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The msm6242_set()/msm6242_clear() functions are used when writing to Control Register D to set or clear the HOLD bit when reading the current time from the RTC. Doing this with a read-modify-write cycle will potentially clear an interrupt condition which occurs between the read and the write. The datasheet states the following about this: When writing the HOLD or 30 second adjust bits of register D, it is necessary to write the IRQ FLAG bit to a "1". Since the only other bits in the register are the 30 second adjust bit (which is not used) and the BUSY bit (which is read-only), the read-modify-write cycle can be replaced by a simple write with the IRQ FLAG bit set to 1 and the other bits (except HOLD) set to 0. Tested-by: Kars de Jong <jongk@linux-m68k.org> Signed-off-by: Kars de Jong <jongk@linux-m68k.org> Link: https://lore.kernel.org/r/20191116114620.9193-1-jongk@linux-m68k.org Reviewed-by: Geert Uytterhoeven <geert@linux-m68k.org> Signed-off-by: Alexandre Belloni <alexandre.belloni@bootlin.com>
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.
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.