1 files changed, 416 insertions, 0 deletions
diff --git a/drivers/rtc/rtc-tegra.c b/drivers/rtc/rtc-tegra.c
new file mode 100644
index 000000000..7fbb17416
--- /dev/null
+++ b/drivers/rtc/rtc-tegra.c
@@ -0,0 +1,416 @@
+// SPDX-License-Identifier: GPL-2.0+
+/*
+ * An RTC driver for the NVIDIA Tegra 200 series internal RTC.
+ *
+ * Copyright (c) 2010-2019, NVIDIA Corporation.
+ */
+
+#include <linux/clk.h>
+#include <linux/delay.h>
+#include <linux/init.h>
+#include <linux/io.h>
+#include <linux/irq.h>
+#include <linux/kernel.h>
+#include <linux/module.h>
+#include <linux/mod_devicetable.h>
+#include <linux/platform_device.h>
+#include <linux/pm.h>
+#include <linux/rtc.h>
+#include <linux/slab.h>
+
+/* Set to 1 = busy every eight 32 kHz clocks during copy of sec+msec to AHB. */
+#define TEGRA_RTC_REG_BUSY			0x004
+#define TEGRA_RTC_REG_SECONDS			0x008
+/* When msec is read, the seconds are buffered into shadow seconds. */
+#define TEGRA_RTC_REG_SHADOW_SECONDS		0x00c
+#define TEGRA_RTC_REG_MILLI_SECONDS		0x010
+#define TEGRA_RTC_REG_SECONDS_ALARM0		0x014
+#define TEGRA_RTC_REG_SECONDS_ALARM1		0x018
+#define TEGRA_RTC_REG_MILLI_SECONDS_ALARM0	0x01c
+#define TEGRA_RTC_REG_INTR_MASK			0x028
+/* write 1 bits to clear status bits */
+#define TEGRA_RTC_REG_INTR_STATUS		0x02c
+
+/* bits in INTR_MASK */
+#define TEGRA_RTC_INTR_MASK_MSEC_CDN_ALARM	(1<<4)
+#define TEGRA_RTC_INTR_MASK_SEC_CDN_ALARM	(1<<3)
+#define TEGRA_RTC_INTR_MASK_MSEC_ALARM		(1<<2)
+#define TEGRA_RTC_INTR_MASK_SEC_ALARM1		(1<<1)
+#define TEGRA_RTC_INTR_MASK_SEC_ALARM0		(1<<0)
+
+/* bits in INTR_STATUS */
+#define TEGRA_RTC_INTR_STATUS_MSEC_CDN_ALARM	(1<<4)
+#define TEGRA_RTC_INTR_STATUS_SEC_CDN_ALARM	(1<<3)
+#define TEGRA_RTC_INTR_STATUS_MSEC_ALARM	(1<<2)
+#define TEGRA_RTC_INTR_STATUS_SEC_ALARM1	(1<<1)
+#define TEGRA_RTC_INTR_STATUS_SEC_ALARM0	(1<<0)
+
+struct tegra_rtc_info {
+	struct platform_device *pdev;
+	struct rtc_device *rtc;
+	void __iomem *base; /* NULL if not initialized */
+	struct clk *clk;
+	int irq; /* alarm and periodic IRQ */
+	spinlock_t lock;
+};
+
+/*
+ * RTC hardware is busy when it is updating its values over AHB once every
+ * eight 32 kHz clocks (~250 us). Outside of these updates the CPU is free to
+ * write. CPU is always free to read.
+ */
+static inline u32 tegra_rtc_check_busy(struct tegra_rtc_info *info)
+{
+	return readl(info->base + TEGRA_RTC_REG_BUSY) & 1;
+}
+
+/*
+ * Wait for hardware to be ready for writing. This function tries to maximize
+ * the amount of time before the next update. It does this by waiting for the
+ * RTC to become busy with its periodic update, then returning once the RTC
+ * first becomes not busy.
+ *
+ * This periodic update (where the seconds and milliseconds are copied to the
+ * AHB side) occurs every eight 32 kHz clocks (~250 us). The behavior of this
+ * function allows us to make some assumptions without introducing a race,
+ * because 250 us is plenty of time to read/write a value.
