FAILED: patch "[PATCH] net: dsa: mv88e6xxx: Save power by disabling SerDes" failed to apply to 5.15-stable tree

[<gregkh@xxxxxxxxxxxxxxxxxxx>]

The patch below does not apply to the 5.15-stable tree.
If someone wants it applied there, or to any other stable or longterm
tree, then please email the backport, including the original git commit
id to <stable@xxxxxxxxxxxxxxx>.

thanks,

greg k-h

------------------ original commit in Linus's tree ------------------

>From 7527d66260ac0c603c6baca5146748061fcddbd6 Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?Marek=20Beh=C3=BAn?= <kabel@xxxxxxxxxx>
Date: Tue, 30 Nov 2021 18:01:48 +0100
Subject: [PATCH] net: dsa: mv88e6xxx: Save power by disabling SerDes
 trasmitter and receiver
MIME-Version: 1.0
Content-Type: text/plain; charset=UTF-8
Content-Transfer-Encoding: 8bit

Save power on 88E6393X by disabling SerDes receiver and transmitter
after SerDes is SerDes is disabled.

Signed-off-by: Marek Behún <kabel@xxxxxxxxxx>
Cc: stable@xxxxxxxxxxxxxxx # de776d0d316f ("net: dsa: mv88e6xxx: add support for mv88e6393x family")
Signed-off-by: David S. Miller <davem@xxxxxxxxxxxxx>

diff --git a/drivers/net/dsa/mv88e6xxx/serdes.c b/drivers/net/dsa/mv88e6xxx/serdes.c
index 3a6244596a67..ceb63d7f1f97 100644
--- a/drivers/net/dsa/mv88e6xxx/serdes.c
+++ b/drivers/net/dsa/mv88e6xxx/serdes.c
@@ -1271,6 +1271,28 @@ void mv88e6390_serdes_get_regs(struct mv88e6xxx_chip *chip, int port, void *_p)
 	}
 }
 
+static int mv88e6393x_serdes_power_lane(struct mv88e6xxx_chip *chip, int lane,
+					bool on)
+{
+	u16 reg;
+	int err;
+
+	err = mv88e6390_serdes_read(chip, lane, MDIO_MMD_PHYXS,
+				    MV88E6393X_SERDES_CTRL1, &reg);
+	if (err)
+		return err;
+
+	if (on)
+		reg &= ~(MV88E6393X_SERDES_CTRL1_TX_PDOWN |
+			 MV88E6393X_SERDES_CTRL1_RX_PDOWN);
+	else
+		reg |= MV88E6393X_SERDES_CTRL1_TX_PDOWN |
+		       MV88E6393X_SERDES_CTRL1_RX_PDOWN;
+
+	return mv88e6390_serdes_write(chip, lane, MDIO_MMD_PHYXS,
+				      MV88E6393X_SERDES_CTRL1, reg);
+}
+
 static int mv88e6393x_serdes_erratum_4_6(struct mv88e6xxx_chip *chip, int lane)
 {
 	u16 reg;
@@ -1297,7 +1319,11 @@ static int mv88e6393x_serdes_erratum_4_6(struct mv88e6xxx_chip *chip, int lane)
 	if (err)
 		return err;
 
-	return mv88e6390_serdes_power_sgmii(chip, lane, false);
+	err = mv88e6390_serdes_power_sgmii(chip, lane, false);
+	if (err)
+		return err;
+
+	return mv88e6393x_serdes_power_lane(chip, lane, false);
 }
 
 int mv88e6393x_serdes_setup_errata(struct mv88e6xxx_chip *chip)
@@ -1362,17 +1388,29 @@ int mv88e6393x_serdes_power(struct mv88e6xxx_chip *chip, int port, int lane,
 		err = mv88e6393x_serdes_erratum_4_8(chip, lane);
 		if (err)
 			return err;
+
+		err = mv88e6393x_serdes_power_lane(chip, lane, true);
+		if (err)
+			return err;
 	}
 
 	switch (cmode) {
 	case MV88E6XXX_PORT_STS_CMODE_SGMII:
 	case MV88E6XXX_PORT_STS_CMODE_1000BASEX:
 	case MV88E6XXX_PORT_STS_CMODE_2500BASEX:
-		return mv88e6390_serdes_power_sgmii(chip, lane, on);
+		err = mv88e6390_serdes_power_sgmii(chip, lane, on);
+		break;
 	case MV88E6393X_PORT_STS_CMODE_5GBASER:
 	case MV88E6393X_PORT_STS_CMODE_10GBASER:
-		return mv88e6390_serdes_power_10g(chip, lane, on);
+		err = mv88e6390_serdes_power_10g(chip, lane, on);
+		break;
 	}
 
-	return 0;
+	if (err)
+		return err;
+
+	if (!on)
+		err = mv88e6393x_serdes_power_lane(chip, lane, false);
+
+	return err;
 }
diff --git a/drivers/net/dsa/mv88e6xxx/serdes.h b/drivers/net/dsa/mv88e6xxx/serdes.h
index cbb3ba30caea..e9292c8beee4 100644
--- a/drivers/net/dsa/mv88e6xxx/serdes.h
+++ b/drivers/net/dsa/mv88e6xxx/serdes.h
@@ -93,6 +93,9 @@
 #define MV88E6393X_SERDES_POC_PCS_MASK		0x0007
 #define MV88E6393X_SERDES_POC_RESET		BIT(15)
 #define MV88E6393X_SERDES_POC_PDOWN		BIT(5)
+#define MV88E6393X_SERDES_CTRL1			0xf003
+#define MV88E6393X_SERDES_CTRL1_TX_PDOWN	BIT(9)
+#define MV88E6393X_SERDES_CTRL1_RX_PDOWN	BIT(8)
 
 #define MV88E6393X_ERRATA_4_8_REG		0xF074
 #define MV88E6393X_ERRATA_4_8_BIT		BIT(14)