netdev - [PATCH net-next v2 3/3] net: phy: dp83867: implement support for io_impedance

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Date:   Tue, 14 Jun 2022 10:46:12 +0200
From:   Rasmus Villemoes <linux@...musvillemoes.dk>
To:     netdev@...r.kernel.org, Andrew Lunn <andrew@...n.ch>,
        Heiner Kallweit <hkallweit1@...il.com>,
        Russell King <linux@...linux.org.uk>
Cc:     devicetree@...r.kernel.org, Rob Herring <robh+dt@...nel.org>,
        Jakub Kicinski <kuba@...nel.org>,
        "David S. Miller" <davem@...emloft.net>,
        Grygorii Strashko <grygorii.strashko@...com>,
        Praneeth Bajjuri <praneeth@...com>,
        linux-kernel@...r.kernel.org,
        Rasmus Villemoes <linux@...musvillemoes.dk>
Subject: [PATCH net-next v2 3/3] net: phy: dp83867: implement support for io_impedance_ctrl nvmem cell

We have a board where measurements indicate that the current three
options - leaving IO_IMPEDANCE_CTRL at the (factory calibrated) reset
value or using one of the two boolean properties to set it to the
min/max value - are too coarse.

Implement support for the newly added binding allowing device tree to
specify an nvmem cell containing an appropriate value for this
specific board.

Signed-off-by: Rasmus Villemoes <linux@...musvillemoes.dk>
---
 drivers/net/phy/dp83867.c | 55 ++++++++++++++++++++++++++++++++++-----
 1 file changed, 49 insertions(+), 6 deletions(-)

diff --git a/drivers/net/phy/dp83867.c b/drivers/net/phy/dp83867.c
index 8561f2d4443b..45d8a9298251 100644
--- a/drivers/net/phy/dp83867.c
+++ b/drivers/net/phy/dp83867.c
@@ -14,6 +14,7 @@
 #include <linux/netdevice.h>
 #include <linux/etherdevice.h>
 #include <linux/bitfield.h>
+#include <linux/nvmem-consumer.h>
 
 #include <dt-bindings/net/ti-dp83867.h>
 
@@ -521,6 +522,51 @@ static int dp83867_verify_rgmii_cfg(struct phy_device *phydev)
 }
 
 #if IS_ENABLED(CONFIG_OF_MDIO)
+static int dp83867_of_init_io_impedance(struct phy_device *phydev)
+{
+	struct dp83867_private *dp83867 = phydev->priv;
+	struct device *dev = &phydev->mdio.dev;
+	struct device_node *of_node = dev->of_node;
+	struct nvmem_cell *cell;
+	u8 *buf, val;
+	int ret;
+
+	cell = of_nvmem_cell_get(of_node, "io_impedance_ctrl");
+	if (IS_ERR(cell)) {
+		ret = PTR_ERR(cell);
+		if (ret != -ENOENT)
+			return phydev_err_probe(phydev, ret,
+						"failed to get nvmem cell io_impedance_ctrl\n");
+
+		/* If no nvmem cell, check for the boolean properties. */
+		if (of_property_read_bool(of_node, "ti,max-output-impedance"))
+			dp83867->io_impedance = DP83867_IO_MUX_CFG_IO_IMPEDANCE_MAX;
+		else if (of_property_read_bool(of_node, "ti,min-output-impedance"))
+			dp83867->io_impedance = DP83867_IO_MUX_CFG_IO_IMPEDANCE_MIN;
+		else
+			dp83867->io_impedance = -1; /* leave at default */
+
+		return 0;
+	}
+
+	buf = nvmem_cell_read(cell, NULL);
+	nvmem_cell_put(cell);
+
+	if (IS_ERR(buf))
+		return PTR_ERR(buf);
+
+	val = *buf;
+	kfree(buf);
+
+	if ((val & DP83867_IO_MUX_CFG_IO_IMPEDANCE_MASK) != val) {
+		phydev_err(phydev, "nvmem cell 'io_impedance_ctrl' contents out of range\n");
+		return -ERANGE;
+	}
+	dp83867->io_impedance = val;
+
+	return 0;
+}
+
 static int dp83867_of_init(struct phy_device *phydev)
 {
 	struct dp83867_private *dp83867 = phydev->priv;
@@ -548,12 +594,9 @@ static int dp83867_of_init(struct phy_device *phydev)
 		}
 	}
 
-	if (of_property_read_bool(of_node, "ti,max-output-impedance"))
-		dp83867->io_impedance = DP83867_IO_MUX_CFG_IO_IMPEDANCE_MAX;
-	else if (of_property_read_bool(of_node, "ti,min-output-impedance"))
-		dp83867->io_impedance = DP83867_IO_MUX_CFG_IO_IMPEDANCE_MIN;
-	else
-		dp83867->io_impedance = -1; /* leave at default */
+	ret = dp83867_of_init_io_impedance(phydev);
+	if (ret)
+		return ret;
 
 	dp83867->rxctrl_strap_quirk = of_property_read_bool(of_node,
 							    "ti,dp83867-rxctrl-strap-quirk");
-- 
2.31.1