Merge branch 'next' of git://git.kernel.org/pub/scm/linux/kernel/git/davej/cpufreq

* 'next' of git://git.kernel.org/pub/scm/linux/kernel/git/davej/cpufreq:
  [CPUFREQ] Fix cast warning in pcc driver.
  [CPUFREQ] Processor Clocking Control interface driver

5 files changed, 844 insertions, 0 deletions

diff --git a/Documentation/cpu-freq/pcc-cpufreq.txt b/Documentation/cpu-freq/pcc-cpufreq.txt
new file mode 100644
index 0000000..9e3c3b3
--- /dev/null
+++ b/Documentation/cpu-freq/pcc-cpufreq.txt
@@ -0,0 +1,207 @@
+/*
+ *  pcc-cpufreq.txt - PCC interface documentation
+ *
+ *  Copyright (C) 2009 Red Hat, Matthew Garrett <mjg@redhat.com>
+ *  Copyright (C) 2009 Hewlett-Packard Development Company, L.P.
+ *      Nagananda Chumbalkar <nagananda.chumbalkar@hp.com>
+ *
+ * ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
+ *
+ *  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, GOOD TITLE or NON
+ *  INFRINGEMENT. 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.,
+ *  675 Mass Ave, Cambridge, MA 02139, USA.
+ *
+ * ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
+ */
+
+
+			Processor Clocking Control Driver
+			---------------------------------
+
+Contents:
+---------
+1.	Introduction
+1.1	PCC interface
+1.1.1   Get Average Frequency
+1.1.2	Set Desired Frequency
+1.2	Platforms affected
+2.	Driver and /sys details
+2.1	scaling_available_frequencies
+2.2	cpuinfo_transition_latency
+2.3	cpuinfo_cur_freq
+2.4	related_cpus
+3.	Caveats
+
+1. Introduction:
+----------------
+Processor Clocking Control (PCC) is an interface between the platform
+firmware and OSPM. It is a mechanism for coordinating processor
+performance (ie: frequency) between the platform firmware and the OS.
+
+The PCC driver (pcc-cpufreq) allows OSPM to take advantage of the PCC
+interface.
+
+OS utilizes the PCC interface to inform platform firmware what frequency the
+OS wants for a logical processor. The platform firmware attempts to achieve
+the requested frequency. If the request for the target frequency could not be
+satisfied by platform firmware, then it usually means that power budget
+conditions are in place, and "power capping" is taking place.
+
+1.1 PCC interface:
+------------------
+The complete PCC specification is available here:
+http://www.acpica.org/download/Processor-Clocking-Control-v1p0.pdf
+
+PCC relies on a shared memory region that provides a channel for communication
+between the OS and platform firmware. PCC also implements a "doorbell" that
+is used by the OS to inform the platform firmware that a command has been
+sent.
+
+The ACPI PCCH() method is used to discover the location of the PCC shared
+memory region. The shared memory region header contains the "command" and
+"status" interface. PCCH() also contains details on how to access the platform
+doorbell.
+
+The following commands are supported by the PCC interface:
+* Get Average Frequency
+* Set Desired Frequency
+
+The ACPI PCCP() method is implemented for each logical processor and is
+used to discover the offsets for the input and output buffers in the shared
+memory region.
+
+When PCC mode is enabled, the platform will not expose processor performance
+or throttle states (_PSS, _TSS and related ACPI objects) to OSPM. Therefore,
+the native P-state driver (such as acpi-cpufreq for Intel, powernow-k8 for
+AMD) will not load.
+
+However, OSPM remains in control of policy. The governor (eg: "ondemand")
+computes the required performance for each processor based on server workload.
+The PCC driver fills in the command interface, and the input buffer and
+communicates the request to the platform firmware. The platform firmware is
+responsible for delivering the requested performance.
+
+Each PCC command is "global" in scope and can affect all the logical CPUs in
+the system. Therefore, PCC is capable of performing "group" updates. With PCC
+the OS is capable of getting/setting the frequency of all the logical CPUs in
+the system with a single call to the BIOS.
+
+1.1.1 Get Average Frequency:
+----------------------------
+This command is used by the OSPM to query the running frequency of the
+processor since the last time this command was completed. The output buffer
+indicates the average unhalted frequency of the logical processor expressed as
+a percentage of the nominal (ie: maximum) CPU frequency. The output buffer
+also signifies if the CPU frequency is limited by a power budget condition.