+ */
+static int tegra_rtc_wait_while_busy(struct device *dev)
+{
+	struct tegra_rtc_info *info = dev_get_drvdata(dev);
+	int retries = 500; /* ~490 us is the worst case, ~250 us is best */
+
+	/*
+	 * First wait for the RTC to become busy. This is when it posts its
+	 * updated seconds+msec registers to AHB side.
+	 */
+	while (tegra_rtc_check_busy(info)) {
+		if (!retries--)
+			goto retry_failed;
+
+		udelay(1);
+	}
+
+	/* now we have about 250 us to manipulate registers */
+	return 0;
+
+retry_failed:
+	dev_err(dev, "write failed: retry count exceeded\n");
+	return -ETIMEDOUT;
+}
+
+static int tegra_rtc_read_time(struct device *dev, struct rtc_time *tm)
+{
+	struct tegra_rtc_info *info = dev_get_drvdata(dev);
+	unsigned long flags;
+	u32 sec;
+
+	/*
+	 * RTC hardware copies seconds to shadow seconds when a read of
+	 * milliseconds occurs. use a lock to keep other threads out.
+	 */
+	spin_lock_irqsave(&info->lock, flags);
+
+	readl(info->base + TEGRA_RTC_REG_MILLI_SECONDS);
+	sec = readl(info->base + TEGRA_RTC_REG_SHADOW_SECONDS);
+
+	spin_unlock_irqrestore(&info->lock, flags);
+
+	rtc_time64_to_tm(sec, tm);
+
+	dev_vdbg(dev, "time read as %u, %ptR\n", sec, tm);
+
+	return 0;
+}
+
+static int tegra_rtc_set_time(struct device *dev, struct rtc_time *tm)
+{
+	struct tegra_rtc_info *info = dev_get_drvdata(dev);
+	u32 sec;
+	int ret;
+
+	/* convert tm to seconds */
+	sec = rtc_tm_to_time64(tm);
+
+	dev_vdbg(dev, "time set to %u, %ptR\n", sec, tm);
+
+	/* seconds only written if wait succeeded */
+	ret = tegra_rtc_wait_while_busy(dev);
+	if (!ret)
+		writel(sec, info->base + TEGRA_RTC_REG_SECONDS);
+
+	dev_vdbg(dev, "time read back as %d\n",
+		 readl(info->base + TEGRA_RTC_REG_SECONDS));
+
+	return ret;
+}
+
+static int tegra_rtc_read_alarm(struct device *dev, struct rtc_wkalrm *alarm)
+{
+	struct tegra_rtc_info *info = dev_get_drvdata(dev);
+	u32 sec, value;
+
+	sec = readl(info->base + TEGRA_RTC_REG_SECONDS_ALARM0);
+
+	if (sec == 0) {
+		/* alarm is disabled */
+		alarm->enabled = 0;
+	} else {
+		/* alarm is enabled */
+		alarm->enabled = 1;
+		rtc_time64_to_tm(sec, &alarm->time);
+	}
+
+	value = readl(info->base + TEGRA_RTC_REG_INTR_STATUS);
+	alarm->pending = (value & TEGRA_RTC_INTR_STATUS_SEC_ALARM0) != 0;
+
+	return 0;
+}
+
+static int tegra_rtc_alarm_irq_enable(struct device *dev, unsigned int enabled)
+{
+	struct tegra_rtc_info *info = dev_get_drvdata(dev);
+	unsigned long flags;
+	u32 status;
+
+	tegra_rtc_wait_while_busy(dev);
+	spin_lock_irqsave(&info->lock, flags);
+
+	/* read the original value, and OR in the flag */
+	status = readl(info->base + TEGRA_RTC_REG_INTR_MASK);
+	if (enabled)
+		status |= TEGRA_RTC_INTR_MASK_SEC_ALARM0; /* set it */
+	else
+		status &= ~TEGRA_RTC_INTR_MASK_SEC_ALARM0; /* clear it */
+
+	writel(status, info->base + TEGRA_RTC_REG_INTR_MASK);
+
+	spin_unlock_irqrestore(&info->lock, flags);
