linux-kernel - [PATCH net-next 2/3] net: phy: Add helper for getting MAC series termination resistance

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Message-Id: <20250307-dp83822-mac-impedance-v1-2-bdd85a759b45@liebherr.com>
Date: Fri, 07 Mar 2025 11:30:02 +0100
From: Dimitri Fedrau via B4 Relay <devnull+dimitri.fedrau.liebherr.com@...nel.org>
To: Andrew Lunn <andrew@...n.ch>, Heiner Kallweit <hkallweit1@...il.com>, 
 Russell King <linux@...linux.org.uk>, 
 "David S. Miller" <davem@...emloft.net>, Eric Dumazet <edumazet@...gle.com>, 
 Jakub Kicinski <kuba@...nel.org>, Paolo Abeni <pabeni@...hat.com>, 
 Rob Herring <robh@...nel.org>, Krzysztof Kozlowski <krzk+dt@...nel.org>, 
 Conor Dooley <conor+dt@...nel.org>, Florian Fainelli <f.fainelli@...il.com>
Cc: netdev@...r.kernel.org, devicetree@...r.kernel.org, 
 linux-kernel@...r.kernel.org, Dimitri Fedrau <dimitri.fedrau@...bherr.com>, 
 Dimitri Fedrau <dima.fedrau@...il.com>
Subject: [PATCH net-next 2/3] net: phy: Add helper for getting MAC series
 termination resistance

From: Dimitri Fedrau <dimitri.fedrau@...bherr.com>

Add helper which returns the MAC series termination resistance value.
Modifying the resistance to an appropriate value can reduce signal
reflections and therefore improve signal quality.

Signed-off-by: Dimitri Fedrau <dimitri.fedrau@...bherr.com>
---
 drivers/net/phy/phy_device.c | 15 +++++++++++++++
 include/linux/phy.h          |  3 +++
 2 files changed, 18 insertions(+)

diff --git a/drivers/net/phy/phy_device.c b/drivers/net/phy/phy_device.c
index b2d32fbc8c8507f6280e4c3c671466f672c1cc8f..575583aa8b4d49bef796e96059e4f0dd56b351f9 100644
--- a/drivers/net/phy/phy_device.c
+++ b/drivers/net/phy/phy_device.c
@@ -2975,6 +2975,21 @@ int phy_get_tx_amplitude_gain(struct phy_device *phydev, struct device *dev,
 }
 EXPORT_SYMBOL_GPL(phy_get_tx_amplitude_gain);

+/**
+ * phy_get_mac_series_termination - stores MAC series termination in @val
+ * @phydev: phy_device struct
+ * @dev: pointer to the devices device struct
+ * @val: MAC series termination
+ *
+ * Returns: 0 on success, < 0 on failure
+ */
+int phy_get_mac_series_termination(struct phy_device *phydev,
+				   struct device *dev, u32 *val)
+{
+	return phy_get_u32_property(dev, "mac-series-termination-ohms", val);
+}
+EXPORT_SYMBOL_GPL(phy_get_mac_series_termination);
+
 static int phy_led_set_brightness(struct led_classdev *led_cdev,
 				  enum led_brightness value)
 {
diff --git a/include/linux/phy.h b/include/linux/phy.h
index c4a6385faf41c3156d1a9086eaf5c746640cddbe..633899c4250c91a366849ee0c11d93feec48262f 100644
--- a/include/linux/phy.h
+++ b/include/linux/phy.h
@@ -2052,6 +2052,9 @@ int phy_get_tx_amplitude_gain(struct phy_device *phydev, struct device *dev,
 			      enum ethtool_link_mode_bit_indices linkmode,
 			      u32 *val);

+int phy_get_mac_series_termination(struct phy_device *phydev,
+				   struct device *dev, u32 *val);
+
 void phy_resolve_pause(unsigned long *local_adv, unsigned long *partner_adv,
 		       bool *tx_pause, bool *rx_pause);

-- 
2.39.5