+
+1.1.2 Set Desired Frequency:
+----------------------------
+This command is used by the OSPM to communicate to the platform firmware the
+desired frequency for a logical processor. The output buffer is currently
+ignored by OSPM. The next invocation of "Get Average Frequency" will inform
+OSPM if the desired frequency was achieved or not.
+
+1.2 Platforms affected:
+-----------------------
+The PCC driver will load on any system where the platform firmware:
+* supports the PCC interface, and the associated PCCH() and PCCP() methods
+* assumes responsibility for managing the hardware clocking controls in order
+to deliver the requested processor performance
+
+Currently, certain HP ProLiant platforms implement the PCC interface. On those
+platforms PCC is the "default" choice.
+
+However, it is possible to disable this interface via a BIOS setting. In
+such an instance, as is also the case on platforms where the PCC interface
+is not implemented, the PCC driver will fail to load silently.
+
+2. Driver and /sys details:
+---------------------------
+When the driver loads, it merely prints the lowest and the highest CPU
+frequencies supported by the platform firmware.
+
+The PCC driver loads with a message such as:
+pcc-cpufreq: (v1.00.00) driver loaded with frequency limits: 1600 MHz, 2933
+MHz
+
+This means that the OPSM can request the CPU to run at any frequency in
+between the limits (1600 MHz, and 2933 MHz) specified in the message.
+
+Internally, there is no need for the driver to convert the "target" frequency
+to a corresponding P-state.
+
+The VERSION number for the driver will be of the format v.xy.ab.
+eg: 1.00.02
+   ----- --
+    |    |
+    |    -- this will increase with bug fixes/enhancements to the driver
+    |-- this is the version of the PCC specification the driver adheres to
+
+
+The following is a brief discussion on some of the fields exported via the
+/sys filesystem and how their values are affected by the PCC driver:
+
+2.1 scaling_available_frequencies:
+----------------------------------
+scaling_available_frequencies is not created in /sys. No intermediate
+frequencies need to be listed because the BIOS will try to achieve any
+frequency, within limits, requested by the governor. A frequency does not have
+to be strictly associated with a P-state.
+
+2.2 cpuinfo_transition_latency:
+-------------------------------
+The cpuinfo_transition_latency field is 0. The PCC specification does
+not include a field to expose this value currently.
+
+2.3 cpuinfo_cur_freq:
+---------------------
+A) Often cpuinfo_cur_freq will show a value different than what is declared
+in the scaling_available_frequencies or scaling_cur_freq, or scaling_max_freq.
+This is due to "turbo boost" available on recent Intel processors. If certain
+conditions are met the BIOS can achieve a slightly higher speed than requested
+by OSPM. An example:
+
+scaling_cur_freq	: 2933000
+cpuinfo_cur_freq	: 3196000
+
+B) There is a round-off error associated with the cpuinfo_cur_freq value.
+Since the driver obtains the current frequency as a "percentage" (%) of the
+nominal frequency from the BIOS, sometimes, the values displayed by
+scaling_cur_freq and cpuinfo_cur_freq may not match. An example:
+
+scaling_cur_freq	: 1600000
+cpuinfo_cur_freq	: 1583000
+
+In this example, the nominal frequency is 2933 MHz. The driver obtains the
+current frequency, cpuinfo_cur_freq, as 54% of the nominal frequency:
+
+	54% of 2933 MHz = 1583 MHz
+
+Nominal frequency is the maximum frequency of the processor, and it usually
+corresponds to the frequency of the P0 P-state.
+
+2.4 related_cpus:
+-----------------
+The related_cpus field is identical to affected_cpus.
+
+affected_cpus	: 4
+related_cpus	: 4
+
+Currently, the PCC driver does not evaluate _PSD. The platforms that support
+PCC do not implement SW_ALL. So OSPM doesn't need to perform any coordination
+to ensure that the same frequency is requested of all dependent CPUs.
