/*
 * rtc-mrst.c: Driver for Moorestown virtual RTC
 *
 * (C) Copyright 2009 Intel Corporation
 * Author: Jacob Pan (jacob.jun.pan@intel.com)
 *         Feng Tang (feng.tang@intel.com)
 *
 * This program is free software; you can redistribute it and/or
 * modify it under the terms of the GNU General Public License
 * as published by the Free Software Foundation; version 2
 * of the License.
 *
 * Note:
 * VRTC is emulated by system controller firmware, the real HW
 * RTC is located in the PMIC device. SCU FW shadows PMIC RTC
 * in a memory mapped IO space that is visible to the host IA
 * processor.
 *
 * This driver is based upon drivers/rtc/rtc-cmos.c
 */

/*
 * Note:
 *  * vRTC only supports binary mode and 24H mode
 *  * vRTC only support PIE and AIE, no UIE, and its PIE only happens
 *    at 23:59:59pm everyday, no support for adjustable frequency
 *  * Alarm function is also limited to hr/min/sec.
 */

#include <linux/mod_devicetable.h>
#include <linux/platform_device.h>
#include <linux/interrupt.h>
#include <linux/spinlock.h>
#include <linux/kernel.h>
#include <linux/mc146818rtc.h>
#include <linux/module.h>
#include <linux/init.h>
#include <linux/sfi.h>

#include <asm/intel_scu_ipc.h>
#include <asm/intel-mid.h>
#include <asm/intel_mid_vrtc.h>

struct mrst_rtc {
        struct rtc_device       *rtc;
        struct device           *dev;
        int                     irq;

        u8                      enabled_wake;
        u8                      suspend_ctrl;
};

static const char driver_name[] = "rtc_mrst";

#define RTC_IRQMASK     (RTC_PF | RTC_AF)

static inline int is_intr(u8 rtc_intr)
{
        if (!(rtc_intr & RTC_IRQF))
                return 0;
        return rtc_intr & RTC_IRQMASK;
}

static inline unsigned char vrtc_is_updating(void)
{
        unsigned char uip;
        unsigned long flags;

        spin_lock_irqsave(&rtc_lock, flags);
        uip = (vrtc_cmos_read(RTC_FREQ_SELECT) & RTC_UIP);
        spin_unlock_irqrestore(&rtc_lock, flags);
        return uip;
}

/*
 * rtc_time's year contains the increment over 1900, but vRTC's YEAR
 * register can't be programmed to value larger than 0x64, so vRTC
 * driver chose to use 1972 (1970 is UNIX time start point) as the base,
 * and does the translation at read/write time.
 *
 * Why not just use 1970 as the offset? it's because using 1972 will
 * make it consistent in leap year setting for both vrtc and low-level
 * physical rtc devices. Then why not use 1960 as the offset? If we use
 * 1960, for a device's first use, its YEAR register is 0 and the system
 * year will be parsed as 1960 which is not a valid UNIX time and will
 * cause many applications to fail mysteriously.
 */
static int mrst_read_time(struct device *dev, struct rtc_time *time)
{
        unsigned long flags;

        if (vrtc_is_updating())
                msleep(20);

        spin_lock_irqsave(&rtc_lock, flags);
        time->tm_sec = vrtc_cmos_read(RTC_SECONDS);
        time->tm_min = vrtc_cmos_read(RTC_MINUTES);
        time->tm_hour = vrtc_cmos_read(RTC_HOURS);
        time->tm_mday = vrtc_cmos_read(RTC_DAY_OF_MONTH);
        time->tm_mon = vrtc_cmos_read(RTC_MONTH);
        time->tm_year = vrtc_cmos_read(RTC_YEAR);
        spin_unlock_irqrestore(&rtc_lock, flags);

        /* Adjust for the 1972/1900 */
        time->tm_year += 72;
        time->tm_mon--;
        return 0;
}

static int mrst_set_time(struct device *dev, struct rtc_time *time)
{
        int ret;
        unsigned long flags;
        unsigned char mon, day, hrs, min, sec;
        unsigned int yrs;

        yrs = time->tm_year;
        mon = time->tm_mon + 1;   /* tm_mon starts at zero */
        day = time->tm_mday;
        hrs = time->tm_hour;
        min = time->tm_min;
        sec = time->tm_sec;

        if (yrs < 72 || yrs > 172)
                return -EINVAL;
        yrs -= 72;

        spin_lock_irqsave(&rtc_lock, flags);

