[PATCH net-next v3 2/2] net: mdio: add a driver for PIC64-HPSC/HX MDIO controller

Charles Perry
2026-03-31T12:40:40Z

This adds an MDIO driver for PIC64-HPSC/HX. The hardware supports C22
and C45 but only C22 is implemented in this commit.

This MDIO hardware is based on a Microsemi design supported in Linux by
mdio-mscc-miim.c. However, The register interface is completely
different with pic64hpsc, hence the need for a separate driver.

The documentation recommends an input clock of 156.25MHz and a prescaler
of 39, which yields an MDIO clock of 1.95MHz.

The hardware supports an interrupt pin or a "TRIGGER" bit that can be
polled to signal transaction completion. This commit uses polling.

This was tested on Microchip HB1301 evalkit with a VSC8574 and a
VSC8541.

Signed-off-by: Charles Perry <charles.perry@microchip.com>
Reviewed-by: Maxime Chevallier <maxime.chevallier@bootlin.com>
---

Notes:
Changes in v3:
- Add a MAINTAINERS entry (Jakub)

Changes in v2:
- Remove #define for unused registers (Maxime)
- Add "c22" to clause 22 read/write ops (Maxime)
- Remove the call to platform_set_drvdata() (Andrew)
- Make the clock mandatory (Andrew)
- Use 2.5MHz if no clock-frequency was specified (Andrew)
- Change the error message for bad clock-frequency (Andrew)
- Fix a use without initialization on bus_freq (Andrew)

MAINTAINERS | 6 +
drivers/net/mdio/Kconfig | 7 ++
drivers/net/mdio/Makefile | 1 +
drivers/net/mdio/mdio-pic64hpsc.c | 192 ++++++++++++++++++++++++++++++
4 files changed, 206 insertions(+)
create mode 100644 drivers/net/mdio/mdio-pic64hpsc.c

diff --git a/MAINTAINERS b/MAINTAINERS
index e08767323763..9297c46dba91 100644
--- a/MAINTAINERS
+++ b/MAINTAINERS
@@ -17216,6 +17216,12 @@ L: linux-serial@vger.kernel.org
S: Maintained
F: drivers/tty/serial/8250/8250_pci1xxxx.c

+MICROCHIP PIC64-HPSC/HX DRIVERS
+M: Charles Perry <charles.perry@microchip.com>
+S: Supported
+F: Documentation/devicetree/bindings/net/microchip,pic64hpsc-mdio.yaml
+F: drivers/net/mdio/mdio-pic64hpsc.c
+
MICROCHIP POLARFIRE FPGA DRIVERS
M: Conor Dooley <conor.dooley@microchip.com>
L: linux-fpga@vger.kernel.org
diff --git a/drivers/net/mdio/Kconfig b/drivers/net/mdio/Kconfig
index 44380378911b..7bdba8c3ddef 100644
--- a/drivers/net/mdio/Kconfig
+++ b/drivers/net/mdio/Kconfig
@@ -146,6 +146,13 @@ config MDIO_OCTEON
buses. It is required by the Octeon and ThunderX ethernet device
drivers on some systems.

