[PATCH net-next v3 0/4] net: phy: dp83822: Add support for changing the MAC series termination

[PATCH net-next v3 0/4] net: phy: dp83822: Add support for changing the MAC series termination

[Dimitri Fedrau via B4 Relay]

The dp83822 provides the possibility to set the resistance value of the
the MAC series termination. Modifying the resistance to an appropriate
value can reduce signal reflections and therefore improve signal quality.

Signed-off-by: Dimitri Fedrau <dimitri.fedrau@liebherr.com>
---
Changes in v3:
- Add maximum to mac-termination-ohms in ethernet-phy.yaml
- Add allowed values for mac-termination-ohms in ti,dp83822.yaml
- Added mac-termination-ohms in sample in ti,dp83822.yaml
- Link to v2: https://lore.kernel.org/r/20250408-dp83822-mac-impedance-v2-0-fefeba4a9804@liebherr.com

Changes in v2:
- Renamed "mac-series-termination-ohms" to "mac-termination-ohms"
- Added description for "mac-termination-ohms"
- Renamed "phy_get_mac_series_termination" to "phy_get_mac_termination"
- Dropped "mac_series_termination_modify" from dp83822_private
- Init mac_termination_index in dp8382x_probe
- Renamed "mac_series_termination" to "mac_termination"
- Link to v1: https://lore.kernel.org/r/20250307-dp83822-mac-impedance-v1-0-bdd85a759b45@liebherr.com

---
Dimitri Fedrau (4):
      dt-bindings: net: ethernet-phy: add property mac-termination-ohms
      dt-bindings: net: dp83822: add constraints for mac-termination-ohms
      net: phy: Add helper for getting MAC termination resistance
      net: phy: dp83822: Add support for changing the MAC termination

 .../devicetree/bindings/net/ethernet-phy.yaml      | 10 +++++++
 .../devicetree/bindings/net/ti,dp83822.yaml        |  4 +++
 drivers/net/phy/dp83822.c                          | 33 ++++++++++++++++++++++
 drivers/net/phy/phy_device.c                       | 15 ++++++++++
 include/linux/phy.h                                |  3 ++
 5 files changed, 65 insertions(+)
---
base-commit: ac1df712442c64b50cfdbe01da0e5aca8319b559
change-id: 20250305-dp83822-mac-impedance-840435b0c9e6

Best regards,
-- 
Dimitri Fedrau <dimitri.fedrau@liebherr.com>

[PATCH net-next v3 1/4] dt-bindings: net: ethernet-phy: add property mac-termination-ohms

[Dimitri Fedrau via B4 Relay]

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

Add property mac-termination-ohms in the device tree bindings for selecting
the resistance value of the builtin series termination resistors of the
PHY. Changing the resistance to an appropriate value can reduce signal
reflections and therefore improve signal quality.

Signed-off-by: Dimitri Fedrau <dimitri.fedrau@liebherr.com>
---
 Documentation/devicetree/bindings/net/ethernet-phy.yaml | 10 ++++++++++
 1 file changed, 10 insertions(+)

diff --git a/Documentation/devicetree/bindings/net/ethernet-phy.yaml b/Documentation/devicetree/bindings/net/ethernet-phy.yaml
index 824bbe4333b7ed95cc39737d3c334a20aa890f01..71e2cd32580f2e9e1af88e6f74517ccb92d1c20f 100644
--- a/Documentation/devicetree/bindings/net/ethernet-phy.yaml
+++ b/Documentation/devicetree/bindings/net/ethernet-phy.yaml
@@ -238,6 +238,16 @@ properties:
       peak-to-peak specified in ANSI X3.263. When omitted, the PHYs default
       will be left as is.
 