        vrtc_cmos_write(yrs, RTC_YEAR);
        vrtc_cmos_write(mon, RTC_MONTH);
        vrtc_cmos_write(day, RTC_DAY_OF_MONTH);
        vrtc_cmos_write(hrs, RTC_HOURS);
        vrtc_cmos_write(min, RTC_MINUTES);
        vrtc_cmos_write(sec, RTC_SECONDS);

        spin_unlock_irqrestore(&rtc_lock, flags);

        ret = intel_scu_ipc_simple_command(IPCMSG_VRTC, IPC_CMD_VRTC_SETTIME);
        return ret;
}

static int mrst_read_alarm(struct device *dev, struct rtc_wkalrm *t)
{
        struct mrst_rtc *mrst = dev_get_drvdata(dev);
        unsigned char rtc_control;

        if (mrst->irq <= 0)
                return -EIO;

        /* vRTC only supports binary mode */
        spin_lock_irq(&rtc_lock);
        t->time.tm_sec = vrtc_cmos_read(RTC_SECONDS_ALARM);
        t->time.tm_min = vrtc_cmos_read(RTC_MINUTES_ALARM);
        t->time.tm_hour = vrtc_cmos_read(RTC_HOURS_ALARM);

        rtc_control = vrtc_cmos_read(RTC_CONTROL);
        spin_unlock_irq(&rtc_lock);

        t->enabled = !!(rtc_control & RTC_AIE);
        t->pending = 0;

        return 0;
}

static void mrst_checkintr(struct mrst_rtc *mrst, unsigned char rtc_control)
{
        unsigned char   rtc_intr;

        /*
         * NOTE after changing RTC_xIE bits we always read INTR_FLAGS;
         * allegedly some older rtcs need that to handle irqs properly
         */
        rtc_intr = vrtc_cmos_read(RTC_INTR_FLAGS);
        rtc_intr &= (rtc_control & RTC_IRQMASK) | RTC_IRQF;
        if (is_intr(rtc_intr))
                rtc_update_irq(mrst->rtc, 1, rtc_intr);
}

static void mrst_irq_enable(struct mrst_rtc *mrst, unsigned char mask)
{
        unsigned char   rtc_control;

        /*
         * Flush any pending IRQ status, notably for update irqs,
         * before we enable new IRQs
         */
        rtc_control = vrtc_cmos_read(RTC_CONTROL);
        mrst_checkintr(mrst, rtc_control);

        rtc_control |= mask;
        vrtc_cmos_write(rtc_control, RTC_CONTROL);

        mrst_checkintr(mrst, rtc_control);
}

static void mrst_irq_disable(struct mrst_rtc *mrst, unsigned char mask)
{
        unsigned char   rtc_control;

        rtc_control = vrtc_cmos_read(RTC_CONTROL);
        rtc_control &= ~mask;
        vrtc_cmos_write(rtc_control, RTC_CONTROL);
        mrst_checkintr(mrst, rtc_control);
}

static int mrst_set_alarm(struct device *dev, struct rtc_wkalrm *t)
{
        struct mrst_rtc *mrst = dev_get_drvdata(dev);
        unsigned char hrs, min, sec;
        int ret = 0;

        if (!mrst->irq)
                return -EIO;

        hrs = t->time.tm_hour;
        min = t->time.tm_min;
        sec = t->time.tm_sec;

        spin_lock_irq(&rtc_lock);
        /* Next rtc irq must not be from previous alarm setting */
        mrst_irq_disable(mrst, RTC_AIE);

        /* Update alarm */
        vrtc_cmos_write(hrs, RTC_HOURS_ALARM);
        vrtc_cmos_write(min, RTC_MINUTES_ALARM);
        vrtc_cmos_write(sec, RTC_SECONDS_ALARM);

        spin_unlock_irq(&rtc_lock);

        ret = intel_scu_ipc_simple_command(IPCMSG_VRTC, IPC_CMD_VRTC_SETALARM);
        if (ret)
                return ret;

        spin_lock_irq(&rtc_lock);
        if (t->enabled)
                mrst_irq_enable(mrst, RTC_AIE);

        spin_unlock_irq(&rtc_lock);

        return 0;
}

/* Currently, the vRTC doesn't support UIE ON/OFF */
static int mrst_rtc_alarm_irq_enable(struct device *dev, unsigned int enabled)
{
        struct mrst_rtc *mrst = dev_get_drvdata(dev);
        unsigned long   flags;

        spin_lock_irqsave(&rtc_lock, flags);
        if (enabled)
                mrst_irq_enable(mrst, RTC_AIE);
        else
                mrst_irq_disable(mrst, RTC_AIE);
        spin_unlock_irqrestore(&rtc_lock, flags);
        return 0;
}


