reset: add driver for lpc18xx rgu

Add reset driver for the Reset Generation Unit (RGU) found on NXP
LPC18xx and LPC43xx devies. This reset controller features up to 64
reset lines connected to different blocks and peripheral in the SoC.
Most reset lines on the controller are self clearing except for
those dealing with the Cortex-M0 cores on LPC43xx devices.

This driver also registers a restart handler that can be used to
reset the entire device.
Signed-off-by: Joachim Eastwood <manabian@gmail.com>
Signed-off-by: Philipp Zabel <p.zabel@pengutronix.de>

drivers/reset/Makefile

 obj-$(CONFIG_RESET_CONTROLLER) += core.o
+obj-$(CONFIG_ARCH_LPC18XX) += reset-lpc18xx.o
 obj-$(CONFIG_ARCH_SOCFPGA) += reset-socfpga.o
 obj-$(CONFIG_ARCH_BERLIN) += reset-berlin.o
 obj-$(CONFIG_ARCH_SUNXI) += reset-sunxi.o

drivers/reset/reset-lpc18xx.c

+/*
+ * Reset driver for NXP LPC18xx/43xx Reset Generation Unit (RGU).
+ *
+ * Copyright (C) 2015 Joachim Eastwood <manabian@gmail.com>
+ *
+ * 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.
+ *
+ */
+
+#include <linux/clk.h>
+#include <linux/delay.h>
+#include <linux/err.h>
+#include <linux/io.h>
+#include <linux/module.h>
+#include <linux/of.h>
+#include <linux/platform_device.h>
+#include <linux/reboot.h>
+#include <linux/reset-controller.h>
+#include <linux/spinlock.h>
+
+/* LPC18xx RGU registers */
+#define LPC18XX_RGU_CTRL0		0x100
+#define LPC18XX_RGU_CTRL1		0x104
+#define LPC18XX_RGU_ACTIVE_STATUS0	0x150
+#define LPC18XX_RGU_ACTIVE_STATUS1	0x154
+
+#define LPC18XX_RGU_RESETS_PER_REG	32
+
+/* Internal reset outputs */
+#define LPC18XX_RGU_CORE_RST	0
+#define LPC43XX_RGU_M0SUB_RST	12
+#define LPC43XX_RGU_M0APP_RST	56
+
+struct lpc18xx_rgu_data {
+	struct reset_controller_dev rcdev;
+	struct clk *clk_delay;
+	struct clk *clk_reg;
+	void __iomem *base;
+	spinlock_t lock;
+	u32 delay_us;
+};
+
+#define to_rgu_data(p) container_of(p, struct lpc18xx_rgu_data, rcdev)
+
+static void __iomem *rgu_base;
+
+static int lpc18xx_rgu_restart(struct notifier_block *this, unsigned long mode,
+			       void *cmd)
+{
+	writel(BIT(LPC18XX_RGU_CORE_RST), rgu_base + LPC18XX_RGU_CTRL0);
+	mdelay(2000);
+
+	pr_emerg("%s: unable to restart system\n", __func__);
+
+	return NOTIFY_DONE;
+}
+
+static struct notifier_block lpc18xx_rgu_restart_nb = {
+	.notifier_call = lpc18xx_rgu_restart,
+	.priority = 192,
+};
+
+/*
+ * The LPC18xx RGU has mostly self-deasserting resets except for the
+ * two reset lines going to the internal Cortex-M0 cores.
+ *
+ * To prevent the M0 core resets from accidentally getting deasserted
+ * status register must be check and bits in control register set to
+ * preserve the state.
+ */
+static int lpc18xx_rgu_setclear_reset(struct reset_controller_dev *rcdev,
+				      unsigned long id, bool set)
+{
+	struct lpc18xx_rgu_data *rc = to_rgu_data(rcdev);
+	u32 stat_offset = LPC18XX_RGU_ACTIVE_STATUS0;
+	u32 ctrl_offset = LPC18XX_RGU_CTRL0;
+	unsigned long flags;
+	u32 stat, rst_bit;
+
+	stat_offset += (id / LPC18XX_RGU_RESETS_PER_REG) * sizeof(u32);
+	ctrl_offset += (id / LPC18XX_RGU_RESETS_PER_REG) * sizeof(u32);
+	rst_bit = 1 << (id % LPC18XX_RGU_RESETS_PER_REG);
+
+	spin_lock_irqsave(&rc->lock, flags);
+	stat = ~readl(rc->base + stat_offset);
+	if (set)
+		writel(stat | rst_bit, rc->base + ctrl_offset);
+	else
+		writel(stat & ~rst_bit, rc->base + ctrl_offset);
+	spin_unlock_irqrestore(&rc->lock, flags);
+
+	return 0;
+}
+
+static int lpc18xx_rgu_assert(struct reset_controller_dev *rcdev,
+			      unsigned long id)
+{
+	return lpc18xx_rgu_setclear_reset(rcdev, id, true);
+}
+
+static int lpc18xx_rgu_deassert(struct reset_controller_dev *rcdev,
+				unsigned long id)
+{
+	return lpc18xx_rgu_setclear_reset(rcdev, id, false);
+}
+
+/* Only M0 cores require explicit reset deassert */
