net: stmmac: Add glue layer for Spacemit K3 SoC

The ethernet controller on Spacemit K3 SoC is Synopsys DesignWare
MAC (version 5.40a), with the following special points:
1. The rate of the tx clock line is auto changed when the mac speed
   rate is changed, and no need for changing the input tx clock.
2. This controller require a extra syscon device to configure the
   interface type, enable wake up interrupt and delay configuration
   if needed.

Add Spacemit dwmac driver support on the Spacemit K3 SoC.

Signed-off-by: Inochi Amaoto <inochiama@gmail.com>
Reviewed-by: Russell King (Oracle) <rmk+kernel@armlinux.org.uk>
Link: https://patch.msgid.link/20260316010041.164360-4-inochiama@gmail.com
Signed-off-by: Jakub Kicinski <kuba@kernel.org>

drivers/net/ethernet/stmicro/stmmac/Kconfig

@@ -216,6 +216,18 @@ config DWMAC_SOPHGO
 	  for the stmmac device driver. This driver is used for the
 	  ethernet controllers on various Sophgo SoCs.
 
+config DWMAC_SPACEMIT
+	tristate "Spacemit dwmac support"
+	depends on OF && (ARCH_SPACEMIT || COMPILE_TEST)
+	select MFD_SYSCON
+	default m if ARCH_SPACEMIT
+	help
+	  Support for ethernet controllers on Spacemit RISC-V SoCs
+
+	  This selects the Spacemit platform specific glue layer support
+	  for the stmmac device driver. This driver is used for the
+	  Spacemit K3 ethernet controllers.
+
 config DWMAC_STARFIVE
 	tristate "StarFive dwmac support"
 	depends on OF && (ARCH_STARFIVE || COMPILE_TEST)

drivers/net/ethernet/stmicro/stmmac/Makefile

@@ -27,6 +27,7 @@ obj-$(CONFIG_DWMAC_RZN1)	+= dwmac-rzn1.o
 obj-$(CONFIG_DWMAC_S32)		+= dwmac-s32.o
 obj-$(CONFIG_DWMAC_SOCFPGA)	+= dwmac-altr-socfpga.o
 obj-$(CONFIG_DWMAC_SOPHGO)	+= dwmac-sophgo.o
+obj-$(CONFIG_DWMAC_SPACEMIT)	+= dwmac-spacemit.o
 obj-$(CONFIG_DWMAC_STARFIVE)	+= dwmac-starfive.o
 obj-$(CONFIG_DWMAC_STI)		+= dwmac-sti.o
 obj-$(CONFIG_DWMAC_STM32)	+= dwmac-stm32.o

