This is provided at Srinivas' request. The LP controller is disabled
for the moment on server FADT profiles in order to avoid disturbing
the performance behavior of small-core servers. In cases where the
default inferred from the BIOS FADT profile is suboptimal, the LP
controller can be forcefully enabled or disabled by passing
"intel_pstate=lp" or "intel_pstate=no_lp" respectively in the kernel
command line.
Signed-off-by: Francisco Jerez <currojerez@xxxxxxxxxx>
---
Documentation/admin-guide/kernel-parameters.txt | 6 +++++
Documentation/admin-guide/pm/intel_pstate.rst | 7 ++++++
drivers/cpufreq/intel_pstate.c | 32 ++++++++++++++++++++++++-
3 files changed, 44 insertions(+), 1 deletion(-)
diff --git a/Documentation/admin-guide/kernel-parameters.txt b/Documentation/admin-guide/kernel-parameters.txt
index 1d1d53f85ddd..0ba112696938 100644
--- a/Documentation/admin-guide/kernel-parameters.txt
+++ b/Documentation/admin-guide/kernel-parameters.txt
@@ -1681,6 +1681,12 @@
per_cpu_perf_limits
Allow per-logical-CPU P-State performance control limits using
cpufreq sysfs interface
+ lp
+ Force use of LP P-state controller. Overrides selection
+ derived from ACPI FADT profile. Has no effect if HWP is
+ available.
+ no_lp
+ Prevent use of LP P-state controller (see "lp" parameter).
intremap= [X86-64, Intel-IOMMU]
on enable Interrupt Remapping (default)
diff --git a/Documentation/admin-guide/pm/intel_pstate.rst b/Documentation/admin-guide/pm/intel_pstate.rst
index d2b6fda3d67b..a5885fc4c039 100644
--- a/Documentation/admin-guide/pm/intel_pstate.rst
+++ b/Documentation/admin-guide/pm/intel_pstate.rst
@@ -642,6 +642,13 @@ of them have to be prepended with the ``intel_pstate=`` prefix.
Use per-logical-CPU P-State limits (see `Coordination of P-state
Limits`_ for details).
+``lp``
+ Force use of LP P-state controller. Overrides selection derived
+ from ACPI FADT profile. Has no effect if HWP is available.
+
+``no_lp``
+ Prevent use of LP P-state controller (see "lp" parameter).
+
Diagnostics and Tuning
======================
diff --git a/drivers/cpufreq/intel_pstate.c b/drivers/cpufreq/intel_pstate.c
index d4b5d0aaa282..d0e212387755 100644
--- a/drivers/cpufreq/intel_pstate.c
+++ b/drivers/cpufreq/intel_pstate.c
@@ -2485,6 +2485,7 @@ static int intel_pstate_update_status(const char *buf, size_t size)
static int no_load __initdata;
static int no_hwp __initdata;
+static int no_lp __initdata;
static int hwp_only __initdata;
static unsigned int force_load __initdata;
@@ -2507,8 +2508,12 @@ static void __init copy_cpu_funcs(struct pstate_funcs *funcs)
pstate_funcs.get_scaling = funcs->get_scaling;
pstate_funcs.get_val = funcs->get_val;
pstate_funcs.get_vid = funcs->get_vid;
- pstate_funcs.update_util = funcs->update_util;
pstate_funcs.get_aperf_mperf_shift = funcs->get_aperf_mperf_shift;
+
+ if (no_lp)
+ pstate_funcs.update_util = intel_pstate_update_util;
+ else
+ pstate_funcs.update_util = funcs->update_util;
}
#ifdef CONFIG_ACPI
@@ -2690,6 +2695,25 @@ static int __init intel_pstate_init(void)
}
device_initcall(intel_pstate_init);
+#ifdef CONFIG_ACPI
+static bool __init is_server_acpi_profile(void)
+{
+ switch (acpi_gbl_FADT.preferred_profile) {
+ case PM_ENTERPRISE_SERVER:
+ case PM_SOHO_SERVER:
+ case PM_PERFORMANCE_SERVER:
+ return true;
+ default:
+ return false;
+ }
+}
+#else
+static bool __init is_server_acpi_profile(void)
+{
+ return false;
+}
+#endif
+
static int __init intel_pstate_setup(char *str)
{
if (!str)
@@ -2713,6 +2737,12 @@ static int __init intel_pstate_setup(char *str)
if (!strcmp(str, "per_cpu_perf_limits"))
per_cpu_limits = true;
+ no_lp = is_server_acpi_profile();
+ if (!strcmp(str, "lp"))
+ no_lp = 0;
+ if (!strcmp(str, "no_lp"))
+ no_lp = 1;
+
#ifdef CONFIG_ACPI
if (!strcmp(str, "support_acpi_ppc"))
acpi_ppc = true;
--
2.16.1
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