From 52c58929fd8d9011e7990c042418624b567ffa1b Mon Sep 17 00:00:00 2001 From: Werner Zeh Date: Wed, 21 Nov 2018 10:38:12 +0100 Subject: intelblocks/cpu: Add function to set CPU clock to minimum value Provide a library function to set the CPU frequency to minimum value. This will result in the lowest possible CPU clock with the lowest possible power consumption. This can be useful in mobile devices where the power dissipation is limited. This setting can be overruled by the OS if it has an p-state driver which can adjust the clock to it's need. Change-Id: I817095b13ab8cbaab82f25c72947b00ee854d549 Signed-off-by: Werner Zeh Reviewed-on: https://review.coreboot.org/c/29771 Tested-by: build bot (Jenkins) Reviewed-by: Mario Scheithauer --- src/soc/intel/common/block/include/intelblocks/cpulib.h | 8 ++++++++ 1 file changed, 8 insertions(+) (limited to 'src/soc/intel/common/block/include/intelblocks/cpulib.h') 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 @@ -72,6 +73,13 @@ 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. -- cgit v1.2.3