Re: [PATCH 3/3] intel_pstate: add module and kernel command line parameter to ignore ACPI _PPC

[ethan zhao <ethan.zhao@oracle.com>]

Linda,

On 2014/11/21 13:00, Linda Knippers wrote:
>
> On 11/20/2014 10:07 PM, Ethan Zhao wrote:
>> Kristen,
>>     Whatever I would like there is a way to load intel_pstate and give
>> it a try even it does not support all the PM features.
>>     I think 'force' is OK.
>> Linda,
>>    Do you like it ? if the 'intel_pstate=force' would force the driver
>> to be loaded on to HP too ?
> I'd prefer that it didn't.  If you force the intel_pstate driver when
> the platform thinks it's doing power management, then the OS and the
> firmware are trying to manage the power at the same time.  That's a
> mess.  If you want that for testing or debugging, what are you actually
> testing or debugging?  On an Oracle box, the firmware wouldn't stop
> doing whatever it's doing just because the intel_pstate driver is
> loaded, would it?
  Yes, the platform wouldn't stop doing PM and the SCI even the intel_pstate
  was loaded.
  That option just give someone a chance who said "whatever I like 
intel_pstate
  On Oracle Servers"
>
> I also wonder what it means to "force" the intel_pstate driver
> on systems with processors that aren't supported by the intel_pstate
> driver.  It wouldn't really be forced, would it?
  Yes, wouldn't, such as AMD cpu-id and some old intel CPUs released 
before SandyBridge.
  So the best way to to do the 'force' should be specific enough for 
"Oracle Sun server"

  Thanks,
  Ethan
>
> -- ljk
>
>> Thanks,
>> Ethan
>>
>> On Fri, Nov 21, 2014 at 5:23 AM, Kristen Carlson Accardi
>> <kristen@linux.intel.com> wrote:
>>> On Thu, 20 Nov 2014 08:57:34 +0800
>>> ethan <ethan.kernel@gmail.com> wrote:
>>>
>>>>
>>>>> 在 2014年11月20日，03:05，Kristen Carlson Accardi <kristen@linux.intel.com> 写道：
>>>>>
>>>>> On Tue, 18 Nov 2014 17:37:06 +0900
>>>>> Ethan Zhao <ethan.zhao@oracle.com> wrote:
>>>>>
>>>>>> Add kernel command line parameter
>>>>>> intel_pstate = ignore_acpi_ppc
>>>>>> and module parameter
>>>>>> ignore_acpi_ppc = 1
>>>>>> to allow driver to ignore the ACPI _PPC existence even for Sun x86 servers.
>>>>>> These parameter could be used for debug\test\workaround etc purpose.
>>>>>>
>>>>>> Signed-off-by: Ethan Zhao <ethan.zhao@oracle.com>
>>>>> What if we used a more generic parameter like "force" that would bypass
>>>>> any vendor specific checks and just load anyway?  This way we don't have
>>>>> to add new parameters everything some new thing shows up that we want to
>>>>> ignore.
>>>>>
>>>> To be honest, I prefer more generic parameter. But to avoid the possible negative affect
>>>> To another vendors. I back to this way.
>>> Well, your parameter can still impact other vendors as it is.  it
>>> is pretty typical to assume that using a parameter like "force" means
>>> you know what you are doing and accept the risks.  Especially if its
>>> documented as such.
>>>
>>>> Thanks,
>>>> Ethan
>>>>>> ---
>>>>>> Documentation/kernel-parameters.txt | 3 +++
>>>>>> drivers/cpufreq/intel_pstate.c      | 8 +++++++-
>>>>>> 2 files changed, 10 insertions(+), 1 deletion(-)
>>>>>>
>>>>>> diff --git a/Documentation/kernel-parameters.txt b/Documentation/kernel-parameters.txt
>>>>>> index 4c81a86..f502b85 100644
>>>>>> --- a/Documentation/kernel-parameters.txt
>>>>>> +++ b/Documentation/kernel-parameters.txt
>>>>>> @@ -1446,6 +1446,9 @@ 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
>>>>>> +               ignore_acpi_ppc
>>>>>> +             Ignore the existence of ACPI method _PPC for Sun x86 servers
>>>>>> +             and load the 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 7c5faea..388387b 100644
>>>>>> --- a/drivers/cpufreq/intel_pstate.c
>>>>>> +++ b/drivers/cpufreq/intel_pstate.c
>>>>>> @@ -870,6 +870,7 @@ static struct cpufreq_driver intel_pstate_driver = {
>>>>>> };
>>>>>>
>>>>>> static int __initdata no_load;
>>>>>> +static unsigned int  ignore_acpi_ppc;
>>>>>>
>>>>>> static int intel_pstate_msrs_not_valid(void)
>>>>>> {
>>>>>> @@ -990,7 +991,7 @@ static bool intel_pstate_platform_pwr_mgmt_exists(void)
>>>>>>             intel_pstate_no_acpi_pss())
>>>>>>             return true;
>>>>>>         if (!strncmp(hdr.oem_id, v_info->oem_id, ACPI_OEM_ID_SIZE) &&
>>>>>> -            intel_pstate_has_acpi_ppc())
>>>>>> +            intel_pstate_has_acpi_ppc() && !ignore_acpi_ppc)
>>>>>>             return true;
>>>>>>     }
>>>>>>
>>>>>> @@ -1066,11 +1067,16 @@ static int __init intel_pstate_setup(char *str)
>>>>>>
>>>>>>     if (!strcmp(str, "disable"))
>>>>>>         no_load = 1;
>>>>>> +    if (!strcmp(str, "ignore_acpi_ppc"))
>>>>>> +        ignore_acpi_ppc = 1;
>>>>>>     return 0;
>>>>>> }
>>>>>> early_param("intel_pstate", intel_pstate_setup);
>>>>>> #endif
>>>>>>
>>>>>> +module_param(ignore_acpi_ppc, uint, 0644);
>>>>>> +MODULE_PARM_DESC(ignore_acpi_ppc,
>>>>>> +    "value 0 or non-zero. non-zero -> ignore ACPI _PPC and load this driver");
>>>>>> MODULE_AUTHOR("Dirk Brandewie <dirk.j.brandewie@intel.com>");
>>>>>> MODULE_DESCRIPTION("'intel_pstate' - P state driver Intel Core processors");
>>>>>> MODULE_LICENSE("GPL");
>> --
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