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Waiting 1ms every time is not necessary, for example on some AMD boxes the RTC_UIP bit is documented as being high for around 270 microseconds in some cases [1], which agreed with experiments on an SB710 southbridge. So 100us seems optimal. This in preparation for mach_get_cmos_time() refactoring. The functions mc146818_get_time() and mach_get_cmos_time() in arch/x86/kernel/rtc.c perform the same function and the code is duplicated. mach_get_cmos_time() is busy waiting for the RTC_UIP bit to clear, so make mc146818_get_time() more similar to it by reducing the polling period. [1] AMD SB700/710/750 Register Reference Guide, page 307, https://developer.amd.com/wordpress/media/2012/10/43009_sb7xx_rrg_pub_1.00.pdf "SB700 A12: The UIP high pulse is 270 μS Typical when SS on SRC clock is OFF and 100μ min when SRC SS is ON." [sic] Signed-off-by: Mateusz Jończyk <mat.jonczyk@o2.pl> Cc: Thomas Gleixner <tglx@linutronix.de> Cc: Ingo Molnar <mingo@redhat.com> Cc: Borislav Petkov <bp@alien8.de> Cc: Dave Hansen <dave.hansen@linux.intel.com> Cc: x86@kernel.org Cc: "H. Peter Anvin" <hpa@zytor.com> Cc: Alessandro Zummo <a.zummo@towertech.it> Cc: Alexandre Belloni <alexandre.belloni@bootlin.com> Signed-off-by: Alexandre Belloni <alexandre.belloni@bootlin.com> Link: https://lore.kernel.org/r/20220225215011.861477-2-mat.jonczyk@o2.pl
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.