renesas_wwdt.c

  1// SPDX-License-Identifier: GPL-2.0
  2/*
  3 * Driver for the Renesas Window Watchdog Timer (WWDT)
  4 *
  5 * The WWDT can only be setup once after boot. Because we cannot know if this
  6 * already happened in early boot stages, it is mandated that the firmware
  7 * configures the watchdog. Linux then adapts according to the given setup.
  8 * Note that this watchdog reports in the default configuration an overflow to
  9 * the Error Control Module which then decides further actions. Or the WWDT is
 10 * configured to generate an interrupt.
 11 */
 12
 13#include <linux/bitfield.h>
 14#include <linux/clk.h>
 15#include <linux/interrupt.h>
 16#include <linux/io.h>
 17#include <linux/kernel.h>
 18#include <linux/module.h>
 19#include <linux/of.h>
 20#include <linux/platform_device.h>
 21#include <linux/watchdog.h>
 22
 23#define WDTA0WDTE	0x00
 24#define WDTA0RUN	BIT(7)
 25#define WDTA0_KEY	0x2c
 26
 27#define WDTA0MD		0x0c
 28#define WDTA0OVF(x)	FIELD_GET(GENMASK(6, 4), x)
 29#define WDTA0WIE	BIT(3)
 30#define WDTA0ERM	BIT(2)
 31#define WDTA0WS(x)	FIELD_GET(GENMASK(1, 0), x)
 32
 33struct wwdt_priv {
 34	void __iomem *base;
 35	struct watchdog_device wdev;
 36};
 37
 38static int wwdt_start(struct watchdog_device *wdev)
 39{
 40	struct wwdt_priv *priv = container_of(wdev, struct wwdt_priv, wdev);
 41
 42	writeb(WDTA0RUN | WDTA0_KEY, priv->base + WDTA0WDTE);
 43	return 0;
 44}
 45
 46static const struct watchdog_info wwdt_ident = {
 47	.options = WDIOF_KEEPALIVEPING | WDIOF_ALARMONLY,
 48	.identity = "Renesas Window Watchdog",
 49};
 50
 51static const struct watchdog_ops wwdt_ops = {
 52	.owner = THIS_MODULE,
 53	.start = wwdt_start,
 54};
 55
 56static irqreturn_t wwdt_error_irq(int irq, void *dev_id)
 57{
 58	struct device *dev = dev_id;
 59
 60	dev_warn(dev, "Watchdog timed out\n");
 61	return IRQ_HANDLED;
 62}
 63
 64static irqreturn_t wwdt_pretimeout_irq(int irq, void *dev_id)
 65{
 66	struct watchdog_device *wdev = dev_id;
 67
 68	watchdog_notify_pretimeout(wdev);
 69	return IRQ_HANDLED;
 70}
 71
 72static int wwdt_probe(struct platform_device *pdev)
 73{
 74	struct device *dev = &pdev->dev;
 75	struct wwdt_priv *priv;
 76	struct watchdog_device *wdev;
 77	struct clk *clk;
 78	unsigned long rate;
 79	unsigned int interval, window_size;
 80	int ret;
 81	u8 val;
 82
 83	priv = devm_kzalloc(dev, sizeof(*priv), GFP_KERNEL);
 84	if (!priv)
 85		return -ENOMEM;
 86
 87	priv->base = devm_platform_ioremap_resource(pdev, 0);
 88	if (IS_ERR(priv->base))
 89		return PTR_ERR(priv->base);
 90
 91	clk = devm_clk_get(dev, "cnt");
 92	if (IS_ERR(clk))
 93		return PTR_ERR(clk);
 94
 95	rate = clk_get_rate(clk);
 96	if (!rate)
 97		return -EINVAL;
 98
 99	wdev = &priv->wdev;
100
101	val = readb(priv->base + WDTA0WDTE);
102	if (val & WDTA0RUN)
103		set_bit(WDOG_HW_RUNNING, &wdev->status);
104
105	val = readb(priv->base + WDTA0MD);
106	interval = 1 << (9 + WDTA0OVF(val));
107	/* size of the closed(!) window per mille */
108	window_size = 250 * (3 - WDTA0WS(val));
109
110	wdev->info = &wwdt_ident;
111	wdev->ops = &wwdt_ops;
112	wdev->parent = dev;
113	wdev->min_hw_heartbeat_ms = window_size * interval / rate;
114	wdev->max_hw_heartbeat_ms = 1000 * interval / rate;
115	wdev->timeout = DIV_ROUND_UP(wdev->max_hw_heartbeat_ms, 1000);
116	watchdog_set_nowayout(wdev, true);
117
118	if (!(val & WDTA0ERM)) {
119		ret = platform_get_irq_byname(pdev, "error");
120		if (ret < 0)
121			return ret;
122
123		ret = devm_request_threaded_irq(dev, ret, NULL, wwdt_error_irq,
124						IRQF_ONESHOT, NULL, dev);
125		if (ret < 0)
126			return ret;
127	}
128
129	if (val & WDTA0WIE) {
130		ret = platform_get_irq_byname(pdev, "pretimeout");
131		if (ret < 0)
132			return ret;
133
134		ret = devm_request_threaded_irq(dev, ret, NULL, wwdt_pretimeout_irq,
135						IRQF_ONESHOT, NULL, wdev);
136		if (ret < 0)
137			return ret;
138	}
139
140	devm_watchdog_register_device(dev, wdev);
141
142	return 0;
143}
144
145static const struct of_device_id renesas_wwdt_ids[] = {
146	{ .compatible = "renesas,rcar-gen3-wwdt", },
147	{ .compatible = "renesas,rcar-gen4-wwdt", },
148	{ /* sentinel */ }
149};
150MODULE_DEVICE_TABLE(of, renesas_wwdt_ids);
151
152static struct platform_driver renesas_wwdt_driver = {
153	.driver = {
154		.name = "renesas_wwdt",
155		.of_match_table = renesas_wwdt_ids,
156	},
157	.probe = wwdt_probe,
158};
159module_platform_driver(renesas_wwdt_driver);
160
161MODULE_DESCRIPTION("Renesas Window Watchdog (WWDT) Driver");
162MODULE_LICENSE("GPL");
163MODULE_AUTHOR("Wolfram Sang <wsa+renesas@sang-engineering.com>");