riscv: Add Canaan Kendryte K210 reset controller

Add a reset controller driver for the Canaan Kendryte K210 SoC. This
driver relies on its syscon compatible parent node (sysctl) for its
register mapping. Default this driver compilation to y when the
SOC_CANAAN option is selected.

The MAINTAINERS file is updated, adding the entry "CANAAN/KENDRYTE K210
SOC RESET CONTROLLER DRIVER" with myself listed as maintainer for this
driver.

Signed-off-by: Damien Le Moal <damien.lemoal@wdc.com>
Reviewed-by: Philipp Zabel <p.zabel@pengutronix.de>
Signed-off-by: Palmer Dabbelt <palmerdabbelt@google.com>

MAINTAINERS

@@ -3860,6 +3860,14 @@ W:	https://github.com/Cascoda/ca8210-linux.git
 F:	Documentation/devicetree/bindings/net/ieee802154/ca8210.txt
 F:	drivers/net/ieee802154/ca8210.c
 
+CANAAN/KENDRYTE K210 SOC RESET CONTROLLER DRIVER
+M:	Damien Le Moal <damien.lemoal@wdc.com>
+L:	linux-kernel@vger.kernel.org
+L:	linux-riscv@lists.infradead.org
+S:	Maintained
+F:	Documentation/devicetree/bindings/reset/canaan,k210-rst.yaml
+F:	drivers/reset/reset-k210.c
+
 CANAAN/KENDRYTE K210 SOC SYSTEM CONTROLLER DRIVER
 M:	Damien Le Moal <damien.lemoal@wdc.com>
 L:	linux-riscv@lists.infradead.org

arch/riscv/Kconfig.socs

@@ -29,6 +29,7 @@ config SOC_CANAAN
 	select SERIAL_SIFIVE if TTY
 	select SERIAL_SIFIVE_CONSOLE if TTY
 	select SIFIVE_PLIC
+	select ARCH_HAS_RESET_CONTROLLER
 	help
 	  This enables support for Canaan Kendryte K210 SoC platform hardware.
 

drivers/reset/Kconfig

@@ -89,6 +89,16 @@ config RESET_INTEL_GW
 	  Say Y to control the reset signals provided by reset controller.
 	  Otherwise, say N.
 
+config RESET_K210
+	bool "Reset controller driver for Canaan Kendryte K210 SoC"
+	depends on (SOC_CANAAN || COMPILE_TEST) && OF
+	select MFD_SYSCON
+	default SOC_CANAAN
+	help
+	  Support for the Canaan Kendryte K210 RISC-V SoC reset controller.
+	  Say Y if you want to control reset signals provided by this
+	  controller.
+
 config RESET_LANTIQ
 	bool "Lantiq XWAY Reset Driver" if COMPILE_TEST
 	default SOC_TYPE_XWAY

drivers/reset/Makefile

@@ -13,6 +13,7 @@ obj-$(CONFIG_RESET_BRCMSTB_RESCAL) += reset-brcmstb-rescal.o
 obj-$(CONFIG_RESET_HSDK) += reset-hsdk.o
 obj-$(CONFIG_RESET_IMX7) += reset-imx7.o
 obj-$(CONFIG_RESET_INTEL_GW) += reset-intel-gw.o
+obj-$(CONFIG_RESET_K210) += reset-k210.o
 obj-$(CONFIG_RESET_LANTIQ) += reset-lantiq.o
 obj-$(CONFIG_RESET_LPC18XX) += reset-lpc18xx.o
 obj-$(CONFIG_RESET_MESON) += reset-meson.o