#if IS_ENABLED(CONFIG_RTC_INTF_PROC)

static int mrst_procfs(struct device *dev, struct seq_file *seq)
{
        unsigned char   rtc_control;

        spin_lock_irq(&rtc_lock);
        rtc_control = vrtc_cmos_read(RTC_CONTROL);
        spin_unlock_irq(&rtc_lock);

        seq_printf(seq,
                   "periodic_IRQ\t: %s\n"
                   "alarm\t\t: %s\n"
                   "BCD\t\t: no\n"
                   "periodic_freq\t: daily (not adjustable)\n",
                   (rtc_control & RTC_PIE) ? "on" : "off",
                   (rtc_control & RTC_AIE) ? "on" : "off");

        return 0;
}

#else
#define mrst_procfs     NULL
#endif

static const struct rtc_class_ops mrst_rtc_ops = {
        .read_time      = mrst_read_time,
        .set_time       = mrst_set_time,
        .read_alarm     = mrst_read_alarm,
        .set_alarm      = mrst_set_alarm,
        .proc           = mrst_procfs,
        .alarm_irq_enable = mrst_rtc_alarm_irq_enable,
};

static struct mrst_rtc  mrst_rtc;

/*
 * When vRTC IRQ is captured by SCU FW, FW will clear the AIE bit in
 * Reg B, so no need for this driver to clear it
 */
static irqreturn_t mrst_rtc_irq(int irq, void *p)
{
        u8 irqstat;

        spin_lock(&rtc_lock);
        /* This read will clear all IRQ flags inside Reg C */
        irqstat = vrtc_cmos_read(RTC_INTR_FLAGS);
        spin_unlock(&rtc_lock);

        irqstat &= RTC_IRQMASK | RTC_IRQF;
        if (is_intr(irqstat)) {
                rtc_update_irq(p, 1, irqstat);
                return IRQ_HANDLED;
        }
        return IRQ_NONE;
}

static int vrtc_mrst_do_probe(struct device *dev, struct resource *iomem,
                              int rtc_irq)
{
        int retval = 0;
        unsigned char rtc_control;

        /* There can be only one ... */
        if (mrst_rtc.dev)
                return -EBUSY;

        if (!iomem)
                return -ENODEV;

        iomem = devm_request_mem_region(dev, iomem->start, resource_size(iomem),
                                        driver_name);
        if (!iomem) {
                dev_dbg(dev, "i/o mem already in use.\n");
                return -EBUSY;
        }

        mrst_rtc.irq = rtc_irq;
        mrst_rtc.dev = dev;
        dev_set_drvdata(dev, &mrst_rtc);

        mrst_rtc.rtc = devm_rtc_allocate_device(dev);
        if (IS_ERR(mrst_rtc.rtc))
                return PTR_ERR(mrst_rtc.rtc);

        mrst_rtc.rtc->ops = &mrst_rtc_ops;

        rename_region(iomem, dev_name(&mrst_rtc.rtc->dev));

        spin_lock_irq(&rtc_lock);
        mrst_irq_disable(&mrst_rtc, RTC_PIE | RTC_AIE);
        rtc_control = vrtc_cmos_read(RTC_CONTROL);
        spin_unlock_irq(&rtc_lock);

        if (!(rtc_control & RTC_24H) || (rtc_control & (RTC_DM_BINARY)))
                dev_dbg(dev, "TODO: support more than 24-hr BCD mode\n");

        if (rtc_irq) {
                retval = devm_request_irq(dev, rtc_irq, mrst_rtc_irq,
                                          0, dev_name(&mrst_rtc.rtc->dev),
                                          mrst_rtc.rtc);
                if (retval < 0) {
                        dev_dbg(dev, "IRQ %d is already in use, err %d\n",
                                rtc_irq, retval);
                        goto cleanup0;
                }
        }

        retval = rtc_register_device(mrst_rtc.rtc);
        if (retval)
                goto cleanup0;

        dev_dbg(dev, "initialised\n");
        return 0;

cleanup0:
        mrst_rtc.dev = NULL;
        dev_err(dev, "rtc-mrst: unable to initialise\n");
        return retval;
}

static void rtc_mrst_do_shutdown(void)
{
        spin_lock_irq(&rtc_lock);
        mrst_irq_disable(&mrst_rtc, RTC_IRQMASK);
        spin_unlock_irq(&rtc_lock);
}

static void rtc_mrst_do_remove(struct device *dev)
{
        struct mrst_rtc *mrst = dev_get_drvdata(dev);

        rtc_mrst_do_shutdown();

        mrst->rtc = NULL;
        mrst->dev = NULL;
}

#ifdef CONFIG_PM_SLEEP
static int mrst_suspend(struct device *dev)
{
        struct mrst_rtc *mrst = dev_get_drvdata(dev);
        unsigned char   tmp;