+
+3. Caveats:
+-----------
+The "cpufreq_stats" module in its present form cannot be loaded and
+expected to work with the PCC driver. Since the "cpufreq_stats" module
+provides information wrt each P-state, it is not applicable to the PCC driver.
diff --git a/arch/x86/kernel/cpu/cpufreq/Kconfig b/arch/x86/kernel/cpu/cpufreq/Kconfig
index f138c6c..870e6cc 100644
--- a/arch/x86/kernel/cpu/cpufreq/Kconfig
+++ b/arch/x86/kernel/cpu/cpufreq/Kconfig
@@ -10,6 +10,20 @@ if CPU_FREQ
 
 comment "CPUFreq processor drivers"
 
+config X86_PCC_CPUFREQ
+	tristate "Processor Clocking Control interface driver"
+	depends on ACPI && ACPI_PROCESSOR
+	help
+	  This driver adds support for the PCC interface.
+
+	  For details, take a look at:
+	  <file:Documentation/cpu-freq/pcc-cpufreq.txt>.
+
+	  To compile this driver as a module, choose M here: the
+	  module will be called pcc-cpufreq.
+
+	  If in doubt, say N.
+
 config X86_ACPI_CPUFREQ
 	tristate "ACPI Processor P-States driver"
 	select CPU_FREQ_TABLE
diff --git a/arch/x86/kernel/cpu/cpufreq/Makefile b/arch/x86/kernel/cpu/cpufreq/Makefile
index 509296d..1840c0a 100644
--- a/arch/x86/kernel/cpu/cpufreq/Makefile
+++ b/arch/x86/kernel/cpu/cpufreq/Makefile
@@ -4,6 +4,7 @@
 
 obj-$(CONFIG_X86_POWERNOW_K8)		+= powernow-k8.o
 obj-$(CONFIG_X86_ACPI_CPUFREQ)		+= acpi-cpufreq.o
+obj-$(CONFIG_X86_PCC_CPUFREQ)		+= pcc-cpufreq.o
 obj-$(CONFIG_X86_POWERNOW_K6)		+= powernow-k6.o
 obj-$(CONFIG_X86_POWERNOW_K7)		+= powernow-k7.o
 obj-$(CONFIG_X86_LONGHAUL)		+= longhaul.o
diff --git a/arch/x86/kernel/cpu/cpufreq/pcc-cpufreq.c b/arch/x86/kernel/cpu/cpufreq/pcc-cpufreq.c
new file mode 100644
index 0000000..ff36d29
--- /dev/null
+++ b/arch/x86/kernel/cpu/cpufreq/pcc-cpufreq.c
@@ -0,0 +1,620 @@
+/*
+ *  pcc-cpufreq.c - Processor Clocking Control firmware cpufreq interface
+ *
+ *  Copyright (C) 2009 Red Hat, Matthew Garrett <mjg@redhat.com>
+ *  Copyright (C) 2009 Hewlett-Packard Development Company, L.P.
+ *	Nagananda Chumbalkar <nagananda.chumbalkar@hp.com>
+ *
+ * ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
+ *
+ *  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, GOOD TITLE or NON
+ *  INFRINGEMENT. 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.,
+ *  675 Mass Ave, Cambridge, MA 02139, USA.
