/* Copyright (c) 2010-2011, Code Aurora Forum. All rights reserved.
 *
 * This program is free software; you can redistribute it and/or modify
 * it under the terms of the GNU General Public License version 2 and
 * only version 2 as published by the Free Software Foundation.
 *
 * This program is distributed in the hope that it will be useful,
 * but WITHOUT ANY WARRANTY; without even the implied warranty of
 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
 * GNU General Public License for more details.
 */

#include <linux/module.h>
#include <linux/init.h>
#include <linux/rtc.h>
#include <linux/pm.h>
#include <linux/slab.h>
#include <linux/spinlock.h>

#include <linux/mfd/pm8xxx/core.h>
#include <linux/mfd/pm8xxx/rtc.h>


/* RTC Register offsets from RTC CTRL REG */
#define PM8XXX_ALARM_CTRL_OFFSET        0x01
#define PM8XXX_RTC_WRITE_OFFSET         0x02
#define PM8XXX_RTC_READ_OFFSET          0x06
#define PM8XXX_ALARM_RW_OFFSET          0x0A

/* RTC_CTRL register bit fields */
#define PM8xxx_RTC_ENABLE               BIT(7)
#define PM8xxx_RTC_ALARM_ENABLE         BIT(1)
#define PM8xxx_RTC_ALARM_CLEAR          BIT(0)

#define NUM_8_BIT_RTC_REGS              0x4

/**
 * struct pm8xxx_rtc -  rtc driver internal structure
 * @rtc:                rtc device for this driver.
 * @rtc_alarm_irq:      rtc alarm irq number.
 * @rtc_base:           address of rtc control register.
 * @rtc_read_base:      base address of read registers.
 * @rtc_write_base:     base address of write registers.
 * @alarm_rw_base:      base address of alarm registers.
 * @ctrl_reg:           rtc control register.
 * @rtc_dev:            device structure.
 * @ctrl_reg_lock:      spinlock protecting access to ctrl_reg.
 */
struct pm8xxx_rtc {
        struct rtc_device *rtc;
        int rtc_alarm_irq;
        int rtc_base;
        int rtc_read_base;
        int rtc_write_base;
        int alarm_rw_base;
        u8  ctrl_reg;
        struct device *rtc_dev;
        spinlock_t ctrl_reg_lock;
};

/*
 * The RTC registers need to be read/written one byte at a time. This is a
 * hardware limitation.
 */
static int pm8xxx_read_wrapper(struct pm8xxx_rtc *rtc_dd, u8 *rtc_val,
                int base, int count)
{
        int i, rc;
        struct device *parent = rtc_dd->rtc_dev->parent;

        for (i = 0; i < count; i++) {
                rc = pm8xxx_readb(parent, base + i, &rtc_val[i]);
                if (rc < 0) {
                        dev_err(rtc_dd->rtc_dev, "PMIC read failed\n");
                        return rc;
                }
        }

        return 0;
}

static int pm8xxx_write_wrapper(struct pm8xxx_rtc *rtc_dd, u8 *rtc_val,
                int base, int count)
{
        int i, rc;
        struct device *parent = rtc_dd->rtc_dev->parent;

        for (i = 0; i < count; i++) {
                rc = pm8xxx_writeb(parent, base + i, rtc_val[i]);
                if (rc < 0) {
                        dev_err(rtc_dd->rtc_dev, "PMIC write failed\n");
                        return rc;
                }
        }

        return 0;
}

/*
 * Steps to write the RTC registers.
 * 1. Disable alarm if enabled.
 * 2. Write 0x00 to LSB.
 * 3. Write Byte[1], Byte[2], Byte[3] then Byte[0].
 * 4. Enable alarm if disabled in step 1.
 */
static int pm8xxx_rtc_set_time(struct device *dev, struct rtc_time *tm)
{
        int rc, i;
        unsigned long secs, irq_flags;
        u8 value[NUM_8_BIT_RTC_REGS], reg = 0, alarm_enabled = 0, ctrl_reg;
        struct pm8xxx_rtc *rtc_dd = dev_get_drvdata(dev);

        rtc_tm_to_time(tm, &secs);

        for (i = 0; i < NUM_8_BIT_RTC_REGS; i++) {
                value[i] = secs & 0xFF;
                secs >>= 8;
        }

        dev_dbg(dev, "Seconds value to be written to RTC = %lu\n", secs);

