net: stmmac: Add DWMAC glue layer for Renesas GBETH

Add the DWMAC glue layer for the GBETH IP found in the Renesas RZ/V2H(P)
SoC.

Signed-off-by: Lad Prabhakar <prabhakar.mahadev-lad.rj@bp.renesas.com>
Reviewed-by: Russell King (Oracle) <rmk+kernel@armlinux.org.uk>
Reviewed-by: Philipp Zabel <p.zabel@pengutronix.de>
Link: https://patch.msgid.link/20250417084015.74154-4-prabhakar.mahadev-lad.rj@bp.renesas.com
Signed-off-by: Jakub Kicinski <kuba@kernel.org>

drivers/net/ethernet/stmicro/stmmac/Kconfig

@@ -131,6 +131,17 @@ config DWMAC_QCOM_ETHQOS
 	  This selects the Qualcomm ETHQOS glue layer support for the
 	  stmmac device driver.
 
+config DWMAC_RENESAS_GBETH
+	tristate "Renesas RZ/V2H(P) GBETH support"
+	default ARCH_RENESAS
+	depends on OF && (ARCH_RENESAS || COMPILE_TEST)
+	help
+	  Support for Gigabit Ethernet Interface (GBETH) on Renesas
+	  RZ/V2H(P) SoCs.
+
+	  This selects the Renesas RZ/V2H(P) Soc specific glue layer support
+	  for the stmmac device driver.
+
 config DWMAC_ROCKCHIP
 	tristate "Rockchip dwmac support"
 	default ARCH_ROCKCHIP

drivers/net/ethernet/stmicro/stmmac/Makefile

@@ -20,6 +20,7 @@ obj-$(CONFIG_DWMAC_LPC18XX)	+= dwmac-lpc18xx.o
 obj-$(CONFIG_DWMAC_MEDIATEK)	+= dwmac-mediatek.o
 obj-$(CONFIG_DWMAC_MESON)	+= dwmac-meson.o dwmac-meson8b.o
 obj-$(CONFIG_DWMAC_QCOM_ETHQOS)	+= dwmac-qcom-ethqos.o
+obj-$(CONFIG_DWMAC_RENESAS_GBETH) += dwmac-renesas-gbeth.o
 obj-$(CONFIG_DWMAC_ROCKCHIP)	+= dwmac-rk.o
 obj-$(CONFIG_DWMAC_RZN1)	+= dwmac-rzn1.o
 obj-$(CONFIG_DWMAC_S32)		+= dwmac-s32.o

