/*
 * Copyright 2008-2009 Freescale Semiconductor, Inc. All Rights Reserved.
 * Copyright 2010 Orex Computed Radiography
 */

/*
 * The code contained herein is licensed under the GNU General Public
 * License. You may obtain a copy of the GNU General Public License
 * Version 2 or later at the following locations:
 *
 * http://www.opensource.org/licenses/gpl-license.html
 * http://www.gnu.org/copyleft/gpl.html
 */

/* based on rtc-mc13892.c */

/*
 * This driver uses the 47-bit 32 kHz counter in the Freescale DryIce block
 * to implement a Linux RTC. Times and alarms are truncated to seconds.
 * Since the RTC framework performs API locking via rtc->ops_lock the
 * only simultaneous accesses we need to deal with is updating DryIce
 * registers while servicing an alarm.
 *
 * Note that reading the DSR (DryIce Status Register) automatically clears
 * the WCF (Write Complete Flag). All DryIce writes are synchronized to the
 * LP (Low Power) domain and set the WCF upon completion. Writes to the
 * DIER (DryIce Interrupt Enable Register) are the only exception. These
 * occur at normal bus speeds and do not set WCF.  Periodic interrupts are
 * not supported by the hardware.
 */

#include <linux/io.h>
#include <linux/clk.h>
#include <linux/delay.h>
#include <linux/module.h>
#include <linux/platform_device.h>
#include <linux/rtc.h>
#include <linux/sched.h>
#include <linux/spinlock.h>
#include <linux/workqueue.h>
#include <linux/of.h>

/* DryIce Register Definitions */

#define DTCMR     0x00           /* Time Counter MSB Reg */
#define DTCLR     0x04           /* Time Counter LSB Reg */

#define DCAMR     0x08           /* Clock Alarm MSB Reg */
#define DCALR     0x0c           /* Clock Alarm LSB Reg */
#define DCAMR_UNSET  0xFFFFFFFF  /* doomsday - 1 sec */

#define DCR       0x10           /* Control Reg */
#define DCR_TCE   (1 << 3)       /* Time Counter Enable */

#define DSR       0x14           /* Status Reg */
#define DSR_WBF   (1 << 10)      /* Write Busy Flag */
#define DSR_WNF   (1 << 9)       /* Write Next Flag */
#define DSR_WCF   (1 << 8)       /* Write Complete Flag */
#define DSR_WEF   (1 << 7)       /* Write Error Flag */
#define DSR_CAF   (1 << 4)       /* Clock Alarm Flag */
#define DSR_NVF   (1 << 1)       /* Non-Valid Flag */
#define DSR_SVF   (1 << 0)       /* Security Violation Flag */

#define DIER      0x18           /* Interrupt Enable Reg */
#define DIER_WNIE (1 << 9)       /* Write Next Interrupt Enable */
#define DIER_WCIE (1 << 8)       /* Write Complete Interrupt Enable */
#define DIER_WEIE (1 << 7)       /* Write Error Interrupt Enable */
#define DIER_CAIE (1 << 4)       /* Clock Alarm Interrupt Enable */

/**
 * struct imxdi_dev - private imxdi rtc data
 * @pdev: pionter to platform dev
 * @rtc: pointer to rtc struct
 * @ioaddr: IO registers pointer
 * @irq: dryice normal interrupt
 * @clk: input reference clock
 * @dsr: copy of the DSR register
 * @irq_lock: interrupt enable register (DIER) lock
 * @write_wait: registers write complete queue
 * @write_mutex: serialize registers write
 * @work: schedule alarm work
 */
struct imxdi_dev {
        struct platform_device *pdev;
        struct rtc_device *rtc;
        void __iomem *ioaddr;
        int irq;
        struct clk *clk;
        u32 dsr;
        spinlock_t irq_lock;
        wait_queue_head_t write_wait;
        struct mutex write_mutex;
        struct work_struct work;
};

/*
 * enable a dryice interrupt
 */
static void di_int_enable(struct imxdi_dev *imxdi, u32 intr)
{
        unsigned long flags;

        spin_lock_irqsave(&imxdi->irq_lock, flags);
        __raw_writel(__raw_readl(imxdi->ioaddr + DIER) | intr,
                        imxdi->ioaddr + DIER);
        spin_unlock_irqrestore(&imxdi->irq_lock, flags);
}

