linux/drivers/rtc/rtc-imxdi.c
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   1/*
   2 * Copyright 2008-2009 Freescale Semiconductor, Inc. All Rights Reserved.
   3 * Copyright 2010 Orex Computed Radiography
   4 */
   5
   6/*
   7 * The code contained herein is licensed under the GNU General Public
   8 * License. You may obtain a copy of the GNU General Public License
   9 * Version 2 or later at the following locations:
  10 *
  11 * http://www.opensource.org/licenses/gpl-license.html
  12 * http://www.gnu.org/copyleft/gpl.html
  13 */
  14
  15/* based on rtc-mc13892.c */
  16
  17/*
  18 * This driver uses the 47-bit 32 kHz counter in the Freescale DryIce block
  19 * to implement a Linux RTC. Times and alarms are truncated to seconds.
  20 * Since the RTC framework performs API locking via rtc->ops_lock the
  21 * only simultaneous accesses we need to deal with is updating DryIce
  22 * registers while servicing an alarm.
  23 *
  24 * Note that reading the DSR (DryIce Status Register) automatically clears
  25 * the WCF (Write Complete Flag). All DryIce writes are synchronized to the
  26 * LP (Low Power) domain and set the WCF upon completion. Writes to the
  27 * DIER (DryIce Interrupt Enable Register) are the only exception. These
  28 * occur at normal bus speeds and do not set WCF.  Periodic interrupts are
  29 * not supported by the hardware.
  30 */
  31
  32#include <linux/io.h>
  33#include <linux/clk.h>
  34#include <linux/delay.h>
  35#include <linux/module.h>
  36#include <linux/platform_device.h>
  37#include <linux/rtc.h>
  38#include <linux/sched.h>
  39#include <linux/spinlock.h>
  40#include <linux/workqueue.h>
  41#include <linux/of.h>
  42
  43/* DryIce Register Definitions */
  44
  45#define DTCMR     0x00           /* Time Counter MSB Reg */
  46#define DTCLR     0x04           /* Time Counter LSB Reg */
  47
  48#define DCAMR     0x08           /* Clock Alarm MSB Reg */
  49#define DCALR     0x0c           /* Clock Alarm LSB Reg */
  50#define DCAMR_UNSET  0xFFFFFFFF  /* doomsday - 1 sec */
  51
  52#define DCR       0x10           /* Control Reg */
  53#define DCR_TCE   (1 << 3)       /* Time Counter Enable */
  54
  55#define DSR       0x14           /* Status Reg */
  56#define DSR_WBF   (1 << 10)      /* Write Busy Flag */
  57#define DSR_WNF   (1 << 9)       /* Write Next Flag */
  58#define DSR_WCF   (1 << 8)       /* Write Complete Flag */
  59#define DSR_WEF   (1 << 7)       /* Write Error Flag */
  60#define DSR_CAF   (1 << 4)       /* Clock Alarm Flag */
  61#define DSR_NVF   (1 << 1)       /* Non-Valid Flag */
  62#define DSR_SVF   (1 << 0)       /* Security Violation Flag */
  63
  64#define DIER      0x18           /* Interrupt Enable Reg */
  65#define DIER_WNIE (1 << 9)       /* Write Next Interrupt Enable */
  66#define DIER_WCIE (1 << 8)       /* Write Complete Interrupt Enable */
  67#define DIER_WEIE (1 << 7)       /* Write Error Interrupt Enable */
  68#define DIER_CAIE (1 << 4)       /* Clock Alarm Interrupt Enable */
  69
  70/**
  71 * struct imxdi_dev - private imxdi rtc data
  72 * @pdev: pionter to platform dev
  73 * @rtc: pointer to rtc struct
  74 * @ioaddr: IO registers pointer
  75 * @irq: dryice normal interrupt
  76 * @clk: input reference clock
  77 * @dsr: copy of the DSR register
  78 * @irq_lock: interrupt enable register (DIER) lock
  79 * @write_wait: registers write complete queue
  80 * @write_mutex: serialize registers write
  81 * @work: schedule alarm work
  82 */
  83struct imxdi_dev {
  84        struct platform_device *pdev;
  85        struct rtc_device *rtc;
  86        void __iomem *ioaddr;
  87        int irq;
  88        struct clk *clk;
  89        u32 dsr;
  90        spinlock_t irq_lock;
  91        wait_queue_head_t write_wait;
