--- /dev/null
+/*
+ * "RTT as Real Time Clock" driver for AT91SAM9 SoC family
+ *
+ * (C) 2007 Michel Benoit
+ *
+ * Based on rtc-at91rm9200.c by Rick Bronson
+ *
+ * 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; either version
+ * 2 of the License, or (at your option) any later version.
+ */
+
+#include <linux/module.h>
+#include <linux/kernel.h>
+#include <linux/platform_device.h>
+#include <linux/time.h>
+#include <linux/rtc.h>
+#include <linux/interrupt.h>
+#include <linux/ioctl.h>
+#include <linux/slab.h>
+#include <linux/platform_data/atmel.h>
+#include <linux/io.h>
+#include <linux/mfd/syscon.h>
+#include <linux/regmap.h>
+#include <linux/suspend.h>
+#include <linux/clk.h>
+
+/*
+ * This driver uses two configurable hardware resources that live in the
+ * AT91SAM9 backup power domain (intended to be powered at all times)
+ * to implement the Real Time Clock interfaces
+ *
+ * - A "Real-time Timer" (RTT) counts up in seconds from a base time.
+ * We can't assign the counter value (CRTV) ... but we can reset it.
+ *
+ * - One of the "General Purpose Backup Registers" (GPBRs) holds the
+ * base time, normally an offset from the beginning of the POSIX
+ * epoch (1970-Jan-1 00:00:00 UTC). Some systems also include the
+ * local timezone's offset.
+ *
+ * The RTC's value is the RTT counter plus that offset. The RTC's alarm
+ * is likewise a base (ALMV) plus that offset.
+ *
+ * Not all RTTs will be used as RTCs; some systems have multiple RTTs to
+ * choose from, or a "real" RTC module. All systems have multiple GPBR
+ * registers available, likewise usable for more than "RTC" support.
+ */
+
+#define AT91_RTT_MR 0x00 /* Real-time Mode Register */
+#define AT91_RTT_RTPRES (0xffff << 0) /* Real-time Timer Prescaler Value */
+#define AT91_RTT_ALMIEN (1 << 16) /* Alarm Interrupt Enable */
+#define AT91_RTT_RTTINCIEN (1 << 17) /* Real Time Timer Increment Interrupt Enable */
+#define AT91_RTT_RTTRST (1 << 18) /* Real Time Timer Restart */
+
+#define AT91_RTT_AR 0x04 /* Real-time Alarm Register */
+#define AT91_RTT_ALMV (0xffffffff) /* Alarm Value */
+
+#define AT91_RTT_VR 0x08 /* Real-time Value Register */
+#define AT91_RTT_CRTV (0xffffffff) /* Current Real-time Value */
+
+#define AT91_RTT_SR 0x0c /* Real-time Status Register */
+#define AT91_RTT_ALMS (1 << 0) /* Real-time Alarm Status */
+#define AT91_RTT_RTTINC (1 << 1) /* Real-time Timer Increment */
+
+/*
+ * We store ALARM_DISABLED in ALMV to record that no alarm is set.
+ * It's also the reset value for that field.
+ */
+#define ALARM_DISABLED ((u32)~0)
+
+
+struct sam9_rtc {
+ void __iomem *rtt;
+ struct rtc_device *rtcdev;
+ u32 imr;
+ struct regmap *gpbr;
+ unsigned int gpbr_offset;
+ int irq;
+ struct clk *sclk;
+ bool suspended;
+ unsigned long events;
+ spinlock_t lock;
+};
+
+#define rtt_readl(rtc, field) \
+ readl((rtc)->rtt + AT91_RTT_ ## field)
+#define rtt_writel(rtc, field, val) \
+ writel((val), (rtc)->rtt + AT91_RTT_ ## field)
+
+static inline unsigned int gpbr_readl(struct sam9_rtc *rtc)
