[Intel-gfx] [PATCH 08/10] cpufreq: intel_pstate: Enable VLP controller based on ACPI FADT profile and CPUID.

[Francisco Jerez]

For the moment the VLP controller is only enabled on ICL platforms
other than server FADT profiles in order to reduce the validation
effort of the initial submission.  It should work on any other
processors that support HWP though (and soon enough on non-HWP too):
In order to override the default behavior (e.g. to test on other
platforms) the VLP controller can be forcefully enabled or disabled by
passing "intel_pstate=vlp" or "intel_pstate=no_vlp" respectively in
the kernel command line.

v2: Handle HWP VLP controller.

Signed-off-by: Francisco Jerez <currojerez at riseup.net>
---
 .../admin-guide/kernel-parameters.txt         |  5 ++++
 Documentation/admin-guide/pm/intel_pstate.rst |  7 ++++++
 drivers/cpufreq/intel_pstate.c                | 25 +++++++++++++++++--
 3 files changed, 35 insertions(+), 2 deletions(-)

diff --git a/Documentation/admin-guide/kernel-parameters.txt b/Documentation/admin-guide/kernel-parameters.txt
index 0c9894247015..9bc55fc2752e 100644
--- a/Documentation/admin-guide/kernel-parameters.txt
+++ b/Documentation/admin-guide/kernel-parameters.txt
@@ -1828,6 +1828,11 @@
 			per_cpu_perf_limits
 			  Allow per-logical-CPU P-State performance control limits using
 			  cpufreq sysfs interface
+			vlp
+			  Force use of VLP P-state controller.  Overrides selection
+			  derived from ACPI FADT profile.
+			no_vlp
+			  Prevent use of VLP P-state controller (see "vlp" 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 67e414e34f37..da6b64812848 100644
--- a/Documentation/admin-guide/pm/intel_pstate.rst
+++ b/Documentation/admin-guide/pm/intel_pstate.rst
@@ -669,6 +669,13 @@ 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).
 
+``vlp``
+	Force use of VLP P-state controller.  Overrides selection derived
+	from ACPI FADT profile.
+
+``no_vlp``
+	Prevent use of VLP P-state controller (see "vlp" parameter).
+
 
 Diagnostics and Tuning
 ======================
diff --git a/drivers/cpufreq/intel_pstate.c b/drivers/cpufreq/intel_pstate.c
index a01eed40d897..050cc8f03c26 100644
--- a/drivers/cpufreq/intel_pstate.c
+++ b/drivers/cpufreq/intel_pstate.c
@@ -3029,6 +3029,7 @@ static int intel_pstate_update_status(const char *buf, size_t size)
 
 static int no_load __initdata;
 static int no_hwp __initdata;
+static int vlp __initdata = -1;
 static int hwp_only __initdata;
 static unsigned int force_load __initdata;
 
@@ -3193,6 +3194,7 @@ static inline void intel_pstate_request_control_from_smm(void) {}
 #endif /* CONFIG_ACPI */
 
 #define INTEL_PSTATE_HWP_BROADWELL	0x01
+#define INTEL_PSTATE_HWP_VLP		0x02
 
 #define ICPU_HWP(model, hwp_mode) \
 	{ X86_VENDOR_INTEL, 6, model, X86_FEATURE_HWP, hwp_mode }
@@ -3200,12 +3202,15 @@ static inline void intel_pstate_request_control_from_smm(void) {}
 static const struct x86_cpu_id hwp_support_ids[] __initconst = {
 	ICPU_HWP(INTEL_FAM6_BROADWELL_X, INTEL_PSTATE_HWP_BROADWELL),
 	ICPU_HWP(INTEL_FAM6_BROADWELL_D, INTEL_PSTATE_HWP_BROADWELL),
+	ICPU_HWP(INTEL_FAM6_ICELAKE, INTEL_PSTATE_HWP_VLP),
+	ICPU_HWP(INTEL_FAM6_ICELAKE_L, INTEL_PSTATE_HWP_VLP),
 	ICPU_HWP(X86_MODEL_ANY, 0),
 	{}
 };
 
 static int __init intel_pstate_init(void)
 {
+	bool use_vlp = vlp == 1;
 	const struct x86_cpu_id *id;
 	int rc;
 
@@ -3222,8 +3227,19 @@ static int __init intel_pstate_init(void)
 			pstate_funcs.update_util = intel_pstate_update_util;
 		} else {
 			hwp_active++;
-			pstate_funcs.update_util = intel_pstate_update_util_hwp;
-			hwp_mode_bdw = id->driver_data;
+
+			if (vlp < 0 && !intel_pstate_acpi_pm_profile_server() &&
+			    (id->driver_data & INTEL_PSTATE_HWP_VLP)) {
+				/* Enable VLP controller by default. */
+				use_vlp = true;
+			}
+
+			pstate_funcs.update_util = use_vlp ?
+				intel_pstate_update_util_hwp_vlp :
+				intel_pstate_update_util_hwp;
+
+			hwp_mode_bdw = (id->driver_data &
+					INTEL_PSTATE_HWP_BROADWELL);
 			intel_pstate.attr = hwp_cpufreq_attrs;
 			goto hwp_cpu_matched;
 		}
@@ -3301,6 +3317,11 @@ static int __init intel_pstate_setup(char *str)
 	if (!strcmp(str, "per_cpu_perf_limits"))
 		per_cpu_limits = true;
 
+	if (!strcmp(str, "vlp"))
+		vlp = 1;
+	if (!strcmp(str, "no_vlp"))
+		vlp = 0;
+
 #ifdef CONFIG_ACPI
 	if (!strcmp(str, "support_acpi_ppc"))
 		acpi_ppc = true;
-- 
2.22.1