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

This reverts commit 790d849bf8.

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)
CC: <stable@vger.kernel.org> # 4.5+
Signed-off-by: Andreas Herrmann <aherrmann@suse.com>
Signed-off-by: Rafael J. Wysocki <rafael.j.wysocki@intel.com>
This commit is contained in:
Andreas Herrmann 2016-07-22 17:14:11 +02:00 committed by Rafael J. Wysocki
parent ae2c1ca686
commit da7d3abe1c
2 changed files with 2 additions and 4 deletions
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4
Documentation/cpu-freq/pcc-cpufreq.txt
View File

@ -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:
---------------------

2
drivers/cpufreq/pcc-cpufreq.c
View File

@ -555,8 +555,6 @@ static int pcc_cpufreq_cpu_init(struct cpufreq_policy *policy)
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: