rtc: move power of 2 periodic frequency check down into drivers

Move the power of 2 check on frequencies down into individual rtc drivers

This is to allow for non power of 2 real time clock periodic interrupts
such as those on the pxa27x to be found in the new pxa27x-rtc driver

Signed-off-by: Jonathan Cameron <jic23@cam.ac.uk>
Signed-off-by: Alessandro Zummo <a.zummo@towertech.it>
Cc: David Brownell <david-b@pacbell.net>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

1 files changed, 3 insertions, 0 deletions

diff --git a/drivers/rtc/rtc-cmos.c b/drivers/rtc/rtc-cmos.c
index cf98a5d8358e..b6d35f50e404 100644
--- a/drivers/rtc/rtc-cmos.c
+++ b/drivers/rtc/rtc-cmos.c
@@ -35,6 +35,7 @@
 #include <linux/spinlock.h>
 #include <linux/platform_device.h>
 #include <linux/mod_devicetable.h>
+#include <linux/log2.h>
 
 /* this is for "generic access to PC-style RTC" using CMOS_READ/CMOS_WRITE */
 #include <asm-generic/rtc.h>
@@ -384,6 +385,8 @@ static int cmos_irq_set_freq(struct device *dev, int freq)
         if (!is_valid_irq(cmos->irq))
                 return -ENXIO;
 
+        if (!is_power_of_2(freq))
+                return -EINVAL;
         /* 0 = no irqs; 1 = 2^15 Hz ... 15 = 2^0 Hz */
         f = ffs(freq);
         if (f-- > 16)