linux-kernel - Re: [PATCH 2/2 V6] intel_pstate: add kernel parameter to force loading on Sun X86 servers.

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Message-ID: <547E5E36.2070603@oracle.com>
Date:	Wed, 03 Dec 2014 08:49:58 +0800
From:	ethan zhao <ethan.zhao@...cle.com>
To:	Kristen Carlson Accardi <kristen@...ux.intel.com>
CC:	dirk.j.brandewie@...el.com, viresh.kumar@...aro.org,
	rjw@...ysocki.net, corbet@....net, linux-doc@...r.kernel.org,
	linux-kernel@...r.kernel.org, linux-pm@...r.kernel.org,
	ethan.kernel@...il.com, joe.jin@...cle.com, brian.maly@...cle.com
Subject: Re: [PATCH 2/2 V6] intel_pstate: add kernel parameter to force loading
 on Sun X86 servers.

Kristen,

On 2014/12/3 2:24, Kristen Carlson Accardi wrote:
> On Fri, 28 Nov 2014 12:36:17 +0900
> Ethan Zhao <ethan.zhao@...cle.com> wrote:
>
>> To force loading on Oracle Sun X86 servers, provide one kernel command line
>> parameter
>>
>>    intel_pstate = ora_force
>>
>> For those who be aware of the risk of no power capping capabily working and
>> try to get better performance with this driver.
> So, is this something you'd expect users to use on production systems,
> or is it just for debug?
    Till now, we couldn't make the decision that users couldn't use 
intel_pstate on product systems at all,
    So we leave one gate, and we could do something even the binary 
kernel was shipped to user. of course,
    a lot of test and debug need to be done in the future.

    It is possible for users to use it on their product system if they 
are aware of all the risk.

   Thanks,
   Ethan
>
> Thanks,
> Kristen
>
>> Signed-off-by: Ethan Zhao <ethan.zhao@...cle.com>
>> ---
>>   v2: change to hardware vendor specific naming parameter.
>>   v4: refine code and doc.
>>   v5&v6: fix a typo in doc.
>>
>>   Documentation/kernel-parameters.txt | 5 +++++
>>   drivers/cpufreq/intel_pstate.c      | 6 +++++-
>>   2 files changed, 10 insertions(+), 1 deletion(-)
>>
>> diff --git a/Documentation/kernel-parameters.txt b/Documentation/kernel-parameters.txt
>> index 479f332..7d0983e 100644
>> --- a/Documentation/kernel-parameters.txt
>> +++ b/Documentation/kernel-parameters.txt
>> @@ -1446,6 +1446,11 @@ bytes respectively. Such letter suffixes can also be entirely omitted.
>>   		       disable
>>   		         Do not enable intel_pstate as the default
>>   		         scaling driver for the supported processors
>> +		       ora_force
>> +			 Force loading intel_pstate on Oracle Sun Servers(X86).
>> +			 only for those who be aware of the risk of no power capping
>> +			 capability working and try to get better performance with this
>> +			 driver.
>>   
>>   	intremap=	[X86-64, Intel-IOMMU]
>>   			on	enable Interrupt Remapping (default)
>> diff --git a/drivers/cpufreq/intel_pstate.c b/drivers/cpufreq/intel_pstate.c
>> index 1bb62ca..2654e13 100644
>> --- a/drivers/cpufreq/intel_pstate.c
>> +++ b/drivers/cpufreq/intel_pstate.c
>> @@ -866,6 +866,7 @@ static struct cpufreq_driver intel_pstate_driver = {
>>   };
>>   
>>   static int __initdata no_load;
>> +static unsigned int  ora_force;
>>   
>>   static int intel_pstate_msrs_not_valid(void)
>>   {
>> @@ -1003,7 +1004,8 @@ static bool intel_pstate_platform_pwr_mgmt_exists(void)
>>   			case PSS:
>>   				return intel_pstate_no_acpi_pss();
>>   			case PCC:
>> -				return intel_pstate_has_acpi_ppc();
>> +				return intel_pstate_has_acpi_ppc() &&
>> +					(!ora_force);
>>   			}
>>   	}
>>   
>> @@ -1078,6 +1080,8 @@ static int __init intel_pstate_setup(char *str)
>>   
>>   	if (!strcmp(str, "disable"))
>>   		no_load = 1;
>> +	if (!strcmp(str, "ora_force"))
>> +		ora_force = 1;
>>   	return 0;
>>   }
>>   early_param("intel_pstate", intel_pstate_setup);

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