rtc/ab8500: add calibration attribute to AB8500 RTC
The rtc_calibration attribute allows user-space to get and set the
AB8500's RtcCalibration register. The AB8500 will then use the value in
this register to compensate for RTC drift every 60 seconds.
[akpm@linux-foundation.org: coding-style fixes]
Signed-off-by: Mark Godfrey <mark.godfrey@stericsson.com>
Signed-off-by: Linus Walleij <linus.walleij@stericsson.com>
Acked-by: Jean-Christophe PLAGNIOL-VILLARD <plagnioj@jcrosoft.com>
Cc: Alessandro Zummo <a.zummo@towertech.it>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
diff --git a/Documentation/ABI/testing/sysfs-class-rtc-rtc0-device-rtc_calibration b/Documentation/ABI/testing/sysfs-class-rtc-rtc0-device-rtc_calibration
new file mode 100644
index 0000000..4cf1e72
--- /dev/null
+++ b/Documentation/ABI/testing/sysfs-class-rtc-rtc0-device-rtc_calibration
@@ -0,0 +1,12 @@
+What: Attribute for calibrating ST-Ericsson AB8500 Real Time Clock
+Date: Oct 2011
+KernelVersion: 3.0
+Contact: Mark Godfrey <mark.godfrey@stericsson.com>
+Description: The rtc_calibration attribute allows the userspace to
+ calibrate the AB8500.s 32KHz Real Time Clock.
+ Every 60 seconds the AB8500 will correct the RTC's value
+ by adding to it the value of this attribute.
+ The range of the attribute is -127 to +127 in units of
+ 30.5 micro-seconds (half-parts-per-million of the 32KHz clock)
+Users: The /vendor/st-ericsson/base_utilities/core/rtc_calibration
+ daemon uses this interface.