1// SPDX-License-Identifier: GPL-2.0-only
2/*
3 * Imagination Technologies PowerDown Controller Watchdog Timer.
4 *
5 * Copyright (c) 2014 Imagination Technologies Ltd.
6 *
7 * Based on drivers/watchdog/sunxi_wdt.c Copyright (c) 2013 Carlo Caione
8 *                                                     2012 Henrik Nordstrom
9 *
10 * Notes
11 * -----
12 * The timeout value is rounded to the next power of two clock cycles.
13 * This is configured using the PDC_WDT_CONFIG register, according to this
14 * formula:
15 *
16 *     timeout = 2^(delay + 1) clock cycles
17 *
18 * Where 'delay' is the value written in PDC_WDT_CONFIG register.
19 *
20 * Therefore, the hardware only allows to program watchdog timeouts, expressed
21 * as a power of two number of watchdog clock cycles. The current implementation
22 * guarantees that the actual watchdog timeout will be _at least_ the value
23 * programmed in the imgpdg_wdt driver.
24 *
25 * The following table shows how the user-configured timeout relates
26 * to the actual hardware timeout (watchdog clock @ 40000 Hz):
27 *
28 * input timeout | WD_DELAY | actual timeout
29 * -----------------------------------
30 *      10       |   18     |  13 seconds
31 *      20       |   19     |  26 seconds
32 *      30       |   20     |  52 seconds
33 *      60       |   21     |  104 seconds
34 *
35 * Albeit coarse, this granularity would suffice most watchdog uses.
36 * If the platform allows it, the user should be able to change the watchdog
37 * clock rate and achieve a finer timeout granularity.
38 */
39
40#include <linux/clk.h>
41#include <linux/io.h>
42#include <linux/log2.h>
43#include <linux/module.h>
44#include <linux/mod_devicetable.h>
45#include <linux/platform_device.h>
46#include <linux/slab.h>
47#include <linux/watchdog.h>
48
49/* registers */
50#define PDC_WDT_SOFT_RESET		0x00
51#define PDC_WDT_CONFIG			0x04
52  #define PDC_WDT_CONFIG_ENABLE		BIT(31)
53  #define PDC_WDT_CONFIG_DELAY_MASK	0x1f
54
55#define PDC_WDT_TICKLE1			0x08
56#define PDC_WDT_TICKLE1_MAGIC		0xabcd1234
57#define PDC_WDT_TICKLE2			0x0c
58#define PDC_WDT_TICKLE2_MAGIC		0x4321dcba
59
60#define PDC_WDT_TICKLE_STATUS_MASK	0x7
61#define PDC_WDT_TICKLE_STATUS_SHIFT	0
62#define PDC_WDT_TICKLE_STATUS_HRESET	0x0  /* Hard reset */
63#define PDC_WDT_TICKLE_STATUS_TIMEOUT	0x1  /* Timeout */
64#define PDC_WDT_TICKLE_STATUS_TICKLE	0x2  /* Tickled incorrectly */
65#define PDC_WDT_TICKLE_STATUS_SRESET	0x3  /* Soft reset */
66#define PDC_WDT_TICKLE_STATUS_USER	0x4  /* User reset */
67
68/* Timeout values are in seconds */
69#define PDC_WDT_MIN_TIMEOUT		1
70#define PDC_WDT_DEF_TIMEOUT		64
71
72static int heartbeat;
73module_param(heartbeat, int, 0);
74MODULE_PARM_DESC(heartbeat, "Watchdog heartbeats in seconds "
75	"(default=" __MODULE_STRING(PDC_WDT_DEF_TIMEOUT) ")");
76
77static bool nowayout = WATCHDOG_NOWAYOUT;
78module_param(nowayout, bool, 0);
79MODULE_PARM_DESC(nowayout, "Watchdog cannot be stopped once started "
80	"(default=" __MODULE_STRING(WATCHDOG_NOWAYOUT) ")");
81
82struct pdc_wdt_dev {
83	struct watchdog_device wdt_dev;
84	struct clk *wdt_clk;
85	struct clk *sys_clk;
86	void __iomem *base;
87};
88
89static int pdc_wdt_keepalive(struct watchdog_device *wdt_dev)
90{
91	struct pdc_wdt_dev *wdt = watchdog_get_drvdata(wdt_dev);
