reset: Add a reset controller driver for the Lantiq XWAY based SoCs

The reset controllers (on xRX200 and newer SoCs have two of them) are
provided by the RCU module. This was initially implemented as a simple
reset controller. However, the RCU module provides more functionality
(ethernet GPHYs, USB PHY, etc.), which makes it a MFD device.
The old reset controller driver implementation from
arch/mips/lantiq/xway/reset.c did not honor this fact.

For some devices the request and the status bits are different.
Signed-off-by: Martin Blumenstingl <martin.blumenstingl@googlemail.com>
Signed-off-by: Hauke Mehrtens <hauke@hauke-m.de>
Reviewed-by: Andy Shevchenko <andy.shevchenko@gmail.com>
Acked-by: Philipp Zabel <p.zabel@pengutronix.de>
Acked-by: Rob Herring <robh@kernel.org>
Cc: john@phrozen.org
Cc: kishon@ti.com
Cc: mark.rutland@arm.com
Cc: linux-mips@linux-mips.org
Cc: linux-mtd@lists.infradead.org
Cc: linux-watchdog@vger.kernel.org
Cc: devicetree@vger.kernel.org
Cc: linux-spi@vger.kernel.org
Patchwork: https://patchwork.linux-mips.org/patch/17125/Signed-off-by: Ralf Baechle <ralf@linux-mips.org>

Documentation/devicetree/bindings/reset/lantiq,reset.txt

+Lantiq XWAY SoC RCU reset controller binding
+============================================
+
+This binding describes a reset-controller found on the RCU module on Lantiq
+XWAY SoCs.
+
+This node has to be a sub node of the Lantiq RCU block.
+
+-------------------------------------------------------------------------------
+Required properties:
+- compatible		: Should be one of
+				"lantiq,danube-reset"
+				"lantiq,xrx200-reset"
+- reg			: Defines the following sets of registers in the parent
+			  syscon device
+			- Offset of the reset set register
+			- Offset of the reset status register
+- #reset-cells		: Specifies the number of cells needed to encode the
+			  reset line, should be 2.
+			  The first cell takes the reset set bit and the
+			  second cell takes the status bit.
+
+-------------------------------------------------------------------------------
+Example for the reset-controllers on the xRX200 SoCs:
+	reset0: reset-controller@10 {
+		compatible = "lantiq,xrx200-reset";
+		reg <0x10 0x04>, <0x14 0x04>;
+
+		#reset-cells = <2>;
+	};

drivers/reset/Kconfig

@@ -48,6 +48,12 @@ config RESET_IMX7
 	help
 	  This enables the reset controller driver for i.MX7 SoCs.
 
+config RESET_LANTIQ
+	bool "Lantiq XWAY Reset Driver" if COMPILE_TEST
+	default SOC_TYPE_XWAY
+	help
+	  This enables the reset controller driver for Lantiq / Intel XWAY SoCs.
+
 config RESET_LPC18XX
 	bool "LPC18xx/43xx Reset Driver" if COMPILE_TEST
 	default ARCH_LPC18XX

drivers/reset/Makefile

@@ -7,6 +7,7 @@ obj-$(CONFIG_RESET_ATH79) += reset-ath79.o
 obj-$(CONFIG_RESET_BERLIN) += reset-berlin.o
 obj-$(CONFIG_RESET_GEMINI) += reset-gemini.o
 obj-$(CONFIG_RESET_IMX7) += reset-imx7.o
+obj-$(CONFIG_RESET_LANTIQ) += reset-lantiq.o
 obj-$(CONFIG_RESET_LPC18XX) += reset-lpc18xx.o
 obj-$(CONFIG_RESET_MESON) += reset-meson.o
 obj-$(CONFIG_RESET_OXNAS) += reset-oxnas.o

