[PATCH v2 3/4] reset: Add support for Armada8K reset controller

[Wilson Ding <dingwei@marvell.com>]

Armada8K has one register for unit soft-reset configuration within the
system controller register area. This patch created a new driver based
on the simple-reset driver to support the reset controller of a SYSCON
device.

Signed-off-by: Wilson Ding <dingwei@marvell.com>
---
 drivers/reset/Kconfig               |  12 ++
 drivers/reset/Makefile              |   1 +
 drivers/reset/reset-simple-syscon.c | 195 ++++++++++++++++++++++++++++
 include/linux/reset/reset-simple.h  |   3 +
 4 files changed, 211 insertions(+)
 create mode 100644 drivers/reset/reset-simple-syscon.c

diff --git a/drivers/reset/Kconfig b/drivers/reset/Kconfig
index 5b3abb6db248..e98b22195317 100644
--- a/drivers/reset/Kconfig
+++ b/drivers/reset/Kconfig
@@ -248,6 +248,18 @@ config RESET_SIMPLE
 	   - SiFive FU740 SoCs
 	   - Sophgo SoCs
 
+config RESET_SIMPLE_SYSCON
+	bool "Simple SYSCON Reset Controller Driver" if COMPILE_TEST || EXPERT
+	depends on HAS_IOMEM
+	select MFD_SYSCON
+	help
+	  This enables a simple reset controller driver for reset lines that
+	  that can be asserted and deasserted by toggling bits in a contiguous,
+	  exclusive register space.
+
+	  Currently this driver supports:
+	   - Marvell Armada8K SoCs
+
 config RESET_SOCFPGA
 	bool "SoCFPGA Reset Driver" if COMPILE_TEST && (!ARM || !ARCH_INTEL_SOCFPGA)
 	default ARM && ARCH_INTEL_SOCFPGA
diff --git a/drivers/reset/Makefile b/drivers/reset/Makefile
index 677c4d1e2632..c43642fe4d9b 100644
--- a/drivers/reset/Makefile
+++ b/drivers/reset/Makefile
@@ -32,6 +32,7 @@ obj-$(CONFIG_RESET_RASPBERRYPI) += reset-raspberrypi.o
 obj-$(CONFIG_RESET_RZG2L_USBPHY_CTRL) += reset-rzg2l-usbphy-ctrl.o
 obj-$(CONFIG_RESET_SCMI) += reset-scmi.o
 obj-$(CONFIG_RESET_SIMPLE) += reset-simple.o
+obj-$(CONFIG_RESET_SIMPLE_SYSCON) += reset-simple-syscon.o
 obj-$(CONFIG_RESET_SOCFPGA) += reset-socfpga.o
 obj-$(CONFIG_RESET_SUNPLUS) += reset-sunplus.o
 obj-$(CONFIG_RESET_SUNXI) += reset-sunxi.o
diff --git a/drivers/reset/reset-simple-syscon.c b/drivers/reset/reset-simple-syscon.c
new file mode 100644
index 000000000000..aeeb9e9550f5
--- /dev/null
+++ b/drivers/reset/reset-simple-syscon.c
@@ -0,0 +1,195 @@
+// SPDX-License-Identifier: GPL-2.0-or-later
+/*
+ * Simple SYSCON Reset Controller Driver
+ *
+ * Copyright (C) 2025 Marvell, Wilson Ding <dingwei@marvell.com>
+ *
+ * Based on Simple Reset Controller Driver
+ *
+ * Copyright (C) 2017 Pengutronix, Philipp Zabel <kernel@pengutronix.de>
+ * Copyright 2013 Maxime Ripard <maxime.ripard@free-electrons.com>
+ *
+ */
+
+#include <linux/delay.h>
+#include <linux/device.h>
+#include <linux/err.h>
+#include <linux/io.h>
+#include <linux/mfd/syscon.h>
+#include <linux/of.h>
+#include <linux/platform_device.h>
+#include <linux/regmap.h>
+#include <linux/reset-controller.h>
+#include <linux/reset/reset-simple.h>
+#include <linux/spinlock.h>
+
+static inline struct reset_simple_data *
+to_reset_simple_data(struct reset_controller_dev *rcdev)
+{
+	return container_of(rcdev, struct reset_simple_data, rcdev);
+}
+
+static int reset_simple_syscon_update(struct reset_controller_dev *rcdev,
+				      unsigned long id, bool assert)
+{
+	struct reset_simple_data *data = to_reset_simple_data(rcdev);
+	int reg_width = sizeof(u32);
+	int bank = id / (reg_width * BITS_PER_BYTE);
+	int offset = id % (reg_width * BITS_PER_BYTE);
+	u32 mask, val;
+
+	mask = BIT(offset);
+
+	if (assert ^ data->active_low)
+		val = mask;
+	else
+		val = 0;
+
+	return regmap_write_bits(data->regmap,
+				 data->reg_offset + (bank * reg_width),
+				 mask, val);
+}
+
+static int reset_simple_syscon_assert(struct reset_controller_dev *rcdev,
+				      unsigned long id)
+{
+	return reset_simple_syscon_update(rcdev, id, true);
+}
+
+static int reset_simple_syscon_deassert(struct reset_controller_dev *rcdev,
+					unsigned long id)
+{
+	return reset_simple_syscon_update(rcdev, id, false);
+}
+
+static int reset_simple_syscon_reset(struct reset_controller_dev *rcdev,
+				     unsigned long id)
+{
+	struct reset_simple_data *data = to_reset_simple_data(rcdev);
+	int ret;
+
+	if (!data->reset_us)
+		return -EINVAL;
+
+	ret = reset_simple_syscon_assert(rcdev, id);
+	if (ret)
+		return ret;
+
+	usleep_range(data->reset_us, data->reset_us * 2);
