rtc: add real-time clock driver for NVIDIA Tegra

This is a platform driver that supports the built-in real-time clock on
Tegra SOCs.

Signed-off-by: Andrew Chew <achew@nvidia.com>
Acked-by: Alessandro Zummo <a.zummo@towertech.it>
Acked-by: Wan ZongShun <mcuos.com@gmail.com>
Acked-by: Jon Mayo <jmayo@nvidia.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

1 files changed, 488 insertions, 0 deletions

diff --git a/drivers/rtc/rtc-tegra.c b/drivers/rtc/rtc-tegra.c
new file mode 100644
index 000000000000..2fc31aac3f4e
--- /dev/null
+++ b/drivers/rtc/rtc-tegra.c
@@ -0,0 +1,488 @@
+/*
+ * An RTC driver for the NVIDIA Tegra 200 series internal RTC.
+ *
+ * Copyright (c) 2010, NVIDIA Corporation.
+ *
+ * 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.
+ *
+ * This program is distributed in the hope that it will be useful, but WITHOUT
+ * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
+ * FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General Public License for
+ * more details.
+ *
+ * You should have received a copy of the GNU General Public License along
+ * with this program; if not, write to the Free Software Foundation, Inc.,
+ * 51 Franklin Street, Fifth Floor, Boston, MA  02110-1301, USA.
+ */
+#include <linux/kernel.h>
+#include <linux/init.h>
+#include <linux/module.h>
+#include <linux/slab.h>
+#include <linux/irq.h>
+#include <linux/io.h>
+#include <linux/delay.h>
+#include <linux/rtc.h>
+#include <linux/platform_device.h>
+
+/* set to 1 = busy every eight 32kHz 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_dev;
+        void __iomem            *rtc_base; /* NULL if not initialized. */
+        int                     tegra_rtc_irq; /* alarm and periodic irq */
+        spinlock_t              tegra_rtc_lock;
+};
+
+/* RTC hardware is busy when it is updating its values over AHB once
+ * every eight 32kHz clocks (~250uS).
+ * 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->rtc_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 32kHz clocks (~250uS).
+ * The behavior of this function allows us to make some assumptions without
+ * introducing a race, because 250uS 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 sec, msec;
+        unsigned long sl_irq_flags;
+
+        /* 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->tegra_rtc_lock, sl_irq_flags);
+
+        msec = readl(info->rtc_base + TEGRA_RTC_REG_MILLI_SECONDS);
+        sec = readl(info->rtc_base + TEGRA_RTC_REG_SHADOW_SECONDS);
+
+        spin_unlock_irqrestore(&info->tegra_rtc_lock, sl_irq_flags);
+
+        rtc_time_to_tm(sec, tm);
+
+        dev_vdbg(dev, "time read as %lu. %d/%d/%d %d:%02u:%02u\n",
+                sec,
+                tm->tm_mon + 1,
+                tm->tm_mday,
+                tm->tm_year + 1900,
+                tm->tm_hour,
+                tm->tm_min,
+                tm->tm_sec
+        );
+
+        return 0;
+}
+
+static int tegra_rtc_set_time(struct device *dev, struct rtc_time *tm)
+{
+        struct tegra_rtc_info *info = dev_get_drvdata(dev);
+        unsigned long sec;
+        int ret;
+
+        /* convert tm to seconds. */
+        ret = rtc_valid_tm(tm);
+        if (ret)
+                return ret;
+
+        rtc_tm_to_time(tm, &sec);
+
+        dev_vdbg(dev, "time set to %lu. %d/%d/%d %d:%02u:%02u\n",
+                sec,
+                tm->tm_mon+1,
+                tm->tm_mday,
+                tm->tm_year+1900,
+                tm->tm_hour,
+                tm->tm_min,
+                tm->tm_sec
+        );
+
+        /* seconds only written if wait succeeded. */
+        ret = tegra_rtc_wait_while_busy(dev);
+        if (!ret)
+                writel(sec, info->rtc_base + TEGRA_RTC_REG_SECONDS);
+
+        dev_vdbg(dev, "time read back as %d\n",
+                readl(info->rtc_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);
+        unsigned long sec;
+        unsigned tmp;
+
+        sec = readl(info->rtc_base + TEGRA_RTC_REG_SECONDS_ALARM0);
+
+        if (sec == 0) {
+                /* alarm is disabled. */
+                alarm->enabled = 0;
