From mboxrd@z Thu Jan 1 00:00:00 1970 From: Linda Knippers Subject: Re: [PATCH 2/2 V8] intel_pstate: add kernel parameter to force loading. Date: Fri, 05 Dec 2014 11:09:29 -0500 Message-ID: <5481D8B9.2030603@hp.com> References: <1417772453-22483-1-git-send-email-ethan.zhao@oracle.com> Mime-Version: 1.0 Content-Type: text/plain; charset=windows-1252 Content-Transfer-Encoding: 8bit Return-path: In-Reply-To: <1417772453-22483-1-git-send-email-ethan.zhao@oracle.com> Sender: linux-doc-owner@vger.kernel.org To: Ethan Zhao , dirk.j.brandewie@intel.com, kristen@linux.intel.com, viresh.kumar@linaro.org, rjw@rjwysocki.net, corbet@lwn.net Cc: linux-doc@vger.kernel.org, linux-kernel@vger.kernel.org, linux-pm@vger.kernel.org, ethan.kernel@gmail.com, alexey.kodanev@oracle.com List-Id: linux-pm@vger.kernel.org On 12/5/2014 4:40 AM, Ethan Zhao wrote: > To force loading on Oracle Sun X86 servers, provide one kernel command line > parameter > > intel_pstate = force > > For those who be aware of the risk of no power capping capabily working and > try to get better performance with this driver. > > Signed-off-by: Ethan Zhao > Tested-by: Alexey Kodanev > --- > v2: change to hardware vendor specific naming parameter. > v4: refine code and doc. > v5&v6: fix a typo in doc. > v7: change enum PCC to PPC. > v8: change the name of kernel command line parameter to generic one. > > 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 > + force > + Enable intel_pstate on systems where it may cause problems to > + happen due to conflicts with platform firmware attempting to > + drive P-states by itself in certain situations (for thermal > + control or power capping in general or other purposes). I suggest something like: Enable intel_pstate on systems that prohibit it by default in favor of acpi-cpufreq. Forcing the intel_pstate driver instead of acpi-cpufreq may disable platform features, such as thermal controls and power capping, that rely on ACPI p-state information being used by the OS and therefore should be used with care. This option does not work with processors that aren't supported by the intel_pstate driver or on platforms that use pcc-cpufreq instead of acpi-cpufreq. Maybe this is too specific but I believe it is accurate. Comments? -- ljk > > 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 force_load; > > 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 PPC: > - return intel_pstate_has_acpi_ppc(); > + return intel_pstate_has_acpi_ppc() && > + (!force_load); > } > } > > @@ -1078,6 +1080,8 @@ static int __init intel_pstate_setup(char *str) > > if (!strcmp(str, "disable")) > no_load = 1; > + if (!strcmp(str, "force")) > + force_load = 1; > return 0; > } > early_param("intel_pstate", intel_pstate_setup); >