Patch "Revert "cpufreq: pcc-cpufreq: update default value of cpuinfo_transition_latency"" has been added to the 4.6-stable tree

[<gregkh@linuxfoundation.org>]

This is a note to let you know that I've just added the patch titled

    Revert "cpufreq: pcc-cpufreq: update default value of cpuinfo_transition_latency"

to the 4.6-stable tree which can be found at:
    http://www.kernel.org/git/?p=linux/kernel/git/stable/stable-queue.git;a=summary

The filename of the patch is:
     revert-cpufreq-pcc-cpufreq-update-default-value-of-cpuinfo_transition_latency.patch
and it can be found in the queue-4.6 subdirectory.

If you, or anyone else, feels it should not be added to the stable tree,
please let <stable@vger.kernel.org> know about it.


>From da7d3abe1c9e5ebac2cf86f97e9e89888a5e2094 Mon Sep 17 00:00:00 2001
From: Andreas Herrmann <aherrmann@suse.com>
Date: Fri, 22 Jul 2016 17:14:11 +0200
Subject: Revert "cpufreq: pcc-cpufreq: update default value of cpuinfo_transition_latency"

From: Andreas Herrmann <aherrmann@suse.com>

commit da7d3abe1c9e5ebac2cf86f97e9e89888a5e2094 upstream.

This reverts commit 790d849bf811a8ab5d4cd2cce0f6fda92f6aebf2.

Using a v4.7-rc7 kernel on a HP ProLiant triggered following messages

 pcc-cpufreq: (v1.10.00) driver loaded with frequency limits: 1200 MHz, 2800 MHz
 cpufreq: ondemand governor failed, too long transition latency of HW, fallback to performance governor

The last line was shown for each CPU in the system.
Testing v4.5 (where commit 790d849b was integrated) triggered
similar messages. Same behaviour on a 2nd HP Proliant system.

So commit 790d849bf (cpufreq: pcc-cpufreq: update default value of
cpuinfo_transition_latency) causes the system to use performance
governor which, I guess, was not the intention of the patch.

Enabling debug output in pcc-cpufreq provides following verbose output:

 pcc-cpufreq: (v1.10.00) driver loaded with frequency limits: 1200 MHz, 2800 MHz
 pcc_get_offset: for CPU 0: pcc_cpu_data input_offset: 0x44, pcc_cpu_data output_offset: 0x48
 init: policy->max is 2800000, policy->min is 1200000
 get: get_freq for CPU 0
 get: SUCCESS: (virtual) output_offset for cpu 0 is 0xffffc9000d7c0048, contains a value of: 0xff06. Speed is: 168000 MHz
 cpufreq: ondemand governor failed, too long transition latency of HW, fallback to performance governor
 target: CPU 0 should go to target freq: 2800000 (virtual) input_offset is 0xffffc9000d7c0044
 target: was SUCCESSFUL for cpu 0

I am asking to revert 790d849bf to re-enable usage of ondemand
governor with pcc-cpufreq.

Fixes: 790d849bf (cpufreq: pcc-cpufreq: update default value of cpuinfo_transition_latency)
Signed-off-by: Andreas Herrmann <aherrmann@suse.com>
Signed-off-by: Rafael J. Wysocki <rafael.j.wysocki@intel.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

---
 Documentation/cpu-freq/pcc-cpufreq.txt |    4 ++--
 drivers/cpufreq/pcc-cpufreq.c          |    2 --
 2 files changed, 2 insertions(+), 4 deletions(-)

--- a/Documentation/cpu-freq/pcc-cpufreq.txt
+++ b/Documentation/cpu-freq/pcc-cpufreq.txt
@@ -159,8 +159,8 @@ to be strictly associated with a P-state
 
 2.2 cpuinfo_transition_latency:
 -------------------------------
-The cpuinfo_transition_latency field is CPUFREQ_ETERNAL. The PCC specification
-does not include a field to expose this value currently.
+The cpuinfo_transition_latency field is 0. The PCC specification does
+not include a field to expose this value currently.
 
 2.3 cpuinfo_cur_freq:
 ---------------------
--- a/drivers/cpufreq/pcc-cpufreq.c
+++ b/drivers/cpufreq/pcc-cpufreq.c
@@ -555,8 +555,6 @@ static int pcc_cpufreq_cpu_init(struct c
 	policy->min = policy->cpuinfo.min_freq =
 		ioread32(&pcch_hdr->minimum_frequency) * 1000;
 
-	policy->cpuinfo.transition_latency = CPUFREQ_ETERNAL;
-
 	pr_debug("init: policy->max is %d, policy->min is %d\n",
 		policy->max, policy->min);
 out:


Patches currently in stable-queue which might be from aherrmann@suse.com are

queue-4.6/revert-cpufreq-pcc-cpufreq-update-default-value-of-cpuinfo_transition_latency.patch