[PATCH 19/32] riscv: Add Kendryte K210 SoC reset controller

[Damien Le Moal <damien.lemoal@wdc.com>]

Add a reset controller driver for the Kendryte K210 SoC. This driver
relies on its syscon compatible parent node for its register mapping.
Automatically select this driver for compilation when the SOC_KENDRYTE
option is selected.

Signed-off-by: Damien Le Moal <damien.lemoal@wdc.com>
---
 arch/riscv/Kconfig.socs    |   3 +
 drivers/reset/Kconfig      |   9 ++
 drivers/reset/Makefile     |   1 +
 drivers/reset/reset-k210.c | 186 +++++++++++++++++++++++++++++++++++++
 4 files changed, 199 insertions(+)
 create mode 100644 drivers/reset/reset-k210.c

diff --git a/arch/riscv/Kconfig.socs b/arch/riscv/Kconfig.socs
index a4c851ffc6b0..4d8e66d0556a 100644
--- a/arch/riscv/Kconfig.socs
+++ b/arch/riscv/Kconfig.socs
@@ -31,6 +31,9 @@ config SOC_KENDRYTE
 	select SIFIVE_PLIC
 	select SOC_K210
 	select CLK_K210
+	select ARCH_HAS_RESET_CONTROLLER
+	select RESET_CONTROLLER
+	select RESET_K210
 	help
 	  This enables support for Kendryte K210 SoC platform hardware.
 
diff --git a/drivers/reset/Kconfig b/drivers/reset/Kconfig
index 07d162b179fc..c943051b5fc8 100644
--- a/drivers/reset/Kconfig
+++ b/drivers/reset/Kconfig
@@ -245,6 +245,15 @@ config RESET_ZYNQ
 	help
 	  This enables the reset controller driver for Xilinx Zynq SoCs.
 
+config RESET_K210
+	bool "Reset controller driver for Kendryte K210 SoC"
+	depends on RISCV && SOC_KENDRYTE
+	depends on OF && MFD_SYSCON
+	help
+	  Support for the Kendryte K210 RISC-V SoC reset controller. If
+          Say Y if you want to control reset signals provided by this
+	  controller.
+
 source "drivers/reset/sti/Kconfig"
 source "drivers/reset/hisilicon/Kconfig"
 source "drivers/reset/tegra/Kconfig"
diff --git a/drivers/reset/Makefile b/drivers/reset/Makefile
index 16947610cc3b..1730a31e6871 100644
--- a/drivers/reset/Makefile
+++ b/drivers/reset/Makefile
@@ -33,4 +33,5 @@ obj-$(CONFIG_RESET_UNIPHIER) += reset-uniphier.o
 obj-$(CONFIG_RESET_UNIPHIER_GLUE) += reset-uniphier-glue.o
 obj-$(CONFIG_RESET_ZYNQ) += reset-zynq.o
 obj-$(CONFIG_ARCH_ZYNQMP) += reset-zynqmp.o
+obj-$(CONFIG_RESET_K210) += reset-k210.o
 
