From: Dirk Brandewie <dirk.brandewie@gmail.com>
To: Ashwin Chaugule <ashwin.chaugule@linaro.org>
Cc: dirk.brandewie@gmail.com, Viresh Kumar <viresh.kumar@linaro.org>,
"rwells@codeaurora.org" <rwells@codeaurora.org>,
"Rafael J. Wysocki" <rjw@rjwysocki.net>,
"linaro-acpi@lists.linaro.org" <linaro-acpi@lists.linaro.org>,
"linux-pm@vger.kernel.org" <linux-pm@vger.kernel.org>,
Catalin Marinas <Catalin.Marinas@arm.com>,
Linda Knippers <linda.knippers@hp.com>
Subject: Re: [RFC PATCH v2 2/3] CPPC as a PID controller backend
Date: Thu, 09 Oct 2014 10:40:01 -0700 [thread overview]
Message-ID: <5436C871.5020404@gmail.com> (raw)
In-Reply-To: <CAJ5Y-eZjBSP3eTs9QVBaaLskoL8HPgCCG0ArkgcpMLcubJAg5A@mail.gmail.com>
On 10/09/2014 10:16 AM, Ashwin Chaugule wrote:
> Hi Dirk,
>
> On 9 October 2014 12:22, Dirk Brandewie <dirk.brandewie@gmail.com> wrote:
>> On 10/08/2014 01:11 PM, Ashwin Chaugule wrote:
>>
>>> +static int __init acpi_pid_init(void)
>>> +{
>>> + int cpu, rc = 0;
>>> +
>>
>>
>> You should add a check here to not bind to Intel CPU. The CPPC interface
>> was created to provided an ACPI interface to to hardware controlled P states
>> (HWP) described in Volume 3 section 14.4 of the Intel SDM.
>> intel_pstate will be enabling HWP by controlling the MSRs directly and
>> not using CPPC.
>>
>> Adding this check will keep us from having to fight load order since
>> this driver and intel_pstate are at the same init level.
>
> Do you have a recommendation for how to check for such CPUs? Would it
> make sense to deselect this driver if intel_pstate is chosen at
> compile time instead?
Probably the simplest is to change the depends line in Kconfig to:
depends on PCC && !X86
This will keep your driver from being selected on X86 and the potentail
issue goes away.
>
> Thanks,
> Ashwin
>
next prev parent reply other threads:[~2014-10-09 17:40 UTC|newest]
Thread overview: 9+ messages / expand[flat|nested] mbox.gz Atom feed top
2014-10-08 20:11 [RFC PATCH v2 0/3] CPPC as PID backend Ashwin Chaugule
2014-10-08 20:11 ` [RFC PATCH v2 1/3] PCC HACKS: Update PCC comm region with MSR data Ashwin Chaugule
2014-10-08 20:11 ` [RFC PATCH v2 2/3] CPPC as a PID controller backend Ashwin Chaugule
2014-10-09 16:22 ` Dirk Brandewie
2014-10-09 17:16 ` Ashwin Chaugule
2014-10-09 17:40 ` Dirk Brandewie [this message]
2014-10-09 18:18 ` Ashwin Chaugule
2014-10-17 13:58 ` Ashwin Chaugule
2014-10-08 20:11 ` [RFC PATCH v2 3/3] CPPC HACKS Ashwin Chaugule
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