Add support for Intel Turbo Boost feature

From wikipedia:
Intel Turbo Boost is a technology implemented by Intel in certain
versions of their Nehalem- and Sandy Bridge-based CPUs, including Core
i5 and Core i7 that enables the processor to run above its base
operating frequency via dynamic control of the CPU's "clock rate".
It is activated when the operating system requests the highest
performance state of the processor.

Change-Id: I166ead7c219083006c2b05859eb18749c6fbe832
Signed-off-by: Duncan Laurie <dlaurie@google.com>
Signed-off-by: Stefan Reinauer <reinauer@google.com>
Reviewed-on: http://review.coreboot.org/844
Tested-by: build bot (Jenkins)
Reviewed-by: Ronald G. Minnich <rminnich@gmail.com>

src/cpu/intel/turbo/Makefile.inc

@@ -0,0 +1 @@
+ramstage-y += turbo.c

src/cpu/intel/turbo/turbo.c

@@ -0,0 +1,90 @@
+/*
+ * This file is part of the coreboot project.
+ *
+ * Copyright (C) 2011 The ChromiumOS Authors. All rights reserved.
+ *
+ * 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.
+ *
+ * This program is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+ * GNU General Public License for more details.
+ *
+ * You should have received a copy of the GNU General Public License
+ * along with this program; if not, write to the Free Software
+ * Foundation, Inc., 51 Franklin St, Fifth Floor, Boston,
+ * MA 02110-1301 USA
+ */
+
+#include <console/console.h>
+#include <cpu/intel/turbo.h>
+#include <cpu/x86/msr.h>
+#include <arch/cpu.h>
+
+static int turbo_state = TURBO_UNKNOWN;
+
+static const char *turbo_state_desc[] = {
+	[TURBO_UNKNOWN]		= "unknown",
+	[TURBO_UNAVAILABLE]	= "unavailable",
+	[TURBO_DISABLED]	= "available but hidden",
+	[TURBO_ENABLED]		= "available and visible"
+};
+
+/*
+ * Determine the current state of Turbo and cache it for later.
+ * Turbo is a package level config so it does not need to be
+ * enabled on every core.
+ */
+int get_turbo_state(void)
+{
+	struct cpuid_result cpuid_regs;
+	int turbo_en, turbo_cap;
+	msr_t msr;
+
+	/* Return cached state if available */
+	if (turbo_state != TURBO_UNKNOWN)
+		return turbo_state;
+
+	cpuid_regs = cpuid(CPUID_LEAF_PM);
+	turbo_cap = !!(cpuid_regs.eax & PM_CAP_TURBO_MODE);
+
+	msr = rdmsr(MSR_IA32_MISC_ENABLES);
+	turbo_en = !(msr.hi & H_MISC_DISABLE_TURBO);
+
+	if (!turbo_cap && turbo_en) {
+		/* Unavailable */
+		turbo_state = TURBO_UNAVAILABLE;
+	} else if (!turbo_cap && !turbo_en) {
+		/* Available but disabled */
+		turbo_state = TURBO_DISABLED;
+	} else if (turbo_cap && turbo_en) {
+		/* Available */
+		turbo_state = TURBO_ENABLED;
+	}
+
+	printk(BIOS_INFO, "Turbo is %s\n", turbo_state_desc[turbo_state]);
+	return turbo_state;
+}
+
+/*
+ * Try to enable Turbo mode.
+ */
+void enable_turbo(void)
+{
+	msr_t msr;
+
+	/* Only possible if turbo is available but hidden */
+	if (get_turbo_state() == TURBO_DISABLED) {
+		/* Clear Turbo Disable bit in Misc Enables */
+		msr = rdmsr(MSR_IA32_MISC_ENABLES);
+		msr.hi &= ~H_MISC_DISABLE_TURBO;
+		wrmsr(MSR_IA32_MISC_ENABLES, msr);
+
+		/* Update cached turbo state */
+		turbo_state = TURBO_ENABLED;
+		printk(BIOS_INFO, "Turbo has been enabled\n");
+	}
+}

src/include/cpu/intel/turbo.h

@@ -0,0 +1,44 @@
+/*
+ * This file is part of the coreboot project.
+ *
+ * Copyright (C) 2011 The ChromiumOS Authors. All rights reserved.
+ *
+ * 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.
+ *
+ * This program is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+ * GNU General Public License for more details.
+ *
+ * You should have received a copy of the GNU General Public License
+ * along with this program; if not, write to the Free Software
+ * Foundation, Inc., 51 Franklin St, Fifth Floor, Boston,
+ * MA 02110-1301 USA
+ */
+
+#ifndef _CPU_INTEL_TURBO_H
+#define _CPU_INTEL_TURBO_H
+
+#define CPUID_LEAF_PM		6
+#define PM_CAP_TURBO_MODE	(1 << 1)
+
+#define MSR_IA32_MISC_ENABLES	0x1a0
+#define H_MISC_DISABLE_TURBO	(1 << 6)
+
+enum {
+	TURBO_UNKNOWN,
+	TURBO_UNAVAILABLE,
+	TURBO_DISABLED,
+	TURBO_ENABLED,
+};
+
+/* Return current turbo state */
+int get_turbo_state(void);
+
+/* Enable turbo */
+void enable_turbo(void);
+
+#endif