drivers/net/ethernet/stmicro/stmmac/dwmac-spacemit.c

@@ -0,0 +1,227 @@
+// SPDX-License-Identifier: GPL-2.0+
+/*
+ * Spacemit DWMAC platform driver
+ *
+ * Copyright (C) 2026 Inochi Amaoto <inochiama@gmail.com>
+ */
+
+#include <linux/clk.h>
+#include <linux/math.h>
+#include <linux/mod_devicetable.h>
+#include <linux/module.h>
+#include <linux/mfd/syscon.h>
+#include <linux/of.h>
+#include <linux/platform_device.h>
+#include <linux/property.h>
+#include <linux/regmap.h>
+
+#include "stmmac_platform.h"
+
+/* ctrl register bits */
+#define CTRL_PHY_INTF_RGMII		BIT(3)
+#define CTRL_PHY_INTF_MII		BIT(4)
+#define CTRL_WAKE_IRQ_EN		BIT(9)
+#define CTRL_PHY_IRQ_EN			BIT(12)
+
+/* dline register bits */
+#define RGMII_RX_DLINE_EN		BIT(0)
+#define RGMII_RX_DLINE_STEP		GENMASK(5, 4)
+#define RGMII_RX_DLINE_CODE		GENMASK(15, 8)
+#define RGMII_TX_DLINE_EN		BIT(16)
+#define RGMII_TX_DLINE_STEP		GENMASK(21, 20)
+#define RGMII_TX_DLINE_CODE		GENMASK(31, 24)
+
+#define MAX_DLINE_DELAY_CODE		0xff
+#define MAX_WORKED_DELAY		2800
+/* Note: the delay step value is at 0.1ps */
+#define K3_DELAY_STEP			367
+
+struct spacmit_dwmac {
+	struct regmap *apmu;
+	unsigned int ctrl_offset;
+	unsigned int dline_offset;
+};
+
+static int spacemit_dwmac_set_delay(struct spacmit_dwmac *dwmac,
+				    unsigned int tx_code, unsigned int rx_code)
+{
+	unsigned int mask, val;
+
+	mask = RGMII_TX_DLINE_STEP | RGMII_TX_DLINE_CODE | RGMII_TX_DLINE_EN |
+	       RGMII_RX_DLINE_STEP | RGMII_RX_DLINE_CODE | RGMII_RX_DLINE_EN;
+
+	/*
+	 * Since the delay step provided by config 0 is small enough, and
+	 * it can cover the range of the valid delay, so there is no needed
+	 * to use other step config.
+	 */
+	val = FIELD_PREP(RGMII_TX_DLINE_STEP, 0) |
+	      FIELD_PREP(RGMII_TX_DLINE_CODE, tx_code) | RGMII_TX_DLINE_EN |
+	      FIELD_PREP(RGMII_RX_DLINE_STEP, 0) |
+	      FIELD_PREP(RGMII_RX_DLINE_CODE, rx_code) | RGMII_RX_DLINE_EN;
+
+	return regmap_update_bits(dwmac->apmu, dwmac->dline_offset,
+				  mask, val);
+}
+
+static int spacemit_dwmac_detected_delay_value(unsigned int delay)
+{
+	if (delay == 0)
+		return 0;
+
+	if (delay > MAX_WORKED_DELAY)
+		return -EINVAL;
+
+	/*
+	 * Note K3 require a specific factor for calculate
+	 * the delay, in this scenario it is 0.9. So the
+	 * formula is code * step / 10 * 0.9
+	 */
+	return DIV_ROUND_CLOSEST(delay * 10 * 10, K3_DELAY_STEP * 9);
+}
+
+static int spacemit_dwmac_fix_delay(struct spacmit_dwmac *dwmac,
+				    unsigned int tx_delay,
+				    unsigned int rx_delay)
+{
+	int rx_code;
+	int tx_code;
+
+	rx_code = spacemit_dwmac_detected_delay_value(rx_delay);
+	if (rx_code < 0)
+		return rx_code;
+
+	tx_code = spacemit_dwmac_detected_delay_value(tx_delay);
+	if (tx_code < 0)
+		return tx_code;
+
+	return spacemit_dwmac_set_delay(dwmac, tx_code, rx_code);
+}
+
+static int spacemit_dwmac_update_irq_config(struct spacmit_dwmac *dwmac,
+					    struct stmmac_resources *stmmac_res)
+{
+	unsigned int val = stmmac_res->wol_irq >= 0 ? CTRL_WAKE_IRQ_EN : 0;
+	unsigned int mask = CTRL_WAKE_IRQ_EN;
+
+	return regmap_update_bits(dwmac->apmu, dwmac->ctrl_offset,
+				  mask, val);
+}
+
+static void spacemit_get_interfaces(struct stmmac_priv *priv, void *bsp_priv,