drivers/net/ethernet/stmicro/stmmac/dwmac-renesas-gbeth.c

@@ -0,0 +1,146 @@
+// SPDX-License-Identifier: GPL-2.0+
+/*
+ * dwmac-renesas-gbeth.c - DWMAC Specific Glue layer for Renesas GBETH
+ *
+ * The Rx and Tx clocks are supplied as follows for the GBETH IP.
+ *
+ *                         Rx / Tx
+ *   -------+------------- on / off -------
+ *          |
+ *          |            Rx-180 / Tx-180
+ *          +---- not ---- on / off -------
+ *
+ * Copyright (C) 2025 Renesas Electronics Corporation
+ */
+
+#include <linux/clk.h>
+#include <linux/device.h>
+#include <linux/module.h>
+#include <linux/platform_device.h>
+#include <linux/reset.h>
+
+#include "stmmac_platform.h"
+
+struct renesas_gbeth {
+	struct plat_stmmacenet_data *plat_dat;
+	struct reset_control *rstc;
+	struct device *dev;
+};
+
+static const char *const renesas_gbeth_clks[] = {
+	"tx", "tx-180", "rx", "rx-180",
+};
+
+static int renesas_gbeth_init(struct platform_device *pdev, void *priv)
+{
+	struct plat_stmmacenet_data *plat_dat;
+	struct renesas_gbeth *gbeth = priv;
+	int ret;
+
+	plat_dat = gbeth->plat_dat;
+
+	ret = reset_control_deassert(gbeth->rstc);
+	if (ret) {
+		dev_err(gbeth->dev, "Reset deassert failed\n");
+		return ret;
+	}
+
+	ret = clk_bulk_prepare_enable(plat_dat->num_clks,
+				      plat_dat->clks);
+	if (ret)
+		reset_control_assert(gbeth->rstc);
+
+	return ret;
+}
+
+static void renesas_gbeth_exit(struct platform_device *pdev, void *priv)
+{
+	struct plat_stmmacenet_data *plat_dat;
+	struct renesas_gbeth *gbeth = priv;
+	int ret;
+
+	plat_dat = gbeth->plat_dat;
+
+	clk_bulk_disable_unprepare(plat_dat->num_clks, plat_dat->clks);
+
+	ret = reset_control_assert(gbeth->rstc);
+	if (ret)
+		dev_err(gbeth->dev, "Reset assert failed\n");
+}
+
+static int renesas_gbeth_probe(struct platform_device *pdev)
+{
+	struct plat_stmmacenet_data *plat_dat;
+	struct stmmac_resources stmmac_res;
+	struct device *dev = &pdev->dev;
+	struct renesas_gbeth *gbeth;
+	unsigned int i;
+	int err;
+
+	err = stmmac_get_platform_resources(pdev, &stmmac_res);
+	if (err)
+		return dev_err_probe(dev, err,
+				     "failed to get resources\n");
+
+	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),
+				     "dt configuration failed\n");
+
+	gbeth = devm_kzalloc(dev, sizeof(*gbeth), GFP_KERNEL);
+	if (!gbeth)
+		return -ENOMEM;
+
+	plat_dat->num_clks = ARRAY_SIZE(renesas_gbeth_clks);
+	plat_dat->clks = devm_kcalloc(dev, plat_dat->num_clks,
+				      sizeof(*plat_dat->clks), GFP_KERNEL);
+	if (!plat_dat->clks)
+		return -ENOMEM;
+
+	for (i = 0; i < plat_dat->num_clks; i++)
+		plat_dat->clks[i].id = renesas_gbeth_clks[i];
+
+	err = devm_clk_bulk_get(dev, plat_dat->num_clks, plat_dat->clks);
+	if (err < 0)
+		return err;
+
+	plat_dat->clk_tx_i = stmmac_pltfr_find_clk(plat_dat, "tx");
+	if (!plat_dat->clk_tx_i)
+		return dev_err_probe(dev, -EINVAL,
+				     "error finding tx clock\n");
+
+	gbeth->rstc = devm_reset_control_get_exclusive(dev, NULL);
+	if (IS_ERR(gbeth->rstc))
+		return PTR_ERR(gbeth->rstc);
+
+	gbeth->dev = dev;
+	gbeth->plat_dat = plat_dat;
+	plat_dat->bsp_priv = gbeth;
+	plat_dat->set_clk_tx_rate = stmmac_set_clk_tx_rate;
+	plat_dat->init = renesas_gbeth_init;
+	plat_dat->exit = renesas_gbeth_exit;
+	plat_dat->flags |= STMMAC_FLAG_HWTSTAMP_CORRECT_LATENCY |
+			   STMMAC_FLAG_EN_TX_LPI_CLK_PHY_CAP |
+			   STMMAC_FLAG_SPH_DISABLE;
+
+	return devm_stmmac_pltfr_probe(pdev, plat_dat, &stmmac_res);
+}
+
+static const struct of_device_id renesas_gbeth_match[] = {
+	{ .compatible = "renesas,rzv2h-gbeth", },
+	{ /* Sentinel */ }
+};
+MODULE_DEVICE_TABLE(of, renesas_gbeth_match);
+
+static struct platform_driver renesas_gbeth_driver = {
+	.probe  = renesas_gbeth_probe,
+	.driver = {
+		.name		= "renesas-gbeth",
+		.of_match_table	= renesas_gbeth_match,
+	},
+};
+module_platform_driver(renesas_gbeth_driver);
+
+MODULE_AUTHOR("Lad Prabhakar <prabhakar.mahadev-lad.rj@bp.renesas.com>");
+MODULE_DESCRIPTION("Renesas GBETH DWMAC Specific Glue layer");
+MODULE_LICENSE("GPL");