1/*
2 * An RTC driver for the NVIDIA Tegra 200 series internal RTC.
3 *
4 * Copyright (c) 2010, NVIDIA Corporation.
5 *
6 * This program is free software; you can redistribute it and/or modify
7 * it under the terms of the GNU General Public License as published by
8 * the Free Software Foundation; either version 2 of the License, or
9 * (at your option) any later version.
10 *
11 * This program is distributed in the hope that it will be useful, but WITHOUT
12 * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
13 * FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General Public License for
14 * more details.
15 *
16 * You should have received a copy of the GNU General Public License along
17 * with this program; if not, write to the Free Software Foundation, Inc.,
18 * 51 Franklin Street, Fifth Floor, Boston, MA  02110-1301, USA.
19 */
20#include <linux/kernel.h>
21#include <linux/init.h>
22#include <linux/module.h>
23#include <linux/slab.h>
24#include <linux/irq.h>
25#include <linux/io.h>
26#include <linux/delay.h>
27#include <linux/rtc.h>
28#include <linux/platform_device.h>
29#include <linux/pm.h>
30
31/* set to 1 = busy every eight 32kHz clocks during copy of sec+msec to AHB */
32#define TEGRA_RTC_REG_BUSY			0x004
33#define TEGRA_RTC_REG_SECONDS			0x008
34/* when msec is read, the seconds are buffered into shadow seconds. */
35#define TEGRA_RTC_REG_SHADOW_SECONDS		0x00c
36#define TEGRA_RTC_REG_MILLI_SECONDS		0x010
37#define TEGRA_RTC_REG_SECONDS_ALARM0		0x014
38#define TEGRA_RTC_REG_SECONDS_ALARM1		0x018
39#define TEGRA_RTC_REG_MILLI_SECONDS_ALARM0	0x01c
40#define TEGRA_RTC_REG_INTR_MASK			0x028
41/* write 1 bits to clear status bits */
42#define TEGRA_RTC_REG_INTR_STATUS		0x02c
43
44/* bits in INTR_MASK */
45#define TEGRA_RTC_INTR_MASK_MSEC_CDN_ALARM	(1<<4)
46#define TEGRA_RTC_INTR_MASK_SEC_CDN_ALARM	(1<<3)
47#define TEGRA_RTC_INTR_MASK_MSEC_ALARM		(1<<2)
48#define TEGRA_RTC_INTR_MASK_SEC_ALARM1		(1<<1)
49#define TEGRA_RTC_INTR_MASK_SEC_ALARM0		(1<<0)
50
51/* bits in INTR_STATUS */
52#define TEGRA_RTC_INTR_STATUS_MSEC_CDN_ALARM	(1<<4)
53#define TEGRA_RTC_INTR_STATUS_SEC_CDN_ALARM	(1<<3)
54#define TEGRA_RTC_INTR_STATUS_MSEC_ALARM	(1<<2)
55#define TEGRA_RTC_INTR_STATUS_SEC_ALARM1	(1<<1)
56#define TEGRA_RTC_INTR_STATUS_SEC_ALARM0	(1<<0)
57
58struct tegra_rtc_info {
59	struct platform_device	*pdev;
60	struct rtc_device	*rtc_dev;
61	void __iomem		*rtc_base; /* NULL if not initialized. */
62	int			tegra_rtc_irq; /* alarm and periodic irq */
63	spinlock_t		tegra_rtc_lock;
64};
65
66/* RTC hardware is busy when it is updating its values over AHB once
67 * every eight 32kHz clocks (~250uS).
68 * outside of these updates the CPU is free to write.
69 * CPU is always free to read.
70 */
71static inline u32 tegra_rtc_check_busy(struct tegra_rtc_info *info)
72{
73	return readl(info->rtc_base + TEGRA_RTC_REG_BUSY) & 1;
74}
75
76/* Wait for hardware to be ready for writing.
77 * This function tries to maximize the amount of time before the next update.
78 * It does this by waiting for the RTC to become busy with its periodic update,
79 * then returning once the RTC first becomes not busy.
80 * This periodic update (where the seconds and milliseconds are copied to the
81 * AHB side) occurs every eight 32kHz clocks (~250uS).
82 * The behavior of this function allows us to make some assumptions without
83 * introducing a race, because 250uS is plenty of time to read/write a value.