        spin_lock_irqsave(&rtc_dd->ctrl_reg_lock, irq_flags);
        ctrl_reg = rtc_dd->ctrl_reg;

        if (ctrl_reg & PM8xxx_RTC_ALARM_ENABLE) {
                alarm_enabled = 1;
                ctrl_reg &= ~PM8xxx_RTC_ALARM_ENABLE;
                rc = pm8xxx_write_wrapper(rtc_dd, &ctrl_reg, rtc_dd->rtc_base,
                                1);
                if (rc < 0) {
                        dev_err(dev, "Write to RTC control register "
                                                                "failed\n");
                        goto rtc_rw_fail;
                }
                rtc_dd->ctrl_reg = ctrl_reg;
        } else
                spin_unlock_irqrestore(&rtc_dd->ctrl_reg_lock, irq_flags);

        /* Write 0 to Byte[0] */
        reg = 0;
        rc = pm8xxx_write_wrapper(rtc_dd, &reg, rtc_dd->rtc_write_base, 1);
        if (rc < 0) {
                dev_err(dev, "Write to RTC write data register failed\n");
                goto rtc_rw_fail;
        }

        /* Write Byte[1], Byte[2], Byte[3] */
        rc = pm8xxx_write_wrapper(rtc_dd, value + 1,
                                        rtc_dd->rtc_write_base + 1, 3);
        if (rc < 0) {
                dev_err(dev, "Write to RTC write data register failed\n");
                goto rtc_rw_fail;
        }

        /* Write Byte[0] */
        rc = pm8xxx_write_wrapper(rtc_dd, value, rtc_dd->rtc_write_base, 1);
        if (rc < 0) {
                dev_err(dev, "Write to RTC write data register failed\n");
                goto rtc_rw_fail;
        }

        if (alarm_enabled) {
                ctrl_reg |= PM8xxx_RTC_ALARM_ENABLE;
                rc = pm8xxx_write_wrapper(rtc_dd, &ctrl_reg, rtc_dd->rtc_base,
                                                                        1);
                if (rc < 0) {
                        dev_err(dev, "Write to RTC control register "
                                                                "failed\n");
                        goto rtc_rw_fail;
                }
                rtc_dd->ctrl_reg = ctrl_reg;
        }

rtc_rw_fail:
        if (alarm_enabled)
                spin_unlock_irqrestore(&rtc_dd->ctrl_reg_lock, irq_flags);

        return rc;
}

static int pm8xxx_rtc_read_time(struct device *dev, struct rtc_time *tm)
{
        int rc;
        u8 value[NUM_8_BIT_RTC_REGS], reg;
        unsigned long secs;
        struct pm8xxx_rtc *rtc_dd = dev_get_drvdata(dev);

        rc = pm8xxx_read_wrapper(rtc_dd, value, rtc_dd->rtc_read_base,
                                                        NUM_8_BIT_RTC_REGS);
        if (rc < 0) {
                dev_err(dev, "RTC read data register failed\n");
                return rc;
        }

        /*
         * Read the LSB again and check if there has been a carry over.
         * If there is, redo the read operation.
         */
        rc = pm8xxx_read_wrapper(rtc_dd, &reg, rtc_dd->rtc_read_base, 1);
        if (rc < 0) {
                dev_err(dev, "RTC read data register failed\n");
                return rc;
        }

        if (unlikely(reg < value[0])) {
                rc = pm8xxx_read_wrapper(rtc_dd, value,
                                rtc_dd->rtc_read_base, NUM_8_BIT_RTC_REGS);
                if (rc < 0) {
                        dev_err(dev, "RTC read data register failed\n");
                        return rc;
                }
        }

        secs = value[0] | (value[1] << 8) | (value[2] << 16) | (value[3] << 24);

        rtc_time_to_tm(secs, tm);

        rc = rtc_valid_tm(tm);
        if (rc < 0) {
                dev_err(dev, "Invalid time read from RTC\n");
                return rc;
        }

        dev_dbg(dev, "secs = %lu, h:m:s == %d:%d:%d, d/m/y = %d/%d/%d\n",
                                secs, tm->tm_hour, tm->tm_min, tm->tm_sec,
                                tm->tm_mday, tm->tm_mon, tm->tm_year);

