[RFC PATCH 2/3] reset: Add th1520 reset driver support

[Kwanghoon Son]

This driver supports th1520 T-HEAD SoC reset platform device.

Signed-off-by: Kwanghoon Son <k.son@xxxxxxxxxxx>
---
 drivers/reset/Kconfig                    |  10 +++
 drivers/reset/Makefile                   |   1 +
 drivers/reset/reset-th1520.c             | 109 +++++++++++++++++++++++
 include/dt-bindings/reset/th1520-reset.h |   9 ++
 4 files changed, 129 insertions(+)
 create mode 100644 drivers/reset/reset-th1520.c
 create mode 100644 include/dt-bindings/reset/th1520-reset.h

diff --git a/drivers/reset/Kconfig b/drivers/reset/Kconfig
index ccd59ddd7610..ec69e6bbba6e 100644
--- a/drivers/reset/Kconfig
+++ b/drivers/reset/Kconfig
@@ -253,6 +253,16 @@ config RESET_SUNXI
 	help
 	  This enables the reset driver for Allwinner SoCs.
 
+config RESET_TH1520
+	bool "TH1520 Reset Driver"
+	depends on (ARCH_THEAD || COMPILE_TEST) && OF
+	select MFD_SYSCON
+	default ARCH_THEAD
+	help
+	  Support for the T-HEAD 1520 RISC-V SoC reset controller.
+	  Say Y if you want to control reset signals provided by this
+	  controller.
+
 config RESET_TI_SCI
 	tristate "TI System Control Interface (TI-SCI) reset driver"
 	depends on TI_SCI_PROTOCOL || (COMPILE_TEST && TI_SCI_PROTOCOL=n)
diff --git a/drivers/reset/Makefile b/drivers/reset/Makefile
index 8270da8a4baa..5c858e62241a 100644
--- a/drivers/reset/Makefile
+++ b/drivers/reset/Makefile
@@ -33,6 +33,7 @@ obj-$(CONFIG_RESET_SIMPLE) += reset-simple.o
 obj-$(CONFIG_RESET_SOCFPGA) += reset-socfpga.o
 obj-$(CONFIG_RESET_SUNPLUS) += reset-sunplus.o
 obj-$(CONFIG_RESET_SUNXI) += reset-sunxi.o
+obj-$(CONFIG_RESET_TH1520) += reset-th1520.o
 obj-$(CONFIG_RESET_TI_SCI) += reset-ti-sci.o
 obj-$(CONFIG_RESET_TI_SYSCON) += reset-ti-syscon.o
 obj-$(CONFIG_RESET_TI_TPS380X) += reset-tps380x.o
diff --git a/drivers/reset/reset-th1520.c b/drivers/reset/reset-th1520.c
new file mode 100644
index 000000000000..4c781377ac23
--- /dev/null
+++ b/drivers/reset/reset-th1520.c
@@ -0,0 +1,109 @@
+// SPDX-License-Identifier: GPL-2.0-only
+
+#include <linux/mfd/syscon.h>
+#include <linux/of_device.h>
+#include <linux/platform_device.h>
+#include <linux/reset-controller.h>
+#include <linux/regmap.h>
+#include <dt-bindings/reset/th1520-reset.h>
+
+struct th1520_rst_signal {
+	unsigned int offset, bit;
+};
+
+struct th1520_rst {
+	struct reset_controller_dev rcdev;
+	struct regmap *regmap;
+	const struct th1520_rst_signal *signals;
+};
+
+enum th1520_rst_registers {
+	RST_WDT0 = 0x0034,
+	RST_WDT1 = 0x0038,
+};
+
+static int th1520_reset_update(struct th1520_rst *rst, unsigned long id,
+			       unsigned int value)
+{
+	const struct th1520_rst_signal *signal = &rst->signals[id];
+
+	return regmap_update_bits(rst->regmap, signal->offset, signal->bit,
+				  value);
+}
+
+static const struct th1520_rst_signal th1520_rst_signals[] = {
+	[TH1520_RESET_WDT0] = { RST_WDT0, BIT(0) },
+	[TH1520_RESET_WDT1] = { RST_WDT1, BIT(0) },
+};
+
+static struct th1520_rst *to_th1520_rst(struct reset_controller_dev *rcdev)
+{
+	return container_of(rcdev, struct th1520_rst, rcdev);
+}
+
+static int th1520_reset_set(struct reset_controller_dev *rcdev,
+			    unsigned long id, bool assert)
+{
+	struct th1520_rst *rst = to_th1520_rst(rcdev);
+	const unsigned int bit = rst->signals[id].bit;
+	unsigned int value = assert ? bit : 0;
+
+	return th1520_reset_update(rst, id, value);
+}
+
+static int th1520_reset_assert(struct reset_controller_dev *rcdev,
+			       unsigned long id)
+{
+	return th1520_reset_set(rcdev, id, false);
+}
+
+static int th1520_reset_deassert(struct reset_controller_dev *rcdev,
+				 unsigned long id)
+{
+	return th1520_reset_set(rcdev, id, true);
+}
+
+static const struct reset_control_ops th1520_rst_ops = {
+	.assert = th1520_reset_assert,
+	.deassert = th1520_reset_deassert,
+};
+
+static int th1520_reset_probe(struct platform_device *pdev)
+{
+	struct device *dev = &pdev->dev;
+	struct th1520_rst *rst;
+	struct regmap_config config = { .name = "rst" };
+
+	rst = devm_kzalloc(dev, sizeof(*rst), GFP_KERNEL);
+	if (!rst)
+		return -ENOMEM;
+
+	rst->signals = th1520_rst_signals;
+	rst->regmap = syscon_node_to_regmap(dev->of_node);
+	if (IS_ERR(rst->regmap))
+		return PTR_ERR(rst->regmap);
+
+	regmap_attach_dev(dev, rst->regmap, &config);
+
+	rst->rcdev.owner = THIS_MODULE;
+	rst->rcdev.dev = dev;
+	rst->rcdev.of_node = dev->of_node;
+	rst->rcdev.ops = &th1520_rst_ops;
+	rst->rcdev.nr_resets = ARRAY_SIZE(th1520_rst_signals);
+
+	return devm_reset_controller_register(dev, &rst->rcdev);
+}
+
+static const struct of_device_id th1520_reset_dt_ids[] = {
+	{ .compatible = "thead,th1520-reset" },
+	{ /* sentinel */ },
+};
+
+static struct platform_driver th1520_reset_driver = {
+	.probe	= th1520_reset_probe,
+	.driver = {
+		.name		= "th1520-reset",
+		.of_match_table	= th1520_reset_dt_ids,
+	},
+};
+builtin_platform_driver(th1520_reset_driver);
diff --git a/include/dt-bindings/reset/th1520-reset.h b/include/dt-bindings/reset/th1520-reset.h
new file mode 100644
index 000000000000..ec10751814e5
--- /dev/null
+++ b/include/dt-bindings/reset/th1520-reset.h
@@ -0,0 +1,9 @@
+/* SPDX-License-Identifier: (GPL-2.0-only OR BSD-2-Clause) */
+
+#ifndef DT_BINDING_RESET_TH1520_H
+#define DT_BINDING_RESET_TH1520_H
+
+#define TH1520_RESET_WDT0 0
+#define TH1520_RESET_WDT1 1
+
+#endif
-- 
2.34.1