romstage.c

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/* SPDX-License-Identifier: GPL-2.0-only */
 
#include <console/console.h>
#include <cpu/intel/haswell/haswell.h>
#include <cpu/x86/msr.h>
 
void set_max_freq(void)
{
        msr_t msr, perf_ctl, platform_info;
 
        /* Check for configurable TDP option */
        platform_info = rdmsr(MSR_PLATFORM_INFO);
 
        if ((platform_info.hi >> 1) & 3) {
                /* Set to nominal TDP ratio */
                msr = rdmsr(MSR_CONFIG_TDP_NOMINAL);
                perf_ctl.lo = (msr.lo & 0xff) << 8;
        } else {
                /* Platform Info bits 15:8 give max ratio */
                msr = rdmsr(MSR_PLATFORM_INFO);
                perf_ctl.lo = msr.lo & 0xff00;
        }
 
        perf_ctl.hi = 0;
        wrmsr(IA32_PERF_CTL, perf_ctl);
 
        printk(BIOS_DEBUG, "CPU: frequency set to %d MHz\n",
               ((perf_ctl.lo >> 8) & 0xff) * CPU_BCLK);
}