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| author | Wolfgang Grandegger <wg@grandegger.com> | 2009-06-17 16:26:11 -0700 |
|---|---|---|
| committer | Linus Torvalds <torvalds@linux-foundation.org> | 2009-06-18 13:03:43 -0700 |
| commit | 3c2b9075cbdb541dbe486bde45925c9610de6f35 (patch) | |
| tree | fee31e499f766469530a803afc40a7ca319ecfae /drivers/rtc/Kconfig | |
| parent | 97f902b7be4dd6ba03c6aa8d3400783ed687ebd1 (diff) | |
| download | lwn-3c2b9075cbdb541dbe486bde45925c9610de6f35.tar.gz lwn-3c2b9075cbdb541dbe486bde45925c9610de6f35.zip | |
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/Kconfig | 9 |
1 files changed, 9 insertions, 0 deletions
diff --git a/drivers/rtc/Kconfig b/drivers/rtc/Kconfig index 277d35d232fa..81adbdbd5042 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" |