+ *
+ * ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
+ */
+
+#include <linux/kernel.h>
+#include <linux/module.h>
+#include <linux/init.h>
+#include <linux/smp.h>
+#include <linux/sched.h>
+#include <linux/cpufreq.h>
+#include <linux/compiler.h>
+
+#include <linux/acpi.h>
+#include <linux/io.h>
+#include <linux/spinlock.h>
+#include <linux/uaccess.h>
+
+#include <acpi/processor.h>
+
+#define PCC_VERSION 	"1.00.00"
+#define POLL_LOOPS 	300
+
+#define CMD_COMPLETE 	0x1
+#define CMD_GET_FREQ 	0x0
+#define CMD_SET_FREQ 	0x1
+
+#define BUF_SZ		4
+
+#define dprintk(msg...) cpufreq_debug_printk(CPUFREQ_DEBUG_DRIVER,	\
+					     "pcc-cpufreq", msg)
+
+struct pcc_register_resource {
+	u8 descriptor;
+	u16 length;
+	u8 space_id;
+	u8 bit_width;
+	u8 bit_offset;
+	u8 access_size;
+	u64 address;
+} __attribute__ ((packed));
+
+struct pcc_memory_resource {
+	u8 descriptor;
+	u16 length;
+	u8 space_id;
+	u8 resource_usage;
+	u8 type_specific;
+	u64 granularity;
+	u64 minimum;
+	u64 maximum;
+	u64 translation_offset;
+	u64 address_length;
+} __attribute__ ((packed));
+
+static struct cpufreq_driver pcc_cpufreq_driver;
+
+struct pcc_header {
+	u32 signature;
+	u16 length;
+	u8 major;
+	u8 minor;
+	u32 features;
+	u16 command;
+	u16 status;
+	u32 latency;
+	u32 minimum_time;
+	u32 maximum_time;
+	u32 nominal;
+	u32 throttled_frequency;
+	u32 minimum_frequency;
+};
+
+static void __iomem *pcch_virt_addr;
+static struct pcc_header __iomem *pcch_hdr;
+
+static DEFINE_SPINLOCK(pcc_lock);
+
+static struct acpi_generic_address doorbell;
+
+static u64 doorbell_preserve;
+static u64 doorbell_write;
+
+static u8 OSC_UUID[16] = {0x63, 0x9B, 0x2C, 0x9F, 0x70, 0x91, 0x49, 0x1f,
+			  0xBB, 0x4F, 0xA5, 0x98, 0x2F, 0xA1, 0xB5, 0x46};
+
+struct pcc_cpu {
+	u32 input_offset;
+	u32 output_offset;
+};
+
+static struct pcc_cpu *pcc_cpu_info;
+
+static int pcc_cpufreq_verify(struct cpufreq_policy *policy)
+{
+	cpufreq_verify_within_limits(policy, policy->cpuinfo.min_freq,
+				     policy->cpuinfo.max_freq);
+	return 0;
+}
+
+static inline void pcc_cmd(void)
+{
+	u64 doorbell_value;
+	int i;
+
+	acpi_read(&doorbell_value, &doorbell);
+	acpi_write((doorbell_value & doorbell_preserve) | doorbell_write,
+		   &doorbell);
+
+	for (i = 0; i < POLL_LOOPS; i++) {
+		if (ioread16(&pcch_hdr->status) & CMD_COMPLETE)
+			break;
+	}
+}
+
+static inline void pcc_clear_mapping(void)
+{
+	if (pcch_virt_addr)
+		iounmap(pcch_virt_addr);
+	pcch_virt_addr = NULL;
+}
+
+static unsigned int pcc_get_freq(unsigned int cpu)
+{
+	struct pcc_cpu *pcc_cpu_data;
+	unsigned int curr_freq;
+	unsigned int freq_limit;
+	u16 status;
+	u32 input_buffer;
+	u32 output_buffer;
+
+	spin_lock(&pcc_lock);
+
+	dprintk("get: get_freq for CPU %d\n", cpu);
+	pcc_cpu_data = per_cpu_ptr(pcc_cpu_info, cpu);
+
+	input_buffer = 0x1;
+	iowrite32(input_buffer,
+			(pcch_virt_addr + pcc_cpu_data->input_offset));
+	iowrite16(CMD_GET_FREQ, &pcch_hdr->command);
+
+	pcc_cmd();
+
+	output_buffer =
+		ioread32(pcch_virt_addr + pcc_cpu_data->output_offset);
+
+	/* Clear the input buffer - we are done with the current command */
+	memset_io((pcch_virt_addr + pcc_cpu_data->input_offset), 0, BUF_SZ);
