Merge branch 'dt-bindings-dp83867-add-binding-for-io_impedance_ctrl-nvmem-cell'

Rasmus Villemoes says:

====================
dt-bindings: dp83867: add binding for io_impedance_ctrl nvmem cell

We have a board where measurements indicate that the current three
options - leaving IO_IMPEDANCE_CTRL at the reset value (which is
factory calibrated to a value corresponding to approximately 50 ohms)
or using one of the two boolean properties to set it to the min/max
value - are too coarse.

This series adds a device tree binding for an nvmem cell which can be
populated during production with a suitable value calibrated for each
board, and corresponding support in the driver. The second patch adds
a trivial phy wrapper for dev_err_probe(), used in the third.
====================

Link: https://lore.kernel.org/r/20220614084612.325229-1-linux@rasmusvillemoes.dk
Signed-off-by: Jakub Kicinski <kuba@kernel.org>

3 files changed, 67 insertions, 9 deletions

diff --git a/Documentation/devicetree/bindings/net/ti,dp83867.yaml b/Documentation/devicetree/bindings/net/ti,dp83867.yaml
index 047d757e8d82..76ff08a477ba 100644
--- a/Documentation/devicetree/bindings/net/ti,dp83867.yaml
+++ b/Documentation/devicetree/bindings/net/ti,dp83867.yaml
@@ -31,6 +31,16 @@ properties:
   reg:
     maxItems: 1
 
+  nvmem-cells:
+    maxItems: 1
+    description:
+      Nvmem data cell containing the value to write to the
+      IO_IMPEDANCE_CTRL field of the IO_MUX_CFG register.
+
+  nvmem-cell-names:
+    items:
+      - const: io_impedance_ctrl
+
   ti,min-output-impedance:
     type: boolean
     description: |
@@ -42,9 +52,11 @@ properties:
     description: |
       MAC Interface Impedance control to set the programmable output impedance
       to a maximum value (70 ohms).
-      Note: ti,min-output-impedance and ti,max-output-impedance are mutually
-        exclusive. When both properties are present ti,max-output-impedance
-        takes precedence.
+      Note: Specifying an io_impedance_ctrl nvmem cell or one of the
+        ti,min-output-impedance, ti,max-output-impedance properties
+        are mutually exclusive. If more than one is present, an nvmem
+        cell takes precedence over ti,max-output-impedance, which in
+        turn takes precedence over ti,min-output-impedance.
 
   tx-fifo-depth:
     $ref: /schemas/types.yaml#/definitions/uint32
diff --git a/drivers/net/phy/dp83867.c b/drivers/net/phy/dp83867.c
index 13dafe7a29bd..1e38039c5c56 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>
 
@@ -522,6 +523,51 @@ 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;
@@ -549,12 +595,9 @@ 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");
diff --git a/include/linux/phy.h b/include/linux/phy.h
index 508f1149665b..bed9a347481b 100644
--- a/include/linux/phy.h
+++ b/include/linux/phy.h
@@ -1539,6 +1539,9 @@ static inline void phy_device_reset(struct phy_device *phydev, int value)
 #define phydev_err(_phydev, format, args...)	\
 	dev_err(&_phydev->mdio.dev, format, ##args)
 
+#define phydev_err_probe(_phydev, err, format, args...)	\
+	dev_err_probe(&_phydev->mdio.dev, err, format, ##args)
+
 #define phydev_info(_phydev, format, args...)	\
 	dev_info(&_phydev->mdio.dev, format, ##args)