[PATCH v7 02/10] reset: Add Realtek basic reset support

[Yu-Chun Lin <eleanor.lin@realtek.com>]

From: Cheng-Yu Lee <cylee12@realtek.com>

Define the reset operations backed by a regmap-based register interface
and prepare the reset controller to be registered through the reset
framework.

Since the reset controllers on Realtek SoCs often share the same register
space with the clock controllers, this common framework is designed to
extract the regmap and device tree node from the parent device
(e.g., an auxiliary device parent).

Signed-off-by: Cheng-Yu Lee <cylee12@realtek.com>
Co-developed-by: Yu-Chun Lin <eleanor.lin@realtek.com>
Signed-off-by: Yu-Chun Lin <eleanor.lin@realtek.com>
---
 MAINTAINERS                    |  1 +
 drivers/reset/Kconfig          |  1 +
 drivers/reset/Makefile         |  1 +
 drivers/reset/realtek/Kconfig  |  8 +++
 drivers/reset/realtek/Makefile |  2 +
 drivers/reset/realtek/common.c | 90 ++++++++++++++++++++++++++++++++++
 drivers/reset/realtek/common.h | 29 +++++++++++
 7 files changed, 132 insertions(+)
 create mode 100644 drivers/reset/realtek/Kconfig
 create mode 100644 drivers/reset/realtek/Makefile
 create mode 100644 drivers/reset/realtek/common.c
 create mode 100644 drivers/reset/realtek/common.h

diff --git a/MAINTAINERS b/MAINTAINERS
index 4af7515664f8..ff0347f6556d 100644
--- a/MAINTAINERS
+++ b/MAINTAINERS
@@ -22434,6 +22434,7 @@ L:	devicetree@vger.kernel.org
 L:	linux-clk@vger.kernel.org
 S:	Supported
 F:	Documentation/devicetree/bindings/clock/realtek*
+F:	drivers/reset/realtek/*
 F:	include/dt-bindings/clock/realtek*
 F:	include/dt-bindings/reset/realtek*
 
diff --git a/drivers/reset/Kconfig b/drivers/reset/Kconfig
index d009eb0849a3..45a4227b5f44 100644
--- a/drivers/reset/Kconfig
+++ b/drivers/reset/Kconfig
@@ -418,6 +418,7 @@ config RESET_ZYNQMP
 