diff --git a/drivers/reset/reset-k210.c b/drivers/reset/reset-k210.c
new file mode 100644
index 000000000000..b6401aef2923
--- /dev/null
+++ b/drivers/reset/reset-k210.c
@@ -0,0 +1,186 @@
+// 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 <dt-bindings/mfd/k210-sysctl.h>
+#include <dt-bindings/reset/k210-rst.h>
+
+struct k210_rst {
+	struct regmap *map;
+	u32 offset;
+	u32 mask;
+	u32 assert_high;
+	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);
+	u32 bit = BIT(id);
+
+	if (!(bit & ksr->mask)) {
+		dev_err(rcdev->dev, "Invalid assert id %lu\n", id);
+		return -EINVAL;
+	}
+
+	dev_dbg(rcdev->dev, "assert %s %lu\n",
+		ksr->assert_high ? "high" : "low", id);
+
+	regmap_update_bits(ksr->map, ksr->offset, bit,
+			   ksr->assert_high ? bit : 0);
+
+	return 0;
+}
+
+static inline int k210_rst_deassert(struct reset_controller_dev *rcdev,
+				    unsigned long id)
+{
+	struct k210_rst *ksr = to_k210_rst(rcdev);
+	u32 bit = BIT(id);
+
+	if (!(bit & ksr->mask)) {
+		dev_err(rcdev->dev, "Invalid deassert id %lu\n", id);
+		return -EINVAL;
+	}
+
+	dev_dbg(rcdev->dev, "deassert %s %lu\n",
+		ksr->assert_high ? "high" : "low", id);
+
+	regmap_update_bits(ksr->map, ksr->offset, bit,
+			   ksr->assert_high ? 0 : bit);
+
+	return 0;
+}
+
+static int k210_rst_reset(struct reset_controller_dev *rcdev,
+			  unsigned long id)
+{
+	struct k210_rst *ksr = to_k210_rst(rcdev);
+	int ret;
+
+	dev_dbg(rcdev->dev, "reset %s %lu\n",
+		ksr->assert_high ? "high" : "low", id);
+
+	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;
+
+	if (!(bit & ksr->mask)) {
+		dev_err(rcdev->dev, "Invalid reset %lx\n", id);
+		return -EINVAL;
+	}
+
+	ret = regmap_read(ksr->map, ksr->offset, &reg);
+	if (ret)
+		return ret;
+
+	if (ksr->assert_high)
+		return ret & bit;
+
+	return !(ret & bit);
+}
+
+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 __init k210_rst_probe(struct platform_device *pdev)
+{
+	struct device *dev = &pdev->dev;
+	struct k210_rst *ksr;
+	int ret, nr_resets;
+
+	dev_info(dev, "K210 reset controller\n");
+
+	ksr = devm_kzalloc(dev, sizeof(*ksr), GFP_KERNEL);
+	if (!ksr)
+		return -ENOMEM;
+
+	ksr->map = syscon_regmap_lookup_by_phandle(dev->of_node, "regmap");
+	if (IS_ERR(ksr->map)) {
+		ksr->map = syscon_node_to_regmap(dev->parent->of_node);
+		if (IS_ERR(ksr->map)) {
+			dev_err(dev, "get register map failed\n");
+			return PTR_ERR(ksr->map);
+		}
+	}
+
+	ret = of_property_read_u32(dev->of_node, "offset", &ksr->offset);
+	ret = of_property_read_u32(dev->of_node, "assert-high",
+				   &ksr->assert_high);
+	if (ret) {
+		dev_err(dev, "unable to read 'offset' and 'assert-high'\n");
+		return -EINVAL;
+	}
+
+	ret = of_property_read_u32(dev->of_node, "mask", &ksr->mask);
+	if (ret) {
+		/* Use default mask */
+		ksr->mask = 0x27FFFFFF;
+	}
+	nr_resets = fls(ksr->mask);
+	if (!nr_resets) {
+		dev_err(dev, "Invalid mask 0x%08x\n", ksr->mask);
+		return -EINVAL;
+	}
+
+	ksr->rcdev.owner = THIS_MODULE;
+	ksr->rcdev.dev = dev;
+	ksr->rcdev.of_node = dev->of_node;
+	ksr->rcdev.nr_resets = nr_resets;
+	ksr->rcdev.ops = &k210_rst_ops;
+
+	return devm_reset_controller_register(dev, &ksr->rcdev);
+}
+
+static const struct of_device_id k210_rst_dt_ids[] = {
+	{ .compatible = "kendryte,k210-rst" },
+};
+
+static struct platform_driver k210_rst_driver = {
+	.probe	= k210_rst_probe,
+	.driver = {
+		.name		= "k210-rst",
+		.of_match_table	= k210_rst_dt_ids,
+	},
+};
+
+/*
+ * Most devices on the K210 SoC need reset as part of their initialization.
+ * So initialize this driver early as part of the post core initialization.
+ */
+static int __init k210_rst_init(void)
+{
+	return platform_driver_register(&k210_rst_driver);
+}
+postcore_initcall(k210_rst_init);
-- 
2.28.0