        return 0;
}

static int pm8xxx_rtc_set_alarm(struct device *dev, struct rtc_wkalrm *alarm)
{
        int rc, i;
        u8 value[NUM_8_BIT_RTC_REGS], ctrl_reg;
        unsigned long secs, irq_flags;
        struct pm8xxx_rtc *rtc_dd = dev_get_drvdata(dev);

        rtc_tm_to_time(&alarm->time, &secs);

        for (i = 0; i < NUM_8_BIT_RTC_REGS; i++) {
                value[i] = secs & 0xFF;
                secs >>= 8;
        }

        spin_lock_irqsave(&rtc_dd->ctrl_reg_lock, irq_flags);

        rc = pm8xxx_write_wrapper(rtc_dd, value, rtc_dd->alarm_rw_base,
                                                        NUM_8_BIT_RTC_REGS);
        if (rc < 0) {
                dev_err(dev, "Write to RTC ALARM register failed\n");
                goto rtc_rw_fail;
        }

        ctrl_reg = rtc_dd->ctrl_reg;
        ctrl_reg = alarm->enabled ? (ctrl_reg | PM8xxx_RTC_ALARM_ENABLE) :
                                        (ctrl_reg & ~PM8xxx_RTC_ALARM_ENABLE);

        rc = pm8xxx_write_wrapper(rtc_dd, &ctrl_reg, rtc_dd->rtc_base, 1);
        if (rc < 0) {
                dev_err(dev, "Write to RTC control register failed\n");
                goto rtc_rw_fail;
        }

        rtc_dd->ctrl_reg = ctrl_reg;

        dev_dbg(dev, "Alarm Set for h:r:s=%d:%d:%d, d/m/y=%d/%d/%d\n",
                                alarm->time.tm_hour, alarm->time.tm_min,
                                alarm->time.tm_sec, alarm->time.tm_mday,
                                alarm->time.tm_mon, alarm->time.tm_year);
rtc_rw_fail:
        spin_unlock_irqrestore(&rtc_dd->ctrl_reg_lock, irq_flags);
        return rc;
}

static int pm8xxx_rtc_read_alarm(struct device *dev, struct rtc_wkalrm *alarm)
{
        int rc;
        u8 value[NUM_8_BIT_RTC_REGS];
        unsigned long secs;
        struct pm8xxx_rtc *rtc_dd = dev_get_drvdata(dev);

        rc = pm8xxx_read_wrapper(rtc_dd, value, rtc_dd->alarm_rw_base,
                        NUM_8_BIT_RTC_REGS);
        if (rc < 0) {
                dev_err(dev, "RTC alarm time read failed\n");
                return rc;
        }

        secs = value[0] | (value[1] << 8) | (value[2] << 16) | (value[3] << 24);

        rtc_time_to_tm(secs, &alarm->time);

        rc = rtc_valid_tm(&alarm->time);
        if (rc < 0) {
                dev_err(dev, "Invalid alarm time read from RTC\n");
                return rc;
        }

        dev_dbg(dev, "Alarm set for - h:r:s=%d:%d:%d, d/m/y=%d/%d/%d\n",
                                alarm->time.tm_hour, alarm->time.tm_min,
                                alarm->time.tm_sec, alarm->time.tm_mday,
                                alarm->time.tm_mon, alarm->time.tm_year);

        return 0;
}

static int pm8xxx_rtc_alarm_irq_enable(struct device *dev, unsigned int enable)
{
        int rc;
        unsigned long irq_flags;
        struct pm8xxx_rtc *rtc_dd = dev_get_drvdata(dev);
        u8 ctrl_reg;

        spin_lock_irqsave(&rtc_dd->ctrl_reg_lock, irq_flags);
        ctrl_reg = rtc_dd->ctrl_reg;
        ctrl_reg = (enable) ? (ctrl_reg | PM8xxx_RTC_ALARM_ENABLE) :
                                (ctrl_reg & ~PM8xxx_RTC_ALARM_ENABLE);

        rc = pm8xxx_write_wrapper(rtc_dd, &ctrl_reg, rtc_dd->rtc_base, 1);
        if (rc < 0) {
                dev_err(dev, "Write to RTC control register failed\n");
                goto rtc_rw_fail;
        }

        rtc_dd->ctrl_reg = ctrl_reg;

rtc_rw_fail:
        spin_unlock_irqrestore(&rtc_dd->ctrl_reg_lock, irq_flags);
        return rc;
}

