From aa4ea34da9e7a2bc0fb98f5add3e4e52872b7d45 Mon Sep 17 00:00:00 2001
From: Ethan Zhao <ethan.zhao@oracle.com>
Date: Tue, 9 Dec 2014 10:43:19 +0900
Subject: [PATCH] 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: Ethan Zhao <ethan.zhao@oracle.com>
Tested-by: Alexey Kodanev <alexey.kodanev@oracle.com>
Reviewed-by: Linda Knippers <linda.knippers@hp.com>
Acked-by: Kristen Carlson Accardi <kristen@linux.intel.com>
Signed-off-by: Rafael J. Wysocki <rafael.j.wysocki@intel.com>
---
Documentation/kernel-parameters.txt | 9 +++++++++
drivers/cpufreq/intel_pstate.c | 6 +++++-
2 files changed, 14 insertions(+), 1 deletion(-)
diff --git a/Documentation/kernel-parameters.txt b/Documentation/kernel-parameters.txt
index 5fdf714f40a06..d006bb22f3cac 100644
--- a/Documentation/kernel-parameters.txt
+++ b/Documentation/kernel-parameters.txt
@@ -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.
diff --git a/drivers/cpufreq/intel_pstate.c b/drivers/cpufreq/intel_pstate.c
index 1405b393c93d9..0e841eecb7433 100644
--- a/drivers/cpufreq/intel_pstate.c
+++ b/drivers/cpufreq/intel_pstate.c
@@ -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);
--
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