+
+	return 0;
+}
+
+static int tegra_rtc_set_alarm(struct device *dev, struct rtc_wkalrm *alarm)
+{
+	struct tegra_rtc_info *info = dev_get_drvdata(dev);
+	u32 sec;
+
+	if (alarm->enabled)
+		sec = rtc_tm_to_time64(&alarm->time);
+	else
+		sec = 0;
+
+	tegra_rtc_wait_while_busy(dev);
+	writel(sec, info->base + TEGRA_RTC_REG_SECONDS_ALARM0);
+	dev_vdbg(dev, "alarm read back as %d\n",
+		 readl(info->base + TEGRA_RTC_REG_SECONDS_ALARM0));
+
+	/* if successfully written and alarm is enabled ... */
+	if (sec) {
+		tegra_rtc_alarm_irq_enable(dev, 1);
+		dev_vdbg(dev, "alarm set as %u, %ptR\n", sec, &alarm->time);
+	} else {
+		/* disable alarm if 0 or write error */
+		dev_vdbg(dev, "alarm disabled\n");
+		tegra_rtc_alarm_irq_enable(dev, 0);
+	}
+
+	return 0;
+}
+
+static int tegra_rtc_proc(struct device *dev, struct seq_file *seq)
+{
+	if (!dev || !dev->driver)
+		return 0;
+
+	seq_printf(seq, "name\t\t: %s\n", dev_name(dev));
+
+	return 0;
+}
+
+static irqreturn_t tegra_rtc_irq_handler(int irq, void *data)
+{
+	struct device *dev = data;
+	struct tegra_rtc_info *info = dev_get_drvdata(dev);
+	unsigned long events = 0, flags;
+	u32 status;
+
+	status = readl(info->base + TEGRA_RTC_REG_INTR_STATUS);
+	if (status) {
+		/* clear the interrupt masks and status on any IRQ */
+		tegra_rtc_wait_while_busy(dev);
+
+		spin_lock_irqsave(&info->lock, flags);
+		writel(0, info->base + TEGRA_RTC_REG_INTR_MASK);
+		writel(status, info->base + TEGRA_RTC_REG_INTR_STATUS);
+		spin_unlock_irqrestore(&info->lock, flags);
+	}
+
+	/* check if alarm */
+	if (status & TEGRA_RTC_INTR_STATUS_SEC_ALARM0)
+		events |= RTC_IRQF | RTC_AF;
+
+	/* check if periodic */
+	if (status & TEGRA_RTC_INTR_STATUS_SEC_CDN_ALARM)
+		events |= RTC_IRQF | RTC_PF;
+
+	rtc_update_irq(info->rtc, 1, events);
+
+	return IRQ_HANDLED;
+}
+
+static const struct rtc_class_ops tegra_rtc_ops = {
+	.read_time = tegra_rtc_read_time,
+	.set_time = tegra_rtc_set_time,
+	.read_alarm = tegra_rtc_read_alarm,
+	.set_alarm = tegra_rtc_set_alarm,
+	.proc = tegra_rtc_proc,
+	.alarm_irq_enable = tegra_rtc_alarm_irq_enable,
+};
+
+static const struct of_device_id tegra_rtc_dt_match[] = {
+	{ .compatible = "nvidia,tegra20-rtc", },
+	{}
+};
+MODULE_DEVICE_TABLE(of, tegra_rtc_dt_match);
+
+static int tegra_rtc_probe(struct platform_device *pdev)
+{
+	struct tegra_rtc_info *info;
+	int ret;
+
+	info = devm_kzalloc(&pdev->dev, sizeof(*info), GFP_KERNEL);
+	if (!info)
+		return -ENOMEM;
+
+	info->base = devm_platform_ioremap_resource(pdev, 0);
+	if (IS_ERR(info->base))
+		return PTR_ERR(info->base);
+
+	ret = platform_get_irq(pdev, 0);
+	if (ret <= 0)
+		return ret;
+
+	info->irq = ret;
+
+	info->rtc = devm_rtc_allocate_device(&pdev->dev);
+	if (IS_ERR(info->rtc))
+		return PTR_ERR(info->rtc);
+
+	info->rtc->ops = &tegra_rtc_ops;
+	info->rtc->range_max = U32_MAX;
+
