RTC: Revert UIE emulation removal

Uwe pointed out that my alarm based UIE emulation is not sufficient
to replace the older timer/polling based UIE emulation on devices
where there is no alarm irq. This causes rtc devices without alarms
to return -EINVAL to UIE ioctls. The fix is to re-instate the old
timer/polling method for devices without alarm irqs.

This patch reverts the following commits:
042620a018afcfba1d678062b62e46 - Remove UIE emulation
1daeddd5962acad1bea55e524fc0fa - Cleanup removed UIE emulation declaration
b5cc8ca1c9c3a37eaddf709b2fd3e1 - Remove Kconfig symbol for UIE emulation

The emulation mode will still need to be wired-in with a following
patch before it will work.

CC: Uwe Kleine-König <u.kleine-koenig@pengutronix.de>
CC: Thomas Gleixner <tglx@linutronix.de>
Reported-by: Uwe Kleine-König <u.kleine-koenig@pengutronix.de>
Signed-off-by: John Stultz <john.stultz@linaro.org>

diff --git a/drivers/rtc/Kconfig b/drivers/rtc/Kconfig
index cdd97192dc693cc84d075e24af1450ba5aebd2e5..4941cade319f5cef06d508d0b1f1354d951c1034 100644 (file)
--- a/drivers/rtc/Kconfig
+++ b/drivers/rtc/Kconfig
@@ -97,6 +97,18 @@ config RTC_INTF_DEV
 
          If unsure, say Y.
 
+config RTC_INTF_DEV_UIE_EMUL
+       bool "RTC UIE emulation on dev interface"
+       depends on RTC_INTF_DEV
+       help
+         Provides an emulation for RTC_UIE if the underlying rtc chip
+         driver does not expose RTC_UIE ioctls. Those requests generate
+         once-per-second update interrupts, used for synchronization.
+
+         The emulation code will read the time from the hardware
+         clock several times per second, please enable this option
+         only if you know that you really need it.
+
 config RTC_DRV_TEST
        tristate "Test driver/device"
        help

diff --git a/drivers/rtc/rtc-dev.c b/drivers/rtc/rtc-dev.c
index 37c3cc1b3dd5e592486fc53504fb017d74b70df1..dfa72c9c26874a0f740d93991228c5125a397ed8 100644 (file)
--- a/drivers/rtc/rtc-dev.c
+++ b/drivers/rtc/rtc-dev.c
@@ -46,6 +46,105 @@ static int rtc_dev_open(struct inode *inode, struct file *file)
        return err;
 }
 
