linux/drivers/rtc/rtc-tegra.c
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   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        return seq_printf(seq, "name\t\t: %s\n", dev_name(dev));
 265}
 266
 267static irqreturn_t tegra_rtc_irq_handler(int irq, void *data)
 268{
 269        struct device *dev = data;
 270        struct tegra_rtc_info *info = dev_get_drvdata(dev);
 271        unsigned long events = 0;
 272        unsigned status;
 273        unsigned long sl_irq_flags;
 274
 275        status = readl(info->rtc_base + TEGRA_RTC_REG_INTR_STATUS);
 276        if (status) {
 277                /* clear the interrupt masks and status on any irq. */
 278                tegra_rtc_wait_while_busy(dev);
 279                spin_lock_irqsave(&info->tegra_rtc_lock, sl_irq_flags);
 280                writel(0, info->rtc_base + TEGRA_RTC_REG_INTR_MASK);
 281                writel(status, info->rtc_base + TEGRA_RTC_REG_INTR_STATUS);
 282                spin_unlock_irqrestore(&info->tegra_rtc_lock, sl_irq_flags);
 283        }
 284
 285        /* check if Alarm */
 286        if ((status & TEGRA_RTC_INTR_STATUS_SEC_ALARM0))
 287                events |= RTC_IRQF | RTC_AF;
 288
 289        /* check if Periodic */
 290        if ((status & TEGRA_RTC_INTR_STATUS_SEC_CDN_ALARM))
 291                events |= RTC_IRQF | RTC_PF;
 292
 293        rtc_update_irq(info->rtc_dev, 1, events);
 294
 295        return IRQ_HANDLED;
 296}
 297
 298static struct rtc_class_ops tegra_rtc_ops = {
 299        .read_time      = tegra_rtc_read_time,
 300        .set_time       = tegra_rtc_set_time,
 301        .read_alarm     = tegra_rtc_read_alarm,
 302        .set_alarm      = tegra_rtc_set_alarm,
 303        .proc           = tegra_rtc_proc,
 304        .alarm_irq_enable = tegra_rtc_alarm_irq_enable,
 305};
 306
 307static const struct of_device_id tegra_rtc_dt_match[] = {
 308        { .compatible = "nvidia,tegra20-rtc", },
 309        {}
 310};
 311MODULE_DEVICE_TABLE(of, tegra_rtc_dt_match);
 312
 313static int __init tegra_rtc_probe(struct platform_device *pdev)
 314{
 315        struct tegra_rtc_info *info;
 316        struct resource *res;
 317        int ret;
 318
 319        info = devm_kzalloc(&pdev->dev, sizeof(struct tegra_rtc_info),
 320                GFP_KERNEL);
 321        if (!info)
 322                return -ENOMEM;
 323
 324        res = platform_get_resource(pdev, IORESOURCE_MEM, 0);
 325        info->rtc_base = devm_ioremap_resource(&pdev->dev, res);
 326        if (IS_ERR(info->rtc_base))
 327                return PTR_ERR(info->rtc_base);
 328
 329        info->tegra_rtc_irq = platform_get_irq(pdev, 0);
 330        if (info->tegra_rtc_irq <= 0)
 331                return -EBUSY;
 332
 333        /* set context info. */
 334        info->pdev = pdev;
 335        spin_lock_init(&info->tegra_rtc_lock);
 336
 337        platform_set_drvdata(pdev, info);
 338
 339        /* clear out the hardware. */
 340        writel(0, info->rtc_base + TEGRA_RTC_REG_SECONDS_ALARM0);
 341        writel(0xffffffff, info->rtc_base + TEGRA_RTC_REG_INTR_STATUS);
 342        writel(0, info->rtc_base + TEGRA_RTC_REG_INTR_MASK);
 343
 344        device_init_wakeup(&pdev->dev, 1);
 345
 346        info->rtc_dev = devm_rtc_device_register(&pdev->dev,
