[PATCH 15/24] net: mdio: Add ZTE ZX279128S MDIO controller

[Navid Ghahremani <ghahramani.navid@gmail.com>]

Provide bounded Clause 22 transactions and managed clock and MDIO-bus
registration.

Assisted-by: LLM
Signed-off-by: Navid Ghahremani <ghahramani.navid@gmail.com>
---
 drivers/net/mdio/Kconfig          |  11 +++
 drivers/net/mdio/Makefile         |   1 +
 drivers/net/mdio/mdio-zx279128s.c | 158 ++++++++++++++++++++++++++++++
 3 files changed, 170 insertions(+)
 create mode 100644 drivers/net/mdio/mdio-zx279128s.c

diff --git a/drivers/net/mdio/Kconfig b/drivers/net/mdio/Kconfig
index a05229838c..59812a082a 100644
--- a/drivers/net/mdio/Kconfig
+++ b/drivers/net/mdio/Kconfig
@@ -199,6 +199,17 @@ config MDIO_THUNDER
 	  ThunderX SoCs when the MDIO bus device appears as a PCI
 	  device.
 
+config MDIO_ZX279128S
+	tristate "ZTE zx279128s MDIO bus controller"
+	depends on ARCH_ZTE || COMPILE_TEST
+	depends on HAS_IOMEM && OF_MDIO
+	help
+	  This driver supports the MDIO controller of the ZTE zx279128s
+	  SoC. It reaches the PHYs of the integrated switch and, on boards
+	  such as the ZTE ZXHN H3600, an external PHY.
+
+	  To compile this driver as a module, choose M here.
+
 menu "MDIO Multiplexers"
 
 config MDIO_BUS_MUX
diff --git a/drivers/net/mdio/Makefile b/drivers/net/mdio/Makefile
index 0485867460..ce21e1496c 100644
--- a/drivers/net/mdio/Makefile
+++ b/drivers/net/mdio/Makefile
@@ -26,6 +26,7 @@ obj-$(CONFIG_MDIO_REGMAP)		+= mdio-regmap.o
 obj-$(CONFIG_MDIO_SUN4I)		+= mdio-sun4i.o
 obj-$(CONFIG_MDIO_THUNDER)		+= mdio-thunder.o
 obj-$(CONFIG_MDIO_XGENE)		+= mdio-xgene.o
+obj-$(CONFIG_MDIO_ZX279128S)		+= mdio-zx279128s.o
 