+
+	status = ioread16(&pcch_hdr->status);
+	if (status != CMD_COMPLETE) {
+		dprintk("get: FAILED: for CPU %d, status is %d\n",
+			cpu, status);
+		goto cmd_incomplete;
+	}
+	iowrite16(0, &pcch_hdr->status);
+	curr_freq = (((ioread32(&pcch_hdr->nominal) * (output_buffer & 0xff))
+			/ 100) * 1000);
+
+	dprintk("get: SUCCESS: (virtual) output_offset for cpu %d is "
+		"0x%x, contains a value of: 0x%x. Speed is: %d MHz\n",
+		cpu, (pcch_virt_addr + pcc_cpu_data->output_offset),
+		output_buffer, curr_freq);
+
+	freq_limit = (output_buffer >> 8) & 0xff;
+	if (freq_limit != 0xff) {
+		dprintk("get: frequency for cpu %d is being temporarily"
+			" capped at %d\n", cpu, curr_freq);
+	}
+
+	spin_unlock(&pcc_lock);
+	return curr_freq;
+
+cmd_incomplete:
+	iowrite16(0, &pcch_hdr->status);
+	spin_unlock(&pcc_lock);
+	return -EINVAL;
+}
+
+static int pcc_cpufreq_target(struct cpufreq_policy *policy,
+			      unsigned int target_freq,
+			      unsigned int relation)
+{
+	struct pcc_cpu *pcc_cpu_data;
+	struct cpufreq_freqs freqs;
+	u16 status;
+	u32 input_buffer;
+	int cpu;
+
+	spin_lock(&pcc_lock);
+	cpu = policy->cpu;
+	pcc_cpu_data = per_cpu_ptr(pcc_cpu_info, cpu);
+
+	dprintk("target: CPU %d should go to target freq: %d "
+		"(virtual) input_offset is 0x%x\n",
+		cpu, target_freq,
+		(pcch_virt_addr + pcc_cpu_data->input_offset));
+
+	freqs.new = target_freq;
+	freqs.cpu = cpu;
+	cpufreq_notify_transition(&freqs, CPUFREQ_PRECHANGE);
+
+	input_buffer = 0x1 | (((target_freq * 100)
+			       / (ioread32(&pcch_hdr->nominal) * 1000)) << 8);
+	iowrite32(input_buffer,
+			(pcch_virt_addr + pcc_cpu_data->input_offset));
+	iowrite16(CMD_SET_FREQ, &pcch_hdr->command);
+
+	pcc_cmd();
+
+	/* Clear the input buffer - we are done with the current command */
+	memset_io((pcch_virt_addr + pcc_cpu_data->input_offset), 0, BUF_SZ);
+
+	status = ioread16(&pcch_hdr->status);
+	if (status != CMD_COMPLETE) {
+		dprintk("target: FAILED for cpu %d, with status: 0x%x\n",
+			cpu, status);
+		goto cmd_incomplete;
+	}
+	iowrite16(0, &pcch_hdr->status);
+
+	cpufreq_notify_transition(&freqs, CPUFREQ_POSTCHANGE);
+	dprintk("target: was SUCCESSFUL for cpu %d\n", cpu);
+	spin_unlock(&pcc_lock);
+
+	return 0;
+
+cmd_incomplete:
+	iowrite16(0, &pcch_hdr->status);
+	spin_unlock(&pcc_lock);
+	return -EINVAL;
+}
+
+static int pcc_get_offset(int cpu)
+{
+	acpi_status status;
+	struct acpi_buffer buffer = {ACPI_ALLOCATE_BUFFER, NULL};
+	union acpi_object *pccp, *offset;
+	struct pcc_cpu *pcc_cpu_data;
+	struct acpi_processor *pr;
+	int ret = 0;
+
+	pr = per_cpu(processors, cpu);
+	pcc_cpu_data = per_cpu_ptr(pcc_cpu_info, cpu);
+
+	status = acpi_evaluate_object(pr->handle, "PCCP", NULL, &buffer);
+	if (ACPI_FAILURE(status))
+		return -ENODEV;
+
+	pccp = buffer.pointer;
+	if (!pccp || pccp->type != ACPI_TYPE_PACKAGE) {
+		ret = -ENODEV;
+		goto out_free;
+	};
+
+	offset = &(pccp->package.elements[0]);
+	if (!offset || offset->type != ACPI_TYPE_INTEGER) {
+		ret = -ENODEV;
+		goto out_free;
+	}
+
+	pcc_cpu_data->input_offset = offset->integer.value;
+
+	offset = &(pccp->package.elements[1]);