 347                                dev_name(&pdev->dev), &tegra_rtc_ops,
 348                                THIS_MODULE);
 349        if (IS_ERR(info->rtc_dev)) {
 350                ret = PTR_ERR(info->rtc_dev);
 351                dev_err(&pdev->dev, "Unable to register device (err=%d).\n",
 352                        ret);
 353                return ret;
 354        }
 355
 356        ret = devm_request_irq(&pdev->dev, info->tegra_rtc_irq,
 357                        tegra_rtc_irq_handler, IRQF_TRIGGER_HIGH,
 358                        dev_name(&pdev->dev), &pdev->dev);
 359        if (ret) {
 360                dev_err(&pdev->dev,
 361                        "Unable to request interrupt for device (err=%d).\n",
 362                        ret);
 363                return ret;
 364        }
 365
 366        dev_notice(&pdev->dev, "Tegra internal Real Time Clock\n");
 367
 368        return 0;
 369}
 370
 371#ifdef CONFIG_PM_SLEEP
 372static int tegra_rtc_suspend(struct device *dev)
 373{
 374        struct tegra_rtc_info *info = dev_get_drvdata(dev);
 375
 376        tegra_rtc_wait_while_busy(dev);
 377
 378        /* only use ALARM0 as a wake source. */
 379        writel(0xffffffff, info->rtc_base + TEGRA_RTC_REG_INTR_STATUS);
 380        writel(TEGRA_RTC_INTR_STATUS_SEC_ALARM0,
 381                info->rtc_base + TEGRA_RTC_REG_INTR_MASK);
 382
 383        dev_vdbg(dev, "alarm sec = %d\n",
 384                readl(info->rtc_base + TEGRA_RTC_REG_SECONDS_ALARM0));
 385
 386        dev_vdbg(dev, "Suspend (device_may_wakeup=%d) irq:%d\n",
 387                device_may_wakeup(dev), info->tegra_rtc_irq);
 388
 389        /* leave the alarms on as a wake source. */
 390        if (device_may_wakeup(dev))
 391                enable_irq_wake(info->tegra_rtc_irq);
 392
 393        return 0;
 394}
 395
 396static int tegra_rtc_resume(struct device *dev)
 397{
 398        struct tegra_rtc_info *info = dev_get_drvdata(dev);
 399
 400        dev_vdbg(dev, "Resume (device_may_wakeup=%d)\n",
 401                device_may_wakeup(dev));
 402        /* alarms were left on as a wake source, turn them off. */
 403        if (device_may_wakeup(dev))
 404                disable_irq_wake(info->tegra_rtc_irq);
 405
 406        return 0;
 407}
 408#endif
 409
 410static SIMPLE_DEV_PM_OPS(tegra_rtc_pm_ops, tegra_rtc_suspend, tegra_rtc_resume);
 411
 412static void tegra_rtc_shutdown(struct platform_device *pdev)
 413{
 414        dev_vdbg(&pdev->dev, "disabling interrupts.\n");
 415        tegra_rtc_alarm_irq_enable(&pdev->dev, 0);
 416}
 417
 418MODULE_ALIAS("platform:tegra_rtc");
 419static struct platform_driver tegra_rtc_driver = {
 420        .shutdown       = tegra_rtc_shutdown,
 421        .driver         = {
 422                .name   = "tegra_rtc",
 423                .owner  = THIS_MODULE,
 424                .of_match_table = tegra_rtc_dt_match,
 425                .pm     = &tegra_rtc_pm_ops,
 426        },
 427};
 428
 429module_platform_driver_probe(tegra_rtc_driver, tegra_rtc_probe);
 430
 431MODULE_AUTHOR("Jon Mayo <jmayo@nvidia.com>");
 432MODULE_DESCRIPTION("driver for Tegra internal RTC");
 433MODULE_LICENSE("GPL");
 434
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