/*
 * disable a dryice interrupt
 */
static void di_int_disable(struct imxdi_dev *imxdi, u32 intr)
{
        unsigned long flags;

        spin_lock_irqsave(&imxdi->irq_lock, flags);
        __raw_writel(__raw_readl(imxdi->ioaddr + DIER) & ~intr,
                        imxdi->ioaddr + DIER);
        spin_unlock_irqrestore(&imxdi->irq_lock, flags);
}

/*
 * This function attempts to clear the dryice write-error flag.
 *
 * A dryice write error is similar to a bus fault and should not occur in
 * normal operation.  Clearing the flag requires another write, so the root
 * cause of the problem may need to be fixed before the flag can be cleared.
 */
static void clear_write_error(struct imxdi_dev *imxdi)
{
        int cnt;

        dev_warn(&imxdi->pdev->dev, "WARNING: Register write error!\n");

        /* clear the write error flag */
        __raw_writel(DSR_WEF, imxdi->ioaddr + DSR);

        /* wait for it to take effect */
        for (cnt = 0; cnt < 1000; cnt++) {
                if ((__raw_readl(imxdi->ioaddr + DSR) & DSR_WEF) == 0)
                        return;
                udelay(10);
        }
        dev_err(&imxdi->pdev->dev,
                        "ERROR: Cannot clear write-error flag!\n");
}

/*
 * Write a dryice register and wait until it completes.
 *
 * This function uses interrupts to determine when the
 * write has completed.
 */
static int di_write_wait(struct imxdi_dev *imxdi, u32 val, int reg)
{
        int ret;
        int rc = 0;

        /* serialize register writes */
        mutex_lock(&imxdi->write_mutex);

        /* enable the write-complete interrupt */
        di_int_enable(imxdi, DIER_WCIE);

        imxdi->dsr = 0;

        /* do the register write */
        __raw_writel(val, imxdi->ioaddr + reg);

        /* wait for the write to finish */
        ret = wait_event_interruptible_timeout(imxdi->write_wait,
                        imxdi->dsr & (DSR_WCF | DSR_WEF), msecs_to_jiffies(1));
        if (ret < 0) {
                rc = ret;
                goto out;
        } else if (ret == 0) {
                dev_warn(&imxdi->pdev->dev,
                                "Write-wait timeout "
                                "val = 0x%08x reg = 0x%08x\n", val, reg);
        }

        /* check for write error */
        if (imxdi->dsr & DSR_WEF) {
                clear_write_error(imxdi);
                rc = -EIO;
        }

out:
        mutex_unlock(&imxdi->write_mutex);

        return rc;
}

/*
 * read the seconds portion of the current time from the dryice time counter
 */
static int dryice_rtc_read_time(struct device *dev, struct rtc_time *tm)
{
        struct imxdi_dev *imxdi = dev_get_drvdata(dev);
        unsigned long now;

        now = __raw_readl(imxdi->ioaddr + DTCMR);
        rtc_time_to_tm(now, tm);

        return 0;
}

/*
 * set the seconds portion of dryice time counter and clear the
 * fractional part.
 */
static int dryice_rtc_set_mmss(struct device *dev, unsigned long secs)
{
        struct imxdi_dev *imxdi = dev_get_drvdata(dev);
        int rc;

        /* zero the fractional part first */
        rc = di_write_wait(imxdi, 0, DTCLR);
        if (rc == 0)
                rc = di_write_wait(imxdi, secs, DTCMR);

        return rc;
}

static int dryice_rtc_alarm_irq_enable(struct device *dev,
                unsigned int enabled)
{
        struct imxdi_dev *imxdi = dev_get_drvdata(dev);

        if (enabled)
                di_int_enable(imxdi, DIER_CAIE);
        else
                di_int_disable(imxdi, DIER_CAIE);

        return 0;
}

/*
 * read the seconds portion of the alarm register.
 * the fractional part of the alarm register is always zero.
 */
static int dryice_rtc_read_alarm(struct device *dev, struct rtc_wkalrm *alarm)
{
        struct imxdi_dev *imxdi = dev_get_drvdata(dev);
        u32 dcamr;

        dcamr = __raw_readl(imxdi->ioaddr + DCAMR);
        rtc_time_to_tm(dcamr, &alarm->time);

        /* alarm is enabled if the interrupt is enabled */
        alarm->enabled = (__raw_readl(imxdi->ioaddr + DIER) & DIER_CAIE) != 0;

        /* don't allow the DSR read to mess up DSR_WCF */
        mutex_lock(&imxdi->write_mutex);