 obj-$(CONFIG_MDIO_BUS_MUX)		+= mdio-mux.o
 obj-$(CONFIG_MDIO_BUS_MUX_BCM6368)	+= mdio-mux-bcm6368.o
diff --git a/drivers/net/mdio/mdio-zx279128s.c b/drivers/net/mdio/mdio-zx279128s.c
new file mode 100644
index 0000000000..4c4a9ada68
--- /dev/null
+++ b/drivers/net/mdio/mdio-zx279128s.c
@@ -0,0 +1,158 @@
+// SPDX-License-Identifier: GPL-2.0-only
+/*
+ * ZTE zx279128s MDIO controller
+ *
+ * Copyright (C) 2026 Navid Ghahremani <ghahramani.navid@gmail.com>
+ */
+
+#include <linux/bitfield.h>
+#include <linux/bits.h>
+#include <linux/clk.h>
+#include <linux/err.h>
+#include <linux/io.h>
+#include <linux/iopoll.h>
+#include <linux/mod_devicetable.h>
+#include <linux/module.h>
+#include <linux/of_mdio.h>
+#include <linux/phy.h>
+#include <linux/platform_device.h>
+
+#define ZX_MDIO_DATA_WR		0x04
+#define ZX_MDIO_DATA_RD		0x08
+#define ZX_MDIO_CFG		0x0c
+#define ZX_MDIO_STATUS		0x10
+#define  ZX_MDIO_STATUS_DONE	BIT(0)
+#define ZX_MDIO_CMD		0x14
+#define  ZX_MDIO_CMD_REG	GENMASK(4, 0)
+#define  ZX_MDIO_CMD_ADDR	GENMASK(9, 5)
+#define  ZX_MDIO_CMD_WR		BIT(10)
+#define  ZX_MDIO_CMD_RD		BIT(11)
+#define  ZX_MDIO_CMD_CLK_DIV	BIT(12)
+#define  ZX_MDIO_CMD_BIT13	BIT(13)
+#define  ZX_MDIO_CMD_START	BIT(14)
+#define  ZX_MDIO_CMD_BIT15	BIT(15)
+
+#define ZX_MDIO_POLL_US		10
+#define ZX_MDIO_TIMEOUT_US	2000
+
+struct zx279128s_mdio {
+	void __iomem *base;
+};
+
+static int zx279128s_mdio_xfer(struct mii_bus *bus, u32 op, int addr,
+			       int regnum, u16 data)
+{
+	struct zx279128s_mdio *priv = bus->priv;
+	void __iomem *base = priv->base;
+	u32 cmd, val;
+	int ret;
+
+	/* Clear the previous command and its status */
+	writel(readl(base + ZX_MDIO_CMD) & ~ZX_MDIO_CMD_START,
+	       base + ZX_MDIO_CMD);
+	writel(0, base + ZX_MDIO_STATUS);
+
+	cmd = readl(base + ZX_MDIO_CMD);
+	cmd &= ~(ZX_MDIO_CMD_WR | ZX_MDIO_CMD_RD | ZX_MDIO_CMD_ADDR |
+		 ZX_MDIO_CMD_REG);
+	cmd |= op | FIELD_PREP(ZX_MDIO_CMD_ADDR, addr) |
+	       FIELD_PREP(ZX_MDIO_CMD_REG, regnum);
+
+	if (op == ZX_MDIO_CMD_WR)
+		writel(data, base + ZX_MDIO_DATA_WR);
+	writel(cmd | ZX_MDIO_CMD_START, base + ZX_MDIO_CMD);
+
+	ret = readl_poll_timeout(base + ZX_MDIO_STATUS, val,
+				 val & ZX_MDIO_STATUS_DONE, ZX_MDIO_POLL_US,
+				 ZX_MDIO_TIMEOUT_US);
+	if (ret) {
+		dev_err_ratelimited(&bus->dev, "timeout (addr %d, reg %d)\n",
+				    addr, regnum);
+		return ret;
+	}
+
+	writel(0, base + ZX_MDIO_STATUS);
+	writel(readl(base + ZX_MDIO_CMD) & ~ZX_MDIO_CMD_START,
+	       base + ZX_MDIO_CMD);
+
+	return 0;
+}
+
+static int zx279128s_mdio_read(struct mii_bus *bus, int addr, int regnum)
+{
+	struct zx279128s_mdio *priv = bus->priv;
+	int ret;
+
+	ret = zx279128s_mdio_xfer(bus, ZX_MDIO_CMD_RD, addr, regnum, 0);
+	if (ret)
+		return ret;
+
+	return readl(priv->base + ZX_MDIO_DATA_RD) & 0xffff;
+}
+
+static int zx279128s_mdio_write(struct mii_bus *bus, int addr, int regnum,
+				u16 val)
+{
+	return zx279128s_mdio_xfer(bus, ZX_MDIO_CMD_WR, addr, regnum, val);
+}
+
+static int zx279128s_mdio_probe(struct platform_device *pdev)
+{
+	struct device *dev = &pdev->dev;
+	struct zx279128s_mdio *priv;
+	struct mii_bus *bus;
+	struct clk *clk;
+	u32 val;
+
+	bus = devm_mdiobus_alloc_size(dev, sizeof(*priv));
+	if (!bus)
+		return -ENOMEM;
+
+	priv = bus->priv;
+	priv->base = devm_platform_ioremap_resource(pdev, 0);
+	if (IS_ERR(priv->base))
+		return PTR_ERR(priv->base);
+
+	clk = devm_clk_get_enabled(dev, "pclk");
+	if (IS_ERR(clk))
+		return dev_err_probe(dev, PTR_ERR(clk),
+				     "failed to get the register clock\n");
+	clk = devm_clk_get_enabled(dev, "wclk");
+	if (IS_ERR(clk))
+		return dev_err_probe(dev, PTR_ERR(clk),
+				     "failed to get the work clock\n");
+
+	val = readl(priv->base + ZX_MDIO_CMD);
+	val &= ~(ZX_MDIO_CMD_START | ZX_MDIO_CMD_BIT15 | ZX_MDIO_CMD_BIT13);
+	val |= ZX_MDIO_CMD_CLK_DIV;
+	writel(val, priv->base + ZX_MDIO_CMD);
+	writel(0, priv->base + ZX_MDIO_STATUS);
+	writel(0, priv->base + ZX_MDIO_CFG);
+
+	bus->name = "zx279128s-mdio";
+	bus->read = zx279128s_mdio_read;
+	bus->write = zx279128s_mdio_write;
+	snprintf(bus->id, MII_BUS_ID_SIZE, "%s", dev_name(dev));
+	bus->parent = dev;
+
+	return devm_of_mdiobus_register(dev, bus, dev->of_node);
+}
+
+static const struct of_device_id zx279128s_mdio_of_match[] = {
+	{ .compatible = "zte,zx279128s-mdio" },
+	{ }
+};
+MODULE_DEVICE_TABLE(of, zx279128s_mdio_of_match);
+
+static struct platform_driver zx279128s_mdio_driver = {
+	.probe = zx279128s_mdio_probe,
+	.driver = {
+		.name = "zx279128s-mdio",
+		.of_match_table = zx279128s_mdio_of_match,
+	},
+};
+module_platform_driver(zx279128s_mdio_driver);
+
+MODULE_AUTHOR("Navid Ghahremani <ghahramani.navid@gmail.com>");
+MODULE_DESCRIPTION("ZTE zx279128s MDIO controller driver");
+MODULE_LICENSE("GPL");
-- 
2.55.0