net: Add Amlogic GXL MDIO Mux driver

Port the mdio-mux-meson-gxl.c Linux driver introduced in [1],
and adapt it to U-Boot.

This driver is needed to boot U-Boot with Linux DT since v6.4,
since it switched the MDIO mux from the mmio to a proper GXL driver.

[1] 9a24e1ff4326 ("net: mdio: add amlogic gxl mdio mux support")

Link: https://lore.kernel.org/r/20231213-u-boot-gxl-mdio-mux-v2-1-c56bb02a75ea@linaro.org
Signed-off-by: Neil Armstrong <neil.armstrong@linaro.org>

drivers/net/Kconfig

@@ -980,4 +980,11 @@ config MDIO_MUX_MESON_G12A
 	  This driver is used for the MDIO mux found on the Amlogic G12A & compatible
 	  SoCs.
 
+config MDIO_MUX_MESON_GXL
+	bool "MDIO MUX for Amlogic Meson GXL SoCs"
+	depends on DM_MDIO_MUX
+	help
+	  This driver is used for the MDIO mux found on the Amlogic GXL & compatible
+	  SoCs.
+
 endif # NETDEVICES

drivers/net/Makefile

@@ -57,6 +57,7 @@ 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_MESON_G12A) += mdio_mux_meson_g12a.o
+obj-$(CONFIG_MDIO_MUX_MESON_GXL) += mdio_mux_meson_gxl.o
 obj-$(CONFIG_MDIO_MUX_MMIOREG) += mdio_mux_mmioreg.o
 obj-$(CONFIG_MDIO_MUX_SANDBOX) += mdio_mux_sandbox.o
 obj-$(CONFIG_MDIO_SANDBOX) += mdio_sandbox.o

drivers/net/mdio_mux_meson_gxl.c

@@ -0,0 +1,138 @@
+// SPDX-License-Identifier: GPL-2.0
+/*
+ * Copyright (c) 2022 Baylibre, SAS.
+ * Author: Jerome Brunet <jbrunet@baylibre.com>
+ * Copyright (c) 2023 Neil Armstrong <neil.armstrong@linaro.org>
+ */
+
+#include <dm.h>
+#include <errno.h>
+#include <log.h>
+#include <miiphy.h>
+#include <asm/io.h>
+#include <linux/bitfield.h>
+#include <linux/delay.h>
+
+#define ETH_REG2		0x0
+#define  REG2_PHYID		GENMASK(21, 0)
+#define   EPHY_GXL_ID		0x110181
+#define  REG2_LEDACT		GENMASK(23, 22)
+#define  REG2_LEDLINK		GENMASK(25, 24)
+#define  REG2_DIV4SEL		BIT(27)
+#define  REG2_ADCBYPASS		BIT(30)
+#define  REG2_CLKINSEL		BIT(31)
+#define ETH_REG3		0x4
+#define  REG3_ENH		BIT(3)
+#define  REG3_CFGMODE		GENMASK(6, 4)
+#define  REG3_AUTOMDIX		BIT(7)
+#define  REG3_PHYADDR		GENMASK(12, 8)
+#define  REG3_PWRUPRST		BIT(21)
+#define  REG3_PWRDOWN		BIT(22)
+#define  REG3_LEDPOL		BIT(23)
+#define  REG3_PHYMDI		BIT(26)
+#define  REG3_CLKINEN		BIT(29)
+#define  REG3_PHYIP		BIT(30)
+#define  REG3_PHYEN		BIT(31)
+#define ETH_REG4		0x8
+#define  REG4_PWRUPRSTSIG	BIT(0)
+
+#define MESON_GXL_MDIO_EXTERNAL_ID 0
+#define MESON_GXL_MDIO_INTERNAL_ID 1
+
+struct mdio_mux_meson_gxl_priv {
+	phys_addr_t regs;
+};
+
+static int meson_gxl_enable_internal_mdio(struct mdio_mux_meson_gxl_priv *priv)
+{
+	u32 val;
+
+	/* Setup the internal phy */
+	val = (REG3_ENH |
+	       FIELD_PREP(REG3_CFGMODE, 0x7) |
+	       REG3_AUTOMDIX |
+	       FIELD_PREP(REG3_PHYADDR, 8) |
+	       REG3_LEDPOL |
+	       REG3_PHYMDI |
+	       REG3_CLKINEN |
+	       REG3_PHYIP);
+
+	writel(REG4_PWRUPRSTSIG, priv->regs + ETH_REG4);
+	writel(val, priv->regs + ETH_REG3);
+	mdelay(10);
+
+	/* NOTE: The HW kept the phy id configurable at runtime.
+	 * The id below is arbitrary. It is the one used in the vendor code.
+	 * The only constraint is that it must match the one in
+	 * drivers/net/phy/meson-gxl.c to properly match the PHY.
+	 */
+	writel(FIELD_PREP(REG2_PHYID, EPHY_GXL_ID),
+	       priv->regs + ETH_REG2);
+
+	/* Enable the internal phy */
+	val |= REG3_PHYEN;
+	writel(val, priv->regs + ETH_REG3);
+	writel(0, priv->regs + ETH_REG4);
+
+	/* The phy needs a bit of time to power up */
+	mdelay(10);
+
+	return 0;
+}
+
+static int meson_gxl_enable_external_mdio(struct mdio_mux_meson_gxl_priv *priv)
+{
+	/* Reset the mdio bus mux to the external phy */
+	writel(0, priv->regs + ETH_REG3);
+
+	return 0;
+}
+
+static int mdio_mux_meson_gxl_select(struct udevice *mux, int cur, int sel)
+{
+	struct mdio_mux_meson_gxl_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 (sel) {
+	case MESON_GXL_MDIO_EXTERNAL_ID:
+		return meson_gxl_enable_external_mdio(priv);
+	case MESON_GXL_MDIO_INTERNAL_ID:
+		return meson_gxl_enable_internal_mdio(priv);
+	default:
+		return -EINVAL;
+	}
+
+	return 0;
+}
+
+static const struct mdio_mux_ops mdio_mux_meson_gxl_ops = {
+	.select = mdio_mux_meson_gxl_select,
+};
+
+static int mdio_mux_meson_gxl_probe(struct udevice *dev)
+{
+	struct mdio_mux_meson_gxl_priv *priv = dev_get_priv(dev);
+
+	priv->regs = dev_read_addr(dev);
+
+	return 0;
+}
+
+static const struct udevice_id mdio_mux_meson_gxl_ids[] = {
+	{ .compatible = "amlogic,gxl-mdio-mux" },
+	{ }
+};
+
+U_BOOT_DRIVER(mdio_mux_meson_gxl) = {
+	.name		= "mdio_mux_meson_gxl",
+	.id		= UCLASS_MDIO_MUX,
+	.of_match	= mdio_mux_meson_gxl_ids,
+	.probe		= mdio_mux_meson_gxl_probe,
+	.ops		= &mdio_mux_meson_gxl_ops,
+	.priv_auto	= sizeof(struct mdio_mux_meson_gxl_priv),
+};