[PATCH v4 09/11] x86/intel_pstate: add a booting param to select the driver to load

[Wei Wang <wei.w.wang@intel.com>]

By default, the old P-state driver (acpi-freq) is used. Adding
"intel_pstate" to the Xen booting param list to enable the
use of intel_pstate. However, if intel_pstate is enabled on a
machine which does not support the driver (e.g. Nehalem), the
old P-state driver will be loaded due to the failure loading of
intel_pstate.

Also, adding the intel_pstate booting parameter to
xen-command-line.markdown.

v4 changes:
1) moved the definition of "load_intel_pstate" right ahead of
intel_pstate_init();
2) merged the previous patch,"adding the booting param to
xen.command-line.markdown", into this one.

Signed-off-by: Wei Wang <wei.w.wang@intel.com>
---
 docs/misc/xen-command-line.markdown      | 7 +++++++
 xen/arch/x86/acpi/cpufreq/cpufreq.c      | 9 ++++++---
 xen/arch/x86/acpi/cpufreq/intel_pstate.c | 6 ++++++
 3 files changed, 19 insertions(+), 3 deletions(-)

diff --git a/docs/misc/xen-command-line.markdown b/docs/misc/xen-command-line.markdown
index 4889e27..249bf65 100644
--- a/docs/misc/xen-command-line.markdown
+++ b/docs/misc/xen-command-line.markdown
@@ -830,6 +830,13 @@ debug hypervisor only).
 ### idle\_latency\_factor
 > `= <integer>`
 
+### intel\_pstate
+> `= <boolean>`
+
+> Default: `false`
+
+Enable the loading of the intel pstate driver.
+
 ### ioapic\_ack
 > `= old | new`
 
diff --git a/xen/arch/x86/acpi/cpufreq/cpufreq.c b/xen/arch/x86/acpi/cpufreq/cpufreq.c
index 643c405..e737437 100644
--- a/xen/arch/x86/acpi/cpufreq/cpufreq.c
+++ b/xen/arch/x86/acpi/cpufreq/cpufreq.c
@@ -41,6 +41,7 @@
 #include <asm/processor.h>
 #include <asm/percpu.h>
 #include <asm/cpufeature.h>
+#include <asm/cpufreq.h>
 #include <acpi/acpi.h>
 #include <acpi/cpufreq/cpufreq.h>
 
@@ -648,9 +649,11 @@ static int __init cpufreq_driver_init(void)
     int ret = 0;
 
     if ((cpufreq_controller == FREQCTL_xen) &&
-        (boot_cpu_data.x86_vendor == X86_VENDOR_INTEL))
-        ret = cpufreq_register_driver(&acpi_cpufreq_driver);
-    else if ((cpufreq_controller == FREQCTL_xen) &&
+        (boot_cpu_data.x86_vendor == X86_VENDOR_INTEL)) {
+            ret = intel_pstate_init();
+            if (ret)
+                ret = cpufreq_register_driver(&acpi_cpufreq_driver);
+    } else if ((cpufreq_controller == FREQCTL_xen) &&
         (boot_cpu_data.x86_vendor == X86_VENDOR_AMD))
         ret = powernow_register_driver();
 
diff --git a/xen/arch/x86/acpi/cpufreq/intel_pstate.c b/xen/arch/x86/acpi/cpufreq/intel_pstate.c
index 19c74cc..5e03625 100644
--- a/xen/arch/x86/acpi/cpufreq/intel_pstate.c
+++ b/xen/arch/x86/acpi/cpufreq/intel_pstate.c
@@ -831,12 +831,18 @@ static void __init copy_cpu_funcs(struct pstate_funcs *funcs)
 	pstate_funcs.get_vid   = funcs->get_vid;
 }
 
+static bool_t __initdata load_intel_pstate;
+boolean_param("intel_pstate", load_intel_pstate);
+
 int __init intel_pstate_init(void)
 {
 	int cpu, rc = 0;
 	const struct x86_cpu_id *id;
 	struct cpu_defaults *cpu_info;
 
+	if (!load_intel_pstate)
+		return -ENODEV;
+
 	id = x86_match_cpu(intel_pstate_cpu_ids);
 	if (!id)
 		return -ENODEV;
-- 
1.9.1