+{
+ unsigned int val;
+
+ regmap_read(rtc->gpbr, rtc->gpbr_offset, &val);
+
+ return val;
+}
+
+static inline void gpbr_writel(struct sam9_rtc *rtc, unsigned int val)
+{
+ regmap_write(rtc->gpbr, rtc->gpbr_offset, val);
+}
+
+/*
+ * Read current time and date in RTC
+ */
+static int at91_rtc_readtime(struct device *dev, struct rtc_time *tm)
+{
+ struct sam9_rtc *rtc = dev_get_drvdata(dev);
+ u32 secs, secs2;
+ u32 offset;
+
+ /* read current time offset */
+ offset = gpbr_readl(rtc);
+ if (offset == 0)
+ return -EILSEQ;
+
+ /* reread the counter to help sync the two clock domains */
+ secs = rtt_readl(rtc, VR);
+ secs2 = rtt_readl(rtc, VR);
+ if (secs != secs2)
+ secs = rtt_readl(rtc, VR);
+
+ rtc_time_to_tm(offset + secs, tm);
+
+ dev_dbg(dev, "%s: %4d-%02d-%02d %02d:%02d:%02d\n", "readtime",
+ 1900 + tm->tm_year, tm->tm_mon, tm->tm_mday,
+ tm->tm_hour, tm->tm_min, tm->tm_sec);
+
+ return 0;
+}
+
+/*
+ * Set current time and date in RTC
+ */
+static int at91_rtc_settime(struct device *dev, struct rtc_time *tm)
+{
+ struct sam9_rtc *rtc = dev_get_drvdata(dev);
+ int err;
+ u32 offset, alarm, mr;
+ unsigned long secs;
+
+ dev_dbg(dev, "%s: %4d-%02d-%02d %02d:%02d:%02d\n", "settime",
+ 1900 + tm->tm_year, tm->tm_mon, tm->tm_mday,
+ tm->tm_hour, tm->tm_min, tm->tm_sec);
+
+ err = rtc_tm_to_time(tm, &secs);
+ if (err != 0)
+ return err;
+
+ mr = rtt_readl(rtc, MR);
+
+ /* disable interrupts */
+ rtt_writel(rtc, MR, mr & ~(AT91_RTT_ALMIEN | AT91_RTT_RTTINCIEN));
+
+ /* read current time offset */
+ offset = gpbr_readl(rtc);
+
+ /* store the new base time in a battery backup register */
+ secs += 1;
+ gpbr_writel(rtc, secs);
+
+ /* adjust the alarm time for the new base */
+ alarm = rtt_readl(rtc, AR);
+ if (alarm != ALARM_DISABLED) {
+ if (offset > secs) {
+ /* time jumped backwards, increase time until alarm */
+ alarm += (offset - secs);
+ } else if ((alarm + offset) > secs) {
+ /* time jumped forwards, decrease time until alarm */
+ alarm -= (secs - offset);
+ } else {
+ /* time jumped past the alarm, disable alarm */
+ alarm = ALARM_DISABLED;
+ mr &= ~AT91_RTT_ALMIEN;
+ }
+ rtt_writel(rtc, AR, alarm);
+ }
+
+ /* reset the timer, and re-enable interrupts */
+ rtt_writel(rtc, MR, mr | AT91_RTT_RTTRST);
+
+ return 0;
+}
+
+static int at91_rtc_readalarm(struct device *dev, struct rtc_wkalrm *alrm)
+{
+ struct sam9_rtc *rtc = dev_get_drvdata(dev);
+ struct rtc_time *tm = &alrm->time;
+ u32 alarm = rtt_readl(rtc, AR);
+ u32 offset;
+
+ offset = gpbr_readl(rtc);
+ if (offset == 0)
+ return -EILSEQ;
+
+ memset(alrm, 0, sizeof(*alrm));
+ if (alarm != ALARM_DISABLED && offset != 0) {
+ rtc_time_to_tm(offset + alarm, tm);
+
+ dev_dbg(dev, "%s: %4d-%02d-%02d %02d:%02d:%02d\n", "readalarm",
+ 1900 + tm->tm_year, tm->tm_mon, tm->tm_mday,
+ tm->tm_hour, tm->tm_min, tm->tm_sec);
+
+ if (rtt_readl(rtc, MR) & AT91_RTT_ALMIEN)
+ alrm->enabled = 1;
+ }
+
+ return 0;
+}
+
+static int at91_rtc_setalarm(struct device *dev, struct rtc_wkalrm *alrm)
+{
+ struct sam9_rtc *rtc = dev_get_drvdata(dev);