drivers/reset/reset-lantiq.c

+/*
+ *  This program is free software; you can redistribute it and/or modify it
+ *  under the terms of the GNU General Public License version 2 as published
+ *  by the Free Software Foundation.
+ *
+ *  Copyright (C) 2010 John Crispin <blogic@phrozen.org>
+ *  Copyright (C) 2013-2015 Lantiq Beteiligungs-GmbH & Co.KG
+ *  Copyright (C) 2016 Martin Blumenstingl <martin.blumenstingl@googlemail.com>
+ *  Copyright (C) 2017 Hauke Mehrtens <hauke@hauke-m.de>
+ */
+
+#include <linux/mfd/syscon.h>
+#include <linux/module.h>
+#include <linux/regmap.h>
+#include <linux/reset-controller.h>
+#include <linux/of_address.h>
+#include <linux/of_platform.h>
+#include <linux/platform_device.h>
+#include <linux/property.h>
+
+#define LANTIQ_RCU_RESET_TIMEOUT	10000
+
+struct lantiq_rcu_reset_priv {
+	struct reset_controller_dev rcdev;
+	struct device *dev;
+	struct regmap *regmap;
+	u32 reset_offset;
+	u32 status_offset;
+};
+
+static struct lantiq_rcu_reset_priv *to_lantiq_rcu_reset_priv(
+	struct reset_controller_dev *rcdev)
+{
+	return container_of(rcdev, struct lantiq_rcu_reset_priv, rcdev);
+}
+
+static int lantiq_rcu_reset_status(struct reset_controller_dev *rcdev,
+				   unsigned long id)
+{
+	struct lantiq_rcu_reset_priv *priv = to_lantiq_rcu_reset_priv(rcdev);
+	unsigned int status = (id >> 8) & 0x1f;
+	u32 val;
+	int ret;
+
+	ret = regmap_read(priv->regmap, priv->status_offset, &val);
+	if (ret)
+		return ret;
+
+	return !!(val & BIT(status));
+}
+
+static int lantiq_rcu_reset_status_timeout(struct reset_controller_dev *rcdev,
+					   unsigned long id, bool assert)
+{
+	int ret;
+	int retry = LANTIQ_RCU_RESET_TIMEOUT;
+
+	do {
+		ret = lantiq_rcu_reset_status(rcdev, id);
+		if (ret < 0)
+			return ret;
+		if (ret == assert)
+			return 0;
+		usleep_range(20, 40);
+	} while (--retry);
+
+	return -ETIMEDOUT;
+}
+
+static int lantiq_rcu_reset_update(struct reset_controller_dev *rcdev,
+				   unsigned long id, bool assert)
+{
+	struct lantiq_rcu_reset_priv *priv = to_lantiq_rcu_reset_priv(rcdev);
+	unsigned int set = id & 0x1f;
+	u32 val = assert ? BIT(set) : 0;
+	int ret;
+
+	ret = regmap_update_bits(priv->regmap, priv->reset_offset, BIT(set),
+				 val);
+	if (ret) {
+		dev_err(priv->dev, "Failed to set reset bit %u\n", set);
+		return ret;
+	}
+
+
+	ret = lantiq_rcu_reset_status_timeout(rcdev, id, assert);
+	if (ret)
+		dev_err(priv->dev, "Failed to %s bit %u\n",
+			assert ? "assert" : "deassert", set);
+
+	return ret;
+}
+
+static int lantiq_rcu_reset_assert(struct reset_controller_dev *rcdev,
+			     unsigned long id)
+{
+	return lantiq_rcu_reset_update(rcdev, id, true);
+}
+
+static int lantiq_rcu_reset_deassert(struct reset_controller_dev *rcdev,
+			       unsigned long id)
+{
+	return lantiq_rcu_reset_update(rcdev, id, false);
+}
+
