[PATCH v2 1/2] net: phy: adin: enable configuration of the LP Termination Register

Osose Itua
2025-12-22T22:22:45Z

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 | 34 ++++++++++++++++++++++++++++++++++
1 file changed, 34 insertions(+)

diff --git a/drivers/net/phy/adin.c b/drivers/net/phy/adin.c
index 7fa713ca8d45..e8b778cb191d 100644
--- a/drivers/net/phy/adin.c
+++ b/drivers/net/phy/adin.c
@@ -4,6 +4,7 @@
*
* Copyright 2019 Analog Devices Inc.
*/
+#include <cerrno>
#include <linux/kernel.h>
#include <linux/bitfield.h>
#include <linux/delay.h>
@@ -89,6 +90,9 @@
#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 +526,32 @@ 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;
+ int reg;
+ int rc;
+
+ if (!(device_property_read_bool(dev, "adi,low-cmode-impedance")))
+ return 0;
+
+ /* set to 0 to configure for lowest common-mode impedance */
+ rc = phy_write_mmd(phydev, MDIO_MMD_VEND1, ADIN1300_B_100_ZPTM_DIMRX, 0x0);
+ if (rc < 0)
+ return rc;
+
+ reg = phy_read_mmd(phydev, MDIO_MMD_VEND1, ADIN1300_B_100_ZPTM_DIMRX);
+ if (reg < 0)
+ return reg;
+
+ if (!(reg & ADIN1300_B_100_ZPTM_EN_DIMRX)) {
+ phydev_err(phydev, "Failed to set lowest common-mode impedance.\n");
+ return -EINVAL;
+ }
+
+ return 0;
+}
+
static int adin_config_init(struct phy_device *phydev)
{
int rc;
@@ -548,6 +578,10 @@ 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));