        /* alarm is pending if the alarm flag is set */
        alarm->pending = (__raw_readl(imxdi->ioaddr + DSR) & DSR_CAF) != 0;

        mutex_unlock(&imxdi->write_mutex);

        return 0;
}

/*
 * set the seconds portion of dryice alarm register
 */
static int dryice_rtc_set_alarm(struct device *dev, struct rtc_wkalrm *alarm)
{
        struct imxdi_dev *imxdi = dev_get_drvdata(dev);
        unsigned long now;
        unsigned long alarm_time;
        int rc;

        rc = rtc_tm_to_time(&alarm->time, &alarm_time);
        if (rc)
                return rc;

        /* don't allow setting alarm in the past */
        now = __raw_readl(imxdi->ioaddr + DTCMR);
        if (alarm_time < now)
                return -EINVAL;

        /* write the new alarm time */
        rc = di_write_wait(imxdi, (u32)alarm_time, DCAMR);
        if (rc)
                return rc;

        if (alarm->enabled)
                di_int_enable(imxdi, DIER_CAIE);  /* enable alarm intr */
        else
                di_int_disable(imxdi, DIER_CAIE); /* disable alarm intr */

        return 0;
}

static struct rtc_class_ops dryice_rtc_ops = {
        .read_time              = dryice_rtc_read_time,
        .set_mmss               = dryice_rtc_set_mmss,
        .alarm_irq_enable       = dryice_rtc_alarm_irq_enable,
        .read_alarm             = dryice_rtc_read_alarm,
        .set_alarm              = dryice_rtc_set_alarm,
};

/*
 * dryice "normal" interrupt handler
 */
static irqreturn_t dryice_norm_irq(int irq, void *dev_id)
{
        struct imxdi_dev *imxdi = dev_id;
        u32 dsr, dier;
        irqreturn_t rc = IRQ_NONE;

        dier = __raw_readl(imxdi->ioaddr + DIER);

        /* handle write complete and write error cases */
        if ((dier & DIER_WCIE)) {
                /*If the write wait queue is empty then there is no pending
                  operations. It means the interrupt is for DryIce -Security.
                  IRQ must be returned as none.*/
                if (list_empty_careful(&imxdi->write_wait.task_list))
                        return rc;

                /* DSR_WCF clears itself on DSR read */
                dsr = __raw_readl(imxdi->ioaddr + DSR);
                if ((dsr & (DSR_WCF | DSR_WEF))) {
                        /* mask the interrupt */
                        di_int_disable(imxdi, DIER_WCIE);

                        /* save the dsr value for the wait queue */
                        imxdi->dsr |= dsr;

                        wake_up_interruptible(&imxdi->write_wait);
                        rc = IRQ_HANDLED;
                }
        }

        /* handle the alarm case */
        if ((dier & DIER_CAIE)) {
                /* DSR_WCF clears itself on DSR read */
                dsr = __raw_readl(imxdi->ioaddr + DSR);
                if (dsr & DSR_CAF) {
                        /* mask the interrupt */
                        di_int_disable(imxdi, DIER_CAIE);

                        /* finish alarm in user context */
                        schedule_work(&imxdi->work);
                        rc = IRQ_HANDLED;
                }
        }
        return rc;
}

/*
 * post the alarm event from user context so it can sleep
 * on the write completion.
 */
static void dryice_work(struct work_struct *work)
{
        struct imxdi_dev *imxdi = container_of(work,
                        struct imxdi_dev, work);

        /* dismiss the interrupt (ignore error) */
        di_write_wait(imxdi, DSR_CAF, DSR);

        /* pass the alarm event to the rtc framework. */
        rtc_update_irq(imxdi->rtc, 1, RTC_AF | RTC_IRQF);
}

/*
 * probe for dryice rtc device
 */
static int dryice_rtc_probe(struct platform_device *pdev)
{
        struct resource *res;
        struct imxdi_dev *imxdi;
        int rc;

        res = platform_get_resource(pdev, IORESOURCE_MEM, 0);
        if (!res)
                return -ENODEV;

        imxdi = devm_kzalloc(&pdev->dev, sizeof(*imxdi), GFP_KERNEL);
        if (!imxdi)
                return -ENOMEM;

        imxdi->pdev = pdev;

        if (!devm_request_mem_region(&pdev->dev, res->start, resource_size(res),
                                pdev->name))
                return -EBUSY;

        imxdi->ioaddr = devm_ioremap(&pdev->dev, res->start,
                        resource_size(res));
        if (imxdi->ioaddr == NULL)
                return -ENOMEM;

        spin_lock_init(&imxdi->irq_lock);

        imxdi->irq = platform_get_irq(pdev, 0);
        if (imxdi->irq < 0)
                return imxdi->irq;

        init_waitqueue_head(&imxdi->write_wait);

