drivers: net: driver for MDIO muxes controlled over I2C

This driver is used for MDIO muxes driven over I2C.  This is currently
used on Freescale LS1028A QDS board, on which the physical MDIO MUX is
controlled by an on-board FPGA which in turn is configured through I2C.

Signed-off-by: Alex Marginean <alexm.osslist@gmail.com>
Acked-by: Joe Hershberger <joe.hershberger@ni.com>
Reviewed-by: Bin Meng <bmeng.cn@gmail.com>

drivers/net/Kconfig

@@ -595,4 +595,12 @@ config FSL_ENETC
 	  This driver supports the NXP ENETC Ethernet controller found on some
 	  of the NXP SoCs.
 
+config MDIO_MUX_I2CREG
+	bool "MDIO MUX accessed as a register over I2C"
+	depends on DM_MDIO_MUX && DM_I2C
+	help
+	  This driver is used for MDIO muxes driven by writing to a register of
+	  an I2C chip.  The board it was developed for uses a mux controlled by
+	  on-board FPGA which in turn is accessed as a chip over I2C.
+
 endif # NETDEVICES

drivers/net/Makefile

@@ -37,6 +37,7 @@ obj-$(CONFIG_LAN91C96) += lan91c96.o
 obj-$(CONFIG_LPC32XX_ETH) += lpc32xx_eth.o
 obj-$(CONFIG_MACB) += macb.o
 obj-$(CONFIG_MCFFEC) += mcffec.o mcfmii.o
+obj-$(CONFIG_MDIO_MUX_I2CREG) += mdio_mux_i2creg.o
 obj-$(CONFIG_MDIO_MUX_SANDBOX) += mdio_mux_sandbox.o
 obj-$(CONFIG_MPC8XX_FEC) += mpc8xx_fec.o
 obj-$(CONFIG_MT7628_ETH) += mt7628-eth.o

drivers/net/mdio_mux_i2creg.c

@@ -0,0 +1,108 @@
+// SPDX-License-Identifier: GPL-2.0+
+/*
+ * (C) Copyright 2019
+ * Alex Marginean, NXP
+ */
+
+#include <dm.h>
+#include <errno.h>
+#include <miiphy.h>
+#include <i2c.h>
+
+/*
+ * This driver is used for MDIO muxes driven by writing to a register of an I2C
+ * chip.  The board it was developed for uses a mux controlled by on-board FPGA
+ * which in turn is accessed as a chip over I2C.
+ */
+
+struct mdio_mux_i2creg_priv {
+	struct udevice *chip;
+	int reg;
+	int mask;
+};
+
+static int mdio_mux_i2creg_select(struct udevice *mux, int cur, int sel)
+{
+	struct mdio_mux_i2creg_priv *priv = dev_get_priv(mux);
+	u8 val, val_old;
+
+	/* if last selection didn't change we're good to go */
+	if (cur == sel)
+		return 0;
+
+	val_old = dm_i2c_reg_read(priv->chip, priv->reg);
+	val = (val_old & ~priv->mask) | (sel & priv->mask);
+	debug("%s: chip %s, reg %x, val %x => %x\n", __func__, priv->chip->name,
+	      priv->reg, val_old, val);
+	dm_i2c_reg_write(priv->chip, priv->reg, val);
+
+	return 0;
+}
+
+static const struct mdio_mux_ops mdio_mux_i2creg_ops = {
+	.select = mdio_mux_i2creg_select,
+};
+
+static int mdio_mux_i2creg_probe(struct udevice *dev)
+{
+	struct mdio_mux_i2creg_priv *priv = dev_get_priv(dev);
+	ofnode chip_node, bus_node;
+	struct udevice *i2c_bus;
+	u32 reg_mask[2];
+	u32 chip_addr;
+	int err;
+
+	/* read the register addr/mask pair */
+	err = dev_read_u32_array(dev, "mux-reg-masks", reg_mask, 2);
+	if (err) {
+		debug("%s: error reading mux-reg-masks property\n", __func__);
+		return err;
+	}
+
+	/* parent should be an I2C chip, grandparent should be an I2C bus */
+	chip_node = ofnode_get_parent(dev->node);
+	bus_node = ofnode_get_parent(chip_node);
+
+	err = uclass_get_device_by_ofnode(UCLASS_I2C, bus_node, &i2c_bus);
+	if (err) {
+		debug("%s: can't find I2C bus for node %s\n", __func__,
+		      ofnode_get_name(bus_node));
+		return err;
+	}
+
+	err = ofnode_read_u32(chip_node, "reg", &chip_addr);
+	if (err) {
+		debug("%s: can't read chip address in %s\n", __func__,
+		      ofnode_get_name(chip_node));
+		return err;
+	}
+
+	err = i2c_get_chip(i2c_bus, (uint)chip_addr, 1, &priv->chip);
+	if (err) {
+		debug("%s: can't find i2c chip device for addr %x\n", __func__,
+		      chip_addr);
+		return err;
+	}
+
+	priv->reg = (int)reg_mask[0];
+	priv->mask = (int)reg_mask[1];
+
+	debug("%s: chip %s, reg %x, mask %x\n", __func__, priv->chip->name,
+	      priv->reg, priv->mask);
+
+	return 0;
+}
+
+static const struct udevice_id mdio_mux_i2creg_ids[] = {
+	{ .compatible = "mdio-mux-i2creg" },
+	{ }
+};
+
+U_BOOT_DRIVER(mdio_mux_i2creg) = {
+	.name		= "mdio_mux_i2creg",
+	.id		= UCLASS_MDIO_MUX,
+	.of_match	= mdio_mux_i2creg_ids,
+	.probe		= mdio_mux_i2creg_probe,
+	.ops		= &mdio_mux_i2creg_ops,
+	.priv_auto_alloc_size = sizeof(struct mdio_mux_i2creg_priv),
+};