[v2,1/4] reset: gpio: Add GPIO-based reset controller

diff --git a/MAINTAINERS b/MAINTAINERS
index 7fe27cd60e1b..a0fbd4814bc7 100644
--- a/MAINTAINERS
+++ b/MAINTAINERS
@@ -8866,6 +8866,11 @@  F:	Documentation/i2c/muxes/i2c-mux-gpio.rst
 F:	drivers/i2c/muxes/i2c-mux-gpio.c
 F:	include/linux/platform_data/i2c-mux-gpio.h
 
+GENERIC GPIO RESET DRIVER
+M:	Krzysztof Kozlowski <krzysztof.kozlowski@linaro.org>
+S:	Maintained
+F:	drivers/reset/reset-gpio.c
+
 GENERIC HDLC (WAN) DRIVERS
 M:	Krzysztof Halasa <khc@pm.waw.pl>
 S:	Maintained
diff --git a/drivers/reset/Kconfig b/drivers/reset/Kconfig
index ccd59ddd7610..bb1b5a326eb7 100644
--- a/drivers/reset/Kconfig
+++ b/drivers/reset/Kconfig
@@ -66,6 +66,15 @@  config RESET_BRCMSTB_RESCAL
 	  This enables the RESCAL reset controller for SATA, PCIe0, or PCIe1 on
 	  BCM7216.
 
+config RESET_GPIO
+	tristate "GPIO reset controller"
+	help
+	  This enables a generic reset controller for resets attached via
+	  GPIOs.  Typically for OF platforms this driver expects "reset-gpios"
+	  property.
+
+	  If compiled as module, it will be called reset-gpio.
+
 config RESET_HSDK
 	bool "Synopsys HSDK Reset Driver"
 	depends on HAS_IOMEM
diff --git a/drivers/reset/Makefile b/drivers/reset/Makefile
index 8270da8a4baa..fd8b49fa46fc 100644
--- a/drivers/reset/Makefile
+++ b/drivers/reset/Makefile
@@ -11,6 +11,7 @@  obj-$(CONFIG_RESET_BCM6345) += reset-bcm6345.o
 obj-$(CONFIG_RESET_BERLIN) += reset-berlin.o
 obj-$(CONFIG_RESET_BRCMSTB) += reset-brcmstb.o
 obj-$(CONFIG_RESET_BRCMSTB_RESCAL) += reset-brcmstb-rescal.o
+obj-$(CONFIG_RESET_GPIO) += reset-gpio.o
 obj-$(CONFIG_RESET_HSDK) += reset-hsdk.o
 obj-$(CONFIG_RESET_IMX7) += reset-imx7.o
 obj-$(CONFIG_RESET_INTEL_GW) += reset-intel-gw.o
diff --git a/drivers/reset/reset-gpio.c b/drivers/reset/reset-gpio.c
new file mode 100644
index 000000000000..cf0a867cbc5f
--- /dev/null
+++ b/drivers/reset/reset-gpio.c
@@ -0,0 +1,121 @@ 
+// SPDX-License-Identifier: GPL-2.0
+
+#include <linux/gpio/consumer.h>
+#include <linux/mod_devicetable.h>
+#include <linux/module.h>
+#include <linux/of.h>
+#include <linux/platform_device.h>
+#include <linux/reset-controller.h>
+
+struct reset_gpio_priv {
+	struct reset_controller_dev rc;
+	struct gpio_desc *reset;
+};
+
+static inline struct reset_gpio_priv
+*rc_to_reset_gpio(struct reset_controller_dev *rc)
+{
+	return container_of(rc, struct reset_gpio_priv, rc);
+}
+
+static int reset_gpio_assert(struct reset_controller_dev *rc, unsigned long id)
+{
+	struct reset_gpio_priv *priv = rc_to_reset_gpio(rc);
+
+	gpiod_set_value_cansleep(priv->reset, 1);
+
+	return 0;
+}
+
+static int reset_gpio_deassert(struct reset_controller_dev *rc,
+			       unsigned long id)
+{
+	struct reset_gpio_priv *priv = rc_to_reset_gpio(rc);
+
+	gpiod_set_value_cansleep(priv->reset, 0);
+
+	return 0;
+}
+
+static int reset_gpio_status(struct reset_controller_dev *rc, unsigned long id)
+{
+	struct reset_gpio_priv *priv = rc_to_reset_gpio(rc);
+
+	return gpiod_get_value_cansleep(priv->reset);
+}
+
+static const struct reset_control_ops reset_gpio_ops = {
+	.assert = reset_gpio_assert,
+	.deassert = reset_gpio_deassert,
+	.status = reset_gpio_status,
+};
+
+static void reset_gpio_of_args_put(void *data)
+{
+	of_node_put(data);
+}
+
+static int reset_gpio_probe(struct platform_device *pdev)
+{
+	struct device *dev = &pdev->dev;
+	struct device_node **platdata = dev_get_platdata(dev);
+	struct of_phandle_args gpio_args;
+	struct reset_gpio_priv *priv;
+	int ret;
+
+	if (!platdata || !*platdata)
+		return -EINVAL;
+
+	priv = devm_kzalloc(dev, sizeof(*priv), GFP_KERNEL);
+	if (!priv)
+		return -ENOMEM;
+
+	platform_set_drvdata(pdev, &priv->rc);
+	device_set_node(dev, of_fwnode_handle(*platdata));
+
+	priv->reset = devm_gpiod_get(dev, "reset", GPIOD_OUT_HIGH);
+	if (IS_ERR(priv->reset))
+		return dev_err_probe(dev, PTR_ERR(priv->reset),
+				     "Could not get reset gpios\n");
+
+	ret = of_parse_phandle_with_args(*platdata, "reset-gpios",
+					 "#gpio-cells", 0, &gpio_args);
+	if (ret)
+		return ret;
+
+	priv->rc.ops = &reset_gpio_ops;
+	priv->rc.owner = THIS_MODULE;
+	priv->rc.dev = dev;
+	priv->rc.nr_resets = 1;
+	priv->rc.of_node = gpio_args.np;
+	ret = devm_add_action_or_reset(dev, reset_gpio_of_args_put,
+				       priv->rc.of_node);
+	if (ret)
+		return ret;
+
+	priv->rc.of_args = devm_kmemdup(dev, &gpio_args, sizeof(gpio_args),
+					GFP_KERNEL);
+	if (!priv->rc.of_args)
+		return -ENOMEM;
+
+	return devm_reset_controller_register(dev, &priv->rc);
+}
+
+static const struct platform_device_id reset_gpio_ids[] = {
+	{ .name = "reset-gpio", },
+	{}
+};
+MODULE_DEVICE_TABLE(platform, reset_gpio_ids);
+
+static struct platform_driver reset_gpio_driver = {
+	.probe		= reset_gpio_probe,
+	.id_table	= reset_gpio_ids,
+	.driver	= {
+		.name = "reset-gpio",
+	},
+};
+module_platform_driver(reset_gpio_driver);
+
+MODULE_AUTHOR("Krzysztof Kozlowski <krzysztof.kozlowski@linaro.org>");
+MODULE_DESCRIPTION("Generic GPIO reset driver");
+MODULE_LICENSE("GPL");