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Prashanth Prakash d4f3388afd cpufreq / CPPC: Set platform specific transition_delay_us 
Add support to specify platform specific transition_delay_us instead
of using the transition delay derived from PCC.

With commit 3d41386d55 (cpufreq: CPPC: Use transition_delay_us
depending transition_latency) we are setting transition_delay_us
directly and not applying the LATENCY_MULTIPLIER. Because of that,
on Qualcomm Centriq we can end up with a very high rate of frequency
change requests when using the schedutil governor (default
rate_limit_us=10 compared to an earlier value of 10000).

The PCC subspace describes the rate at which the platform can accept
commands on the CPPC's PCC channel. This includes read and write
command on the PCC channel that can be used for reasons other than
frequency transitions. Moreover the same PCC subspace can be used by
multiple freq domains and deriving transition_delay_us from it as we
do now can be sub-optimal.

Moreover if a platform does not use PCC for desired_perf register then
there is no way to compute the transition latency or the delay_us.

CPPC does not have a standard defined mechanism to get the transition
rate or the latency at the moment.

Given the above limitations, it is simpler to have a platform specific
transition_delay_us and rely on PCC derived value only if a platform
specific value is not available.

Signed-off-by: Prashanth Prakash <pprakash@codeaurora.org>
Cc: 4.14+ <stable@vger.kernel.org> # 4.14+
Fixes: 3d41386d55 (cpufreq: CPPC: Use transition_delay_us depending transition_latency)
Signed-off-by: Rafael J. Wysocki <rafael.j.wysocki@intel.com>
 		2018-04-30 10:14:08 +02:00
Documentation Merge branch 'timers-urgent-for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip 2018-04-29 09:03:25 -07:00
LICENSES LICENSES: Add MPL-1.1 license 2018-01-06 10:59:44 -07:00
arch Merge branch 'x86-urgent-for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip 2018-04-29 10:06:05 -07:00
block Revert "blk-mq: remove code for dealing with remapping queue" 2018-04-25 09:49:22 -06:00
certs certs/blacklist_nohashes.c: fix const confusion in certs blacklist 2018-02-21 15:35:43 -08:00
crypto crypto: drbg - set freed buffers to NULL 2018-04-21 00:57:00 +08:00
drivers cpufreq / CPPC: Set platform specific transition_delay_us 2018-04-30 10:14:08 +02:00
firmware kbuild: remove all dummy assignments to obj- 2017-11-18 11:46:06 +09:00
fs Fix misc. bugs and a regression for ext4. 2018-04-28 20:07:21 -07:00
include Merge branch 'timers-urgent-for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip 2018-04-29 09:03:25 -07:00
init Merge branch 'x86-urgent-for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip 2018-04-15 16:12:35 -07:00
ipc ipc/shm: fix use-after-free of shm file via remap_file_pages() 2018-04-13 17:10:27 -07:00
kernel Merge branch 'timers-urgent-for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip 2018-04-29 09:03:25 -07:00
lib Driver core fixes for 4.17-rc3 2018-04-27 10:12:20 -07:00
mm x86/pti: Filter at vma->vm_page_prot population 2018-04-25 11:02:51 +02:00
net A CephFS quota follow-up and fixes for two older issues in the 2018-04-27 10:56:29 -07:00
samples Merge branch 'for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/jikos/livepatching 2018-04-20 08:51:55 -07:00
scripts Kbuild updates for v4.17 (2nd) 2018-04-15 17:21:30 -07:00
security Merge branch 'userns-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/ebiederm/user-namespace 2018-04-24 17:58:51 -07:00
sound ALSA: dice: fix error path to destroy initialized stream data 2018-04-26 15:24:54 +02:00
tools Merge branch 'x86-pti-for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip 2018-04-29 09:36:22 -07:00
usr kbuild: rename built-in.o to built-in.a 2018-03-26 02:01:19 +09:00
virt KVM fixes for v4.17-rc3 2018-04-27 16:13:31 -07:00
.clang-format clang-format: add configuration file 2018-04-11 10:28:35 -07:00
.cocciconfig scripts: add Linux .cocciconfig for coccinelle 2016-07-22 12:13:39 +02:00
.get_maintainer.ignore
…
.gitattributes .gitattributes: set git diff driver for C source code files 2016-10-07 18:46:30 -07:00
.gitignore Kbuild updates for v4.17 (2nd) 2018-04-15 17:21:30 -07:00
.mailmap Merge candidates for 4.17 merge window 2018-04-06 17:35:43 -07:00
COPYING COPYING: use the new text with points to the license files 2018-03-23 12:41:45 -06:00
CREDITS MAINTAINERS/CREDITS: Drop METAG ARCHITECTURE 2018-03-05 16:34:24 +00:00
Kbuild Kbuild updates for v4.15 2017-11-17 17:45:29 -08:00
Kconfig License cleanup: add SPDX GPL-2.0 license identifier to files with no license 2017-11-02 11:10:55 +01:00
MAINTAINERS MAINTAINERS: add myself as maintainer of AFFS 2018-04-28 10:30:47 -07:00
Makefile Linux v4.17-rc3 2018-04-29 14:17:42 -07:00
README Docs: Added a pointer to the formatted docs to README 2018-03-21 09:02:53 -06:00

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.
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.