Skylake: Support Intel Speed Shift Technology based on config

Intel Speed Shift Technology is a new mechanism that replaces
Legacy P-state. ISST allows OS hints about energy/performance
preference. H/W performs the actual P-state control (autonomous)

1. Optimization frequency seclection for low residency workloads,
no longer a static knee point.
2. Optimized frequency selection for best energy to performance
trade offs.
3. Kick down frequency (from idle) fpr best responsiveness while
taking energy consumption init account.

Coreboot's responsiblity is to configure MSR 0x1AA ISST_EN bits
which will reflect in CPUID.06h:EAX[Bit 7] that driver checkes
and enable HWP accordingly.

BUG=chrome-os-partner:47517
BRANCH=None
TEST=Booted kunimitsu and verify HWP getting enabled/disabled
using Intel P-state driver.

Change-Id: I91722aa1077f4ef6c8620b103be3e29cfcd974e5
Signed-off-by: Patrick Georgi <pgeorgi@google.com>
Original-Commit-Id: aa7d004cb2e19047e4434e3e2544cf69393ce28f
Original-Change-Id: Ie617da337babde7f196a7af712263e37f7eed56f
Original-Signed-off-by: Robbie Zhang <robbie.zhang@intel.com>
Original-Signed-off-by: Subrata Banik <subrata.banik@intel.com>
Original-Reviewed-on: https://chromium-review.googlesource.com/313107
Original-Reviewed-by: Aaron Durbin <adurbin@chromium.org>
Original-Reviewed-by: Wenkai Du <wenkai.du@intel.com>
Reviewed-on: https://review.coreboot.org/13835
Tested-by: build bot (Jenkins)
Reviewed-by: Stefan Reinauer <stefan.reinauer@coreboot.org>

3 files changed, 34 insertions, 0 deletions

diff --git a/src/soc/intel/skylake/chip.h b/src/soc/intel/skylake/chip.h
index 0b87f2d08e..6203916088 100644
--- a/src/soc/intel/skylake/chip.h
+++ b/src/soc/intel/skylake/chip.h
@@ -326,6 +326,8 @@ struct soc_intel_skylake_config {
 	/* PL2 Override value in Watts */
 	u32 tdp_pl2_override;
 	u8 PmTimerDisabled;
+	/* Intel Speed Shift Technology */
+	u8 speed_shift_enable;
 };
 
 typedef struct soc_intel_skylake_config config_t;
diff --git a/src/soc/intel/skylake/cpu.c b/src/soc/intel/skylake/cpu.c
index 2fa858257d..327bee90c3 100644
--- a/src/soc/intel/skylake/cpu.c
+++ b/src/soc/intel/skylake/cpu.c
@@ -207,6 +207,32 @@ static void configure_thermal_target(void)
 	}
 }
 
+static void configure_isst(void)
+{
+	device_t dev = SA_DEV_ROOT;
+	config_t *conf = dev->chip_info;
+	msr_t msr;
+
+	if (conf->speed_shift_enable) {
+		/*
+		* Kernel driver checks CPUID.06h:EAX[Bit 7] to determine if HWP
+		  is supported or not. Coreboot needs to configure MSR 0x1AA
+		  which is then reflected in the CPUID register.
+		*/
+		msr = rdmsr(MSR_MISC_PWR_MGMT);
+		msr.lo |= MISC_PWR_MGMT_ISST_EN; /* Enable Speed Shift */
+		msr.lo |= MISC_PWR_MGMT_ISST_EN_INT; /* Enable Interrupt */
+		msr.lo |= MISC_PWR_MGMT_ISST_EN_EPP; /* Enable EPP */
+		wrmsr(MSR_MISC_PWR_MGMT, msr);
+	} else {
+		msr = rdmsr(MSR_MISC_PWR_MGMT);
+		msr.lo &= ~MISC_PWR_MGMT_ISST_EN; /* Disable Speed Shift */
+		msr.lo &= ~MISC_PWR_MGMT_ISST_EN_INT; /* Disable Interrupt */
+		msr.lo &= ~MISC_PWR_MGMT_ISST_EN_EPP; /* Disable EPP */
+		wrmsr(MSR_MISC_PWR_MGMT, msr);
+	}
+}
+
 static void configure_misc(void)
 {
 	msr_t msr;
@@ -335,6 +361,9 @@ static void cpu_core_init(device_t cpu)
 	/* Configure Enhanced SpeedStep and Thermal Sensors */
 	configure_misc();
 
+	/* Configure Intel Speed Shift */
+	configure_isst();
+
 	/* Thermal throttle activation offset */
 	configure_thermal_target();
 
diff --git a/src/soc/intel/skylake/include/soc/msr.h b/src/soc/intel/skylake/include/soc/msr.h
index db154b788f..4d295e186f 100644
--- a/src/soc/intel/skylake/include/soc/msr.h
+++ b/src/soc/intel/skylake/include/soc/msr.h
@@ -36,6 +36,9 @@
 #define IA32_MISC_ENABLE		0x1a0
 #define MSR_MISC_PWR_MGMT		0x1aa
 #define  MISC_PWR_MGMT_EIST_HW_DIS	(1 << 0)
+#define  MISC_PWR_MGMT_ISST_EN	(1 << 6)
+#define  MISC_PWR_MGMT_ISST_EN_INT	(1 << 7)
+#define  MISC_PWR_MGMT_ISST_EN_EPP	(1 << 12)
 #define MSR_TURBO_RATIO_LIMIT		0x1ad
 #define MSR_TEMPERATURE_TARGET		0x1a2
 #define IA32_PERF_CTL			0x199