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Filename Latest commit message Latest commit date
Srinivas Pandruvada 3f8ed54aee cpufreq: intel_pstate: Correct frequency setting in the HWP mode
In the functions intel_pstate_hwp_set(), min/max range from HWP capability
MSR along with max_perf_pct and min_perf_pct, is used to set the HWP
request MSR. In some cases this doesn't result in the correct HWP max/min
in HWP request.

For example: In the following case:

HWP capabilities from MSR 0x771
0x70a1220

Here cpufreq min/max frequencies from above MSR dump are 700MHz and 3.2GHz
respectively.

This will result in
hwp_min = 0x07
hwp_max = 0x20

To limit max frequency to 2GHz:

perf_limits->max_perf_pct = 63 (2GHz as a percent of 3.2GHz rounded up)

With the current calculation:
adj_range = max_perf_pct * range / 100;
adj_range = 63 * (32 - 7) / 100
adj_range = 15

max = hw_min + adj_range;
max = 7 + 15 = 22

This will result in HWP request of 0x160f, which will result in a
frequency cap of 2.2GHz not 2GHz.

The problem with the above calculation is that hwp_min of 7 is treated
as 0% in the range. But max_perf_pct is calculated with respect to minimum
as 0 and max as 3.2GHz or hwp_max, so adding hwp_min to it will result in
more than the desired.

Since the min_perf_pct and max_perf_pct is already a percent of max
frequency or hwp_max, this min/max HWP request value can be calculated
directly applying these percentage to hwp_max.

Signed-off-by: Srinivas Pandruvada <srinivas.pandruvada@linux.intel.com>
Signed-off-by: Rafael J. Wysocki <rafael.j.wysocki@intel.com>
2017-03-14 03:56:39 +01:00
arch Merge branch 'for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/s390/linux 2017-03-12 14:22:25 -07:00
block
certs
crypto
Documentation Merge branch 'irq-urgent-for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip 2017-03-12 14:11:38 -07:00
drivers cpufreq: intel_pstate: Correct frequency setting in the HWP mode 2017-03-14 03:56:39 +01:00
firmware
fs Merge branch 'prep-for-5level' 2017-03-10 08:59:07 -08:00
include Merge branch 'x86-urgent-for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip 2017-03-12 14:18:49 -07:00
init Change get_random_{int,log} to use the CRNG used by /dev/urandom and 2017-03-11 09:08:47 -08:00
ipc
kernel Merge branch 'x86-urgent-for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip 2017-03-12 14:18:49 -07:00
lib
mm Merge branch 'prep-for-5level' 2017-03-10 08:59:07 -08:00
net
samples
scripts Merge branch 'akpm' (patches from Andrew) 2017-03-10 08:34:42 -08:00
security
sound scripts/spelling.txt: add "disble(d)" pattern and fix typo instances 2017-03-09 17:01:09 -08:00
tools userfaultfd: selftest: vm: allow to build in vm/ directory 2017-03-09 17:01:10 -08:00
usr
virt
.cocciconfig
.get_maintainer.ignore
.gitattributes
.gitignore
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COPYING
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Makefile Linux 4.11-rc2 2017-03-12 14:47:08 -07:00
README

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.