intel_pstate: provide option to only use intel_pstate with HWP

[cascardo/linux.git] / Documentation / kernel-parameters.txt

diff --git a/Documentation/kernel-parameters.txt b/Documentation/kernel-parameters.txt
index 1de8335..07e6701 100644 (file)
--- a/Documentation/kernel-parameters.txt
+++ b/Documentation/kernel-parameters.txt
@@ -1457,9 +1457,21 @@ 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.
+               hwp_only
+                       Only load intel_pstate on systems which support
+                       hardware P state control (HWP) if available.
 
        intremap=       [X86-64, Intel-IOMMU]
                        on      enable Interrupt Remapping (default)
@@ -3570,6 +3582,24 @@ bytes respectively. Such letter suffixes can also be entirely omitted.
                        See also Documentation/trace/ftrace.txt "trace options"
                        section.
 
+       tp_printk[FTRACE]
+                       Have the tracepoints sent to printk as well as the
+                       tracing ring buffer. This is useful for early boot up
+                       where the system hangs or reboots and does not give the
+                       option for reading the tracing buffer or performing a
+                       ftrace_dump_on_oops.
+
+                       To turn off having tracepoints sent to printk,
+                        echo 0 > /proc/sys/kernel/tracepoint_printk
+                       Note, echoing 1 into this file without the
+                       tracepoint_printk kernel cmdline option has no effect.
+
+                       ** CAUTION **
+
+                       Having tracepoints sent to printk() and activating high
+                       frequency tracepoints such as irq or sched, can cause
+                       the system to live lock.
+
        traceoff_on_warning
                        [FTRACE] enable this option to disable tracing when a
                        warning is hit. This turns off "tracing_on". Tracing can