+  mac-termination-ohms:
+    maximum: 200
+    description:
+      The xMII signals need series termination on the driver side to match both
+      the output driver impedance and the line characteristic impedance, to
+      prevent reflections and EMI problems. Select a resistance value which is
+      supported by the builtin resistors of the PHY, otherwise the resistors may
+      have to be placed on board. When omitted, the PHYs default will be left as
+      is.
+
   leds:
     type: object
 

-- 
2.39.5

[PATCH net-next v3 2/4] dt-bindings: net: dp83822: add constraints for mac-termination-ohms

[Dimitri Fedrau via B4 Relay]

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

Property mac-termination-ohms is defined in ethernet-phy.yaml. Add allowed
values for the property.

Signed-off-by: Dimitri Fedrau <dimitri.fedrau@liebherr.com>
---
 Documentation/devicetree/bindings/net/ti,dp83822.yaml | 4 ++++
 1 file changed, 4 insertions(+)

diff --git a/Documentation/devicetree/bindings/net/ti,dp83822.yaml b/Documentation/devicetree/bindings/net/ti,dp83822.yaml
index 50c24248df266f1950371b950cd9c4d417835f97..28a0bddb9af940e79a7a768a35ef588e28ec5bd4 100644
--- a/Documentation/devicetree/bindings/net/ti,dp83822.yaml
+++ b/Documentation/devicetree/bindings/net/ti,dp83822.yaml
@@ -122,6 +122,9 @@ properties:
       - free-running
       - recovered
 
+  mac-termination-ohms:
+    enum: [43, 44, 46, 48, 50, 53, 55, 58, 61, 65, 69, 73, 78, 84, 91, 99]
+
 required:
   - reg
 
@@ -137,6 +140,7 @@ examples:
         rx-internal-delay-ps = <1>;
         tx-internal-delay-ps = <1>;
         ti,gpio2-clk-out = "xi";
+        mac-termination-ohms = <43>;
       };
     };
 

-- 
2.39.5

[PATCH net-next v3 3/4] net: phy: Add helper for getting MAC termination resistance

[Dimitri Fedrau via B4 Relay]

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

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

Reviewed-by: Russell King (Oracle) <rmk+kernel@armlinux.org.uk>
Signed-off-by: Dimitri Fedrau <dimitri.fedrau@liebherr.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 cc6c209fe702293c25e619899a699a53638f0f66..f85c172c446c56e1da1d13baa18c581f2213dcc5 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_termination - stores MAC termination in @val
+ * @phydev: phy_device struct
+ * @dev: pointer to the devices device struct
+ * @val: MAC termination
+ *
+ * Returns: 0 on success, < 0 on failure
+ */
+int phy_get_mac_termination(struct phy_device *phydev, struct device *dev,
+			    u32 *val)
+{
+	return phy_get_u32_property(dev, "mac-termination-ohms", val);
+}
+EXPORT_SYMBOL_GPL(phy_get_mac_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 fb755358d965b728d502bfc1c0d6e5a6b779f1ef..066a28a4b64b25a7c6033a3bb1e3bc48b20c96dc 100644
--- a/include/linux/phy.h
+++ b/include/linux/phy.h
@@ -2040,6 +2040,9 @@ 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_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

[PATCH net-next v3 4/4] net: phy: dp83822: Add support for changing the MAC termination

[Dimitri Fedrau via B4 Relay]

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

The dp83822 provides the possibility to set the resistance value of the
the MAC termination. Modifying the resistance to an appropriate value can
reduce signal reflections and therefore improve signal quality.