  92        struct mutex write_mutex;
  93        struct work_struct work;
  94};
  95
  96/*
  97 * enable a dryice interrupt
  98 */
  99static void di_int_enable(struct imxdi_dev *imxdi, u32 intr)
 100{
 101        unsigned long flags;
 102
 103        spin_lock_irqsave(&imxdi->irq_lock, flags);
 104        __raw_writel(__raw_readl(imxdi->ioaddr + DIER) | intr,
 105                        imxdi->ioaddr + DIER);
 106        spin_unlock_irqrestore(&imxdi->irq_lock, flags);
 107}
 108
 109/*
 110 * disable a dryice interrupt
 111 */
 112static void di_int_disable(struct imxdi_dev *imxdi, u32 intr)
 113{
 114        unsigned long flags;
 115
 116        spin_lock_irqsave(&imxdi->irq_lock, flags);
 117        __raw_writel(__raw_readl(imxdi->ioaddr + DIER) & ~intr,
 118                        imxdi->ioaddr + DIER);
 119        spin_unlock_irqrestore(&imxdi->irq_lock, flags);
 120}
 121
 122/*
 123 * This function attempts to clear the dryice write-error flag.
 124 *
 125 * A dryice write error is similar to a bus fault and should not occur in
 126 * normal operation.  Clearing the flag requires another write, so the root
 127 * cause of the problem may need to be fixed before the flag can be cleared.
 128 */
 129static void clear_write_error(struct imxdi_dev *imxdi)
 130{
 131        int cnt;
 132
 133        dev_warn(&imxdi->pdev->dev, "WARNING: Register write error!\n");
 134
 135        /* clear the write error flag */
 136        __raw_writel(DSR_WEF, imxdi->ioaddr + DSR);
 137
 138        /* wait for it to take effect */
 139        for (cnt = 0; cnt < 1000; cnt++) {
 140                if ((__raw_readl(imxdi->ioaddr + DSR) & DSR_WEF) == 0)
 141                        return;
 142                udelay(10);
 143        }
 144        dev_err(&imxdi->pdev->dev,
 145                        "ERROR: Cannot clear write-error flag!\n");
 146}
 147
 148/*
 149 * Write a dryice register and wait until it completes.
 150 *
 151 * This function uses interrupts to determine when the
 152 * write has completed.
 153 */
 154static int di_write_wait(struct imxdi_dev *imxdi, u32 val, int reg)
 155{
 156        int ret;
 157        int rc = 0;
 158
 159        /* serialize register writes */
 160        mutex_lock(&imxdi->write_mutex);
 161
 162        /* enable the write-complete interrupt */
 163        di_int_enable(imxdi, DIER_WCIE);
 164
 165        imxdi->dsr = 0;
 166
 167        /* do the register write */
 168        __raw_writel(val, imxdi->ioaddr + reg);
 169
 170        /* wait for the write to finish */
 171        ret = wait_event_interruptible_timeout(imxdi->write_wait,
 172                        imxdi->dsr & (DSR_WCF | DSR_WEF), msecs_to_jiffies(1));
 173        if (ret < 0) {
 174                rc = ret;
 175                goto out;
 176        } else if (ret == 0) {
 177                dev_warn(&imxdi->pdev->dev,
 178                                "Write-wait timeout "
 179                                "val = 0x%08x reg = 0x%08x\n", val, reg);
 180        }
 181
 182        /* check for write error */
 183        if (imxdi->dsr & DSR_WEF) {
 184                clear_write_error(imxdi);
 185                rc = -EIO;
 186        }
 187
 188out:
 189        mutex_unlock(&imxdi->write_mutex);
 190
 191        return rc;
 192}
 193
 194/*
 195 * read the seconds portion of the current time from the dryice time counter
 196 */
 197static int dryice_rtc_read_time(struct device *dev, struct rtc_time *tm)
 198{
 199        struct imxdi_dev *imxdi = dev_get_drvdata(dev);
 200        unsigned long now;
 201
 202        now = __raw_readl(imxdi->ioaddr + DTCMR);
 203        rtc_time_to_tm(now, tm);
 204
 205        return 0;
 206}
 207
 208/*
 209 * set the seconds portion of dryice time counter and clear the
 210 * fractional part.