 source "drivers/reset/amlogic/Kconfig"
 source "drivers/reset/hisilicon/Kconfig"
+source "drivers/reset/realtek/Kconfig"
 source "drivers/reset/spacemit/Kconfig"
 source "drivers/reset/starfive/Kconfig"
 source "drivers/reset/sti/Kconfig"
diff --git a/drivers/reset/Makefile b/drivers/reset/Makefile
index 3e52569bd276..7330fee91365 100644
--- a/drivers/reset/Makefile
+++ b/drivers/reset/Makefile
@@ -2,6 +2,7 @@
 obj-y += core.o
 obj-y += amlogic/
 obj-y += hisilicon/
+obj-y += realtek/
 obj-y += spacemit/
 obj-y += starfive/
 obj-y += sti/
diff --git a/drivers/reset/realtek/Kconfig b/drivers/reset/realtek/Kconfig
new file mode 100644
index 000000000000..bb6dd856a64a
--- /dev/null
+++ b/drivers/reset/realtek/Kconfig
@@ -0,0 +1,8 @@
+# SPDX-License-Identifier: GPL-2.0-only
+config RESET_RTK_COMMON
+	tristate "Realtek common reset driver" if COMPILE_TEST
+	help
+	  This option enables the common reset controller library for
+	  Realtek SoCs. It provides shared reset control operations
+	  (assert, deassert, status) and a registration helper function
+	  that other Realtek-specific reset drivers can use.
diff --git a/drivers/reset/realtek/Makefile b/drivers/reset/realtek/Makefile
new file mode 100644
index 000000000000..b59a3f7f2453
--- /dev/null
+++ b/drivers/reset/realtek/Makefile
@@ -0,0 +1,2 @@
+# SPDX-License-Identifier: GPL-2.0-only
+obj-$(CONFIG_RESET_RTK_COMMON) += common.o
diff --git a/drivers/reset/realtek/common.c b/drivers/reset/realtek/common.c
new file mode 100644
index 000000000000..2ce20c25377b
--- /dev/null
+++ b/drivers/reset/realtek/common.c
@@ -0,0 +1,90 @@
+// SPDX-License-Identifier: GPL-2.0-only
+/*
+ * Copyright (C) 2019-2026 Realtek Semiconductor Corporation
+ */
+
+#include <linux/device.h>
+#include <linux/export.h>
+#include <linux/module.h>
+#include <linux/of.h>
+#include <linux/regmap.h>
+#include "common.h"
+
+static inline struct rtk_reset_data *to_rtk_reset_controller(struct reset_controller_dev *r)
+{
+	return container_of(r, struct rtk_reset_data, rcdev);
+}
+
+static inline const struct rtk_reset_desc *rtk_reset_get_desc(struct rtk_reset_data *data,
+							      unsigned long idx)
+{
+	return &data->descs[idx];
+}
+
+static int rtk_reset_assert(struct reset_controller_dev *rcdev,
+			    unsigned long idx)
+{
+	struct rtk_reset_data *data = to_rtk_reset_controller(rcdev);
+	const struct rtk_reset_desc *desc;
+	u32 mask, val;
+
+	desc = rtk_reset_get_desc(data, idx);
+	mask = desc->write_en ? (0x3U << desc->bit) : BIT(desc->bit);
+	val  = desc->write_en ? (0x2U << desc->bit) : 0;
+
+	return regmap_update_bits(data->regmap, desc->ofs, mask, val);
+}
+
+static int rtk_reset_deassert(struct reset_controller_dev *rcdev,
+			      unsigned long idx)
+{
+	struct rtk_reset_data *data = to_rtk_reset_controller(rcdev);
+	const struct rtk_reset_desc *desc;
+	u32 mask, val;
+
+	desc = rtk_reset_get_desc(data, idx);
+	mask = desc->write_en ? (0x3U << desc->bit) : BIT(desc->bit);
+	val = mask;
+
+	return regmap_update_bits(data->regmap, desc->ofs, mask, val);
+}
+
+static int rtk_reset_status(struct reset_controller_dev *rcdev,
+			    unsigned long idx)
+{
+	struct rtk_reset_data *data = to_rtk_reset_controller(rcdev);
+	const struct rtk_reset_desc *desc;
+	u32 val;
+	int ret;
+
+	desc = rtk_reset_get_desc(data, idx);
+	ret = regmap_read(data->regmap, desc->ofs, &val);
+	if (ret)
+		return ret;
+
+	return !((val >> desc->bit) & 1);
+}
+
+static const struct reset_control_ops rtk_reset_ops = {
+	.assert   = rtk_reset_assert,
+	.deassert = rtk_reset_deassert,
+	.status   = rtk_reset_status,
+};
+
+/* The caller must initialize data->descs, data->rcdev.nr_resets and
+ * data->rcdev.owner before calling rtk_reset_controller_add().
+ */
+int rtk_reset_controller_add(struct device *dev,
+			     struct rtk_reset_data *data)
+{
+	data->regmap          = dev_get_platdata(dev);
+	data->rcdev.ops       = &rtk_reset_ops;
+	data->rcdev.dev       = dev;
+	data->rcdev.of_node   = dev->parent->of_node;
+
+	return devm_reset_controller_register(dev, &data->rcdev);
+}
+EXPORT_SYMBOL_NS_GPL(rtk_reset_controller_add, "REALTEK_RESET");
+
+MODULE_DESCRIPTION("realtek reset infrastructure");
+MODULE_LICENSE("GPL");
diff --git a/drivers/reset/realtek/common.h b/drivers/reset/realtek/common.h
new file mode 100644
index 000000000000..42eb41eae2ec
--- /dev/null
+++ b/drivers/reset/realtek/common.h
@@ -0,0 +1,29 @@
+/* SPDX-License-Identifier: GPL-2.0-only */
+/*
+ * Copyright (C) 2026 Realtek Semiconductor Corporation
+ * Author: Yu-Chun Lin <eleanor.lin@realtek.com>
+ */
+
+#ifndef __RESET_REALTEK_COMMON_H
+#define __RESET_REALTEK_COMMON_H
+
+#include <linux/reset-controller.h>
+
+struct regmap;
+
+struct rtk_reset_desc {
+	u32 ofs;
+	u32 bit;
+	bool write_en;
+};
+
+struct rtk_reset_data {
+	struct reset_controller_dev rcdev;
+	const struct rtk_reset_desc *descs;
+	struct regmap *regmap;
+};
+
+int rtk_reset_controller_add(struct device *dev,
+			     struct rtk_reset_data *initdata);
+
+#endif /* __RESET_REALTEK_COMMON_H */
-- 
2.34.1