+	info->clk = devm_clk_get(&pdev->dev, NULL);
+	if (IS_ERR(info->clk))
+		return PTR_ERR(info->clk);
+
+	ret = clk_prepare_enable(info->clk);
+	if (ret < 0)
+		return ret;
+
+	/* set context info */
+	info->pdev = pdev;
+	spin_lock_init(&info->lock);
+
+	platform_set_drvdata(pdev, info);
+
+	/* clear out the hardware */
+	writel(0, info->base + TEGRA_RTC_REG_SECONDS_ALARM0);
+	writel(0xffffffff, info->base + TEGRA_RTC_REG_INTR_STATUS);
+	writel(0, info->base + TEGRA_RTC_REG_INTR_MASK);
+
+	device_init_wakeup(&pdev->dev, 1);
+
+	ret = devm_request_irq(&pdev->dev, info->irq, tegra_rtc_irq_handler,
+			       IRQF_TRIGGER_HIGH, dev_name(&pdev->dev),
+			       &pdev->dev);
+	if (ret) {
+		dev_err(&pdev->dev, "failed to request interrupt: %d\n", ret);
+		goto disable_clk;
+	}
+
+	ret = rtc_register_device(info->rtc);
+	if (ret)
+		goto disable_clk;
+
+	dev_notice(&pdev->dev, "Tegra internal Real Time Clock\n");
+
+	return 0;
+
+disable_clk:
+	clk_disable_unprepare(info->clk);
+	return ret;
+}
+
+static int tegra_rtc_remove(struct platform_device *pdev)
+{
+	struct tegra_rtc_info *info = platform_get_drvdata(pdev);
+
+	clk_disable_unprepare(info->clk);
+
+	return 0;
+}
+
+#ifdef CONFIG_PM_SLEEP
+static int tegra_rtc_suspend(struct device *dev)
+{
+	struct tegra_rtc_info *info = dev_get_drvdata(dev);
+
+	tegra_rtc_wait_while_busy(dev);
+
+	/* only use ALARM0 as a wake source */
+	writel(0xffffffff, info->base + TEGRA_RTC_REG_INTR_STATUS);
+	writel(TEGRA_RTC_INTR_STATUS_SEC_ALARM0,
+	       info->base + TEGRA_RTC_REG_INTR_MASK);
+
+	dev_vdbg(dev, "alarm sec = %d\n",
+		 readl(info->base + TEGRA_RTC_REG_SECONDS_ALARM0));
+
+	dev_vdbg(dev, "Suspend (device_may_wakeup=%d) IRQ:%d\n",
+		 device_may_wakeup(dev), info->irq);
+
+	/* leave the alarms on as a wake source */
+	if (device_may_wakeup(dev))
+		enable_irq_wake(info->irq);
+
+	return 0;
+}
+
+static int tegra_rtc_resume(struct device *dev)
+{
+	struct tegra_rtc_info *info = dev_get_drvdata(dev);
+
+	dev_vdbg(dev, "Resume (device_may_wakeup=%d)\n",
+		 device_may_wakeup(dev));
+
+	/* alarms were left on as a wake source, turn them off */
+	if (device_may_wakeup(dev))
+		disable_irq_wake(info->irq);
+
+	return 0;
+}
+#endif
+
+static SIMPLE_DEV_PM_OPS(tegra_rtc_pm_ops, tegra_rtc_suspend, tegra_rtc_resume);
+
+static void tegra_rtc_shutdown(struct platform_device *pdev)
+{
+	dev_vdbg(&pdev->dev, "disabling interrupts\n");
+	tegra_rtc_alarm_irq_enable(&pdev->dev, 0);
+}
+
+static struct platform_driver tegra_rtc_driver = {
+	.probe = tegra_rtc_probe,
+	.remove = tegra_rtc_remove,
+	.shutdown = tegra_rtc_shutdown,
+	.driver = {
+		.name = "tegra_rtc",
+		.of_match_table = tegra_rtc_dt_match,
+		.pm = &tegra_rtc_pm_ops,
+	},
+};
+module_platform_driver(tegra_rtc_driver);
+
+MODULE_AUTHOR("Jon Mayo <jmayo@nvidia.com>");
+MODULE_DESCRIPTION("driver for Tegra internal RTC");
+MODULE_LICENSE("GPL");