Reviewed-by: Russell King (Oracle) <rmk+kernel@armlinux.org.uk>
Signed-off-by: Dimitri Fedrau <dimitri.fedrau@liebherr.com>
---
 drivers/net/phy/dp83822.c | 33 +++++++++++++++++++++++++++++++++
 1 file changed, 33 insertions(+)

diff --git a/drivers/net/phy/dp83822.c b/drivers/net/phy/dp83822.c
index 14f36154963841dff98be5af4dfbd2760325c13d..490c9f4e5d4e4dc866ef99f426f7497b5e1b49b4 100644
--- a/drivers/net/phy/dp83822.c
+++ b/drivers/net/phy/dp83822.c
@@ -33,6 +33,7 @@
 #define MII_DP83822_MLEDCR	0x25
 #define MII_DP83822_LDCTRL	0x403
 #define MII_DP83822_LEDCFG1	0x460
+#define MII_DP83822_IOCTRL	0x461
 #define MII_DP83822_IOCTRL1	0x462
 #define MII_DP83822_IOCTRL2	0x463
 #define MII_DP83822_GENCFG	0x465
@@ -118,6 +119,9 @@
 #define DP83822_LEDCFG1_LED1_CTRL	GENMASK(11, 8)
 #define DP83822_LEDCFG1_LED3_CTRL	GENMASK(7, 4)
 
+/* IOCTRL bits */
+#define DP83822_IOCTRL_MAC_IMPEDANCE_CTRL	GENMASK(4, 1)
+
 /* IOCTRL1 bits */
 #define DP83822_IOCTRL1_GPIO3_CTRL		GENMASK(10, 8)
 #define DP83822_IOCTRL1_GPIO3_CTRL_LED3		BIT(0)
@@ -202,6 +206,7 @@ struct dp83822_private {
 	u32 gpio2_clk_out;
 	bool led_pin_enable[DP83822_MAX_LED_PINS];
 	int tx_amplitude_100base_tx_index;
+	int mac_termination_index;
 };
 
 static int dp83822_config_wol(struct phy_device *phydev,
@@ -533,6 +538,12 @@ static int dp83822_config_init(struct phy_device *phydev)
 			       FIELD_PREP(DP83822_100BASE_TX_LINE_DRIVER_SWING,
 					  dp83822->tx_amplitude_100base_tx_index));
 
+	if (dp83822->mac_termination_index >= 0)
+		phy_modify_mmd(phydev, MDIO_MMD_VEND2, MII_DP83822_IOCTRL,
+			       DP83822_IOCTRL_MAC_IMPEDANCE_CTRL,
+			       FIELD_PREP(DP83822_IOCTRL_MAC_IMPEDANCE_CTRL,
+					  dp83822->mac_termination_index));
+
 	err = dp83822_config_init_leds(phydev);
 	if (err)
 		return err;
@@ -736,6 +747,10 @@ static const u32 tx_amplitude_100base_tx_gain[] = {
 	93, 95, 97, 98, 100, 102, 103, 105,
 };
 
+static const u32 mac_termination[] = {
+	99, 91, 84, 78, 73, 69, 65, 61, 58, 55, 53, 50, 48, 46, 44, 43,
+};
+
 static int dp83822_of_init_leds(struct phy_device *phydev)
 {
 	struct device_node *node = phydev->mdio.dev.of_node;
@@ -852,6 +867,23 @@ static int dp83822_of_init(struct phy_device *phydev)
 		}
 	}
 
+	ret = phy_get_mac_termination(phydev, dev, &val);
+	if (!ret) {
+		for (i = 0; i < ARRAY_SIZE(mac_termination); i++) {
+			if (mac_termination[i] == val) {
+				dp83822->mac_termination_index = i;
+				break;
+			}
+		}
+
+		if (dp83822->mac_termination_index < 0) {
+			phydev_err(phydev,
+				   "Invalid value for mac-termination-ohms property (%u)\n",
+				   val);
+			return -EINVAL;
+		}
+	}
+
 	return dp83822_of_init_leds(phydev);
 }
 
@@ -931,6 +963,7 @@ static int dp8382x_probe(struct phy_device *phydev)
 		return -ENOMEM;
 
 	dp83822->tx_amplitude_100base_tx_index = -1;
+	dp83822->mac_termination_index = -1;
 	phydev->priv = dp83822;
 
 	return 0;

-- 
2.39.5

Re: [PATCH net-next v3 2/4] dt-bindings: net: dp83822: add constraints for mac-termination-ohms

