rtc: add stand-alone driver for RX8025 chip
Add support for the Epson RX-8025SA/NB RTC chips. It includes support for
alarms, periodic interrupts (1 Hz) and clock precision adjustment.
For clock precision adjustment, the SYSFS file "clock_adjust_ppb" gets
created in "/sys/class/rtc/rtcX/device". It permits to set and get the
clock adjustment in ppb (parts per billion), e.g.:
# echo -183000 > /sys/class/rtc/rtc0/device/clock_adjust_ppb
# cat /sys/class/rtc/rtc0/device/clock_adjust_ppb
-183000
This allows to compensate temperature dependent clock drifts. According
to the RX8025 SA/NB application manual the frequency and temperature
characteristics can be approximated using the following equation:
df = a * (ut - t)**2
df: Frequency deviation in any temperature
a : Coefficient = (-35 +-5) * 10**-9
ut: Ultimate temperature in degree = +25 +-5 degree
t : Any temperature in degree
Signed-off-by: Wolfgang Grandegger <wg@grandegger.com>
Signed-off-by: Sergei Poselenov <sposelenov@emcraft.com>
Signed-off-by: Yuri Tikhonov <yur@emcraft.com>
Signed-off-by: Dmitry Rakhchev <rda@emcraft.com>
Signed-off-by: Matthias Fuchs <matthias.fuchs@esd.eu>
Acked-by: Jean Delvare <khali@linux-fr.org>
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>
diff --git a/drivers/rtc/Makefile b/drivers/rtc/Makefile
index 6c0639a..3c0f2b2 100644
--- a/drivers/rtc/Makefile
+++ b/drivers/rtc/Makefile
@@ -62,6 +62,7 @@
obj-$(CONFIG_RTC_DRV_RS5C313) += rtc-rs5c313.o
obj-$(CONFIG_RTC_DRV_RS5C348) += rtc-rs5c348.o
obj-$(CONFIG_RTC_DRV_RS5C372) += rtc-rs5c372.o
+obj-$(CONFIG_RTC_DRV_RX8025) += rtc-rx8025.o
obj-$(CONFIG_RTC_DRV_RX8581) += rtc-rx8581.o
obj-$(CONFIG_RTC_DRV_S35390A) += rtc-s35390a.o
obj-$(CONFIG_RTC_DRV_S3C) += rtc-s3c.o