84 */
85static int tegra_rtc_wait_while_busy(struct device *dev)
86{
87	struct tegra_rtc_info *info = dev_get_drvdata(dev);
88
89	int retries = 500; /* ~490 us is the worst case, ~250 us is best. */
90
91	/* first wait for the RTC to become busy. this is when it
92	 * posts its updated seconds+msec registers to AHB side. */
93	while (tegra_rtc_check_busy(info)) {
94		if (!retries--)
95			goto retry_failed;
96		udelay(1);
97	}
98
99	/* now we have about 250 us to manipulate registers */
100	return 0;
101
102retry_failed:
103	dev_err(dev, "write failed:retry count exceeded.\n");
104	return -ETIMEDOUT;
105}
106
107static int tegra_rtc_read_time(struct device *dev, struct rtc_time *tm)
108{
109	struct tegra_rtc_info *info = dev_get_drvdata(dev);
110	unsigned long sec, msec;
111	unsigned long sl_irq_flags;
112
113	/* RTC hardware copies seconds to shadow seconds when a read
114	 * of milliseconds occurs. use a lock to keep other threads out. */
115	spin_lock_irqsave(&info->tegra_rtc_lock, sl_irq_flags);
116
117	msec = readl(info->rtc_base + TEGRA_RTC_REG_MILLI_SECONDS);
118	sec = readl(info->rtc_base + TEGRA_RTC_REG_SHADOW_SECONDS);
119
120	spin_unlock_irqrestore(&info->tegra_rtc_lock, sl_irq_flags);
121
122	rtc_time_to_tm(sec, tm);
123
124	dev_vdbg(dev, "time read as %lu. %d/%d/%d %d:%02u:%02u\n",
125		sec,
126		tm->tm_mon + 1,
127		tm->tm_mday,
128		tm->tm_year + 1900,
129		tm->tm_hour,
130		tm->tm_min,
131		tm->tm_sec
132	);
133
134	return 0;
135}
136
137static int tegra_rtc_set_time(struct device *dev, struct rtc_time *tm)
138{
139	struct tegra_rtc_info *info = dev_get_drvdata(dev);
140	unsigned long sec;
141	int ret;
142
143	/* convert tm to seconds. */
144	ret = rtc_valid_tm(tm);
145	if (ret)
146		return ret;
147
148	rtc_tm_to_time(tm, &sec);
149
150	dev_vdbg(dev, "time set to %lu. %d/%d/%d %d:%02u:%02u\n",
151		sec,
152		tm->tm_mon+1,
153		tm->tm_mday,
154		tm->tm_year+1900,
155		tm->tm_hour,
156		tm->tm_min,
157		tm->tm_sec
158	);
159
160	/* seconds only written if wait succeeded. */
161	ret = tegra_rtc_wait_while_busy(dev);
162	if (!ret)
163		writel(sec, info->rtc_base + TEGRA_RTC_REG_SECONDS);
164
165	dev_vdbg(dev, "time read back as %d\n",
166		readl(info->rtc_base + TEGRA_RTC_REG_SECONDS));
167
168	return ret;
169}
170
171static int tegra_rtc_read_alarm(struct device *dev, struct rtc_wkalrm *alarm)
172{
173	struct tegra_rtc_info *info = dev_get_drvdata(dev);
174	unsigned long sec;
175	unsigned tmp;
176
177	sec = readl(info->rtc_base + TEGRA_RTC_REG_SECONDS_ALARM0);
178
179	if (sec == 0) {
180		/* alarm is disabled. */
181		alarm->enabled = 0;
182		alarm->time.tm_mon = -1;
183		alarm->time.tm_mday = -1;
184		alarm->time.tm_year = -1;
185		alarm->time.tm_hour = -1;
186		alarm->time.tm_min = -1;
187		alarm->time.tm_sec = -1;
188	} else {
189		/* alarm is enabled. */
190		alarm->enabled = 1;
191		rtc_time_to_tm(sec, &alarm->time);
192	}
193
194	tmp = readl(info->rtc_base + TEGRA_RTC_REG_INTR_STATUS);
195	alarm->pending = (tmp & TEGRA_RTC_INTR_STATUS_SEC_ALARM0) != 0;
196
197	return 0;
198}
199
200static int tegra_rtc_alarm_irq_enable(struct device *dev, unsigned int enabled)
201{
202	struct tegra_rtc_info *info = dev_get_drvdata(dev);
203	unsigned status;
204	unsigned long sl_irq_flags;
205
206	tegra_rtc_wait_while_busy(dev);
207	spin_lock_irqsave(&info->tegra_rtc_lock, sl_irq_flags);
