From 3c2b9075cbdb541dbe486bde45925c9610de6f35 Mon Sep 17 00:00:00 2001 From: Wolfgang Grandegger Date: Wed, 17 Jun 2009 16:26:11 -0700 Subject: 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 Signed-off-by: Sergei Poselenov Signed-off-by: Yuri Tikhonov Signed-off-by: Dmitry Rakhchev Signed-off-by: Matthias Fuchs Acked-by: Jean Delvare Signed-off-by: Alessandro Zummo Cc: David Brownell Signed-off-by: Andrew Morton Signed-off-by: Linus Torvalds --- drivers/rtc/Kconfig | 9 +++++++++ 1 file changed, 9 insertions(+) (limited to 'drivers/rtc/Kconfig') 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" -- cgit v1.2.3