arch/x86/platform/intel-mid/mrfld.c

/*
 * Intel Merrifield platform specific setup code
 *
 * (C) Copyright 2013 Intel Corporation
 *
 * 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 the Free Software Foundation; version 2
 * of the License.
 */

#include <linux/init.h>

#include <asm/apic.h>
#include <asm/intel-mid.h>

#include "intel_mid_weak_decls.h"

static unsigned long __init tangier_calibrate_tsc(void)
{
	unsigned long fast_calibrate;
	u32 lo, hi, ratio, fsb, bus_freq;

	/* *********************** */
	/* Compute TSC:Ratio * FSB */
	/* *********************** */

	/* Compute Ratio */
	rdmsr(MSR_PLATFORM_INFO, lo, hi);
	pr_debug("IA32 PLATFORM_INFO is 0x%x : %x\n", hi, lo);

	ratio = (lo >> 8) & 0xFF;
	pr_debug("ratio is %d\n", ratio);
	if (!ratio) {
		pr_err("Read a zero ratio, force tsc ratio to 4 ...\n");
		ratio = 4;
	}

	/* Compute FSB */
	rdmsr(MSR_FSB_FREQ, lo, hi);
	pr_debug("Actual FSB frequency detected by SOC 0x%x : %x\n",
			hi, lo);

	bus_freq = lo & 0x7;
	pr_debug("bus_freq = 0x%x\n", bus_freq);

	if (bus_freq == 0)
		fsb = FSB_FREQ_100SKU;
	else if (bus_freq == 1)
		fsb = FSB_FREQ_100SKU;
	else if (bus_freq == 2)
		fsb = FSB_FREQ_133SKU;
	else if (bus_freq == 3)
		fsb = FSB_FREQ_167SKU;
	else if (bus_freq == 4)
		fsb = FSB_FREQ_83SKU;
	else if (bus_freq == 5)
		fsb = FSB_FREQ_400SKU;
	else if (bus_freq == 6)
		fsb = FSB_FREQ_267SKU;
	else if (bus_freq == 7)
		fsb = FSB_FREQ_333SKU;
	else {
		BUG();
		pr_err("Invalid bus_freq! Setting to minimal value!\n");
		fsb = FSB_FREQ_100SKU;
	}

	/* TSC = FSB Freq * Resolved HFM Ratio */
	fast_calibrate = ratio * fsb;
	pr_debug("calculate tangier tsc %lu KHz\n", fast_calibrate);

	/* ************************************ */
	/* Calculate Local APIC Timer Frequency */
	/* ************************************ */
	lapic_timer_frequency = (fsb * 1000) / HZ;

	pr_debug("Setting lapic_timer_frequency = %d\n",
			lapic_timer_frequency);

	/*
	 * TSC on Intel Atom SoCs is reliable and of known frequency.
	 * See tsc_msr.c for details.
	 */
	setup_force_cpu_cap(X86_FEATURE_TSC_KNOWN_FREQ);
	setup_force_cpu_cap(X86_FEATURE_TSC_RELIABLE);

	return fast_calibrate;
}

static void __init tangier_arch_setup(void)
{
	x86_platform.calibrate_tsc = tangier_calibrate_tsc;
}

/* tangier arch ops */
static struct intel_mid_ops tangier_ops = {
	.arch_setup = tangier_arch_setup,
};

void *get_tangier_ops(void)
{
	return &tangier_ops;
}