+config MDIO_PIC64HPSC
+ tristate "PIC64-HPSC/HX MDIO interface support"
+ depends on HAS_IOMEM && OF_MDIO
+ help
+ This driver supports the MDIO interface found on the PIC64-HPSC/HX
+ SoCs.
+
config MDIO_IPQ4019
tristate "Qualcomm IPQ4019 MDIO interface support"
depends on HAS_IOMEM && OF_MDIO
diff --git a/drivers/net/mdio/Makefile b/drivers/net/mdio/Makefile
index fbec636700e7..048586746026 100644
--- a/drivers/net/mdio/Makefile
+++ b/drivers/net/mdio/Makefile
@@ -20,6 +20,7 @@ obj-$(CONFIG_MDIO_MOXART) += mdio-moxart.o
obj-$(CONFIG_MDIO_MSCC_MIIM) += mdio-mscc-miim.o
obj-$(CONFIG_MDIO_MVUSB) += mdio-mvusb.o
obj-$(CONFIG_MDIO_OCTEON) += mdio-octeon.o
+obj-$(CONFIG_MDIO_PIC64HPSC) += mdio-pic64hpsc.o
obj-$(CONFIG_MDIO_REALTEK_RTL9300) += mdio-realtek-rtl9300.o
obj-$(CONFIG_MDIO_REGMAP) += mdio-regmap.o
obj-$(CONFIG_MDIO_SUN4I) += mdio-sun4i.o
diff --git a/drivers/net/mdio/mdio-pic64hpsc.c b/drivers/net/mdio/mdio-pic64hpsc.c
new file mode 100644
index 000000000000..0ca6f5af5396
--- /dev/null
+++ b/drivers/net/mdio/mdio-pic64hpsc.c
@@ -0,0 +1,192 @@
+// SPDX-License-Identifier: GPL-2.0
+/* Microchip PIC64-HPSC/HX MDIO controller driver
+ *
+ * Copyright (c) 2026 Microchip Technology Inc. and its subsidiaries.
+ */
+
+#include <linux/bitops.h>
+#include <linux/clk.h>
+#include <linux/io.h>
+#include <linux/iopoll.h>
+#include <linux/kernel.h>
+#include <linux/module.h>
+#include <linux/of_mdio.h>
+#include <linux/platform_device.h>
+
+#define MDIO_REG_PRESCALER 0x20
+#define MDIO_CFG_PRESCALE_MASK GENMASK(7, 0)
+
+#define MDIO_REG_FRAME_CFG_1 0x24
+#define MDIO_WDATA_MASK GENMASK(15, 0)
+
+#define MDIO_REG_FRAME_CFG_2 0x28
+#define MDIO_TRIGGER_BIT BIT(31)
+#define MDIO_REG_DEV_ADDR_MASK GENMASK(20, 16)
+#define MDIO_PHY_PRT_ADDR_MASK GENMASK(8, 4)
+#define MDIO_OPERATION_MASK GENMASK(3, 2)
+#define MDIO_START_OF_FRAME_MASK GENMASK(1, 0)
+
+/* Possible value of MDIO_OPERATION_MASK */
+#define MDIO_OPERATION_WRITE BIT(0)
+#define MDIO_OPERATION_READ BIT(1)
+
+#define MDIO_REG_FRAME_STATUS 0x2C
+#define MDIO_READOK_BIT BIT(24)
+#define MDIO_RDATA_MASK GENMASK(15, 0)
+
+struct pic64hpsc_mdio_dev {
+ void __iomem *regs;
+};
+
+static int pic64hpsc_mdio_wait_trigger(struct mii_bus *bus)
+{
+ struct pic64hpsc_mdio_dev *priv = bus->priv;
+ u32 val;
+ int ret;
+
+ /* The MDIO_TRIGGER bit returns 0 when a transaction has completed. */
+ ret = readl_poll_timeout(priv->regs + MDIO_REG_FRAME_CFG_2, val,
+ !(val & MDIO_TRIGGER_BIT), 50, 10000);
+
+ if (ret < 0)
+ dev_dbg(&bus->dev, "TRIGGER bit timeout: %x\n", val);
+
+ return ret;
+}
+
+static int pic64hpsc_mdio_c22_read(struct mii_bus *bus, int mii_id, int regnum)
+{
+ struct pic64hpsc_mdio_dev *priv = bus->priv;
+ u32 val;
+ int ret;
+
+ ret = pic64hpsc_mdio_wait_trigger(bus);
+ if (ret)
+ return ret;
+
+ writel(MDIO_TRIGGER_BIT | FIELD_PREP(MDIO_REG_DEV_ADDR_MASK, regnum) |
+ FIELD_PREP(MDIO_PHY_PRT_ADDR_MASK, mii_id) |
+ FIELD_PREP(MDIO_OPERATION_MASK, MDIO_OPERATION_READ) |
+ FIELD_PREP(MDIO_START_OF_FRAME_MASK, 1),
+ priv->regs + MDIO_REG_FRAME_CFG_2);
+
+ ret = pic64hpsc_mdio_wait_trigger(bus);
+ if (ret)
+ return ret;
+
+ val = readl(priv->regs + MDIO_REG_FRAME_STATUS);