+	if (!offset || offset->type != ACPI_TYPE_INTEGER) {
+		ret = -ENODEV;
+		goto out_free;
+	}
+
+	pcc_cpu_data->output_offset = offset->integer.value;
+
+	memset_io((pcch_virt_addr + pcc_cpu_data->input_offset), 0, BUF_SZ);
+	memset_io((pcch_virt_addr + pcc_cpu_data->output_offset), 0, BUF_SZ);
+
+	dprintk("pcc_get_offset: for CPU %d: pcc_cpu_data "
+		"input_offset: 0x%x, pcc_cpu_data output_offset: 0x%x\n",
+		cpu, pcc_cpu_data->input_offset, pcc_cpu_data->output_offset);
+out_free:
+	kfree(buffer.pointer);
+	return ret;
+}
+
+static int __init pcc_cpufreq_do_osc(acpi_handle *handle)
+{
+	acpi_status status;
+	struct acpi_object_list input;
+	struct acpi_buffer output = {ACPI_ALLOCATE_BUFFER, NULL};
+	union acpi_object in_params[4];
+	union acpi_object *out_obj;
+	u32 capabilities[2];
+	u32 errors;
+	u32 supported;
+	int ret = 0;
+
+	input.count = 4;
+	input.pointer = in_params;
+	input.count = 4;
+	input.pointer = in_params;
+	in_params[0].type               = ACPI_TYPE_BUFFER;
+	in_params[0].buffer.length      = 16;
+	in_params[0].buffer.pointer     = OSC_UUID;
+	in_params[1].type               = ACPI_TYPE_INTEGER;
+	in_params[1].integer.value      = 1;
+	in_params[2].type               = ACPI_TYPE_INTEGER;
+	in_params[2].integer.value      = 2;
+	in_params[3].type               = ACPI_TYPE_BUFFER;
+	in_params[3].buffer.length      = 8;
+	in_params[3].buffer.pointer     = (u8 *)&capabilities;
+
+	capabilities[0] = OSC_QUERY_ENABLE;
+	capabilities[1] = 0x1;
+
+	status = acpi_evaluate_object(*handle, "_OSC", &input, &output);
+	if (ACPI_FAILURE(status))
+		return -ENODEV;
+
+	if (!output.length)
+		return -ENODEV;
+
+	out_obj = output.pointer;
+	if (out_obj->type != ACPI_TYPE_BUFFER) {
+		ret = -ENODEV;
+		goto out_free;
+	}
+
+	errors = *((u32 *)out_obj->buffer.pointer) & ~(1 << 0);
+	if (errors) {
+		ret = -ENODEV;
+		goto out_free;
+	}
+
+	supported = *((u32 *)(out_obj->buffer.pointer + 4));
+	if (!(supported & 0x1)) {
+		ret = -ENODEV;
+		goto out_free;
+	}
+
+	kfree(output.pointer);
+	capabilities[0] = 0x0;
+	capabilities[1] = 0x1;
+
+	status = acpi_evaluate_object(*handle, "_OSC", &input, &output);
+	if (ACPI_FAILURE(status))
+		return -ENODEV;
+
+	if (!output.length)
+		return -ENODEV;
+
+	out_obj = output.pointer;
+	if (out_obj->type != ACPI_TYPE_BUFFER) {
+		ret = -ENODEV;
+		goto out_free;
+	}
+
+	errors = *((u32 *)out_obj->buffer.pointer) & ~(1 << 0);
+	if (errors) {
+		ret = -ENODEV;
+		goto out_free;
+	}
+
+	supported = *((u32 *)(out_obj->buffer.pointer + 4));
+	if (!(supported & 0x1)) {
+		ret = -ENODEV;
+		goto out_free;
+	}
+
+out_free:
+	kfree(output.pointer);
+	return ret;
+}
+
+static int __init pcc_cpufreq_probe(void)
+{
+	acpi_status status;
+	struct acpi_buffer output = {ACPI_ALLOCATE_BUFFER, NULL};
+	struct pcc_memory_resource *mem_resource;
+	struct pcc_register_resource *reg_resource;
+	union acpi_object *out_obj, *member;
+	acpi_handle handle, osc_handle;
+	int ret = 0;
+
+	status = acpi_get_handle(NULL, "\\_SB", &handle);
+	if (ACPI_FAILURE(status))
+		return -ENODEV;
+
+	status = acpi_get_handle(handle, "_OSC", &osc_handle);
+	if (ACPI_SUCCESS(status)) {
+		ret = pcc_cpufreq_do_osc(&osc_handle);