static struct rtc_class_ops pm8xxx_rtc_ops = {
        .read_time      = pm8xxx_rtc_read_time,
        .set_alarm      = pm8xxx_rtc_set_alarm,
        .read_alarm     = pm8xxx_rtc_read_alarm,
        .alarm_irq_enable = pm8xxx_rtc_alarm_irq_enable,
};

static irqreturn_t pm8xxx_alarm_trigger(int irq, void *dev_id)
{
        struct pm8xxx_rtc *rtc_dd = dev_id;
        u8 ctrl_reg;
        int rc;
        unsigned long irq_flags;

        rtc_update_irq(rtc_dd->rtc, 1, RTC_IRQF | RTC_AF);

        spin_lock_irqsave(&rtc_dd->ctrl_reg_lock, irq_flags);

        /* Clear the alarm enable bit */
        ctrl_reg = rtc_dd->ctrl_reg;
        ctrl_reg &= ~PM8xxx_RTC_ALARM_ENABLE;

        rc = pm8xxx_write_wrapper(rtc_dd, &ctrl_reg, rtc_dd->rtc_base, 1);
        if (rc < 0) {
                spin_unlock_irqrestore(&rtc_dd->ctrl_reg_lock, irq_flags);
                dev_err(rtc_dd->rtc_dev, "Write to RTC control register "
                                                                "failed\n");
                goto rtc_alarm_handled;
        }

        rtc_dd->ctrl_reg = ctrl_reg;
        spin_unlock_irqrestore(&rtc_dd->ctrl_reg_lock, irq_flags);

        /* Clear RTC alarm register */
        rc = pm8xxx_read_wrapper(rtc_dd, &ctrl_reg, rtc_dd->rtc_base +
                                                PM8XXX_ALARM_CTRL_OFFSET, 1);
        if (rc < 0) {
                dev_err(rtc_dd->rtc_dev, "RTC Alarm control register read "
                                                                "failed\n");
                goto rtc_alarm_handled;
        }

        ctrl_reg &= ~PM8xxx_RTC_ALARM_CLEAR;
        rc = pm8xxx_write_wrapper(rtc_dd, &ctrl_reg, rtc_dd->rtc_base +
                                                PM8XXX_ALARM_CTRL_OFFSET, 1);
        if (rc < 0)
                dev_err(rtc_dd->rtc_dev, "Write to RTC Alarm control register"
                                                                " failed\n");

rtc_alarm_handled:
        return IRQ_HANDLED;
}

static int pm8xxx_rtc_probe(struct platform_device *pdev)
{
        int rc;
        u8 ctrl_reg;
        bool rtc_write_enable = false;
        struct pm8xxx_rtc *rtc_dd;
        struct resource *rtc_resource;
        const struct pm8xxx_rtc_platform_data *pdata =
                                                dev_get_platdata(&pdev->dev);

        if (pdata != NULL)
                rtc_write_enable = pdata->rtc_write_enable;

        rtc_dd = kzalloc(sizeof(*rtc_dd), GFP_KERNEL);
        if (rtc_dd == NULL) {
                dev_err(&pdev->dev, "Unable to allocate memory!\n");
                return -ENOMEM;
        }

        /* Initialise spinlock to protect RTC control register */
        spin_lock_init(&rtc_dd->ctrl_reg_lock);

        rtc_dd->rtc_alarm_irq = platform_get_irq(pdev, 0);
        if (rtc_dd->rtc_alarm_irq < 0) {
                dev_err(&pdev->dev, "Alarm IRQ resource absent!\n");
                rc = -ENXIO;
                goto fail_rtc_enable;
        }

        rtc_resource = platform_get_resource_byname(pdev, IORESOURCE_IO,
                                                        "pmic_rtc_base");
        if (!(rtc_resource && rtc_resource->start)) {
                dev_err(&pdev->dev, "RTC IO resource absent!\n");
                rc = -ENXIO;
                goto fail_rtc_enable;
        }

        rtc_dd->rtc_base = rtc_resource->start;

        /* Setup RTC register addresses */
        rtc_dd->rtc_write_base = rtc_dd->rtc_base + PM8XXX_RTC_WRITE_OFFSET;
        rtc_dd->rtc_read_base = rtc_dd->rtc_base + PM8XXX_RTC_READ_OFFSET;
        rtc_dd->alarm_rw_base = rtc_dd->rtc_base + PM8XXX_ALARM_RW_OFFSET;

        rtc_dd->rtc_dev = &pdev->dev;

