspend,
+ 		.resume		= rtlgen_resume,
+@@ -1035,6 +1058,7 @@ static struct phy_driver realtek_drvs[]
+ 		.name           = "RTL8226-CG 2.5Gbps PHY",
+ 		.get_features   = rtl822x_get_features,
+ 		.config_aneg    = rtl822x_config_aneg,
++		.probe          = rtl822x_probe,
+ 		.read_status    = rtl822x_read_status,
+ 		.suspend        = genphy_suspend,
+ 		.resume         = rtlgen_resume,
+@@ -1046,6 +1070,7 @@ static struct phy_driver realtek_drvs[]
+ 		.name           = "RTL8226B-CG_RTL8221B-CG 2.5Gbps PHY",
+ 		.get_features   = rtl822x_get_features,
+ 		.config_aneg    = rtl822x_config_aneg,
++		.probe          = rtl822x_probe,
+ 		.read_status    = rtl822x_read_status,
+ 		.suspend        = genphy_suspend,
+ 		.resume         = rtlgen_resume,
+@@ -1058,6 +1083,7 @@ static struct phy_driver realtek_drvs[]
+ 		.get_features   = rtl822x_get_features,
+ 		.config_init    = rtl8221b_config_init,
+ 		.config_aneg    = rtl822x_config_aneg,
++		.probe          = rtl822x_probe,
+ 		.read_status    = rtl822x_read_status,
+ 		.suspend        = genphy_suspend,
+ 		.resume         = rtlgen_resume,
+@@ -1070,6 +1096,7 @@ static struct phy_driver realtek_drvs[]
+ 		.get_features   = rtl822x_get_features,
+ 		.config_aneg    = rtl822x_config_aneg,
+ 		.config_init    = rtl8221b_config_init,
++		.probe          = rtl822x_probe,
+ 		.read_status    = rtl822x_read_status,
+ 		.suspend        = genphy_suspend,
+ 		.resume         = rtlgen_resume,