+		if (ret)
+			dprintk("probe: _OSC evaluation did not succeed\n");
+		/* Firmware's use of _OSC is optional */
+		ret = 0;
+	}
+
+	status = acpi_evaluate_object(handle, "PCCH", NULL, &output);
+	if (ACPI_FAILURE(status))
+		return -ENODEV;
+
+	out_obj = output.pointer;
+	if (out_obj->type != ACPI_TYPE_PACKAGE) {
+		ret = -ENODEV;
+		goto out_free;
+	}
+
+	member = &out_obj->package.elements[0];
+	if (member->type != ACPI_TYPE_BUFFER) {
+		ret = -ENODEV;
+		goto out_free;
+	}
+
+	mem_resource = (struct pcc_memory_resource *)member->buffer.pointer;
+
+	dprintk("probe: mem_resource descriptor: 0x%x,"
+		" length: %d, space_id: %d, resource_usage: %d,"
+		" type_specific: %d, granularity: 0x%llx,"
+		" minimum: 0x%llx, maximum: 0x%llx,"
+		" translation_offset: 0x%llx, address_length: 0x%llx\n",
+		mem_resource->descriptor, mem_resource->length,
+		mem_resource->space_id, mem_resource->resource_usage,
+		mem_resource->type_specific, mem_resource->granularity,
+		mem_resource->minimum, mem_resource->maximum,
+		mem_resource->translation_offset,
+		mem_resource->address_length);
+
+	if (mem_resource->space_id != ACPI_ADR_SPACE_SYSTEM_MEMORY) {
+		ret = -ENODEV;
+		goto out_free;
+	}
+
+	pcch_virt_addr = ioremap_nocache(mem_resource->minimum,
+					mem_resource->address_length);
+	if (pcch_virt_addr == NULL) {
+		dprintk("probe: could not map shared mem region\n");
+		goto out_free;
+	}
+	pcch_hdr = pcch_virt_addr;
+
+	dprintk("probe: PCCH header (virtual) addr: 0x%p\n", pcch_hdr);
+	dprintk("probe: PCCH header is at physical address: 0x%llx,"
+		" signature: 0x%x, length: %d bytes, major: %d, minor: %d,"
+		" supported features: 0x%x, command field: 0x%x,"
+		" status field: 0x%x, nominal latency: %d us\n",
+		mem_resource->minimum, ioread32(&pcch_hdr->signature),
+		ioread16(&pcch_hdr->length), ioread8(&pcch_hdr->major),
+		ioread8(&pcch_hdr->minor), ioread32(&pcch_hdr->features),
+		ioread16(&pcch_hdr->command), ioread16(&pcch_hdr->status),
+		ioread32(&pcch_hdr->latency));
+
+	dprintk("probe: min time between commands: %d us,"
+		" max time between commands: %d us,"
+		" nominal CPU frequency: %d MHz,"
+		" minimum CPU frequency: %d MHz,"
+		" minimum CPU frequency without throttling: %d MHz\n",
+		ioread32(&pcch_hdr->minimum_time),
+		ioread32(&pcch_hdr->maximum_time),
+		ioread32(&pcch_hdr->nominal),
+		ioread32(&pcch_hdr->throttled_frequency),
+		ioread32(&pcch_hdr->minimum_frequency));
+
+	member = &out_obj->package.elements[1];
+	if (member->type != ACPI_TYPE_BUFFER) {
+		ret = -ENODEV;
+		goto pcch_free;
+	}
+
+	reg_resource = (struct pcc_register_resource *)member->buffer.pointer;
+
+	doorbell.space_id = reg_resource->space_id;
+	doorbell.bit_width = reg_resource->bit_width;
+	doorbell.bit_offset = reg_resource->bit_offset;
+	doorbell.access_width = 64;
+	doorbell.address = reg_resource->address;
+
+	dprintk("probe: doorbell: space_id is %d, bit_width is %d, "
+		"bit_offset is %d, access_width is %d, address is 0x%llx\n",
+		doorbell.space_id, doorbell.bit_width, doorbell.bit_offset,
+		doorbell.access_width, reg_resource->address);
+
+	member = &out_obj->package.elements[2];