+static int lantiq_rcu_reset_reset(struct reset_controller_dev *rcdev,
+			    unsigned long id)
+{
+	int ret;
+
+	ret = lantiq_rcu_reset_assert(rcdev, id);
+	if (ret)
+		return ret;
+
+	return lantiq_rcu_reset_deassert(rcdev, id);
+}
+
+static const struct reset_control_ops lantiq_rcu_reset_ops = {
+	.assert = lantiq_rcu_reset_assert,
+	.deassert = lantiq_rcu_reset_deassert,
+	.status = lantiq_rcu_reset_status,
+	.reset	= lantiq_rcu_reset_reset,
+};
+
+static int lantiq_rcu_reset_of_parse(struct platform_device *pdev,
+			       struct lantiq_rcu_reset_priv *priv)
+{
+	struct device *dev = &pdev->dev;
+	const __be32 *offset;
+
+	priv->regmap = syscon_node_to_regmap(dev->of_node->parent);
+	if (IS_ERR(priv->regmap)) {
+		dev_err(&pdev->dev, "Failed to lookup RCU regmap\n");
+		return PTR_ERR(priv->regmap);
+	}
+
+	offset = of_get_address(dev->of_node, 0, NULL, NULL);
+	if (!offset) {
+		dev_err(&pdev->dev, "Failed to get RCU reset offset\n");
+		return -ENOENT;
+	}
+	priv->reset_offset = __be32_to_cpu(*offset);
+
+	offset = of_get_address(dev->of_node, 1, NULL, NULL);
+	if (!offset) {
+		dev_err(&pdev->dev, "Failed to get RCU status offset\n");
+		return -ENOENT;
+	}
+	priv->status_offset = __be32_to_cpu(*offset);
+
+	return 0;
+}
+
+static int lantiq_rcu_reset_xlate(struct reset_controller_dev *rcdev,
+				  const struct of_phandle_args *reset_spec)
+{
+	unsigned int status, set;
+
+	set = reset_spec->args[0];
+	status = reset_spec->args[1];
+
+	if (set >= rcdev->nr_resets || status >= rcdev->nr_resets)
+		return -EINVAL;
+
+	return (status << 8) | set;
+}
+
+static int lantiq_rcu_reset_probe(struct platform_device *pdev)
+{
+	struct lantiq_rcu_reset_priv *priv;
+	int err;
+
+	priv = devm_kzalloc(&pdev->dev, sizeof(*priv), GFP_KERNEL);
+	if (!priv)
+		return -ENOMEM;
+
+	priv->dev = &pdev->dev;
+	platform_set_drvdata(pdev, priv);
+
+	err = lantiq_rcu_reset_of_parse(pdev, priv);
+	if (err)
+		return err;
+
+	priv->rcdev.ops = &lantiq_rcu_reset_ops;
+	priv->rcdev.owner = THIS_MODULE;
+	priv->rcdev.of_node = pdev->dev.of_node;
+	priv->rcdev.nr_resets = 32;
+	priv->rcdev.of_xlate = lantiq_rcu_reset_xlate;
+	priv->rcdev.of_reset_n_cells = 2;
+
+	return reset_controller_register(&priv->rcdev);
+}
+
+static const struct of_device_id lantiq_rcu_reset_dt_ids[] = {
+	{ .compatible = "lantiq,danube-reset", },
+	{ .compatible = "lantiq,xrx200-reset", },
+	{ },
+};
+MODULE_DEVICE_TABLE(of, lantiq_rcu_reset_dt_ids);
+
+static struct platform_driver lantiq_rcu_reset_driver = {
+	.probe	= lantiq_rcu_reset_probe,
+	.driver = {
+		.name		= "lantiq-reset",
+		.of_match_table	= lantiq_rcu_reset_dt_ids,
+	},
+};
+module_platform_driver(lantiq_rcu_reset_driver);
+
+MODULE_AUTHOR("Martin Blumenstingl <martin.blumenstingl@googlemail.com>");
+MODULE_DESCRIPTION("Lantiq XWAY RCU Reset Controller Driver");
+MODULE_LICENSE("GPL");