cpufreq: Add the "cpufreq.off=1" cmdline option

Add the "cpufreq.off=1" cmdline option.

At boot-time, this allows a user to request CONFIG_CPU_FREQ=n
behavior from a kernel built with CONFIG_CPU_FREQ=y.

This is analogous to the existing "cpuidle.off=1" option
and CONFIG_CPU_IDLE=y

This capability is valuable when we need to debug end-user
issues in the BIOS or in Linux.  It is also convenient
for enabling comparisons, which may otherwise require a new kernel,
or help from BIOS SETUP, which may be buggy or unavailable.

Signed-off-by: Len Brown <len.brown@intel.com>
Signed-off-by: Rafael J. Wysocki <rafael.j.wysocki@intel.com>

diff --git a/Documentation/admin-guide/kernel-parameters.txt b/Documentation/admin-guide/kernel-parameters.txt
index be7c0d9..3988d23 100644 (file)
--- a/Documentation/admin-guide/kernel-parameters.txt
+++ b/Documentation/admin-guide/kernel-parameters.txt
@@ -662,6 +662,9 @@
        cpuidle.off=1   [CPU_IDLE]
                        disable the cpuidle sub-system
 
+       cpufreq.off=1   [CPU_FREQ]
+                       disable the cpufreq sub-system
+
        cpu_init_udelay=N
                        [X86] Delay for N microsec between assert and de-assert
                        of APIC INIT to start processors.  This delay occurs

diff --git a/drivers/cpufreq/cpufreq.c b/drivers/cpufreq/cpufreq.c
index 80a785a..7790db2 100644 (file)
--- a/drivers/cpufreq/cpufreq.c
+++ b/drivers/cpufreq/cpufreq.c
@@ -2532,4 +2532,5 @@ static int __init cpufreq_core_init(void)
 
        return 0;
 }
+module_param(off, int, 0444);
 core_initcall(cpufreq_core_init);