208
209	/* read the original value, and OR in the flag. */
210	status = readl(info->rtc_base + TEGRA_RTC_REG_INTR_MASK);
211	if (enabled)
212		status |= TEGRA_RTC_INTR_MASK_SEC_ALARM0; /* set it */
213	else
214		status &= ~TEGRA_RTC_INTR_MASK_SEC_ALARM0; /* clear it */
215
216	writel(status, info->rtc_base + TEGRA_RTC_REG_INTR_MASK);
217
218	spin_unlock_irqrestore(&info->tegra_rtc_lock, sl_irq_flags);
219
220	return 0;
221}
222
223static int tegra_rtc_set_alarm(struct device *dev, struct rtc_wkalrm *alarm)
224{
225	struct tegra_rtc_info *info = dev_get_drvdata(dev);
226	unsigned long sec;
227
228	if (alarm->enabled)
229		rtc_tm_to_time(&alarm->time, &sec);
230	else
231		sec = 0;
232
233	tegra_rtc_wait_while_busy(dev);
234	writel(sec, info->rtc_base + TEGRA_RTC_REG_SECONDS_ALARM0);
235	dev_vdbg(dev, "alarm read back as %d\n",
236		readl(info->rtc_base + TEGRA_RTC_REG_SECONDS_ALARM0));
237
238	/* if successfully written and alarm is enabled ... */
239	if (sec) {
240		tegra_rtc_alarm_irq_enable(dev, 1);
241
242		dev_vdbg(dev, "alarm set as %lu. %d/%d/%d %d:%02u:%02u\n",
243			sec,
244			alarm->time.tm_mon+1,
245			alarm->time.tm_mday,
246			alarm->time.tm_year+1900,
247			alarm->time.tm_hour,
248			alarm->time.tm_min,
249			alarm->time.tm_sec);
250	} else {
251		/* disable alarm if 0 or write error. */
252		dev_vdbg(dev, "alarm disabled\n");
253		tegra_rtc_alarm_irq_enable(dev, 0);
254	}
255
256	return 0;
257}
258
259static int tegra_rtc_proc(struct device *dev, struct seq_file *seq)
260{
261	if (!dev || !dev->driver)
262		return 0;
263
264	seq_printf(seq, "name\t\t: %s\n", dev_name(dev));
265
266	return 0;
267}
268
269static irqreturn_t tegra_rtc_irq_handler(int irq, void *data)
270{
271	struct device *dev = data;
272	struct tegra_rtc_info *info = dev_get_drvdata(dev);
273	unsigned long events = 0;
274	unsigned status;
275	unsigned long sl_irq_flags;
276
277	status = readl(info->rtc_base + TEGRA_RTC_REG_INTR_STATUS);
278	if (status) {
279		/* clear the interrupt masks and status on any irq. */
280		tegra_rtc_wait_while_busy(dev);
281		spin_lock_irqsave(&info->tegra_rtc_lock, sl_irq_flags);
282		writel(0, info->rtc_base + TEGRA_RTC_REG_INTR_MASK);
283		writel(status, info->rtc_base + TEGRA_RTC_REG_INTR_STATUS);
284		spin_unlock_irqrestore(&info->tegra_rtc_lock, sl_irq_flags);
285	}
286
287	/* check if Alarm */
288	if ((status & TEGRA_RTC_INTR_STATUS_SEC_ALARM0))
289		events |= RTC_IRQF | RTC_AF;
290
291	/* check if Periodic */
292	if ((status & TEGRA_RTC_INTR_STATUS_SEC_CDN_ALARM))
293		events |= RTC_IRQF | RTC_PF;
294
295	rtc_update_irq(info->rtc_dev, 1, events);
296
297	return IRQ_HANDLED;
298}
299
300static struct rtc_class_ops tegra_rtc_ops = {
301	.read_time	= tegra_rtc_read_time,
302	.set_time	= tegra_rtc_set_time,
303	.read_alarm	= tegra_rtc_read_alarm,
304	.set_alarm	= tegra_rtc_set_alarm,
305	.proc		= tegra_rtc_proc,
306	.alarm_irq_enable = tegra_rtc_alarm_irq_enable,
307};
308
309static const struct of_device_id tegra_rtc_dt_match[] = {
310	{ .compatible = "nvidia,tegra20-rtc", },
311	{}
312};
313MODULE_DEVICE_TABLE(of, tegra_rtc_dt_match);
314
315static int __init tegra_rtc_probe(struct platform_device *pdev)
316{
317	struct tegra_rtc_info *info;
318	struct resource *res;
319	int ret;
320
321	info = devm_kzalloc(&pdev->dev, sizeof(struct tegra_rtc_info),