 211 */
 212static int dryice_rtc_set_mmss(struct device *dev, unsigned long secs)
 213{
 214        struct imxdi_dev *imxdi = dev_get_drvdata(dev);
 215        int rc;
 216
 217        /* zero the fractional part first */
 218        rc = di_write_wait(imxdi, 0, DTCLR);
 219        if (rc == 0)
 220                rc = di_write_wait(imxdi, secs, DTCMR);
 221
 222        return rc;
 223}
 224
 225static int dryice_rtc_alarm_irq_enable(struct device *dev,
 226                unsigned int enabled)
 227{
 228        struct imxdi_dev *imxdi = dev_get_drvdata(dev);
 229
 230        if (enabled)
 231                di_int_enable(imxdi, DIER_CAIE);
 232        else
 233                di_int_disable(imxdi, DIER_CAIE);
 234
 235        return 0;
 236}
 237
 238/*
 239 * read the seconds portion of the alarm register.
 240 * the fractional part of the alarm register is always zero.
 241 */
 242static int dryice_rtc_read_alarm(struct device *dev, struct rtc_wkalrm *alarm)
 243{
 244        struct imxdi_dev *imxdi = dev_get_drvdata(dev);
 245        u32 dcamr;
 246
 247        dcamr = __raw_readl(imxdi->ioaddr + DCAMR);
 248        rtc_time_to_tm(dcamr, &alarm->time);
 249
 250        /* alarm is enabled if the interrupt is enabled */
 251        alarm->enabled = (__raw_readl(imxdi->ioaddr + DIER) & DIER_CAIE) != 0;
 252
 253        /* don't allow the DSR read to mess up DSR_WCF */
 254        mutex_lock(&imxdi->write_mutex);
 255
 256        /* alarm is pending if the alarm flag is set */
 257        alarm->pending = (__raw_readl(imxdi->ioaddr + DSR) & DSR_CAF) != 0;
 258
 259        mutex_unlock(&imxdi->write_mutex);
 260
 261        return 0;
 262}
 263
 264/*
 265 * set the seconds portion of dryice alarm register
 266 */
 267static int dryice_rtc_set_alarm(struct device *dev, struct rtc_wkalrm *alarm)
 268{
 269        struct imxdi_dev *imxdi = dev_get_drvdata(dev);
 270        unsigned long now;
 271        unsigned long alarm_time;
 272        int rc;
 273
 274        rc = rtc_tm_to_time(&alarm->time, &alarm_time);
 275        if (rc)
 276                return rc;
 277
 278        /* don't allow setting alarm in the past */
 279        now = __raw_readl(imxdi->ioaddr + DTCMR);
 280        if (alarm_time < now)
 281                return -EINVAL;
 282
 283        /* write the new alarm time */
 284        rc = di_write_wait(imxdi, (u32)alarm_time, DCAMR);
 285        if (rc)
 286                return rc;
 287
 288        if (alarm->enabled)
 289                di_int_enable(imxdi, DIER_CAIE);  /* enable alarm intr */
 290        else
 291                di_int_disable(imxdi, DIER_CAIE); /* disable alarm intr */
 292
 293        return 0;
 294}
 295
 296static struct rtc_class_ops dryice_rtc_ops = {
 297        .read_time              = dryice_rtc_read_time,
 298        .set_mmss               = dryice_rtc_set_mmss,
 299        .alarm_irq_enable       = dryice_rtc_alarm_irq_enable,
 300        .read_alarm             = dryice_rtc_read_alarm,
 301        .set_alarm              = dryice_rtc_set_alarm,
 302};
 303
 304/*
 305 * dryice "normal" interrupt handler
 306 */
 307static irqreturn_t dryice_norm_irq(int irq, void *dev_id)
 308{
 309        struct imxdi_dev *imxdi = dev_id;
 310        u32 dsr, dier;
 311        irqreturn_t rc = IRQ_NONE;
 312
 313        dier = __raw_readl(imxdi->ioaddr + DIER);
 314
 315        /* handle write complete and write error cases */
 316        if ((dier & DIER_WCIE)) {
 317                /*If the write wait queue is empty then there is no pending
 318                  operations. It means the interrupt is for DryIce -Security.