        /* Check if the RTC is on, else turn it on */
        rc = pm8xxx_read_wrapper(rtc_dd, &ctrl_reg, rtc_dd->rtc_base, 1);
        if (rc < 0) {
                dev_err(&pdev->dev, "RTC control register read failed!\n");
                goto fail_rtc_enable;
        }

        if (!(ctrl_reg & PM8xxx_RTC_ENABLE)) {
                ctrl_reg |= PM8xxx_RTC_ENABLE;
                rc = pm8xxx_write_wrapper(rtc_dd, &ctrl_reg, rtc_dd->rtc_base,
                                                                        1);
                if (rc < 0) {
                        dev_err(&pdev->dev, "Write to RTC control register "
                                                                "failed\n");
                        goto fail_rtc_enable;
                }
        }

        rtc_dd->ctrl_reg = ctrl_reg;
        if (rtc_write_enable == true)
                pm8xxx_rtc_ops.set_time = pm8xxx_rtc_set_time;

        platform_set_drvdata(pdev, rtc_dd);

        /* Register the RTC device */
        rtc_dd->rtc = rtc_device_register("pm8xxx_rtc", &pdev->dev,
                                &pm8xxx_rtc_ops, THIS_MODULE);
        if (IS_ERR(rtc_dd->rtc)) {
                dev_err(&pdev->dev, "%s: RTC registration failed (%ld)\n",
                                        __func__, PTR_ERR(rtc_dd->rtc));
                rc = PTR_ERR(rtc_dd->rtc);
                goto fail_rtc_enable;
        }

        /* Request the alarm IRQ */
        rc = request_any_context_irq(rtc_dd->rtc_alarm_irq,
                                 pm8xxx_alarm_trigger, IRQF_TRIGGER_RISING,
                                 "pm8xxx_rtc_alarm", rtc_dd);
        if (rc < 0) {
                dev_err(&pdev->dev, "Request IRQ failed (%d)\n", rc);
                goto fail_req_irq;
        }

        device_init_wakeup(&pdev->dev, 1);

        dev_dbg(&pdev->dev, "Probe success !!\n");

        return 0;

fail_req_irq:
        rtc_device_unregister(rtc_dd->rtc);
fail_rtc_enable:
        platform_set_drvdata(pdev, NULL);
        kfree(rtc_dd);
        return rc;
}

static int pm8xxx_rtc_remove(struct platform_device *pdev)
{
        struct pm8xxx_rtc *rtc_dd = platform_get_drvdata(pdev);

        device_init_wakeup(&pdev->dev, 0);
        free_irq(rtc_dd->rtc_alarm_irq, rtc_dd);
        rtc_device_unregister(rtc_dd->rtc);
        platform_set_drvdata(pdev, NULL);
        kfree(rtc_dd);

        return 0;
}

#ifdef CONFIG_PM_SLEEP
static int pm8xxx_rtc_resume(struct device *dev)
{
        struct pm8xxx_rtc *rtc_dd = dev_get_drvdata(dev);

        if (device_may_wakeup(dev))
                disable_irq_wake(rtc_dd->rtc_alarm_irq);

        return 0;
}

static int pm8xxx_rtc_suspend(struct device *dev)
{
        struct pm8xxx_rtc *rtc_dd = dev_get_drvdata(dev);

        if (device_may_wakeup(dev))
                enable_irq_wake(rtc_dd->rtc_alarm_irq);

        return 0;
}
#endif

static SIMPLE_DEV_PM_OPS(pm8xxx_rtc_pm_ops, pm8xxx_rtc_suspend, pm8xxx_rtc_resume);

static struct platform_driver pm8xxx_rtc_driver = {
        .probe          = pm8xxx_rtc_probe,
        .remove         = pm8xxx_rtc_remove,
        .driver = {
                .name   = PM8XXX_RTC_DEV_NAME,
                .owner  = THIS_MODULE,
                .pm     = &pm8xxx_rtc_pm_ops,
        },
};

module_platform_driver(pm8xxx_rtc_driver);

MODULE_ALIAS("platform:rtc-pm8xxx");
MODULE_DESCRIPTION("PMIC8xxx RTC driver");
MODULE_LICENSE("GPL v2");
MODULE_AUTHOR("Anirudh Ghayal <aghayal@codeaurora.org>");