+ struct rtc_time *tm = &alrm->time;
+ unsigned long secs;
+ u32 offset;
+ u32 mr;
+ int err;
+
+ err = rtc_tm_to_time(tm, &secs);
+ if (err != 0)
+ return err;
+
+ offset = gpbr_readl(rtc);
+ if (offset == 0) {
+ /* time is not set */
+ return -EILSEQ;
+ }
+ mr = rtt_readl(rtc, MR);
+ rtt_writel(rtc, MR, mr & ~AT91_RTT_ALMIEN);
+
+ /* alarm in the past? finish and leave disabled */
+ if (secs <= offset) {
+ rtt_writel(rtc, AR, ALARM_DISABLED);
+ return 0;
+ }
+
+ /* else set alarm and maybe enable it */
+ rtt_writel(rtc, AR, secs - offset);
+ if (alrm->enabled)
+ rtt_writel(rtc, MR, mr | AT91_RTT_ALMIEN);
+
+ dev_dbg(dev, "%s: %4d-%02d-%02d %02d:%02d:%02d\n", "setalarm",
+ tm->tm_year, tm->tm_mon, tm->tm_mday, tm->tm_hour,
+ tm->tm_min, tm->tm_sec);
+
+ return 0;
+}
+
+static int at91_rtc_alarm_irq_enable(struct device *dev, unsigned int enabled)
+{
+ struct sam9_rtc *rtc = dev_get_drvdata(dev);
+ u32 mr = rtt_readl(rtc, MR);
+
+ dev_dbg(dev, "alarm_irq_enable: enabled=%08x, mr %08x\n", enabled, mr);
+ if (enabled)
+ rtt_writel(rtc, MR, mr | AT91_RTT_ALMIEN);
+ else
+ rtt_writel(rtc, MR, mr & ~AT91_RTT_ALMIEN);
+ return 0;
+}
+
+/*
+ * Provide additional RTC information in /proc/driver/rtc
+ */
+static int at91_rtc_proc(struct device *dev, struct seq_file *seq)
+{
+ struct sam9_rtc *rtc = dev_get_drvdata(dev);
+ u32 mr = mr = rtt_readl(rtc, MR);
+
+ seq_printf(seq, "update_IRQ\t: %s\n",
+ (mr & AT91_RTT_RTTINCIEN) ? "yes" : "no");
+ return 0;
+}
+
+static irqreturn_t at91_rtc_cache_events(struct sam9_rtc *rtc)
+{
+ u32 sr, mr;
+
+ /* Shared interrupt may be for another device. Note: reading
+ * SR clears it, so we must only read it in this irq handler!
+ */
+ mr = rtt_readl(rtc, MR) & (AT91_RTT_ALMIEN | AT91_RTT_RTTINCIEN);
+ sr = rtt_readl(rtc, SR) & (mr >> 16);
+ if (!sr)
+ return IRQ_NONE;
+
+ /* alarm status */
+ if (sr & AT91_RTT_ALMS)
+ rtc->events |= (RTC_AF | RTC_IRQF);
+
+ /* timer update/increment */
+ if (sr & AT91_RTT_RTTINC)
+ rtc->events |= (RTC_UF | RTC_IRQF);
+
+ return IRQ_HANDLED;
+}
+
+static void at91_rtc_flush_events(struct sam9_rtc *rtc)
+{
+ if (!rtc->events)
+ return;
+
+ rtc_update_irq(rtc->rtcdev, 1, rtc->events);
+ rtc->events = 0;
+
+ pr_debug("%s: num=%ld, events=0x%02lx\n", __func__,
+ rtc->events >> 8, rtc->events & 0x000000FF);
+}
+
+/*
+ * IRQ handler for the RTC
+ */
+static irqreturn_t at91_rtc_interrupt(int irq, void *_rtc)
+{
+ struct sam9_rtc *rtc = _rtc;
+ int ret;
+
+ spin_lock(&rtc->lock);
+
+ ret = at91_rtc_cache_events(rtc);
+
+ /* We're called in suspended state */
+ if (rtc->suspended) {
+ /* Mask irqs coming from this peripheral */
+ rtt_writel(rtc, MR,
+ rtt_readl(rtc, MR) &
+ ~(AT91_RTT_ALMIEN | AT91_RTT_RTTINCIEN));
+ /* Trigger a system wakeup */
+ pm_system_wakeup();
+ } else {
+ at91_rtc_flush_events(rtc);
+ }
+
+ spin_unlock(&rtc->lock);
+
+ return ret;
+}
+
+static const struct rtc_class_ops at91_rtc_ops = {
+ .read_time = at91_rtc_readtime,
+ .set_time = at91_rtc_settime,
+ .read_alarm = at91_rtc_readalarm,