+                alarm->time.tm_mon = -1;
+                alarm->time.tm_mday = -1;
+                alarm->time.tm_year = -1;
+                alarm->time.tm_hour = -1;
+                alarm->time.tm_min = -1;
+                alarm->time.tm_sec = -1;
+        } else {
+                /* alarm is enabled. */
+                alarm->enabled = 1;
+                rtc_time_to_tm(sec, &alarm->time);
+        }
+
+        tmp = readl(info->rtc_base + TEGRA_RTC_REG_INTR_STATUS);
+        alarm->pending = (tmp & 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 status;
+        unsigned long sl_irq_flags;
+
+        tegra_rtc_wait_while_busy(dev);
+        spin_lock_irqsave(&info->tegra_rtc_lock, sl_irq_flags);
+
+        /* read the original value, and OR in the flag. */
+        status = readl(info->rtc_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->rtc_base + TEGRA_RTC_REG_INTR_MASK);
+
+        spin_unlock_irqrestore(&info->tegra_rtc_lock, sl_irq_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);
+        unsigned long sec;
+
+        if (alarm->enabled)
+                rtc_tm_to_time(&alarm->time, &sec);
+        else
+                sec = 0;
+
+        tegra_rtc_wait_while_busy(dev);
+        writel(sec, info->rtc_base + TEGRA_RTC_REG_SECONDS_ALARM0);
+        dev_vdbg(dev, "alarm read back as %d\n",
+                readl(info->rtc_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 %lu. %d/%d/%d %d:%02u:%02u\n",
+                        sec,
+                        alarm->time.tm_mon+1,
+                        alarm->time.tm_mday,
+                        alarm->time.tm_year+1900,
+                        alarm->time.tm_hour,
+                        alarm->time.tm_min,
+                        alarm->time.tm_sec);
+        } 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;
+
+        return seq_printf(seq, "name\t\t: %s\n", dev_name(dev));
+}
+
+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;
+        unsigned status;
+        unsigned long sl_irq_flags;
+
+        status = readl(info->rtc_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->tegra_rtc_lock, sl_irq_flags);
+                writel(0, info->rtc_base + TEGRA_RTC_REG_INTR_MASK);
+                writel(status, info->rtc_base + TEGRA_RTC_REG_INTR_STATUS);
+                spin_unlock_irqrestore(&info->tegra_rtc_lock, sl_irq_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_dev, 1, events);
+
+        return IRQ_HANDLED;
+}
+
+static 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 int __devinit tegra_rtc_probe(struct platform_device *pdev)
+{
+        struct tegra_rtc_info *info;
+        struct resource *res;
+        int ret;
+
+        info = kzalloc(sizeof(struct tegra_rtc_info), GFP_KERNEL);
+        if (!info)
+                return -ENOMEM;
+
+        res = platform_get_resource(pdev, IORESOURCE_MEM, 0);
+        if (!res) {
+                dev_err(&pdev->dev,
+                        "Unable to allocate resources for device.\n");
+                ret = -EBUSY;
+                goto err_free_info;
+        }
+
+        if (!request_mem_region(res->start, resource_size(res), pdev->name)) {
+                dev_err(&pdev->dev,
+                        "Unable to request mem region for device.\n");
+                ret = -EBUSY;
+                goto err_free_info;
+        }
+
+        info->tegra_rtc_irq = platform_get_irq(pdev, 0);
+        if (info->tegra_rtc_irq <= 0) {
+                ret = -EBUSY;
+                goto err_release_mem_region;
+        }
+
+        info->rtc_base = ioremap_nocache(res->start, resource_size(res));
+        if (!info->rtc_base) {
+                dev_err(&pdev->dev, "Unable to grab IOs for device.\n");
+                ret = -EBUSY;
+                goto err_release_mem_region;
+        }
+
+        /* set context info. */
+        info->pdev = pdev;
+        info->tegra_rtc_lock = __SPIN_LOCK_UNLOCKED(info->tegra_rtc_lock);
+
+        platform_set_drvdata(pdev, info);
+
+        /* clear out the hardware. */
+        writel(0, info->rtc_base + TEGRA_RTC_REG_SECONDS_ALARM0);