92
93	writel(PDC_WDT_TICKLE1_MAGIC, wdt->base + PDC_WDT_TICKLE1);
94	writel(PDC_WDT_TICKLE2_MAGIC, wdt->base + PDC_WDT_TICKLE2);
95
96	return 0;
97}
98
99static int pdc_wdt_stop(struct watchdog_device *wdt_dev)
100{
101	unsigned int val;
102	struct pdc_wdt_dev *wdt = watchdog_get_drvdata(wdt_dev);
103
104	val = readl(wdt->base + PDC_WDT_CONFIG);
105	val &= ~PDC_WDT_CONFIG_ENABLE;
106	writel(val, wdt->base + PDC_WDT_CONFIG);
107
108	/* Must tickle to finish the stop */
109	pdc_wdt_keepalive(wdt_dev);
110
111	return 0;
112}
113
114static void __pdc_wdt_set_timeout(struct pdc_wdt_dev *wdt)
115{
116	unsigned long clk_rate = clk_get_rate(wdt->wdt_clk);
117	unsigned int val;
118
119	val = readl(wdt->base + PDC_WDT_CONFIG) & ~PDC_WDT_CONFIG_DELAY_MASK;
120	val |= order_base_2(wdt->wdt_dev.timeout * clk_rate) - 1;
121	writel(val, wdt->base + PDC_WDT_CONFIG);
122}
123
124static int pdc_wdt_set_timeout(struct watchdog_device *wdt_dev,
125			       unsigned int new_timeout)
126{
127	struct pdc_wdt_dev *wdt = watchdog_get_drvdata(wdt_dev);
128
129	wdt->wdt_dev.timeout = new_timeout;
130
131	__pdc_wdt_set_timeout(wdt);
132
133	return 0;
134}
135
136/* Start the watchdog timer (delay should already be set) */
137static int pdc_wdt_start(struct watchdog_device *wdt_dev)
138{
139	unsigned int val;
140	struct pdc_wdt_dev *wdt = watchdog_get_drvdata(wdt_dev);
141
142	__pdc_wdt_set_timeout(wdt);
143
144	val = readl(wdt->base + PDC_WDT_CONFIG);
145	val |= PDC_WDT_CONFIG_ENABLE;
146	writel(val, wdt->base + PDC_WDT_CONFIG);
147
148	return 0;
149}
150
151static int pdc_wdt_restart(struct watchdog_device *wdt_dev,
152			   unsigned long action, void *data)
153{
154	struct pdc_wdt_dev *wdt = watchdog_get_drvdata(wdt_dev);
155
156	/* Assert SOFT_RESET */
157	writel(0x1, wdt->base + PDC_WDT_SOFT_RESET);
158
159	return 0;
160}
161
162static const struct watchdog_info pdc_wdt_info = {
163	.identity	= "IMG PDC Watchdog",
164	.options	= WDIOF_SETTIMEOUT |
165			  WDIOF_KEEPALIVEPING |
166			  WDIOF_MAGICCLOSE,
167};
168
169static const struct watchdog_ops pdc_wdt_ops = {
170	.owner		= THIS_MODULE,
171	.start		= pdc_wdt_start,
172	.stop		= pdc_wdt_stop,
173	.ping		= pdc_wdt_keepalive,
174	.set_timeout	= pdc_wdt_set_timeout,
175	.restart        = pdc_wdt_restart,
176};
177
178static void pdc_clk_disable_unprepare(void *data)
179{
180	clk_disable_unprepare(data);
181}
182
183static int pdc_wdt_probe(struct platform_device *pdev)
184{
185	struct device *dev = &pdev->dev;
186	u64 div;
187	int ret, val;
188	unsigned long clk_rate;
189	struct pdc_wdt_dev *pdc_wdt;
190
191	pdc_wdt = devm_kzalloc(dev, sizeof(*pdc_wdt), GFP_KERNEL);
192	if (!pdc_wdt)
193		return -ENOMEM;
194
195	pdc_wdt->base = devm_platform_ioremap_resource(pdev, 0);
196	if (IS_ERR(pdc_wdt->base))
197		return PTR_ERR(pdc_wdt->base);
198
199	pdc_wdt->sys_clk = devm_clk_get(dev, "sys");
200	if (IS_ERR(pdc_wdt->sys_clk)) {
201		dev_err(dev, "failed to get the sys clock\n");
202		return PTR_ERR(pdc_wdt->sys_clk);
203	}
204
205	pdc_wdt->wdt_clk = devm_clk_get(dev, "wdt");
206	if (IS_ERR(pdc_wdt->wdt_clk)) {
207		dev_err(dev, "failed to get the wdt clock\n");
208		return PTR_ERR(pdc_wdt->wdt_clk);
209	}
210
211	ret = clk_prepare_enable(pdc_wdt->sys_clk);
212	if (ret) {
