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Subject[PATCH 1/1 V4] rtc: Add real-time clock driver for Tegra.
Date
From: Andrew Chew <achew@nvidia.com>

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>
---
Applied Alessandro Zummo's corrections.
Applied Wan ZongShun's corrections.
Jon Mayo addressed comments by Erik Gilling, to wit:
Removed RTC_TEGRA_RETRIES.
Renamed macros to match the prefix used in the rest of the code.
Improved function comments to provide more detail.
Implemented the TODO in tegra_rtc_wait_while_busy(), commented.
Removed tegra_rtc_write_not_busy.
Fixed several places where tegra_rtc_check_busy() was called before a call to
tegra_rtc_wait_while_busy().
Removed locks on some read-only accesses.
Commented the lock in tegra_rtc_read_time() to explain why it was necessary.
Fixed race in tegra_rtc_alarm_irq_enable()
Protect tegra_rtc_irq_handler() with a busy check that uses udelay().
Fixed a race with clearing of all interrupts. Only clear the ones that
activated the interrupt.
Added request_mem_region() (and a corresponding release_mem_region()).
Protected tegra_rtc_suspend() with a busy flag check.
In addition:
Removed unnecessary status/interrupt code from tegra_rtc_resume().
Fixed all races and bad behavior with waiting/sleeping between spinlocks.
drivers/rtc/Kconfig | 10 +
drivers/rtc/Makefile | 1 +
drivers/rtc/rtc-tegra.c | 488 +++++++++++++++++++++++++++++++++++++++++++++++
3 files changed, 499 insertions(+), 0 deletions(-)
create mode 100644 drivers/rtc/rtc-tegra.c
diff --git a/drivers/rtc/Kconfig b/drivers/rtc/Kconfig
index 2432541..ca0da79 100644
--- a/drivers/rtc/Kconfig
+++ b/drivers/rtc/Kconfig
@@ -963,4 +963,14 @@ config RTC_DRV_JZ4740
This driver can also be buillt as a module. If so, the module
will be called rtc-jz4740.

+config RTC_DRV_TEGRA
+ tristate "NVIDIA Tegra Internal RTC driver"
+ depends on RTC_CLASS && ARCH_TEGRA
+ help
+ If you say yes here you get support for the
+ Tegra 200 series internal RTC module.
+
+ This drive can also be built as a module. If so, the module
+ will be called rtc-tegra.
+
endif # RTC_CLASS
diff --git a/drivers/rtc/Makefile b/drivers/rtc/Makefile
index 4ff4b88..a7f3617 100644
--- a/drivers/rtc/Makefile
+++ b/drivers/rtc/Makefile
@@ -91,6 +91,7 @@ obj-$(CONFIG_RTC_DRV_STARFIRE) += rtc-starfire.o
obj-$(CONFIG_RTC_DRV_STK17TA8) += rtc-stk17ta8.o
obj-$(CONFIG_RTC_DRV_STMP) += rtc-stmp3xxx.o
obj-$(CONFIG_RTC_DRV_SUN4V) += rtc-sun4v.o
+obj-$(CONFIG_RTC_DRV_TEGRA) += rtc-tegra.o
obj-$(CONFIG_RTC_DRV_TEST) += rtc-test.o
obj-$(CONFIG_RTC_DRV_TWL4030) += rtc-twl.o
obj-$(CONFIG_RTC_DRV_TX4939) += rtc-tx4939.o
diff --git a/drivers/rtc/rtc-tegra.c b/drivers/rtc/rtc-tegra.c
new file mode 100644
index 0000000..2fc31aa
--- /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");
--
1.7.0.4


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