+ .set_alarm = at91_rtc_setalarm,
+ .proc = at91_rtc_proc,
+ .alarm_irq_enable = at91_rtc_alarm_irq_enable,
+};
+
+static const struct regmap_config gpbr_regmap_config = {
+ .reg_bits = 32,
+ .val_bits = 32,
+ .reg_stride = 4,
+};
+
+/*
+ * Initialize and install RTC driver
+ */
+static int at91_rtc_probe(struct platform_device *pdev)
+{
+ struct resource *r;
+ struct sam9_rtc *rtc;
+ int ret, irq;
+ u32 mr;
+ unsigned int sclk_rate;
+
+ irq = platform_get_irq(pdev, 0);
+ if (irq < 0) {
+ dev_err(&pdev->dev, "failed to get interrupt resource\n");
+ return irq;
+ }
+
+ rtc = devm_kzalloc(&pdev->dev, sizeof(*rtc), GFP_KERNEL);
+ if (!rtc)
+ return -ENOMEM;
+
+ rtc->irq = irq;
+
+ /* platform setup code should have handled this; sigh */
+ if (!device_can_wakeup(&pdev->dev))
+ device_init_wakeup(&pdev->dev, 1);
+
+ platform_set_drvdata(pdev, rtc);
+
+ r = platform_get_resource(pdev, IORESOURCE_MEM, 0);
+ rtc->rtt = devm_ioremap_resource(&pdev->dev, r);
+ if (IS_ERR(rtc->rtt))
+ return PTR_ERR(rtc->rtt);
+
+ if (!pdev->dev.of_node) {
+ /*
+ * TODO: Remove this code chunk when removing non DT board
+ * support. Remember to remove the gpbr_regmap_config
+ * variable too.
+ */
+ void __iomem *gpbr;
+
+ r = platform_get_resource(pdev, IORESOURCE_MEM, 1);
+ gpbr = devm_ioremap_resource(&pdev->dev, r);
+ if (IS_ERR(gpbr))
+ return PTR_ERR(gpbr);
+
+ rtc->gpbr = regmap_init_mmio(NULL, gpbr,
+ &gpbr_regmap_config);
+ } else {
+ struct of_phandle_args args;
+
+ ret = of_parse_phandle_with_fixed_args(pdev->dev.of_node,
+ "atmel,rtt-rtc-time-reg", 1, 0,
+ &args);
+ if (ret)
+ return ret;
+
+ rtc->gpbr = syscon_node_to_regmap(args.np);
+ rtc->gpbr_offset = args.args[0];
+ }
+
+ if (IS_ERR(rtc->gpbr)) {
+ dev_err(&pdev->dev, "failed to retrieve gpbr regmap, aborting.\n");
+ return -ENOMEM;
+ }
+
+ rtc->sclk = devm_clk_get(&pdev->dev, NULL);
+ if (IS_ERR(rtc->sclk))
+ return PTR_ERR(rtc->sclk);
+
+ sclk_rate = clk_get_rate(rtc->sclk);
+ if (!sclk_rate || sclk_rate > AT91_RTT_RTPRES) {
+ dev_err(&pdev->dev, "Invalid slow clock rate\n");
+ return -EINVAL;
+ }
+
+ ret = clk_prepare_enable(rtc->sclk);
+ if (ret) {
+ dev_err(&pdev->dev, "Could not enable slow clock\n");
+ return ret;
+ }
+
+ mr = rtt_readl(rtc, MR);
+
+ /* unless RTT is counting at 1 Hz, re-initialize it */
+ if ((mr & AT91_RTT_RTPRES) != sclk_rate) {
+ mr = AT91_RTT_RTTRST | (sclk_rate & AT91_RTT_RTPRES);
+ gpbr_writel(rtc, 0);
+ }
+
+ /* disable all interrupts (same as on shutdown path) */
+ mr &= ~(AT91_RTT_ALMIEN | AT91_RTT_RTTINCIEN);
+ rtt_writel(rtc, MR, mr);
+
+ rtc->rtcdev = devm_rtc_device_register(&pdev->dev, pdev->name,
+ &at91_rtc_ops, THIS_MODULE);
+ if (IS_ERR(rtc->rtcdev))
+ return PTR_ERR(rtc->rtcdev);
+
+ /* register irq handler after we know what name we'll use */
+ ret = devm_request_irq(&pdev->dev, rtc->irq, at91_rtc_interrupt,
+ IRQF_SHARED | IRQF_COND_SUSPEND,
+ dev_name(&rtc->rtcdev->dev), rtc);
+ if (ret) {
+ dev_dbg(&pdev->dev, "can't share IRQ %d?\n", rtc->irq);
+ return ret;
+ }
+