+        writel(0xffffffff, info->rtc_base + TEGRA_RTC_REG_INTR_STATUS);
+        writel(0, info->rtc_base + TEGRA_RTC_REG_INTR_MASK);
+
+        device_init_wakeup(&pdev->dev, 1);
+
+        info->rtc_dev = rtc_device_register(
+                pdev->name, &pdev->dev, &tegra_rtc_ops, THIS_MODULE);
+        if (IS_ERR(info->rtc_dev)) {
+                ret = PTR_ERR(info->rtc_dev);
+                info->rtc_dev = NULL;
+                dev_err(&pdev->dev,
+                        "Unable to register device (err=%d).\n",
+                        ret);
+                goto err_iounmap;
+        }
+
+        ret = request_irq(info->tegra_rtc_irq, tegra_rtc_irq_handler,
+                IRQF_TRIGGER_HIGH, "rtc alarm", &pdev->dev);
+        if (ret) {
+                dev_err(&pdev->dev,
+                        "Unable to request interrupt for device (err=%d).\n",
+                        ret);
+                goto err_dev_unreg;
+        }
+
+        dev_notice(&pdev->dev, "Tegra internal Real Time Clock\n");
+
+        return 0;
+
+err_dev_unreg:
+        rtc_device_unregister(info->rtc_dev);
+err_iounmap:
+        iounmap(info->rtc_base);
+err_release_mem_region:
+        release_mem_region(res->start, resource_size(res));
+err_free_info:
+        kfree(info);
+
+        return ret;
+}
+
+static int __devexit tegra_rtc_remove(struct platform_device *pdev)
+{
+        struct tegra_rtc_info *info = platform_get_drvdata(pdev);
+        struct resource *res;
+
+        res = platform_get_resource(pdev, IORESOURCE_MEM, 0);
+        if (!res)
+                return -EBUSY;
+
+        free_irq(info->tegra_rtc_irq, &pdev->dev);
+        rtc_device_unregister(info->rtc_dev);
+        iounmap(info->rtc_base);
+        release_mem_region(res->start, resource_size(res));
+        kfree(info);
+
+        platform_set_drvdata(pdev, NULL);
+
+        return 0;
+}
+
+#ifdef CONFIG_PM
+static int tegra_rtc_suspend(struct platform_device *pdev, pm_message_t state)
+{
+        struct device *dev = &pdev->dev;
+        struct tegra_rtc_info *info = platform_get_drvdata(pdev);
+
+        tegra_rtc_wait_while_busy(dev);
+
+        /* only use ALARM0 as a wake source. */
+        writel(0xffffffff, info->rtc_base + TEGRA_RTC_REG_INTR_STATUS);
+        writel(TEGRA_RTC_INTR_STATUS_SEC_ALARM0,
+                info->rtc_base + TEGRA_RTC_REG_INTR_MASK);
+
+        dev_vdbg(dev, "alarm sec = %d\n",
+                readl(info->rtc_base + TEGRA_RTC_REG_SECONDS_ALARM0));
+
+        dev_vdbg(dev, "Suspend (device_may_wakeup=%d) irq:%d\n",
+                device_may_wakeup(dev), info->tegra_rtc_irq);
+
+        /* leave the alarms on as a wake source. */
+        if (device_may_wakeup(dev))
+                enable_irq_wake(info->tegra_rtc_irq);
+
+        return 0;
+}
+
+static int tegra_rtc_resume(struct platform_device *pdev)
+{
+        struct device *dev = &pdev->dev;
+        struct tegra_rtc_info *info = platform_get_drvdata(pdev);
+
+        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->tegra_rtc_irq);
+
+        return 0;
+}
+#endif
+
+static void tegra_rtc_shutdown(struct platform_device *pdev)
+{
+        dev_vdbg(&pdev->dev, "disabling interrupts.\n");
+        tegra_rtc_alarm_irq_enable(&pdev->dev, 0);
+}
+
+MODULE_ALIAS("platform:tegra_rtc");
+static struct platform_driver tegra_rtc_driver = {
+        .remove         = __devexit_p(tegra_rtc_remove),
+        .shutdown       = tegra_rtc_shutdown,
+        .driver         = {
+                .name   = "tegra_rtc",
+                .owner  = THIS_MODULE,
+        },
+#ifdef CONFIG_PM
+        .suspend        = tegra_rtc_suspend,
+        .resume         = tegra_rtc_resume,
+#endif
+};
+
+static int __init tegra_rtc_init(void)
+{
+        return platform_driver_probe(&tegra_rtc_driver, tegra_rtc_probe);
+}
+module_init(tegra_rtc_init);
+
+static void __exit tegra_rtc_exit(void)
+{
+        platform_driver_unregister(&tegra_rtc_driver);
+}
+module_exit(tegra_rtc_exit);
+
+MODULE_AUTHOR("Jon Mayo <jmayo@nvidia.com>");
+MODULE_DESCRIPTION("driver for Tegra internal RTC");
+MODULE_LICENSE("GPL");