 319                  IRQ must be returned as none.*/
 320                if (list_empty_careful(&imxdi->write_wait.task_list))
 321                        return rc;
 322
 323                /* DSR_WCF clears itself on DSR read */
 324                dsr = __raw_readl(imxdi->ioaddr + DSR);
 325                if ((dsr & (DSR_WCF | DSR_WEF))) {
 326                        /* mask the interrupt */
 327                        di_int_disable(imxdi, DIER_WCIE);
 328
 329                        /* save the dsr value for the wait queue */
 330                        imxdi->dsr |= dsr;
 331
 332                        wake_up_interruptible(&imxdi->write_wait);
 333                        rc = IRQ_HANDLED;
 334                }
 335        }
 336
 337        /* handle the alarm case */
 338        if ((dier & DIER_CAIE)) {
 339                /* DSR_WCF clears itself on DSR read */
 340                dsr = __raw_readl(imxdi->ioaddr + DSR);
 341                if (dsr & DSR_CAF) {
 342                        /* mask the interrupt */
 343                        di_int_disable(imxdi, DIER_CAIE);
 344
 345                        /* finish alarm in user context */
 346                        schedule_work(&imxdi->work);
 347                        rc = IRQ_HANDLED;
 348                }
 349        }
 350        return rc;
 351}
 352
 353/*
 354 * post the alarm event from user context so it can sleep
 355 * on the write completion.
 356 */
 357static void dryice_work(struct work_struct *work)
 358{
 359        struct imxdi_dev *imxdi = container_of(work,
 360                        struct imxdi_dev, work);
 361
 362        /* dismiss the interrupt (ignore error) */
 363        di_write_wait(imxdi, DSR_CAF, DSR);
 364
 365        /* pass the alarm event to the rtc framework. */
 366        rtc_update_irq(imxdi->rtc, 1, RTC_AF | RTC_IRQF);
 367}
 368
 369/*
 370 * probe for dryice rtc device
 371 */
 372static int __init dryice_rtc_probe(struct platform_device *pdev)
 373{
 374        struct resource *res;
 375        struct imxdi_dev *imxdi;
 376        int rc;
 377
 378        imxdi = devm_kzalloc(&pdev->dev, sizeof(*imxdi), GFP_KERNEL);
 379        if (!imxdi)
 380                return -ENOMEM;
 381
 382        imxdi->pdev = pdev;
 383
 384        res = platform_get_resource(pdev, IORESOURCE_MEM, 0);
 385        imxdi->ioaddr = devm_ioremap_resource(&pdev->dev, res);
 386        if (IS_ERR(imxdi->ioaddr))
 387                return PTR_ERR(imxdi->ioaddr);
 388
 389        spin_lock_init(&imxdi->irq_lock);
 390
 391        imxdi->irq = platform_get_irq(pdev, 0);
 392        if (imxdi->irq < 0)
 393                return imxdi->irq;
 394
 395        init_waitqueue_head(&imxdi->write_wait);
 396
 397        INIT_WORK(&imxdi->work, dryice_work);
 398
 399        mutex_init(&imxdi->write_mutex);
 400
 401        imxdi->clk = devm_clk_get(&pdev->dev, NULL);
 402        if (IS_ERR(imxdi->clk))
 403                return PTR_ERR(imxdi->clk);
 404        clk_prepare_enable(imxdi->clk);
 405
 406        /*
 407         * Initialize dryice hardware
 408         */
 409
 410        /* mask all interrupts */
 411        __raw_writel(0, imxdi->ioaddr + DIER);
 412
 413        rc = devm_request_irq(&pdev->dev, imxdi->irq, dryice_norm_irq,