322		GFP_KERNEL);
323	if (!info)
324		return -ENOMEM;
325
326	res = platform_get_resource(pdev, IORESOURCE_MEM, 0);
327	info->rtc_base = devm_ioremap_resource(&pdev->dev, res);
328	if (IS_ERR(info->rtc_base))
329		return PTR_ERR(info->rtc_base);
330
331	info->tegra_rtc_irq = platform_get_irq(pdev, 0);
332	if (info->tegra_rtc_irq <= 0)
333		return -EBUSY;
334
335	/* set context info. */
336	info->pdev = pdev;
337	spin_lock_init(&info->tegra_rtc_lock);
338
339	platform_set_drvdata(pdev, info);
340
341	/* clear out the hardware. */
342	writel(0, info->rtc_base + TEGRA_RTC_REG_SECONDS_ALARM0);
343	writel(0xffffffff, info->rtc_base + TEGRA_RTC_REG_INTR_STATUS);
344	writel(0, info->rtc_base + TEGRA_RTC_REG_INTR_MASK);
345
346	device_init_wakeup(&pdev->dev, 1);
347
348	info->rtc_dev = devm_rtc_device_register(&pdev->dev,
349				dev_name(&pdev->dev), &tegra_rtc_ops,
350				THIS_MODULE);
351	if (IS_ERR(info->rtc_dev)) {
352		ret = PTR_ERR(info->rtc_dev);
353		dev_err(&pdev->dev, "Unable to register device (err=%d).\n",
354			ret);
355		return ret;
356	}
357
358	ret = devm_request_irq(&pdev->dev, info->tegra_rtc_irq,
359			tegra_rtc_irq_handler, IRQF_TRIGGER_HIGH,
360			dev_name(&pdev->dev), &pdev->dev);
361	if (ret) {
362		dev_err(&pdev->dev,
363			"Unable to request interrupt for device (err=%d).\n",
364			ret);
365		return ret;
366	}
367
368	dev_notice(&pdev->dev, "Tegra internal Real Time Clock\n");
369
370	return 0;
371}
372
373#ifdef CONFIG_PM_SLEEP
374static int tegra_rtc_suspend(struct device *dev)
375{
376	struct tegra_rtc_info *info = dev_get_drvdata(dev);
377
378	tegra_rtc_wait_while_busy(dev);
379
380	/* only use ALARM0 as a wake source. */
381	writel(0xffffffff, info->rtc_base + TEGRA_RTC_REG_INTR_STATUS);
382	writel(TEGRA_RTC_INTR_STATUS_SEC_ALARM0,
383		info->rtc_base + TEGRA_RTC_REG_INTR_MASK);
384
385	dev_vdbg(dev, "alarm sec = %d\n",
386		readl(info->rtc_base + TEGRA_RTC_REG_SECONDS_ALARM0));
387
388	dev_vdbg(dev, "Suspend (device_may_wakeup=%d) irq:%d\n",
389		device_may_wakeup(dev), info->tegra_rtc_irq);
390
391	/* leave the alarms on as a wake source. */
392	if (device_may_wakeup(dev))
393		enable_irq_wake(info->tegra_rtc_irq);
394
395	return 0;
396}
397
398static int tegra_rtc_resume(struct device *dev)
399{
400	struct tegra_rtc_info *info = dev_get_drvdata(dev);
401
402	dev_vdbg(dev, "Resume (device_may_wakeup=%d)\n",
403		device_may_wakeup(dev));
404	/* alarms were left on as a wake source, turn them off. */
405	if (device_may_wakeup(dev))
406		disable_irq_wake(info->tegra_rtc_irq);
407
408	return 0;
409}
410#endif
411
412static SIMPLE_DEV_PM_OPS(tegra_rtc_pm_ops, tegra_rtc_suspend, tegra_rtc_resume);
413
414static void tegra_rtc_shutdown(struct platform_device *pdev)
415{
416	dev_vdbg(&pdev->dev, "disabling interrupts.\n");
417	tegra_rtc_alarm_irq_enable(&pdev->dev, 0);
418}
419
420MODULE_ALIAS("platform:tegra_rtc");
421static struct platform_driver tegra_rtc_driver = {
422	.shutdown	= tegra_rtc_shutdown,
423	.driver		= {
424		.name	= "tegra_rtc",
425		.of_match_table = tegra_rtc_dt_match,
426		.pm	= &tegra_rtc_pm_ops,
427	},
428};
429
430module_platform_driver_probe(tegra_rtc_driver, tegra_rtc_probe);
431
432MODULE_AUTHOR("Jon Mayo <jmayo@nvidia.com>");
433MODULE_DESCRIPTION("driver for Tegra internal RTC");
434MODULE_LICENSE("GPL");
435