+#ifdef CONFIG_RTC_INTF_DEV_UIE_EMUL
+/*
+ * Routine to poll RTC seconds field for change as often as possible,
+ * after first RTC_UIE use timer to reduce polling
+ */
+static void rtc_uie_task(struct work_struct *work)
+{
+       struct rtc_device *rtc =
+               container_of(work, struct rtc_device, uie_task);
+       struct rtc_time tm;
+       int num = 0;
+       int err;
+
+       err = rtc_read_time(rtc, &tm);
+
+       spin_lock_irq(&rtc->irq_lock);
+       if (rtc->stop_uie_polling || err) {
+               rtc->uie_task_active = 0;
+       } else if (rtc->oldsecs != tm.tm_sec) {
+               num = (tm.tm_sec + 60 - rtc->oldsecs) % 60;
+               rtc->oldsecs = tm.tm_sec;
+               rtc->uie_timer.expires = jiffies + HZ - (HZ/10);
+               rtc->uie_timer_active = 1;
+               rtc->uie_task_active = 0;
+               add_timer(&rtc->uie_timer);
+       } else if (schedule_work(&rtc->uie_task) == 0) {
+               rtc->uie_task_active = 0;
+       }
+       spin_unlock_irq(&rtc->irq_lock);
+       if (num)
+               rtc_update_irq(rtc, num, RTC_UF | RTC_IRQF);
+}
+static void rtc_uie_timer(unsigned long data)
+{
+       struct rtc_device *rtc = (struct rtc_device *)data;
+       unsigned long flags;
+
+       spin_lock_irqsave(&rtc->irq_lock, flags);
+       rtc->uie_timer_active = 0;
+       rtc->uie_task_active = 1;
+       if ((schedule_work(&rtc->uie_task) == 0))
+               rtc->uie_task_active = 0;
+       spin_unlock_irqrestore(&rtc->irq_lock, flags);
+}
+
+static int clear_uie(struct rtc_device *rtc)
+{
+       spin_lock_irq(&rtc->irq_lock);
+       if (rtc->uie_irq_active) {
+               rtc->stop_uie_polling = 1;
+               if (rtc->uie_timer_active) {
+                       spin_unlock_irq(&rtc->irq_lock);
+                       del_timer_sync(&rtc->uie_timer);
+                       spin_lock_irq(&rtc->irq_lock);
+                       rtc->uie_timer_active = 0;
+               }
+               if (rtc->uie_task_active) {
+                       spin_unlock_irq(&rtc->irq_lock);
+                       flush_scheduled_work();
+                       spin_lock_irq(&rtc->irq_lock);
+               }
+               rtc->uie_irq_active = 0;
+       }
+       spin_unlock_irq(&rtc->irq_lock);
+       return 0;
+}
+
+static int set_uie(struct rtc_device *rtc)
+{
+       struct rtc_time tm;
+       int err;
+
+       err = rtc_read_time(rtc, &tm);
+       if (err)
+               return err;
+       spin_lock_irq(&rtc->irq_lock);
+       if (!rtc->uie_irq_active) {
+               rtc->uie_irq_active = 1;
+               rtc->stop_uie_polling = 0;
+               rtc->oldsecs = tm.tm_sec;
+               rtc->uie_task_active = 1;
+               if (schedule_work(&rtc->uie_task) == 0)
+                       rtc->uie_task_active = 0;
+       }
+       rtc->irq_data = 0;
+       spin_unlock_irq(&rtc->irq_lock);
+       return 0;
+}
+
+int rtc_dev_update_irq_enable_emul(struct rtc_device *rtc, unsigned int enabled)
+{
+       if (enabled)
+               return set_uie(rtc);
+       else
+               return clear_uie(rtc);
+}
+EXPORT_SYMBOL(rtc_dev_update_irq_enable_emul);
+
+#endif /* CONFIG_RTC_INTF_DEV_UIE_EMUL */
 
 static ssize_t
 rtc_dev_read(struct file *file, char __user *buf, size_t count, loff_t *ppos)
@@ -387,6 +486,11 @@ void rtc_dev_prepare(struct rtc_device *rtc)
 
        rtc->dev.devt = MKDEV(MAJOR(rtc_devt), rtc->id);
 
+#ifdef CONFIG_RTC_INTF_DEV_UIE_EMUL
+       INIT_WORK(&rtc->uie_task, rtc_uie_task);
+       setup_timer(&rtc->uie_timer, rtc_uie_timer, (unsigned long)rtc);
+#endif
+
        cdev_init(&rtc->char_dev, &rtc_dev_fops);
        rtc->char_dev.owner = rtc->owner;
 }

diff --git a/include/linux/rtc.h b/include/linux/rtc.h
index a0b639f8e805b2390026999d6e7279b4158c636f..80408e711bed2f39363d22f166d7b2b3c1b47ee3 100644 (file)
--- a/include/linux/rtc.h
+++ b/include/linux/rtc.h
@@ -203,6 +203,18 @@ struct rtc_device
        struct hrtimer pie_timer; /* sub second exp, so needs hrtimer */
        int pie_enabled;
        struct work_struct irqwork;
+
+
+#ifdef CONFIG_RTC_INTF_DEV_UIE_EMUL
+       struct work_struct uie_task;
+       struct timer_list uie_timer;
+       /* Those fields are protected by rtc->irq_lock */
+       unsigned int oldsecs;
+       unsigned int uie_irq_active:1;
+       unsigned int stop_uie_polling:1;
+       unsigned int uie_task_active:1;
+       unsigned int uie_timer_active:1;
+#endif
 };
 #define to_rtc_device(d) container_of(d, struct rtc_device, dev)
 
@@ -235,6 +247,8 @@ extern int rtc_irq_set_freq(struct rtc_device *rtc,
                                struct rtc_task *task, int freq);
 extern int rtc_update_irq_enable(struct rtc_device *rtc, unsigned int enabled);
 extern int rtc_alarm_irq_enable(struct rtc_device *rtc, unsigned int enabled);
+extern int rtc_dev_update_irq_enable_emul(struct rtc_device *rtc,
+                                               unsigned int enabled);
 
 void rtc_aie_update_irq(void *private);
 void rtc_uie_update_irq(void *private);