rtc-mrst.c

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/*
 * rtc-mrst.c: Driver for Moorestown virtual RTC
 *
 * (C) Copyright 2009 Intel Corporation
 * Author: Jacob Pan ([email protected])
 *     Feng Tang ([email protected])
 *
 * 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/module.h>
#include <linux/init.h>
#include <linux/sfi.h>

#include <asm-generic/rtc.h>
#include <asm/intel_scu_ipc.h>
#include <asm/mrst.h>
#include <asm/mrst-vrtc.h>

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

    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())
        mdelay(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 rtc_valid_tm(time);
}

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 > 138)
        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;

    /* Basic alarms only support hour, minute, and seconds fields.
     * Some also support day and month, for alarms up to a year in
     * the future.
     */
    t->time.tm_mday = -1;
    t->time.tm_mon = -1;
    t->time.tm_year = -1;

    /* 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 defined(CONFIG_RTC_INTF_PROC) || defined(CONFIG_RTC_INTF_PROC_MODULE)

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

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

    return 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");
}

#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 __devinit
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 = request_mem_region(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.iomem = iomem;
    mrst_rtc.dev = dev;
    dev_set_drvdata(dev, &mrst_rtc);

    mrst_rtc.rtc = rtc_device_register(driver_name, dev,
                &mrst_rtc_ops, THIS_MODULE);
    if (IS_ERR(mrst_rtc.rtc)) {
        retval = PTR_ERR(mrst_rtc.rtc);
        goto cleanup0;
    }

    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 = request_irq(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 cleanup1;
        }
    }
    dev_dbg(dev, "initialised\n");
    return 0;

cleanup1:
    rtc_device_unregister(mrst_rtc.rtc);
cleanup0:
    dev_set_drvdata(dev, NULL);
    mrst_rtc.dev = NULL;
    release_mem_region(iomem->start, resource_size(iomem));
    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 __devexit rtc_mrst_do_remove(struct device *dev)
{
    struct mrst_rtc *mrst = dev_get_drvdata(dev);
    struct resource *iomem;

    rtc_mrst_do_shutdown();

    if (mrst->irq)
        free_irq(mrst->irq, mrst->rtc);

    rtc_device_unregister(mrst->rtc);
    mrst->rtc = NULL;

    iomem = mrst->iomem;
    release_mem_region(iomem->start, resource_size(iomem));
    mrst->iomem = NULL;

    mrst->dev = NULL;
    dev_set_drvdata(dev, NULL);
}

#ifdef  CONFIG_PM
static int mrst_suspend(struct device *dev, pm_message_t mesg)
{
    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, PMSG_HIBERNATE);
}

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;
}

#else
#define mrst_suspend    NULL
#define mrst_resume NULL

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

#endif

static int __devinit 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 __devexit 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     = __devexit_p(vrtc_mrst_platform_remove),
    .shutdown   = vrtc_mrst_platform_shutdown,
    .driver = {
        .name       = (char *) driver_name,
        .suspend    = mrst_suspend,
        .resume     = mrst_resume,
    }
};

module_platform_driver(vrtc_mrst_platform_driver);

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