+
+ /* The MDIO_READOK is a 1-bit value reflecting the inverse of the MDIO
+ * bus value captured during the 2nd TA cycle. A PHY/Port should drive
+ * the MDIO bus with a logic 0 on the 2nd TA cycle, however, the
+ * PHY/Port could optionally drive a logic 1, to communicate a read
+ * failure. This feature is optional, not defined by the 802.3 standard
+ * and not supported in standard external PHYs.
+ */
+ if (!(bus->phy_ignore_ta_mask & 1 << mii_id) &&
+ !FIELD_GET(MDIO_READOK_BIT, val)) {
+ dev_dbg(&bus->dev, "READOK bit cleared\n");
+ return -EIO;
+ }
+
+ ret = FIELD_GET(MDIO_RDATA_MASK, val);
+
+ return ret;
+}
+
+static int pic64hpsc_mdio_c22_write(struct mii_bus *bus, int mii_id, int regnum,
+ u16 value)
+{
+ struct pic64hpsc_mdio_dev *priv = bus->priv;
+ int ret;
+
+ ret = pic64hpsc_mdio_wait_trigger(bus);
+ if (ret < 0)
+ return ret;
+
+ writel(FIELD_PREP(MDIO_WDATA_MASK, value),
+ priv->regs + MDIO_REG_FRAME_CFG_1);
+
+ writel(MDIO_TRIGGER_BIT | FIELD_PREP(MDIO_REG_DEV_ADDR_MASK, regnum) |
+ FIELD_PREP(MDIO_PHY_PRT_ADDR_MASK, mii_id) |
+ FIELD_PREP(MDIO_OPERATION_MASK, MDIO_OPERATION_WRITE) |
+ FIELD_PREP(MDIO_START_OF_FRAME_MASK, 1),
+ priv->regs + MDIO_REG_FRAME_CFG_2);
+
+ return 0;
+}
+
+static int pic64hpsc_mdio_probe(struct platform_device *pdev)
+{
+ struct device_node *np = pdev->dev.of_node;
+ struct device *dev = &pdev->dev;
+ struct pic64hpsc_mdio_dev *priv;
+ struct mii_bus *bus;
+ unsigned long rate;
+ struct clk *clk;
+ u32 bus_freq;
+ u32 div;
+ int ret;
+
+ bus = devm_mdiobus_alloc_size(dev, sizeof(*priv));
+ if (!bus)
+ return -ENOMEM;
+
+ priv = bus->priv;
+
+ priv->regs = devm_platform_ioremap_resource(pdev, 0);
+ if (IS_ERR(priv->regs))
+ return PTR_ERR(priv->regs);
+
+ bus->name = KBUILD_MODNAME;
+ bus->read = pic64hpsc_mdio_c22_read;
+ bus->write = pic64hpsc_mdio_c22_write;
+ snprintf(bus->id, MII_BUS_ID_SIZE, "%s", dev_name(dev));
+ bus->parent = dev;
+
+ clk = devm_clk_get_enabled(dev, NULL);
+ if (IS_ERR(clk))
+ return PTR_ERR(clk);
+
+ if (of_property_read_u32(np, "clock-frequency", &bus_freq))
+ bus_freq = 2500000;
+
+ rate = clk_get_rate(clk);
+
+ div = DIV_ROUND_UP(rate, 2 * bus_freq) - 1;
+ if (div == 0 || div & ~MDIO_CFG_PRESCALE_MASK) {
+ dev_err(dev, "MDIO clock-frequency out of range\n");
+ return -EINVAL;
+ }
+
+ dev_dbg(dev, "rate=%lu bus_freq=%u real_bus_freq=%lu div=%u\n", rate,
+ bus_freq, rate / (2 * (1 + div)), div);
+ writel(div, priv->regs + MDIO_REG_PRESCALER);
+
+ ret = devm_of_mdiobus_register(dev, bus, np);
+ if (ret) {
+ dev_err(dev, "Cannot register MDIO bus (%d)\n", ret);
+ return ret;
+ }
+
+ return 0;
+}
+
+static const struct of_device_id pic64hpsc_mdio_match[] = {
+ { .compatible = "microchip,pic64hpsc-mdio" },
+ {}
+};
+MODULE_DEVICE_TABLE(of, pic64hpsc_mdio_match);
+
+static struct platform_driver pic64hpsc_mdio_driver = {
+ .probe = pic64hpsc_mdio_probe,
+ .driver = {
+ .name = KBUILD_MODNAME,
+ .of_match_table = pic64hpsc_mdio_match,
+ },
+};
+module_platform_driver(pic64hpsc_mdio_driver);
+
+MODULE_AUTHOR("Charles Perry <charles.perry@microchip.com>");
+MODULE_DESCRIPTION("Microchip PIC64-HPSC/HX MDIO driver");
+MODULE_LICENSE("GPL");
--
2.47.3