8352a3fec2
commit b511203093489eb1829cb4de86e8214752205ac6 upstream.
The INTEL_FAM6_SKYLAKE_X hardcoded crystal_khz value of 25MHZ is
problematic:
- SKX workstations (with same model # as server variants) use a 24 MHz
crystal. This results in a -4.0% time drift rate on SKX workstations.
- SKX servers subject the crystal to an EMI reduction circuit that reduces its
actual frequency by (approximately) -0.25%. This results in -1 second per
10 minute time drift as compared to network time.
This issue can also trigger a timer and power problem, on configurations
that use the LAPIC timer (versus the TSC deadline timer). Clock ticks
scheduled with the LAPIC timer arrive a few usec before the time they are
expected (according to the slow TSC). This causes Linux to poll-idle, when
it should be in an idle power saving state. The idle and clock code do not
graciously recover from this error, sometimes resulting in significant
polling and measurable power impact.
Stop using native_calibrate_tsc() for INTEL_FAM6_SKYLAKE_X.
native_calibrate_tsc() will return 0, boot will run with tsc_khz = cpu_khz,
and the TSC refined calibration will update tsc_khz to correct for the
difference.
[ tglx: Sanitized change log ]
Fixes: 6baf3d61821f ("x86/tsc: Add additional Intel CPU models to the crystal quirk list")
Signed-off-by: Len Brown <len.brown@intel.com>
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Cc: peterz@infradead.org
Cc: Prarit Bhargava <prarit@redhat.com>
Link: https://lkml.kernel.org/r/ff6dcea166e8ff8f2f6a03c17beab2cb436aa779.1513920414.git.len.brown@intel.com
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Linux kernel ============ This file was moved to Documentation/admin-guide/README.rst Please notice that there are several guides for kernel developers and users. These guides can be rendered in a number of formats, like HTML and PDF. In order to build the documentation, use ``make htmldocs`` or ``make pdfdocs``. 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.