1 files changed, 547 insertions, 0 deletions
diff --git a/drivers/rtc/rtc-at91sam9.c b/drivers/rtc/rtc-at91sam9.c
new file mode 100644
index 000000000..e39e89867
--- /dev/null
+++ b/drivers/rtc/rtc-at91sam9.c
@@ -0,0 +1,547 @@
+// SPDX-License-Identifier: GPL-2.0+
+/*
+ * "RTT as Real Time Clock" driver for AT91SAM9 SoC family
+ *
+ * (C) 2007 Michel Benoit
+ *
+ * Based on rtc-at91rm9200.c by Rick Bronson
+ */
+
+#include <linux/clk.h>
+#include <linux/interrupt.h>
+#include <linux/ioctl.h>
+#include <linux/io.h>
+#include <linux/kernel.h>
+#include <linux/mfd/syscon.h>
+#include <linux/module.h>
+#include <linux/of.h>
+#include <linux/platform_device.h>
+#include <linux/regmap.h>
+#include <linux/rtc.h>
+#include <linux/slab.h>
+#include <linux/suspend.h>
+#include <linux/time.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)	/* Timer Prescaler Value */
+#define AT91_RTT_ALMIEN		BIT(16)		/* Alarm Interrupt Enable */
+#define AT91_RTT_RTTINCIEN	BIT(17)		/* Increment Interrupt Enable */
+#define AT91_RTT_RTTRST		BIT(18)		/* 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		BIT(0)		/* Alarm Status */
+#define AT91_RTT_RTTINC		BIT(1)		/* 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_time64_to_tm(offset + secs, tm);
+
+	dev_dbg(dev, "%s: %ptR\n", __func__, tm);
+
+	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);
+	u32 offset, alarm, mr;
+	unsigned long secs;
+
+	dev_dbg(dev, "%s: %ptR\n", __func__, tm);
+
+	secs = rtc_tm_to_time64(tm);
+
+	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_time64_to_tm(offset + alarm, tm);
+
+		dev_dbg(dev, "%s: %ptR\n", __func__, tm);
+
+		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;
+
+	secs = rtc_tm_to_time64(tm);
+
+	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: %ptR\n", __func__, tm);
+
+	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 = 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,
+};
+
+/*
+ * Initialize and install RTC driver
+ */
+static int at91_rtc_probe(struct platform_device *pdev)
+{
+	struct sam9_rtc	*rtc;
+	int		ret, irq;
+	u32		mr;
+	unsigned int	sclk_rate;
+	struct of_phandle_args args;
+
+	irq = platform_get_irq(pdev, 0);
+	if (irq < 0)
+		return irq;
+
+	rtc = devm_kzalloc(&pdev->dev, sizeof(*rtc), GFP_KERNEL);
+	if (!rtc)
+		return -ENOMEM;
+
+	spin_lock_init(&rtc->lock);
+	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);
+
+	rtc->rtt = devm_platform_ioremap_resource(pdev, 0);
+	if (IS_ERR(rtc->rtt))
+		return PTR_ERR(rtc->rtt);
+
+	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);
+
+	ret = clk_prepare_enable(rtc->sclk);
+	if (ret) {
+		dev_err(&pdev->dev, "Could not enable slow clock\n");
+		return ret;
+	}
+
+	sclk_rate = clk_get_rate(rtc->sclk);
+	if (!sclk_rate || sclk_rate > AT91_RTT_RTPRES) {
+		dev_err(&pdev->dev, "Invalid slow clock rate\n");
+		ret = -EINVAL;
+		goto err_clk;
+	}
+
+	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_allocate_device(&pdev->dev);
+	if (IS_ERR(rtc->rtcdev)) {
+		ret = PTR_ERR(rtc->rtcdev);
+		goto err_clk;
+	}
+
+	rtc->rtcdev->ops = &at91_rtc_ops;
+	rtc->rtcdev->range_max = U32_MAX;
+
+	/* 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);
+		goto err_clk;
+	}
+
+	/* 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 rtc_register_device(rtc->rtcdev);
+
+err_clk:
+	clk_disable_unprepare(rtc->sclk);
+
+	return ret;
+}
+
+/*
+ * 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));
+
+	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);
+
+static const struct of_device_id at91_rtc_dt_ids[] = {
+	{ .compatible = "atmel,at91sam9260-rtt" },
+	{ /* sentinel */ }
+};
+MODULE_DEVICE_TABLE(of, at91_rtc_dt_ids);
+
+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");