+				    unsigned long *interfaces)
+{
+	__set_bit(PHY_INTERFACE_MODE_MII, interfaces);
+	__set_bit(PHY_INTERFACE_MODE_RMII, interfaces);
+	phy_interface_set_rgmii(interfaces);
+}
+
+static int spacemit_set_phy_intf_sel(void *bsp_priv, u8 phy_intf_sel)
+{
+	unsigned int mask = CTRL_PHY_INTF_MII | CTRL_PHY_INTF_RGMII;
+	struct spacmit_dwmac *dwmac = bsp_priv;
+	unsigned int val = 0;
+
+	switch (phy_intf_sel) {
+	case PHY_INTF_SEL_GMII_MII:
+		val = CTRL_PHY_INTF_MII;
+		break;
+
+	case PHY_INTF_SEL_RMII:
+		break;
+
+	case PHY_INTF_SEL_RGMII:
+		val = CTRL_PHY_INTF_RGMII;
+		break;
+
+	default:
+		return -EINVAL;
+	}
+
+	return regmap_update_bits(dwmac->apmu, dwmac->ctrl_offset,
+				  mask, val);
+}
+
+static int spacemit_dwmac_probe(struct platform_device *pdev)
+{
+	struct plat_stmmacenet_data *plat_dat;
+	struct stmmac_resources stmmac_res;
+	struct device *dev = &pdev->dev;
+	struct spacmit_dwmac *dwmac;
+	unsigned int offset[2];
+	struct regmap *apmu;
+	struct clk *clk_tx;
+	u32 rx_delay = 0;
+	u32 tx_delay = 0;
+	int ret;
+
+	ret = stmmac_get_platform_resources(pdev, &stmmac_res);
+	if (ret)
+		return dev_err_probe(dev, ret,
+				     "failed to get platform resources\n");
+
+	dwmac = devm_kzalloc(&pdev->dev, sizeof(*dwmac), GFP_KERNEL);
+	if (!dwmac)
+		return -ENOMEM;
+
+	plat_dat = devm_stmmac_probe_config_dt(pdev, stmmac_res.mac);
+	if (IS_ERR(plat_dat))
+		return dev_err_probe(dev, PTR_ERR(plat_dat),
+				     "failed to parse DT parameters\n");
+
+	clk_tx = devm_clk_get_enabled(&pdev->dev, "tx");
+	if (IS_ERR(clk_tx))
+		return dev_err_probe(&pdev->dev, PTR_ERR(clk_tx),
+				     "failed to get tx clock\n");
+
+	apmu = syscon_regmap_lookup_by_phandle_args(pdev->dev.of_node,
+						    "spacemit,apmu", 2,
+						    offset);
+	if (IS_ERR(apmu))
+		return dev_err_probe(dev, PTR_ERR(apmu),
+				     "Failed to get apmu regmap\n");
+
+	dwmac->apmu = apmu;
+	dwmac->ctrl_offset = offset[0];
+	dwmac->dline_offset = offset[1];
+
+	ret = spacemit_dwmac_update_irq_config(dwmac, &stmmac_res);
+	if (ret)
+		return dev_err_probe(dev, ret, "Failed to configure irq config\n");
+
+	of_property_read_u32(pdev->dev.of_node, "tx-internal-delay-ps",
+			     &tx_delay);
+	of_property_read_u32(pdev->dev.of_node, "rx-internal-delay-ps",
+			     &rx_delay);
+
+	plat_dat->get_interfaces = spacemit_get_interfaces;
+	plat_dat->set_phy_intf_sel = spacemit_set_phy_intf_sel;
+	plat_dat->bsp_priv = dwmac;
+
+	ret = spacemit_dwmac_fix_delay(dwmac, tx_delay, rx_delay);
+	if (ret)
+		return dev_err_probe(dev, ret, "Failed to configure delay\n");
+
+	return stmmac_dvr_probe(dev, plat_dat, &stmmac_res);
+}
+
+static const struct of_device_id spacemit_dwmac_match[] = {
+	{ .compatible = "spacemit,k3-dwmac" },
+	{ /* sentinel */ }
+};
+MODULE_DEVICE_TABLE(of, spacemit_dwmac_match);
+
+static struct platform_driver spacemit_dwmac_driver = {
+	.probe  = spacemit_dwmac_probe,
+	.remove = stmmac_pltfr_remove,
+	.driver = {
+		.name = "spacemit-dwmac",
+		.pm = &stmmac_pltfr_pm_ops,
+		.of_match_table = spacemit_dwmac_match,
+	},
+};
+module_platform_driver(spacemit_dwmac_driver);
+
+MODULE_AUTHOR("Inochi Amaoto <inochiama@gmail.com>");
+MODULE_DESCRIPTION("Spacemit DWMAC platform driver");
+MODULE_LICENSE("GPL");