+ /* NOTE: sam9260 rev A silicon has a ROM bug which resets the
+ * RTT on at least some reboots. If you have that chip, you must
+ * initialize the time from some external source like a GPS, wall
+ * clock, discrete RTC, etc
+ */
+
+ if (gpbr_readl(rtc) == 0)
+ dev_warn(&pdev->dev, "%s: SET TIME!\n",
+ dev_name(&rtc->rtcdev->dev));
+
+ return 0;
+}
+
+/*
+ * Disable and remove the RTC driver
+ */
+static int at91_rtc_remove(struct platform_device *pdev)
+{
+ struct sam9_rtc *rtc = platform_get_drvdata(pdev);
+ u32 mr = rtt_readl(rtc, MR);
+
+ /* disable all interrupts */
+ rtt_writel(rtc, MR, mr & ~(AT91_RTT_ALMIEN | AT91_RTT_RTTINCIEN));
+
+ if (!IS_ERR(rtc->sclk))
+ clk_disable_unprepare(rtc->sclk);
+
+ return 0;
+}
+
+static void at91_rtc_shutdown(struct platform_device *pdev)
+{
+ struct sam9_rtc *rtc = platform_get_drvdata(pdev);
+ u32 mr = rtt_readl(rtc, MR);
+
+ rtc->imr = mr & (AT91_RTT_ALMIEN | AT91_RTT_RTTINCIEN);
+ rtt_writel(rtc, MR, mr & ~rtc->imr);
+}
+
+#ifdef CONFIG_PM_SLEEP
+
+/* AT91SAM9 RTC Power management control */
+
+static int at91_rtc_suspend(struct device *dev)
+{
+ struct sam9_rtc *rtc = dev_get_drvdata(dev);
+ u32 mr = rtt_readl(rtc, MR);
+
+ /*
+ * This IRQ is shared with DBGU and other hardware which isn't
+ * necessarily a wakeup event source.
+ */
+ rtc->imr = mr & (AT91_RTT_ALMIEN | AT91_RTT_RTTINCIEN);
+ if (rtc->imr) {
+ if (device_may_wakeup(dev) && (mr & AT91_RTT_ALMIEN)) {
+ unsigned long flags;
+
+ enable_irq_wake(rtc->irq);
+ spin_lock_irqsave(&rtc->lock, flags);
+ rtc->suspended = true;
+ spin_unlock_irqrestore(&rtc->lock, flags);
+ /* don't let RTTINC cause wakeups */
+ if (mr & AT91_RTT_RTTINCIEN)
+ rtt_writel(rtc, MR, mr & ~AT91_RTT_RTTINCIEN);
+ } else
+ rtt_writel(rtc, MR, mr & ~rtc->imr);
+ }
+
+ return 0;
+}
+
+static int at91_rtc_resume(struct device *dev)
+{
+ struct sam9_rtc *rtc = dev_get_drvdata(dev);
+ u32 mr;
+
+ if (rtc->imr) {
+ unsigned long flags;
+
+ if (device_may_wakeup(dev))
+ disable_irq_wake(rtc->irq);
+ mr = rtt_readl(rtc, MR);
+ rtt_writel(rtc, MR, mr | rtc->imr);
+
+ spin_lock_irqsave(&rtc->lock, flags);
+ rtc->suspended = false;
+ at91_rtc_cache_events(rtc);
+ at91_rtc_flush_events(rtc);
+ spin_unlock_irqrestore(&rtc->lock, flags);
+ }
+
+ return 0;
+}
+#endif
+
+static SIMPLE_DEV_PM_OPS(at91_rtc_pm_ops, at91_rtc_suspend, at91_rtc_resume);
+
+#ifdef CONFIG_OF
+static const struct of_device_id at91_rtc_dt_ids[] = {
+ { .compatible = "atmel,at91sam9260-rtt" },
+ { /* sentinel */ }
+};
+MODULE_DEVICE_TABLE(of, at91_rtc_dt_ids);
+#endif
+
+static struct platform_driver at91_rtc_driver = {
+ .probe = at91_rtc_probe,
+ .remove = at91_rtc_remove,
+ .shutdown = at91_rtc_shutdown,
+ .driver = {
+ .name = "rtc-at91sam9",
+ .pm = &at91_rtc_pm_ops,
+ .of_match_table = of_match_ptr(at91_rtc_dt_ids),
+ },
+};
+
+module_platform_driver(at91_rtc_driver);
+
+MODULE_AUTHOR("Michel Benoit");
+MODULE_DESCRIPTION("RTC driver for Atmel AT91SAM9x");
+MODULE_LICENSE("GPL");
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