+
+	return reset_simple_syscon_deassert(rcdev, id);
+}
+
+static int reset_simple_syscon_status(struct reset_controller_dev *rcdev,
+				      unsigned long id)
+{
+	struct reset_simple_data *data = to_reset_simple_data(rcdev);
+	int reg_width = sizeof(u32);
+	int bank = id / (reg_width * BITS_PER_BYTE);
+	int offset = id % (reg_width * BITS_PER_BYTE);
+	u32 reg;
+	int ret;
+
+	ret = regmap_read(data->regmap, data->reg_offset + (bank * reg_width),
+			  &reg);
+	if (ret)
+		return ret;
+
+	return !(reg & BIT(offset)) ^ !data->status_active_low;
+}
+
+const struct reset_control_ops reset_simple_syscon_ops = {
+	.assert		= reset_simple_syscon_assert,
+	.deassert	= reset_simple_syscon_deassert,
+	.reset		= reset_simple_syscon_reset,
+	.status		= reset_simple_syscon_status,
+};
+EXPORT_SYMBOL_GPL(reset_simple_syscon_ops);
+
+/**
+ * struct reset_simple_syscon_devdata - simple reset controller properties
+ * @reg_offset: offset between base address and first reset register.
+ * @nr_resets: number of resets. If not set, default to resource size in bits.
+ * @active_low: if true, bits are cleared to assert the reset. Otherwise, bits
+ *              are set to assert the reset.
+ * @status_active_low: if true, bits read back as cleared while the reset is
+ *                     asserted. Otherwise, bits read back as set while the
+ *                     reset is asserted.
+ */
+struct reset_simple_syscon_devdata {
+	u32 reg_offset;
+	u32 nr_resets;
+	bool active_low;
+	bool status_active_low;
+};
+
+static const struct reset_simple_syscon_devdata reset_simple_syscon_armada8k = {
+	.nr_resets = 32,
+	.active_low = true,
+	.status_active_low = true,
+};
+
+static const struct of_device_id reset_simple_syscon_dt_ids[] = {
+	{ .compatible = "marvell,armada8k-reset",
+		.data = &reset_simple_syscon_armada8k },
+	{ /* sentinel */ },
+};
+
+static int reset_simple_syscon_probe(struct platform_device *pdev)
+{
+	struct device *dev = &pdev->dev;
+	const struct reset_simple_syscon_devdata *devdata;
+	struct reset_simple_data *data;
+	u32 reg[2];
+
+	devdata = of_device_get_match_data(dev);
+
+	data = devm_kzalloc(dev, sizeof(*data), GFP_KERNEL);
+	if (!data)
+		return -ENOMEM;
+
+	data->regmap = syscon_node_to_regmap(pdev->dev.parent->of_node);
+	if (IS_ERR(data->regmap))
+		return PTR_ERR(data->regmap);
+
+	/*
+	 * If the "reg" property is available, retrieve the reg_offset and
+	 * calculate the nr_resets based on the register size. If "reg" is not
+	 * available, attempt to read the "offset" property for reg_offset and
+	 * use nr_resets from devdata. If "offset" is also not available,
+	 * default to using reg_offset from devdata.
+	 */
+	if (device_property_read_u32_array(&pdev->dev, "reg", reg, 2)) {
+		if (device_property_read_u32(&pdev->dev, "offset",
+					     &data->reg_offset))
+			data->reg_offset = devdata->reg_offset;
+		data->rcdev.nr_resets = devdata->nr_resets;
+	} else {
+		data->reg_offset = reg[0];
+		data->rcdev.nr_resets = reg[1] * BITS_PER_BYTE;
+	}
+
+	data->active_low = devdata->active_low;
+	data->status_active_low = devdata->status_active_low;
+
+	if (data->rcdev.nr_resets == 0) {
+		dev_err(dev, "no reset lines\n");
+		return -EINVAL;
+	}
+
+	spin_lock_init(&data->lock);
+	data->rcdev.owner = THIS_MODULE;
+	data->rcdev.ops = &reset_simple_syscon_ops;
+	data->rcdev.of_node = dev->of_node;
+
+	return devm_reset_controller_register(dev, &data->rcdev);
+}
+
+static struct platform_driver reset_simple_syscon_driver = {
+	.probe	= reset_simple_syscon_probe,
+	.driver = {
+		.name		= "simple-reset-syscon",
+		.of_match_table	= reset_simple_syscon_dt_ids,
+	},
+};
+builtin_platform_driver(reset_simple_syscon_driver);
diff --git a/include/linux/reset/reset-simple.h b/include/linux/reset/reset-simple.h
index c3e44f45b0f7..9a8eebd5892f 100644
--- a/include/linux/reset/reset-simple.h
+++ b/include/linux/reset/reset-simple.h
@@ -13,6 +13,7 @@
 #define __RESET_SIMPLE_H__
 
 #include <linux/io.h>
+#include <linux/regmap.h>
 #include <linux/reset-controller.h>
 #include <linux/spinlock.h>
 
@@ -37,6 +38,8 @@
 struct reset_simple_data {
 	spinlock_t			lock;
 	void __iomem			*membase;
+	struct regmap			*regmap;
+	u32				reg_offset;
 	struct reset_controller_dev	rcdev;
 	bool				active_low;
 	bool				status_active_low;
-- 
2.43.0