Blackfin RTC driver: the frequency function is in units of Hz, not units of seconds, so lock our driver down to 1 Hz

Signed-off-by: Mike Frysinger <michael.frysinger@analog.com>
Signed-off-by: Bryan Wu <bryan.wu@analog.com>
Acked-by: Alessandro Zummo <alessandro.zummo@towertech.it>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

1 files changed, 17 insertions, 7 deletions

diff --git a/drivers/rtc/rtc-bfin.c b/drivers/rtc/rtc-bfin.c
index 1aa709dda0d6..303ed6e91d3f 100644
--- a/drivers/rtc/rtc-bfin.c
+++ b/drivers/rtc/rtc-bfin.c
@@ -72,7 +72,7 @@ struct bfin_rtc {
 #define SEC_BITS_OFF    0
 
 /* Some helper functions to convert between the common RTC notion of time
- * and the internal Blackfin notion that is stored in 32bits.
+ * and the internal Blackfin notion that is encoded in 32bits.
  */
 static inline u32 rtc_time_to_bfin(unsigned long now)
 {
@@ -112,6 +112,11 @@ static inline void rtc_bfin_to_tm(u32 rtc_bfin, struct rtc_time *tm)
  * If anyone can point out the obvious solution here, i'm listening :).  This
  * shouldn't be an issue on an SMP or preempt system as this function should
  * only be called with the rtc lock held.
+ *
+ * Other options:
+ *  - disable PREN so the sync happens at 32.768kHZ ... but this changes the
+ *    inc rate for all RTC registers from 1HZ to 32.768kHZ ...
+ *  - use the write complete IRQ
  */
 static void rtc_bfin_sync_pending(void)
 {
@@ -356,12 +361,18 @@ static int bfin_rtc_proc(struct device *dev, struct seq_file *seq)
         return 0;
 }
 
+/**
+ *      bfin_irq_set_freq - make sure hardware supports requested freq
+ *      @dev: pointer to RTC device structure
+ *      @freq: requested frequency rate
+ *
+ *      The Blackfin RTC can only generate periodic events at 1 per
+ *      second (1 Hz), so reject any attempt at changing it.
+ */
 static int bfin_irq_set_freq(struct device *dev, int freq)
 {
-        struct bfin_rtc *rtc = dev_get_drvdata(dev);
         stampit();
-        rtc->rtc_dev->irq_freq = freq;
-        return 0;
+        return -ENOTTY;
 }
 
 static struct rtc_class_ops bfin_rtc_ops = {
@@ -394,14 +405,13 @@ static int __devinit bfin_rtc_probe(struct platform_device *pdev)
                 ret = PTR_ERR(rtc->rtc_dev);
                 goto err;
         }
-        rtc->rtc_dev->irq_freq = 0;
-        rtc->rtc_dev->max_user_freq = (2 << 16); /* stopwatch is an unsigned 16 bit reg */
+        rtc->rtc_dev->irq_freq = 1;
 
         platform_set_drvdata(pdev, rtc);
 
         return 0;
 
-err:
+ err:
         kfree(rtc);
         return ret;
 }