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authorWolfgang Grandegger <wg@grandegger.com>2009-06-17 16:26:11 -0700
committerLinus Torvalds <torvalds@linux-foundation.org>2009-06-18 13:03:43 -0700
commit3c2b9075cbdb541dbe486bde45925c9610de6f35 (patch)
treefee31e499f766469530a803afc40a7ca319ecfae /drivers/rtc/Kconfig
parent97f902b7be4dd6ba03c6aa8d3400783ed687ebd1 (diff)
downloadlinux-2.6.38-lt-ux500-3c2b9075cbdb541dbe486bde45925c9610de6f35.tar.gz
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>
Diffstat (limited to 'drivers/rtc/Kconfig')
-rw-r--r--drivers/rtc/Kconfig9
1 files changed, 9 insertions, 0 deletions
diff --git a/drivers/rtc/Kconfig b/drivers/rtc/Kconfig
index 277d35d232f..81adbdbd504 100644
--- a/drivers/rtc/Kconfig
+++ b/drivers/rtc/Kconfig
@@ -296,6 +296,15 @@ config RTC_DRV_RX8581
This driver can also be built as a module. If so the module
will be called rtc-rx8581.
+config RTC_DRV_RX8025
+ tristate "Epson RX-8025SA/NB"
+ help
+ If you say yes here you get support for the Epson
+ RX-8025SA/NB RTC chips.
+
+ This driver can also be built as a module. If so, the module
+ will be called rtc-rx8025.
+
endif # I2C
comment "SPI RTC drivers"