        /* Only the alarm might be a wakeup event source */
        spin_lock_irq(&rtc_lock);
        mrst->suspend_ctrl = tmp = vrtc_cmos_read(RTC_CONTROL);
        if (tmp & (RTC_PIE | RTC_AIE)) {
                unsigned char   mask;

                if (device_may_wakeup(dev))
                        mask = RTC_IRQMASK & ~RTC_AIE;
                else
                        mask = RTC_IRQMASK;
                tmp &= ~mask;
                vrtc_cmos_write(tmp, RTC_CONTROL);

                mrst_checkintr(mrst, tmp);
        }
        spin_unlock_irq(&rtc_lock);

        if (tmp & RTC_AIE) {
                mrst->enabled_wake = 1;
                enable_irq_wake(mrst->irq);
        }

        dev_dbg(&mrst_rtc.rtc->dev, "suspend%s, ctrl %02x\n",
                        (tmp & RTC_AIE) ? ", alarm may wake" : "",
                        tmp);

        return 0;
}

/*
 * We want RTC alarms to wake us from the deep power saving state
 */
static inline int mrst_poweroff(struct device *dev)
{
        return mrst_suspend(dev);
}

static int mrst_resume(struct device *dev)
{
        struct mrst_rtc *mrst = dev_get_drvdata(dev);
        unsigned char tmp = mrst->suspend_ctrl;

        /* Re-enable any irqs previously active */
        if (tmp & RTC_IRQMASK) {
                unsigned char   mask;

                if (mrst->enabled_wake) {
                        disable_irq_wake(mrst->irq);
                        mrst->enabled_wake = 0;
                }

                spin_lock_irq(&rtc_lock);
                do {
                        vrtc_cmos_write(tmp, RTC_CONTROL);

                        mask = vrtc_cmos_read(RTC_INTR_FLAGS);
                        mask &= (tmp & RTC_IRQMASK) | RTC_IRQF;
                        if (!is_intr(mask))
                                break;

                        rtc_update_irq(mrst->rtc, 1, mask);
                        tmp &= ~RTC_AIE;
                } while (mask & RTC_AIE);
                spin_unlock_irq(&rtc_lock);
        }

        dev_dbg(&mrst_rtc.rtc->dev, "resume, ctrl %02x\n", tmp);

        return 0;
}

static SIMPLE_DEV_PM_OPS(mrst_pm_ops, mrst_suspend, mrst_resume);
#define MRST_PM_OPS (&mrst_pm_ops)

#else
#define MRST_PM_OPS NULL

static inline int mrst_poweroff(struct device *dev)
{
        return -ENOSYS;
}

#endif

static int vrtc_mrst_platform_probe(struct platform_device *pdev)
{
        return vrtc_mrst_do_probe(&pdev->dev,
                        platform_get_resource(pdev, IORESOURCE_MEM, 0),
                        platform_get_irq(pdev, 0));
}

static int vrtc_mrst_platform_remove(struct platform_device *pdev)
{
        rtc_mrst_do_remove(&pdev->dev);
        return 0;
}

static void vrtc_mrst_platform_shutdown(struct platform_device *pdev)
{
        if (system_state == SYSTEM_POWER_OFF && !mrst_poweroff(&pdev->dev))
                return;

        rtc_mrst_do_shutdown();
}

MODULE_ALIAS("platform:vrtc_mrst");

static struct platform_driver vrtc_mrst_platform_driver = {
        .probe          = vrtc_mrst_platform_probe,
        .remove         = vrtc_mrst_platform_remove,
        .shutdown       = vrtc_mrst_platform_shutdown,
        .driver = {
                .name   = driver_name,
                .pm     = MRST_PM_OPS,
        }
};

module_platform_driver(vrtc_mrst_platform_driver);

MODULE_AUTHOR("Jacob Pan; Feng Tang");
MODULE_DESCRIPTION("Driver for Moorestown virtual RTC");
MODULE_LICENSE("GPL");