213		dev_err(dev, "could not prepare or enable sys clock\n");
214		return ret;
215	}
216	ret = devm_add_action_or_reset(dev, pdc_clk_disable_unprepare,
217				       pdc_wdt->sys_clk);
218	if (ret)
219		return ret;
220
221	ret = clk_prepare_enable(pdc_wdt->wdt_clk);
222	if (ret) {
223		dev_err(dev, "could not prepare or enable wdt clock\n");
224		return ret;
225	}
226	ret = devm_add_action_or_reset(dev, pdc_clk_disable_unprepare,
227				       pdc_wdt->wdt_clk);
228	if (ret)
229		return ret;
230
231	/* We use the clock rate to calculate the max timeout */
232	clk_rate = clk_get_rate(pdc_wdt->wdt_clk);
233	if (clk_rate == 0) {
234		dev_err(dev, "failed to get clock rate\n");
235		return -EINVAL;
236	}
237
238	if (order_base_2(clk_rate) > PDC_WDT_CONFIG_DELAY_MASK + 1) {
239		dev_err(dev, "invalid clock rate\n");
240		return -EINVAL;
241	}
242
243	if (order_base_2(clk_rate) == 0)
244		pdc_wdt->wdt_dev.min_timeout = PDC_WDT_MIN_TIMEOUT + 1;
245	else
246		pdc_wdt->wdt_dev.min_timeout = PDC_WDT_MIN_TIMEOUT;
247
248	pdc_wdt->wdt_dev.info = &pdc_wdt_info;
249	pdc_wdt->wdt_dev.ops = &pdc_wdt_ops;
250
251	div = 1ULL << (PDC_WDT_CONFIG_DELAY_MASK + 1);
252	do_div(div, clk_rate);
253	pdc_wdt->wdt_dev.max_timeout = div;
254	pdc_wdt->wdt_dev.timeout = PDC_WDT_DEF_TIMEOUT;
255	pdc_wdt->wdt_dev.parent = dev;
256	watchdog_set_drvdata(&pdc_wdt->wdt_dev, pdc_wdt);
257
258	watchdog_init_timeout(&pdc_wdt->wdt_dev, heartbeat, dev);
259
260	pdc_wdt_stop(&pdc_wdt->wdt_dev);
261
262	/* Find what caused the last reset */
263	val = readl(pdc_wdt->base + PDC_WDT_TICKLE1);
264	val = (val & PDC_WDT_TICKLE_STATUS_MASK) >> PDC_WDT_TICKLE_STATUS_SHIFT;
265	switch (val) {
266	case PDC_WDT_TICKLE_STATUS_TICKLE:
267	case PDC_WDT_TICKLE_STATUS_TIMEOUT:
268		pdc_wdt->wdt_dev.bootstatus |= WDIOF_CARDRESET;
269		dev_info(dev, "watchdog module last reset due to timeout\n");
270		break;
271	case PDC_WDT_TICKLE_STATUS_HRESET:
272		dev_info(dev,
273			 "watchdog module last reset due to hard reset\n");
274		break;
275	case PDC_WDT_TICKLE_STATUS_SRESET:
276		dev_info(dev,
277			 "watchdog module last reset due to soft reset\n");
278		break;
279	case PDC_WDT_TICKLE_STATUS_USER:
280		dev_info(dev,
281			 "watchdog module last reset due to user reset\n");
282		break;
283	default:
284		dev_info(dev, "contains an illegal status code (%08x)\n", val);
285		break;
286	}
287
288	watchdog_set_nowayout(&pdc_wdt->wdt_dev, nowayout);
289	watchdog_set_restart_priority(&pdc_wdt->wdt_dev, 128);
290
291	platform_set_drvdata(pdev, pdc_wdt);
292
293	watchdog_stop_on_reboot(&pdc_wdt->wdt_dev);
294	watchdog_stop_on_unregister(&pdc_wdt->wdt_dev);
295	return devm_watchdog_register_device(dev, &pdc_wdt->wdt_dev);
296}
297
298static const struct of_device_id pdc_wdt_match[] = {
299	{ .compatible = "img,pdc-wdt" },
300	{}
301};
302MODULE_DEVICE_TABLE(of, pdc_wdt_match);
303
304static struct platform_driver pdc_wdt_driver = {
305	.driver = {
306		.name = "imgpdc-wdt",
307		.of_match_table	= pdc_wdt_match,
308	},
309	.probe = pdc_wdt_probe,
310};
311module_platform_driver(pdc_wdt_driver);
312
313MODULE_AUTHOR("Jude Abraham <Jude.Abraham@imgtec.com>");
314MODULE_AUTHOR("Naidu Tellapati <Naidu.Tellapati@imgtec.com>");
315MODULE_DESCRIPTION("Imagination Technologies PDC Watchdog Timer Driver");
316MODULE_LICENSE("GPL v2");
317