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-rw-r--r--src/soc/intel/common/block/cpu/cpulib.c20
-rw-r--r--src/soc/intel/common/block/include/intelblocks/cpulib.h8
2 files changed, 28 insertions, 0 deletions
diff --git a/src/soc/intel/common/block/cpu/cpulib.c b/src/soc/intel/common/block/cpu/cpulib.c
index 0c042df8b2..f2142d93cc 100644
--- a/src/soc/intel/common/block/cpu/cpulib.c
+++ b/src/soc/intel/common/block/cpu/cpulib.c
@@ -3,6 +3,7 @@
*
* Copyright (C) 2014 Google Inc.
* Copyright (C) 2015-2018 Intel Corporation.
+ * Copyright (C) 2018 Siemens AG
*
* This program is free software; you can redistribute it and/or modify
* it under the terms of the GNU General Public License as published by
@@ -141,6 +142,25 @@ void cpu_set_p_state_to_max_non_turbo_ratio(void)
}
/*
+ * Set PERF_CTL MSR (0x199) P_Req (14:8 bits) with the value
+ * for maximum efficiency. This value is reported in PLATFORM_INFO MSR (0xCE)
+ * in Bits 47:40 and is extracted with cpu_get_min_ratio().
+ */
+void cpu_set_p_state_to_min_clock_ratio(void)
+{
+ uint32_t min_ratio;
+ msr_t perf_ctl;
+
+ /* Read the minimum ratio for the best efficiency. */
+ min_ratio = cpu_get_min_ratio();
+ perf_ctl.lo = (min_ratio << 8) & 0xff00;
+ perf_ctl.hi = 0;
+ wrmsr(IA32_PERF_CTL, perf_ctl);
+ printk(BIOS_DEBUG, "CPU: frequency set to %u MHz\n",
+ (min_ratio * CONFIG_CPU_BCLK_MHZ));
+}
+
+/*
* Get the Burst/Turbo Mode State from MSR IA32_MISC_ENABLE 0x1A0
* Bit 38 - TURBO_MODE_DISABLE Bit to get state ENABLED / DISABLED.
* Also check for the cpuid 0x6 to check whether Burst mode unsupported.
diff --git a/src/soc/intel/common/block/include/intelblocks/cpulib.h b/src/soc/intel/common/block/include/intelblocks/cpulib.h
index 88f04b439a..0d51146752 100644
--- a/src/soc/intel/common/block/include/intelblocks/cpulib.h
+++ b/src/soc/intel/common/block/include/intelblocks/cpulib.h
@@ -2,6 +2,7 @@
* This file is part of the coreboot project.
*
* Copyright (C) 2017 Intel Corporation.
+ * Copyright (C) 2018 Siemens AG
*
* This program is free software; you can redistribute it and/or modify
* it under the terms of the GNU General Public License as published by
@@ -73,6 +74,13 @@ void cpu_set_p_state_to_nominal_tdp_ratio(void);
void cpu_set_p_state_to_max_non_turbo_ratio(void);
/*
+ * Set PERF_CTL MSR (0x199) P_Req (14:8 bits) with the value
+ * for maximum efficiency. This value is reported in PLATFORM_INFO MSR (0xCE)
+ * in Bits 47:40 and is extracted with cpu_get_min_ratio().
+ */
+void cpu_set_p_state_to_min_clock_ratio(void);
+
+/*
* Get the Burst/Turbo Mode State from MSR IA32_MISC_ENABLE 0x1A0
* Bit 38 - TURBO_MODE_DISABLE Bit to get state ENABLED / DISABLED.
* Also check for the cpuid 0x6 to check whether Burst mode unsupported.