drivers/reset/reset-k210.c

@@ -0,0 +1,131 @@
+// SPDX-License-Identifier: GPL-2.0-or-later
+/*
+ * Copyright (c) 2020 Western Digital Corporation or its affiliates.
+ */
+#include <linux/of.h>
+#include <linux/of_device.h>
+#include <linux/platform_device.h>
+#include <linux/reset-controller.h>
+#include <linux/delay.h>
+#include <linux/mfd/syscon.h>
+#include <linux/regmap.h>
+#include <soc/canaan/k210-sysctl.h>
+
+#include <dt-bindings/reset/k210-rst.h>
+
+#define K210_RST_MASK	0x27FFFFFF
+
+struct k210_rst {
+	struct regmap *map;
+	struct reset_controller_dev rcdev;
+};
+
+static inline struct k210_rst *
+to_k210_rst(struct reset_controller_dev *rcdev)
+{
+	return container_of(rcdev, struct k210_rst, rcdev);
+}
+
+static inline int k210_rst_assert(struct reset_controller_dev *rcdev,
+				  unsigned long id)
+{
+	struct k210_rst *ksr = to_k210_rst(rcdev);
+
+	return regmap_update_bits(ksr->map, K210_SYSCTL_PERI_RESET, BIT(id), 1);
+}
+
+static inline int k210_rst_deassert(struct reset_controller_dev *rcdev,
+				    unsigned long id)
+{
+	struct k210_rst *ksr = to_k210_rst(rcdev);
+
+	return regmap_update_bits(ksr->map, K210_SYSCTL_PERI_RESET, BIT(id), 0);
+}
+
+static int k210_rst_reset(struct reset_controller_dev *rcdev,
+			  unsigned long id)
+{
+	int ret;
+
+	ret = k210_rst_assert(rcdev, id);
+	if (ret == 0) {
+		udelay(10);
+		ret = k210_rst_deassert(rcdev, id);
+	}
+
+	return ret;
+}
+
+static int k210_rst_status(struct reset_controller_dev *rcdev,
+			   unsigned long id)
+{
+	struct k210_rst *ksr = to_k210_rst(rcdev);
+	u32 reg, bit = BIT(id);
+	int ret;
+
+	ret = regmap_read(ksr->map, K210_SYSCTL_PERI_RESET, &reg);
+	if (ret)
+		return ret;
+
+	return reg & bit;
+}
+
+static int k210_rst_xlate(struct reset_controller_dev *rcdev,
+			  const struct of_phandle_args *reset_spec)
+{
+	unsigned long id = reset_spec->args[0];
+
+	if (!(BIT(id) & K210_RST_MASK))
+		return -EINVAL;
+
+	return id;
+}
+
+static const struct reset_control_ops k210_rst_ops = {
+	.assert		= k210_rst_assert,
+	.deassert	= k210_rst_deassert,
+	.reset		= k210_rst_reset,
+	.status		= k210_rst_status,
+};
+
+static int k210_rst_probe(struct platform_device *pdev)
+{
+	struct device *dev = &pdev->dev;
+	struct device_node *parent_np = of_get_parent(dev->of_node);
+	struct k210_rst *ksr;
+
+	dev_info(dev, "K210 reset controller\n");
+
+	ksr = devm_kzalloc(dev, sizeof(*ksr), GFP_KERNEL);
+	if (!ksr)
+		return -ENOMEM;
+
+	ksr->map = syscon_node_to_regmap(parent_np);
+	of_node_put(parent_np);
+	if (IS_ERR(ksr->map))
+		return PTR_ERR(ksr->map);
+
+	ksr->rcdev.owner = THIS_MODULE;
+	ksr->rcdev.dev = dev;
+	ksr->rcdev.of_node = dev->of_node;
+	ksr->rcdev.ops = &k210_rst_ops;
+	ksr->rcdev.nr_resets = fls(K210_RST_MASK);
+	ksr->rcdev.of_reset_n_cells = 1;
+	ksr->rcdev.of_xlate = k210_rst_xlate;
+
+	return devm_reset_controller_register(dev, &ksr->rcdev);
+}
+
+static const struct of_device_id k210_rst_dt_ids[] = {
+	{ .compatible = "canaan,k210-rst" },
+	{ /* sentinel */ },
+};
+
+static struct platform_driver k210_rst_driver = {
+	.probe	= k210_rst_probe,
+	.driver = {
+		.name		= "k210-rst",
+		.of_match_table	= k210_rst_dt_ids,
+	},
+};
+builtin_platform_driver(k210_rst_driver);