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Commit aa4ea34d authored by Ethan Zhao's avatar Ethan Zhao Committed by Rafael J. Wysocki
Browse files

intel_pstate: add kernel parameter to force loading 



To force loading on Oracle Sun X86 servers, provide one kernel command line
parameter

  intel_pstate = force

For those who are aware of the risk of no power capping capabily working
and try to get better performance with this driver.

Signed-off-by: default avatarEthan Zhao <ethan.zhao@oracle.com>
Tested-by: default avatarAlexey Kodanev <alexey.kodanev@oracle.com>
Reviewed-by: default avatarLinda Knippers <linda.knippers@hp.com>
Acked-by: default avatarKristen Carlson Accardi <kristen@linux.intel.com>
Signed-off-by: default avatarRafael J. Wysocki <rafael.j.wysocki@intel.com>
parent 966916ea

Documentation/kernel-parameters.txt

+9 −0
Original line number Diff line number Diff line
@@ -1446,6 +1446,15 @@ 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 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-States information being indicated to OSPM and therefore

			 should be used with caution. 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.

		       no_hwp

		         Do not enable hardware P state control (HWP)

			 if available.

drivers/cpufreq/intel_pstate.c

+5 −1
Original line number Diff line number Diff line
@@ -948,6 +948,7 @@ static struct cpufreq_driver intel_pstate_driver = { 


static int __initdata no_load;

static int __initdata no_hwp;

static unsigned int force_load;



static int intel_pstate_msrs_not_valid(void)

{
@@ -1094,7 +1095,8 @@ 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);

			}

	}
@@ -1175,6 +1177,8 @@ static int __init intel_pstate_setup(char *str) 
		no_load = 1;

	if (!strcmp(str, "no_hwp"))

		no_hwp = 1;

	if (!strcmp(str, "force"))

		force_load = 1;

	return 0;

}

early_param("intel_pstate", intel_pstate_setup);