[PATCH v3 0/2] net: phy: adin: enable configuration of the LP Termination Register

[PATCH v3 0/2] net: phy: adin: enable configuration of the LP Termination Register

[Osose Itua]

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Changes in v3:
- put bindings patch first in the patchset
- update commit message of the bindings patch and improve the bindings
  description to better explain why the added property is needed (as
  suggested by Nuno Sá and Andrew Lunn)
- rework bit clearing to use phy_clear_bits_mmd() instead of
  phy_write_mmd() since only a single bit needs to be cleared (as noted
  by Subbaraya Sundeep)
- remove redundant phy_read_mmd() and error checking (as suggested by
  Nuno Sá)
- remove unnecessary C++ <cerrno> include that was causing build issues

Changes in v2:
- rework phy_read_mmd() error handling

Osose Itua (2):
  dt-bindings: net: adi,adin: document LP Termination property
  net: phy: adin: enable configuration of the LP Termination Register

 .../devicetree/bindings/net/adi,adin.yaml     | 14 +++++++++++++
 drivers/net/phy/adin.c                        | 20 +++++++++++++++++++
 2 files changed, 34 insertions(+)

[PATCH v3 1/2] dt-bindings: net: adi,adin: document LP Termination property

[Osose Itua]

Add "adi,low-cmode-impedance" boolean property which, when present,
configures the PHY for the lowest common-mode impedance on the receive
pair for 100BASE-TX operation by clearing the B_100_ZPTM_EN_DIMRX bit.
This is suited for capacitive coupled applications and other
applications where there may be a path for high common-mode noise to
reach the PHY.

If this value is not present, the value of the bit by default is 1,
which is normal termination (zero-power termination) mode.

Signed-off-by: Osose Itua <osose.itua@savoirfairelinux.com>
---
 .../devicetree/bindings/net/adi,adin.yaml          | 14 ++++++++++++++
 1 file changed, 14 insertions(+)

diff --git a/Documentation/devicetree/bindings/net/adi,adin.yaml b/Documentation/devicetree/bindings/net/adi,adin.yaml
index c425a9f1886d..f594055c2b15 100644
--- a/Documentation/devicetree/bindings/net/adi,adin.yaml
+++ b/Documentation/devicetree/bindings/net/adi,adin.yaml
@@ -52,6 +52,20 @@ properties:
     description: Enable 25MHz reference clock output on CLK25_REF pin.
     type: boolean
 
+  adi,low-cmode-impedance:
+    description: |
+      Configure PHY for the lowest common-mode impedance on the receive pair
+      for 100BASE-TX. This is suited for capacitive coupled applications and
+      other applications where there may be a path for high common-mode noise
+      to reach the PHY.
+      If not present, by default the PHY is configured for normal termination
+      (zero-power termination) mode.
+
+      Note: There is a trade-off of 12 mW increased power consumption with
+        the lowest common-mode impedance setting, but in all cases the
+        differential impedance is 100 ohms.
+    type: boolean
+
 unevaluatedProperties: false
 
 examples:

[PATCH v3 2/2] net: phy: adin: enable configuration of the LP Termination Register

[Osose Itua]

The ADIN1200/ADIN1300 provide a control bit that selects between normal
receive termination and the lowest common mode impedance for 100BASE-TX
operation. This behavior is controlled through the Low Power Termination
register (B_100_ZPTM_EN_DIMRX).

Bit 0 of this register enables normal termination when set (this is the
default), and selects the lowest common mode impedance when cleared.

Signed-off-by: Osose Itua <osose.itua@savoirfairelinux.com>
---
 drivers/net/phy/adin.c | 20 ++++++++++++++++++++
 1 file changed, 20 insertions(+)

diff --git a/drivers/net/phy/adin.c b/drivers/net/phy/adin.c
index 7fa713ca8d45..3a934051b574 100644
--- a/drivers/net/phy/adin.c
+++ b/drivers/net/phy/adin.c
@@ -89,6 +89,9 @@
 #define ADIN1300_CLOCK_STOP_REG			0x9400
 #define ADIN1300_LPI_WAKE_ERR_CNT_REG		0xa000
 
+#define ADIN1300_B_100_ZPTM_DIMRX		0xB685
+#define ADIN1300_B_100_ZPTM_EN_DIMRX		BIT(0)
+
 #define ADIN1300_CDIAG_RUN			0xba1b
 #define   ADIN1300_CDIAG_RUN_EN			BIT(0)
 
