net: add MMIO Register MDIO MUX driver

Add support for MMIO register MDIO muxes based on the Linux mdio-mux-mmioreg driver.

Signed-off-by: Neil Armstrong <narmstrong@baylibre.com>
Reviewed-by: Ramon Fried <rfried.dev@gmail.com>

drivers/net/Kconfig

@@ -790,4 +790,11 @@ config FSL_LS_MDIO
 	  This driver supports the MDIO bus found on the Fman 10G Ethernet MACs and
 	  on the mEMAC (which supports both Clauses 22 and 45).
 
+config MDIO_MUX_MMIOREG
+	bool "MDIO MUX accessed as a MMIO register access"
+	depends on DM_MDIO_MUX
+	help
+	  This driver is used for MDIO muxes driven by writing to a register in
+	  the MMIO physical memory.
+
 endif # NETDEVICES

drivers/net/Makefile

@@ -43,6 +43,7 @@ obj-$(CONFIG_MACB) += macb.o
 obj-$(CONFIG_MCFFEC) += mcffec.o mcfmii.o
 obj-$(CONFIG_MDIO_IPQ4019) += mdio-ipq4019.o
 obj-$(CONFIG_MDIO_MUX_I2CREG) += mdio_mux_i2creg.o
+obj-$(CONFIG_MDIO_MUX_MMIOREG) += mdio_mux_mmioreg.o
 obj-$(CONFIG_MDIO_MUX_SANDBOX) += mdio_mux_sandbox.o
 obj-$(CONFIG_MPC8XX_FEC) += mpc8xx_fec.o
 obj-$(CONFIG_MT7620_ETH) += mt7620-eth.o

drivers/net/mdio_mux_mmioreg.c

@@ -0,0 +1,129 @@
+// SPDX-License-Identifier: GPL-2.0
+/*
+ * (C) Copyright 2021 BayLibre, SAS
+ * Author: Neil Armstrong <narmstrong@baylibre.com>
+ *
+ * Based on linux/drivers/net/phy/mdio-mux-mmioreg.c :
+ *   Copyright 2012 Freescale Semiconductor, Inc.
+ */
+
+#include <dm.h>
+#include <errno.h>
+#include <log.h>
+#include <miiphy.h>
+#include <linux/io.h>
+
+struct mdio_mux_mmioreg_priv {
+	struct udevice *chip;
+	phys_addr_t phys;
+	unsigned int iosize;
+	unsigned int mask;
+};
+
+static int mdio_mux_mmioreg_select(struct udevice *mux, int cur, int sel)
+{
+	struct mdio_mux_mmioreg_priv *priv = dev_get_priv(mux);
+
+	debug("%s: %x -> %x\n", __func__, (u32)cur, (u32)sel);
+
+	/* if last selection didn't change we're good to go */
+	if (cur == sel)
+		return 0;
+
+	switch (priv->iosize) {
+	case sizeof(u8): {
+		u8 x, y;
+
+		x = ioread8((void *)priv->phys);
+		y = (x & ~priv->mask) | (u32)sel;
+		if (x != y) {
+			iowrite8((x & ~priv->mask) | sel, (void *)priv->phys);
+			debug("%s: %02x -> %02x\n", __func__, x, y);
+		}
+
+		break;
+	}
+	case sizeof(u16): {
+		u16 x, y;
+
+		x = ioread16((void *)priv->phys);
+		y = (x & ~priv->mask) | (u32)sel;
+		if (x != y) {
+			iowrite16((x & ~priv->mask) | sel, (void *)priv->phys);
+			debug("%s: %04x -> %04x\n", __func__, x, y);
+		}
+
+		break;
+	}
+	case sizeof(u32): {
+		u32 x, y;
+
+		x = ioread32((void *)priv->phys);
+		y = (x & ~priv->mask) | (u32)sel;
+		if (x != y) {
+			iowrite32((x & ~priv->mask) | sel, (void *)priv->phys);
+			debug("%s: %08x -> %08x\n", __func__, x, y);
+		}
+
+		break;
+	}
+	}
+
+	return 0;
+}
+
+static const struct mdio_mux_ops mdio_mux_mmioreg_ops = {
+	.select = mdio_mux_mmioreg_select,
+};
+
+static int mdio_mux_mmioreg_probe(struct udevice *dev)
+{
+	struct mdio_mux_mmioreg_priv *priv = dev_get_priv(dev);
+	phys_addr_t reg_base, reg_size;
+	u32 reg_mask;
+	int err;
+
+	reg_base = ofnode_get_addr_size_index(dev_ofnode(dev), 0, &reg_size);
+	if (reg_base == FDT_ADDR_T_NONE)
+		return -EINVAL;
+
+	if (reg_size != sizeof(u8) &&
+	    reg_size != sizeof(u16) &&
+	    reg_size != sizeof(u32)) {
+		printf("%s: only 8/16/32-bit registers are supported\n", __func__);
+		return -EINVAL;
+	}
+
+	err = dev_read_u32(dev, "mux-mask", &reg_mask);
+	if (err) {
+		debug("%s: error reading mux-mask property\n", __func__);
+		return err;
+	}
+
+	if (reg_mask >= BIT(reg_size * 8)) {
+		printf("%s: mask doesn't fix in register width\n", __func__);
+		return -EINVAL;
+	}
+
+	priv->phys = reg_base;
+	priv->iosize = reg_size;
+	priv->mask = reg_mask;
+
+	debug("%s: %llx@%lld / %x\n", __func__, reg_base, reg_size, reg_mask);
+
+	return 0;
+}
+
+static const struct udevice_id mdio_mux_mmioreg_ids[] = {
+	{ .compatible = "mdio-mux-mmioreg" },
+	{ }
+};
+
+U_BOOT_DRIVER(mdio_mux_mmioreg) = {
+	.name		= "mdio_mux_mmioreg",
+	.id		= UCLASS_MDIO_MUX,
+	.of_match	= mdio_mux_mmioreg_ids,
+	.probe		= mdio_mux_mmioreg_probe,
+	.ops		= &mdio_mux_mmioreg_ops,
+	.priv_auto	= sizeof(struct mdio_mux_mmioreg_priv),
+};