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Filename Latest commit message Latest commit date
Daniel Drake 604dc9170f x86/tsc: Use CPUID.0x16 to calculate missing crystal frequency
native_calibrate_tsc() had a data mapping Intel CPU families
and crystal clock speed, but hardcoded tables are not ideal, and this
approach was already problematic at least in the Skylake X case, as
seen in commit:

  b511203093 ("x86/tsc: Fix erroneous TSC rate on Skylake Xeon")

By examining CPUID data from http://instlatx64.atw.hu/ and units
in the lab, we have found that 3 different scenarios need to be dealt
with, and we can eliminate most of the hardcoded data using an approach a
little more advanced than before:

 1. ApolloLake, GeminiLake, CannonLake (and presumably all new chipsets
    from this point) report the crystal frequency directly via CPUID.0x15.
    That's definitive data that we can rely upon.

 2. Skylake, Kabylake and all variants of those two chipsets report a
    crystal frequency of zero, however we can calculate the crystal clock
    speed by condidering data from CPUID.0x16.

    This method correctly distinguishes between the two crystal clock
    frequencies present on different Skylake X variants that caused
    headaches before.

    As the calculations do not quite match the previously-hardcoded values
    in some cases (e.g. 23913043Hz instead of 24MHz), TSC refinement is
    enabled on all platforms where we had to calculate the crystal
    frequency in this way.

 3. Denverton (GOLDMONT_X) reports a crystal frequency of zero and does
    not support CPUID.0x16, so we leave this entry hardcoded.

Suggested-by: Thomas Gleixner <tglx@linutronix.de>
Signed-off-by: Daniel Drake <drake@endlessm.com>
Reviewed-by: Thomas Gleixner <tglx@linutronix.de>
Cc: Andy Lutomirski <luto@kernel.org>
Cc: Borislav Petkov <bp@alien8.de>
Cc: H. Peter Anvin <hpa@zytor.com>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: len.brown@intel.com
Cc: linux@endlessm.com
Cc: rafael.j.wysocki@intel.com
Link: http://lkml.kernel.org/r/20190509055417.13152-1-drake@endlessm.com
Link: https://lkml.kernel.org/r/20190419083533.32388-1-drake@endlessm.com
Signed-off-by: Ingo Molnar <mingo@kernel.org>
2019-05-09 11:06:48 +02:00
arch x86/tsc: Use CPUID.0x16 to calculate missing crystal frequency 2019-05-09 11:06:48 +02:00
block bfq: update internal depth state when queue depth changes 2019-04-13 19:08:22 -06:00
certs
crypto crypto: lrw - Fix atomic sleep when walking skcipher 2019-04-18 22:13:46 +08:00
Documentation * amd64_edac: Family 0x17, models 0x30-.. enablement (Yazen Ghannam) 2019-05-06 19:53:11 -07:00
drivers Merge branch 'ras-core-for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip 2019-05-06 19:54:57 -07:00
fs Merge branch 'core-stacktrace-for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip 2019-05-06 13:11:48 -07:00
include * amd64_edac: Family 0x17, models 0x30-.. enablement (Yazen Ghannam) 2019-05-06 19:53:11 -07:00
init x86/mm: Initialize PGD cache during mm initialization 2019-05-05 20:32:46 +02:00
ipc Merge branch 'work.mount' of git://git.kernel.org/pub/scm/linux/kernel/git/viro/vfs 2019-03-12 14:08:19 -07:00
kernel Power management updates for 5.2-rc1 2019-05-06 19:40:31 -07:00
lib Merge branch 'core-stacktrace-for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip 2019-05-06 13:11:48 -07:00
LICENSES
mm arm64 updates for 5.2 2019-05-06 17:54:22 -07:00
net Merge branch 'timers-core-for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip 2019-05-06 14:50:46 -07:00
samples Merge git://git.kernel.org/pub/scm/linux/kernel/git/davem/net 2019-03-11 08:54:01 -07:00
scripts Merge branch 'core-objtool-for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip 2019-05-06 11:39:17 -07:00
security s390 updates for the 5.2 merge window 2019-05-06 16:42:54 -07:00
sound ACPI updates for 5.2-rc1 2019-05-06 19:35:13 -07:00
tools ACPI updates for 5.2-rc1 2019-05-06 19:35:13 -07:00
usr
virt arm64 updates for 5.2 2019-05-06 17:54:22 -07:00
.clang-format clang-format: Update with the latest for_each macro list 2019-04-12 12:49:54 +02:00
.cocciconfig
.get_maintainer.ignore
.gitattributes
.gitignore
.mailmap Update Nicolas Pitre's email address 2019-04-02 18:12:44 -10:00
COPYING
CREDITS Char/Misc driver patches for 5.1-rc1 2019-03-06 14:18:59 -08:00
Kbuild Kbuild updates for v5.1 2019-03-10 17:48:21 -07:00
Kconfig
MAINTAINERS Merge branch 'ras-core-for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip 2019-05-06 19:54:57 -07:00
Makefile Linux 5.1 2019-05-05 17:42:58 -07:00
README

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.