 414                        IRQF_SHARED, pdev->name, imxdi);
 415        if (rc) {
 416                dev_warn(&pdev->dev, "interrupt not available.\n");
 417                goto err;
 418        }
 419
 420        /* put dryice into valid state */
 421        if (__raw_readl(imxdi->ioaddr + DSR) & DSR_NVF) {
 422                rc = di_write_wait(imxdi, DSR_NVF | DSR_SVF, DSR);
 423                if (rc)
 424                        goto err;
 425        }
 426
 427        /* initialize alarm */
 428        rc = di_write_wait(imxdi, DCAMR_UNSET, DCAMR);
 429        if (rc)
 430                goto err;
 431        rc = di_write_wait(imxdi, 0, DCALR);
 432        if (rc)
 433                goto err;
 434
 435        /* clear alarm flag */
 436        if (__raw_readl(imxdi->ioaddr + DSR) & DSR_CAF) {
 437                rc = di_write_wait(imxdi, DSR_CAF, DSR);
 438                if (rc)
 439                        goto err;
 440        }
 441
 442        /* the timer won't count if it has never been written to */
 443        if (__raw_readl(imxdi->ioaddr + DTCMR) == 0) {
 444                rc = di_write_wait(imxdi, 0, DTCMR);
 445                if (rc)
 446                        goto err;
 447        }
 448
 449        /* start keeping time */
 450        if (!(__raw_readl(imxdi->ioaddr + DCR) & DCR_TCE)) {
 451                rc = di_write_wait(imxdi,
 452                                __raw_readl(imxdi->ioaddr + DCR) | DCR_TCE,
 453                                DCR);
 454                if (rc)
 455                        goto err;
 456        }
 457
 458        platform_set_drvdata(pdev, imxdi);
 459        imxdi->rtc = devm_rtc_device_register(&pdev->dev, pdev->name,
 460                                  &dryice_rtc_ops, THIS_MODULE);
 461        if (IS_ERR(imxdi->rtc)) {
 462                rc = PTR_ERR(imxdi->rtc);
 463                goto err;
 464        }
 465
 466        return 0;
 467
 468err:
 469        clk_disable_unprepare(imxdi->clk);
 470
 471        return rc;
 472}
 473
 474static int __exit dryice_rtc_remove(struct platform_device *pdev)
 475{
 476        struct imxdi_dev *imxdi = platform_get_drvdata(pdev);
 477
 478        flush_work(&imxdi->work);
 479
 480        /* mask all interrupts */
 481        __raw_writel(0, imxdi->ioaddr + DIER);
 482
 483        clk_disable_unprepare(imxdi->clk);
 484
 485        return 0;
 486}
 487
 488#ifdef CONFIG_OF
 489static const struct of_device_id dryice_dt_ids[] = {
 490        { .compatible = "fsl,imx25-rtc" },
 491        { /* sentinel */ }
 492};
 493
 494MODULE_DEVICE_TABLE(of, dryice_dt_ids);
 495#endif
 496
 497static struct platform_driver dryice_rtc_driver = {
 498        .driver = {
 499                   .name = "imxdi_rtc",
 500                   .owner = THIS_MODULE,
 501                   .of_match_table = of_match_ptr(dryice_dt_ids),
 502                   },
 503        .remove = __exit_p(dryice_rtc_remove),
 504};
 505
 506module_platform_driver_probe(dryice_rtc_driver, dryice_rtc_probe);
 507
 508MODULE_AUTHOR("Freescale Semiconductor, Inc.");
 509MODULE_AUTHOR("Baruch Siach <baruch@tkos.co.il>");
 510MODULE_DESCRIPTION("IMX DryIce Realtime Clock Driver (RTC)");
 511MODULE_LICENSE("GPL");
 512
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