+static int lpc18xx_rgu_reset(struct reset_controller_dev *rcdev,
+			     unsigned long id)
+{
+	struct lpc18xx_rgu_data *rc = to_rgu_data(rcdev);
+
+	lpc18xx_rgu_assert(rcdev, id);
+	udelay(rc->delay_us);
+
+	switch (id) {
+	case LPC43XX_RGU_M0SUB_RST:
+	case LPC43XX_RGU_M0APP_RST:
+		lpc18xx_rgu_setclear_reset(rcdev, id, false);
+	}
+
+	return 0;
+}
+
+static int lpc18xx_rgu_status(struct reset_controller_dev *rcdev,
+			      unsigned long id)
+{
+	struct lpc18xx_rgu_data *rc = to_rgu_data(rcdev);
+	u32 bit, offset = LPC18XX_RGU_ACTIVE_STATUS0;
+
+	offset += (id / LPC18XX_RGU_RESETS_PER_REG) * sizeof(u32);
+	bit = 1 << (id % LPC18XX_RGU_RESETS_PER_REG);
+
+	return !(readl(rc->base + offset) & bit);
+}
+
+static struct reset_control_ops lpc18xx_rgu_ops = {
+	.reset		= lpc18xx_rgu_reset,
+	.assert		= lpc18xx_rgu_assert,
+	.deassert	= lpc18xx_rgu_deassert,
+	.status		= lpc18xx_rgu_status,
+};
+
+static int lpc18xx_rgu_probe(struct platform_device *pdev)
+{
+	struct lpc18xx_rgu_data *rc;
+	struct resource *res;
+	u32 fcclk, firc;
+	int ret;
+
+	rc = devm_kzalloc(&pdev->dev, sizeof(*rc), GFP_KERNEL);
+	if (!rc)
+		return -ENOMEM;
+
+	res = platform_get_resource(pdev, IORESOURCE_MEM, 0);
+	rc->base = devm_ioremap_resource(&pdev->dev, res);
+	if (IS_ERR(rc->base))
+		return PTR_ERR(rc->base);
+
+	rc->clk_reg = devm_clk_get(&pdev->dev, "reg");
+	if (IS_ERR(rc->clk_reg)) {
+		dev_err(&pdev->dev, "reg clock not found\n");
+		return PTR_ERR(rc->clk_reg);
+	}
+
+	rc->clk_delay = devm_clk_get(&pdev->dev, "delay");
+	if (IS_ERR(rc->clk_delay)) {
+		dev_err(&pdev->dev, "delay clock not found\n");
+		return PTR_ERR(rc->clk_delay);
+	}
+
+	ret = clk_prepare_enable(rc->clk_reg);
+	if (ret) {
+		dev_err(&pdev->dev, "unable to enable reg clock\n");
+		return ret;
+	}
+
+	ret = clk_prepare_enable(rc->clk_delay);
+	if (ret) {
+		dev_err(&pdev->dev, "unable to enable delay clock\n");
+		goto dis_clk_reg;
+	}
+
+	fcclk = clk_get_rate(rc->clk_reg) / USEC_PER_SEC;
+	firc = clk_get_rate(rc->clk_delay) / USEC_PER_SEC;
+	if (fcclk == 0 || firc == 0)
+		rc->delay_us = 2;
+	else
+		rc->delay_us = DIV_ROUND_UP(fcclk, firc * firc);
+
+	spin_lock_init(&rc->lock);
+
+	rc->rcdev.owner = THIS_MODULE;
+	rc->rcdev.nr_resets = 64;
+	rc->rcdev.ops = &lpc18xx_rgu_ops;
+	rc->rcdev.of_node = pdev->dev.of_node;
+
+	platform_set_drvdata(pdev, rc);
+
+	ret = reset_controller_register(&rc->rcdev);
+	if (ret) {
+		dev_err(&pdev->dev, "unable to register device\n");
+		goto dis_clks;
+	}
+
+	rgu_base = rc->base;
+	ret = register_restart_handler(&lpc18xx_rgu_restart_nb);
+	if (ret)
+		dev_warn(&pdev->dev, "failed to register restart handler\n");
+
+	return 0;
+
+dis_clks:
+	clk_disable_unprepare(rc->clk_delay);
+dis_clk_reg:
+	clk_disable_unprepare(rc->clk_reg);
+
+	return ret;
+}
+
+static int lpc18xx_rgu_remove(struct platform_device *pdev)
+{
+	struct lpc18xx_rgu_data *rc = platform_get_drvdata(pdev);
+	int ret;
+
+	ret = unregister_restart_handler(&lpc18xx_rgu_restart_nb);
+	if (ret)
+		dev_warn(&pdev->dev, "failed to unregister restart handler\n");
+
+	reset_controller_unregister(&rc->rcdev);
+
+	clk_disable_unprepare(rc->clk_delay);
+	clk_disable_unprepare(rc->clk_reg);
+
+	return 0;
+}
+
+static const struct of_device_id lpc18xx_rgu_match[] = {
+	{ .compatible = "nxp,lpc1850-rgu" },
+	{ }
+};
+MODULE_DEVICE_TABLE(of, lpc18xx_rgu_match);
+
+static struct platform_driver lpc18xx_rgu_driver = {
+	.probe	= lpc18xx_rgu_probe,
+	.remove	= lpc18xx_rgu_remove,
+	.driver	= {
+		.name		= "lpc18xx-reset",
+		.of_match_table	= lpc18xx_rgu_match,
+	},
+};
+module_platform_driver(lpc18xx_rgu_driver);
+
+MODULE_AUTHOR("Joachim Eastwood <manabian@gmail.com>");
+MODULE_DESCRIPTION("Reset driver for LPC18xx/43xx RGU");
+MODULE_LICENSE("GPL v2");