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@rasmusvillemoes.dk>
Signed-off-by: Jakub Kicinski <kuba@kernel.org>

diff --git a/drivers/net/phy/dp83867.c b/drivers/net/phy/dp83867.c
index 13dafe7..1e38039 100644 (file)
--- 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");