        INIT_WORK(&imxdi->work, dryice_work);

        mutex_init(&imxdi->write_mutex);

        imxdi->clk = clk_get(&pdev->dev, NULL);
        if (IS_ERR(imxdi->clk))
                return PTR_ERR(imxdi->clk);
        clk_prepare_enable(imxdi->clk);

        /*
         * Initialize dryice hardware
         */

        /* mask all interrupts */
        __raw_writel(0, imxdi->ioaddr + DIER);

        rc = devm_request_irq(&pdev->dev, imxdi->irq, dryice_norm_irq,
                        IRQF_SHARED, pdev->name, imxdi);
        if (rc) {
                dev_warn(&pdev->dev, "interrupt not available.\n");
                goto err;
        }

        /* put dryice into valid state */
        if (__raw_readl(imxdi->ioaddr + DSR) & DSR_NVF) {
                rc = di_write_wait(imxdi, DSR_NVF | DSR_SVF, DSR);
                if (rc)
                        goto err;
        }

        /* initialize alarm */
        rc = di_write_wait(imxdi, DCAMR_UNSET, DCAMR);
        if (rc)
                goto err;
        rc = di_write_wait(imxdi, 0, DCALR);
        if (rc)
                goto err;

        /* clear alarm flag */
        if (__raw_readl(imxdi->ioaddr + DSR) & DSR_CAF) {
                rc = di_write_wait(imxdi, DSR_CAF, DSR);
                if (rc)
                        goto err;
        }

        /* the timer won't count if it has never been written to */
        if (__raw_readl(imxdi->ioaddr + DTCMR) == 0) {
                rc = di_write_wait(imxdi, 0, DTCMR);
                if (rc)
                        goto err;
        }

        /* start keeping time */
        if (!(__raw_readl(imxdi->ioaddr + DCR) & DCR_TCE)) {
                rc = di_write_wait(imxdi,
                                __raw_readl(imxdi->ioaddr + DCR) | DCR_TCE,
                                DCR);
                if (rc)
                        goto err;
        }

        platform_set_drvdata(pdev, imxdi);
        imxdi->rtc = rtc_device_register(pdev->name, &pdev->dev,
                                  &dryice_rtc_ops, THIS_MODULE);
        if (IS_ERR(imxdi->rtc)) {
                rc = PTR_ERR(imxdi->rtc);
                goto err;
        }

        return 0;

err:
        clk_disable_unprepare(imxdi->clk);
        clk_put(imxdi->clk);

        return rc;
}

static int dryice_rtc_remove(struct platform_device *pdev)
{
        struct imxdi_dev *imxdi = platform_get_drvdata(pdev);

        flush_work(&imxdi->work);

        /* mask all interrupts */
        __raw_writel(0, imxdi->ioaddr + DIER);

        rtc_device_unregister(imxdi->rtc);

        clk_disable_unprepare(imxdi->clk);
        clk_put(imxdi->clk);

        return 0;
}

#ifdef CONFIG_OF
static const struct of_device_id dryice_dt_ids[] = {
        { .compatible = "fsl,imx25-rtc" },
        { /* sentinel */ }
};

MODULE_DEVICE_TABLE(of, dryice_dt_ids);
#endif

static struct platform_driver dryice_rtc_driver = {
        .driver = {
                   .name = "imxdi_rtc",
                   .owner = THIS_MODULE,
                   .of_match_table = of_match_ptr(dryice_dt_ids),
                   },
        .remove = dryice_rtc_remove,
};

static int __init dryice_rtc_init(void)
{
        return platform_driver_probe(&dryice_rtc_driver, dryice_rtc_probe);
}

static void __exit dryice_rtc_exit(void)
{
        platform_driver_unregister(&dryice_rtc_driver);
}

module_init(dryice_rtc_init);
module_exit(dryice_rtc_exit);

MODULE_AUTHOR("Freescale Semiconductor, Inc.");
MODULE_AUTHOR("Baruch Siach <baruch@tkos.co.il>");
MODULE_DESCRIPTION("IMX DryIce Realtime Clock Driver (RTC)");
MODULE_LICENSE("GPL");