+	if (member->type != ACPI_TYPE_INTEGER) {
+		ret = -ENODEV;
+		goto pcch_free;
+	}
+
+	doorbell_preserve = member->integer.value;
+
+	member = &out_obj->package.elements[3];
+	if (member->type != ACPI_TYPE_INTEGER) {
+		ret = -ENODEV;
+		goto pcch_free;
+	}
+
+	doorbell_write = member->integer.value;
+
+	dprintk("probe: doorbell_preserve: 0x%llx,"
+		" doorbell_write: 0x%llx\n",
+		doorbell_preserve, doorbell_write);
+
+	pcc_cpu_info = alloc_percpu(struct pcc_cpu);
+	if (!pcc_cpu_info) {
+		ret = -ENOMEM;
+		goto pcch_free;
+	}
+
+	printk(KERN_DEBUG "pcc-cpufreq: (v%s) driver loaded with frequency"
+	       " limits: %d MHz, %d MHz\n", PCC_VERSION,
+	       ioread32(&pcch_hdr->minimum_frequency),
+	       ioread32(&pcch_hdr->nominal));
+	kfree(output.pointer);
+	return ret;
+pcch_free:
+	pcc_clear_mapping();
+out_free:
+	kfree(output.pointer);
+	return ret;
+}
+
+static int pcc_cpufreq_cpu_init(struct cpufreq_policy *policy)
+{
+	unsigned int cpu = policy->cpu;
+	unsigned int result = 0;
+
+	if (!pcch_virt_addr) {
+		result = -1;
+		goto pcch_null;
+	}
+
+	result = pcc_get_offset(cpu);
+	if (result) {
+		dprintk("init: PCCP evaluation failed\n");
+		goto free;
+	}
+
+	policy->max = policy->cpuinfo.max_freq =
+		ioread32(&pcch_hdr->nominal) * 1000;
+	policy->min = policy->cpuinfo.min_freq =
+		ioread32(&pcch_hdr->minimum_frequency) * 1000;
+	policy->cur = pcc_get_freq(cpu);
+
+	dprintk("init: policy->max is %d, policy->min is %d\n",
+		policy->max, policy->min);
+
+	return 0;
+free:
+	pcc_clear_mapping();
+	free_percpu(pcc_cpu_info);
+pcch_null:
+	return result;
+}
+
+static int pcc_cpufreq_cpu_exit(struct cpufreq_policy *policy)
+{
+	return 0;
+}
+
+static struct cpufreq_driver pcc_cpufreq_driver = {
+	.flags = CPUFREQ_CONST_LOOPS,
+	.get = pcc_get_freq,
+	.verify = pcc_cpufreq_verify,
+	.target = pcc_cpufreq_target,
+	.init = pcc_cpufreq_cpu_init,
+	.exit = pcc_cpufreq_cpu_exit,
+	.name = "pcc-cpufreq",
+	.owner = THIS_MODULE,
+};
+
+static int __init pcc_cpufreq_init(void)
+{
+	int ret;
+
+	if (acpi_disabled)
+		return 0;
+
+	ret = pcc_cpufreq_probe();
+	if (ret) {
+		dprintk("pcc_cpufreq_init: PCCH evaluation failed\n");
+		return ret;
+	}
+
+	ret = cpufreq_register_driver(&pcc_cpufreq_driver);
+
+	return ret;
+}
+
+static void __exit pcc_cpufreq_exit(void)
+{
+	cpufreq_unregister_driver(&pcc_cpufreq_driver);
+
+	pcc_clear_mapping();
+
+	free_percpu(pcc_cpu_info);
+}
+
+MODULE_AUTHOR("Matthew Garrett, Naga Chumbalkar");
+MODULE_VERSION(PCC_VERSION);
+MODULE_DESCRIPTION("Processor Clocking Control interface driver");
+MODULE_LICENSE("GPL");
+
+late_initcall(pcc_cpufreq_init);
+module_exit(pcc_cpufreq_exit);
diff --git a/drivers/acpi/processor_core.c b/drivers/acpi/processor_core.c
index 9863c98..e9b7b40 100644
--- a/drivers/acpi/processor_core.c
+++ b/drivers/acpi/processor_core.c
@@ -123,6 +123,8 @@ static const struct file_operations acpi_processor_info_fops = {
 #endif
 
 DEFINE_PER_CPU(struct acpi_processor *, processors);
+EXPORT_PER_CPU_SYMBOL(processors);
+
 struct acpi_processor_errata errata __read_mostly;
 
 /* --------------------------------------------------------------------------