The RTC has a valid bit in the seconds register that indicates whether
power was lost since the pevious time set. This bit is currently read
once at probe time, cached and updated with set_time.
Howeever, caching the bit may prevent detecting power loss at runtime
(which can happen if the RTC's supply is distinct from the the platform's).
Writing the seconds register when setting time will clear the bit,
so there should be no downside in reading the bit directly instead of
caching it.
Change-Id: I85d1dcfb32b12ed24d5f42f67fb9beb5d8d03876
Signed-off-by: Paul Kocialkowski <paul.kocialkowski@bootlin.com>
Link: https://lore.kernel.org/r/20191212153111.966923-2-paul.kocialkowski@bootlin.com
Signed-off-by: Alexandre Belloni <alexandre.belloni@bootlin.com>
Signed-off-by: Elaine Zhang <zhangqing@rock-chips.com>
(cherry picked from commit e2ed7507ae)
Linux kernel
============
There are several guides for kernel developers and users. These guides can
be rendered in a number of formats, like HTML and PDF. Please read
Documentation/admin-guide/README.rst first.
In order to build the documentation, use ``make htmldocs`` or
``make pdfdocs``. The formatted documentation can also be read online at:
https://www.kernel.org/doc/html/latest/
There are various text files in the Documentation/ subdirectory,
several of them using the Restructured Text markup notation.
See Documentation/00-INDEX for a list of what is contained in each file.
Please read the Documentation/process/changes.rst file, as it contains the
requirements for building and running the kernel, and information about
the problems which may result by upgrading your kernel.
f8e9631789