@@ -522,6 +525,19 @@ static int adin_config_clk_out(struct phy_device *phydev)
 			      ADIN1300_GE_CLK_CFG_MASK, sel);
 }
 
+static int adin_config_zptm100(struct phy_device *phydev)
+{
+	struct device *dev = &phydev->mdio.dev;
+
+	if (!(device_property_read_bool(dev, "adi,low-cmode-impedance")))
+		return 0;
+
+	/* clear bit 0 to configure for lowest common-mode impedance */
+	return phy_clear_bits_mmd(phydev, MDIO_MMD_VEND1,
+					  ADIN1300_B_100_ZPTM_DIMRX,
+					  ADIN1300_B_100_ZPTM_EN_DIMRX);
+}
+
 static int adin_config_init(struct phy_device *phydev)
 {
 	int rc;
@@ -548,6 +564,10 @@ static int adin_config_init(struct phy_device *phydev)
 	if (rc < 0)
 		return rc;
 
+	rc = adin_config_zptm100(phydev);
+	if (rc < 0)
+		return rc;
+
 	phydev_dbg(phydev, "PHY is using mode '%s'\n",
 		   phy_modes(phydev->interface));
 

Re: [PATCH v3 0/2] net: phy: adin: enable configuration of the LP Termination Register

[Nuno Sá]

On Wed, 2026-01-07 at 17:16 -0500, Osose Itua wrote:
> Changes in v3:
> - put bindings patch first in the patchset
> - update commit message of the bindings patch and improve the bindings
>   description to better explain why the added property is needed (as
>   suggested by Nuno Sá and Andrew Lunn)
> - rework bit clearing to use phy_clear_bits_mmd() instead of
>   phy_write_mmd() since only a single bit needs to be cleared (as noted
>   by Subbaraya Sundeep)
> - remove redundant phy_read_mmd() and error checking (as suggested by
>   Nuno Sá)
> - remove unnecessary C++ <cerrno> include that was causing build issues
> 
> Changes in v2:
> - rework phy_read_mmd() error handling
> 
> Osose Itua (2):
>   dt-bindings: net: adi,adin: document LP Termination property
>   net: phy: adin: enable configuration of the LP Termination Register
> 
>  .../devicetree/bindings/net/adi,adin.yaml     | 14 +++++++++++++
>  drivers/net/phy/adin.c                        | 20 +++++++++++++++++++
>  2 files changed, 34 insertions(+)

LGTM!

Acked-by: Nuno Sá <nuno.sa@analog.com>

Re: [PATCH v3 1/2] dt-bindings: net: adi,adin: document LP Termination property

[Rob Herring (Arm)]

On Wed, 07 Jan 2026 17:16:52 -0500, Osose Itua wrote:
> Add "adi,low-cmode-impedance" boolean property which, when present,
> configures the PHY for the lowest common-mode impedance on the receive
> pair for 100BASE-TX operation by clearing the B_100_ZPTM_EN_DIMRX bit.
> This is suited for capacitive coupled applications and other
> applications where there may be a path for high common-mode noise to
> reach the PHY.
> 
> If this value is not present, the value of the bit by default is 1,
> which is normal termination (zero-power termination) mode.
> 
> Signed-off-by: Osose Itua <osose.itua@savoirfairelinux.com>
> ---
>  .../devicetree/bindings/net/adi,adin.yaml          | 14 ++++++++++++++
>  1 file changed, 14 insertions(+)
> 

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

Re: [PATCH v3 0/2] net: phy: adin: enable configuration of the LP Termination Register

[patchwork-bot+netdevbpf]

Hello:

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

On Wed,  7 Jan 2026 17:16:51 -0500 you wrote:
> Changes in v3:
> - put bindings patch first in the patchset
> - update commit message of the bindings patch and improve the bindings
>   description to better explain why the added property is needed (as
>   suggested by Nuno Sá and Andrew Lunn)
> - rework bit clearing to use phy_clear_bits_mmd() instead of
>   phy_write_mmd() since only a single bit needs to be cleared (as noted
>   by Subbaraya Sundeep)
> - remove redundant phy_read_mmd() and error checking (as suggested by
>   Nuno Sá)
> - remove unnecessary C++ <cerrno> include that was causing build issues
> 
> [...]

Here is the summary with links:
  - [v3,1/2] dt-bindings: net: adi,adin: document LP Termination property
    https://git.kernel.org/netdev/net-next/c/7376ba2db168
  - [v3,2/2] net: phy: adin: enable configuration of the LP Termination Register
    https://git.kernel.org/netdev/net-next/c/a6733836527d

You are awesome, thank you!
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