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rtc/ab8500: add calibration attribute to AB8500 RTC

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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>
This commit is contained in:
Mark Godfrey
2012-01-10 15:10:42 -08:00
committed by Linus Torvalds
parent 012e52e15e
commit dda367ac06
2 changed files with 124 additions and 0 deletions
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Documentation/ABI/testing/sysfs-class-rtc-rtc0-device-rtc_calibration Normal file
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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.