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path: root/drivers/rtc/rtc-rk808.c
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2015-12-20rtc: rk808: Compensate for Rockchip calendar deviation on November 31stJulius Werner
In A.D. 1582 Pope Gregory XIII found that the existing Julian calendar insufficiently represented reality, and changed the rules about calculating leap years to account for this. Similarly, in A.D. 2013 Rockchip hardware engineers found that the new Gregorian calendar still contained flaws, and that the month of November should be counted up to 31 days instead. Unfortunately it takes a long time for calendar changes to gain widespread adoption, and just like more than 300 years went by before the last Protestant nation implemented Greg's proposal, we will have to wait a while until all religions and operating system kernels acknowledge the inherent advantages of the Rockchip system. Until then we need to translate dates read from (and written to) Rockchip hardware back to the Gregorian format. This patch works by defining Jan 1st, 2016 as the arbitrary anchor date on which Rockchip and Gregorian calendars are in sync. From that we can translate arbitrary later dates back and forth by counting the number of November/December transitons since the anchor date to determine the offset between the calendars. We choose this method (rather than trying to regularly "correct" the date stored in hardware) since it's the only way to ensure perfect time-keeping even if the system may be shut down for an unknown number of years. The drawback is that other software reading the same hardware (e.g. mainboard firmware) must use the same translation convention (including the same anchor date) to be able to read and write correct timestamps from/to the RTC. Signed-off-by: Julius Werner <jwerner@chromium.org> Reviewed-by: Douglas Anderson <dianders@chromium.org> Signed-off-by: Alexandre Belloni <alexandre.belloni@free-electrons.com>
2015-02-13drivers/rtc/rtc-rk808.c: fix rtc time reading issueChris Zhong
After we set the GET_TIME bit, the rtc time can't be read immediately. We should wait up to 31.25 us, about one cycle of 32khz. Otherwise reading RTC time will return a old time. If we clear the GET_TIME bit after setting, the time of i2c transfer is certainly more than 31.25us. Doug said: : I think we are safe. At 400kHz (the max speed of this part) each bit can : be transferred no faster than 2.5us. In order to do a valid i2c : transaction we need to _at least_ write the address of the device and the : data onto the bus, which is 16 bits. 16 * 2.5us = 40us. That's above the : 31.25us [akpm@linux-foundation.org: tweak comment per review discussion] Signed-off-by: Chris Zhong <zyw@rock-chips.com> Reviewed-by: Doug Anderson <dianders@chromium.org> Cc: Sonny Rao <sonnyrao@chromium.org> Cc: Heiko Stübner <heiko@sntech.de> 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>
2014-10-14RTC: RK808: add RTC driver for RK808Chris Zhong
This is the initial version of the RK808 PMIC. This is a power management IC for multimedia products. It provides regulators that are able to supply power to processor cores and other components. The chip provides other modules including RTC, Clockout. Add RTC driver for supporting RTC device present inside RK808 PMIC. [akpm@linux-foundation.org: make tm_def static] Signed-off-by: Chris Zhong <zyw@rock-chips.com> Signed-off-by: Zhang Qing <zhangqing@rock-chips.com> Tested-by: Heiko Stuebner <heiko@sntech.de> Reviewed-by: Doug Anderson <dianders@chromium.org> Tested-by: Doug Anderson <dianders@chromium.org> Cc: Pawel Moll <pawel.moll@arm.com> Cc: Mark Rutland <mark.rutland@arm.com> Cc: Ian Campbell <ijc+devicetree@hellion.org.uk> Cc: Samuel Ortiz <sameo@linux.intel.com> says: Cc: Alessandro Zummo <a.zummo@towertech.it> Cc: Olof Johansson <olof@lixom.net> Cc: Dmitry Torokhov <dtor@chromium.org> Cc: Javier Martinez Canillas <javier.martinez@collabora.co.uk> Cc: Kever Yang <kever.yang@rock-chips.com> Cc: Li Zhong <zhong@linux.vnet.ibm.com> Signed-off-by: Andrew Morton <akpm@linux-foundation.org> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>