[Andrew Lunn]

On Wed, Apr 16, 2025 at 07:14:48PM +0200, Dimitri Fedrau via B4 Relay wrote:
> From: Dimitri Fedrau <dimitri.fedrau@liebherr.com>
> 
> Property mac-termination-ohms is defined in ethernet-phy.yaml. Add allowed
> values for the property.
> 
> Signed-off-by: Dimitri Fedrau <dimitri.fedrau@liebherr.com>

Reviewed-by: Andrew Lunn <andrew@lunn.ch>

    Andrew

Re: [PATCH net-next v3 1/4] dt-bindings: net: ethernet-phy: add property mac-termination-ohms

[Rob Herring (Arm)]

On Wed, 16 Apr 2025 19:14:47 +0200, Dimitri Fedrau wrote:
> Add property mac-termination-ohms in the device tree bindings for selecting
> the resistance value of the builtin series termination resistors of the
> PHY. Changing the resistance to an appropriate value can reduce signal
> reflections and therefore improve signal quality.
> 
> Signed-off-by: Dimitri Fedrau <dimitri.fedrau@liebherr.com>
> ---
>  Documentation/devicetree/bindings/net/ethernet-phy.yaml | 10 ++++++++++
>  1 file changed, 10 insertions(+)
> 

Reviewed-by: Rob Herring (Arm) <robh@kernel.org>

Re: [PATCH net-next v3 2/4] dt-bindings: net: dp83822: add constraints for mac-termination-ohms

[Rob Herring (Arm)]

On Wed, 16 Apr 2025 19:14:48 +0200, Dimitri Fedrau wrote:
> Property mac-termination-ohms is defined in ethernet-phy.yaml. Add allowed
> values for the property.
> 
> Signed-off-by: Dimitri Fedrau <dimitri.fedrau@liebherr.com>
> ---
>  Documentation/devicetree/bindings/net/ti,dp83822.yaml | 4 ++++
>  1 file changed, 4 insertions(+)
> 

Reviewed-by: Rob Herring (Arm) <robh@kernel.org>

Re: [PATCH net-next v3 0/4] net: phy: dp83822: Add support for changing the MAC series termination

[patchwork-bot+netdevbpf]

Hello:

This series was applied to netdev/net-next.git (main)
by Jakub Kicinski <kuba@kernel.org>:

On Wed, 16 Apr 2025 19:14:46 +0200 you wrote:
> The dp83822 provides the possibility to set the resistance value of the
> the MAC series termination. Modifying the resistance to an appropriate
> value can reduce signal reflections and therefore improve signal quality.
> 
> Signed-off-by: Dimitri Fedrau <dimitri.fedrau@liebherr.com>
> ---
> Changes in v3:
> - Add maximum to mac-termination-ohms in ethernet-phy.yaml
> - Add allowed values for mac-termination-ohms in ti,dp83822.yaml
> - Added mac-termination-ohms in sample in ti,dp83822.yaml
> - Link to v2: https://lore.kernel.org/r/20250408-dp83822-mac-impedance-v2-0-fefeba4a9804@liebherr.com
> 
> [...]

Here is the summary with links:
  - [net-next,v3,1/4] dt-bindings: net: ethernet-phy: add property mac-termination-ohms
    https://git.kernel.org/netdev/net-next/c/4cb6316d33d8
  - [net-next,v3,2/4] dt-bindings: net: dp83822: add constraints for mac-termination-ohms
    https://git.kernel.org/netdev/net-next/c/1de1390ee014
  - [net-next,v3,3/4] net: phy: Add helper for getting MAC termination resistance
    https://git.kernel.org/netdev/net-next/c/145436ae0119
  - [net-next,v3,4/4] net: phy: dp83822: Add support for changing the MAC termination
    https://git.kernel.org/netdev/net-next/c/6c3c3c230a13

You are awesome, thank you!
-- 
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