path: root/patches/linux-3.6.7/0140-Add-cpufreq-driver.patch

From: popcornmix <popcornmix@gmail.com>
Date: Sun, 9 Sep 2012 23:47:03 +0100
Subject: [PATCH] Add cpufreq driver

---
 arch/arm/Kconfig                          |   1 +
 arch/arm/configs/bcmrpi_defconfig         |   6 +
 arch/arm/mach-bcm2708/include/mach/vcio.h |  81 +++++++++-
 arch/arm/mach-bcm2708/vc_mem.c            |  47 +++---
 arch/arm/mach-bcm2708/vcio.c              |  34 +++++
 drivers/cpufreq/Kconfig.arm               |   9 ++
 drivers/cpufreq/Makefile                  |   1 +
 drivers/cpufreq/bcm2835-cpufreq.c         | 239 ++++++++++++++++++++++++++++++
 8 files changed, 381 insertions(+), 37 deletions(-)
 create mode 100755 drivers/cpufreq/bcm2835-cpufreq.c

diff --git a/arch/arm/Kconfig b/arch/arm/Kconfig
index 4dd71eb..14afaea 100644
--- a/arch/arm/Kconfig
+++ b/arch/arm/Kconfig
@@ -1006,6 +1006,7 @@ config ARCH_BCM2708
 	select HAVE_SCHED_CLOCK
 	select NEED_MACH_MEMORY_H
 	select CLKDEV_LOOKUP
+	select ARCH_HAS_CPUFREQ
 	select GENERIC_CLOCKEVENTS
 	select ARM_ERRATA_411920
 	select MACH_BCM2708
diff --git a/arch/arm/configs/bcmrpi_defconfig b/arch/arm/configs/bcmrpi_defconfig
index 5ed9c30..35c5042 100644
--- a/arch/arm/configs/bcmrpi_defconfig
+++ b/arch/arm/configs/bcmrpi_defconfig
@@ -46,6 +46,12 @@ CONFIG_ZBOOT_ROM_TEXT=0x0
 CONFIG_ZBOOT_ROM_BSS=0x0
 CONFIG_CMDLINE="dwc_otg.lpm_enable=0 console=ttyAMA0,115200 kgdboc=ttyAMA0,115200 root=/dev/mmcblk0p2 rootfstype=ext3 rootwait"
 CONFIG_KEXEC=y
+CONFIG_CPU_FREQ=y
+CONFIG_CPU_FREQ_STAT=m
+CONFIG_CPU_FREQ_DEFAULT_GOV_ONDEMAND=y
+CONFIG_CPU_FREQ_GOV_POWERSAVE=y
+CONFIG_CPU_FREQ_GOV_USERSPACE=y
+CONFIG_CPU_FREQ_GOV_CONSERVATIVE=y
 CONFIG_CPU_IDLE=y
 CONFIG_VFP=y
 CONFIG_BINFMT_MISC=m
diff --git a/arch/arm/mach-bcm2708/include/mach/vcio.h b/arch/arm/mach-bcm2708/include/mach/vcio.h
index ace4ea4..7dfd14e 100644
--- a/arch/arm/mach-bcm2708/include/mach/vcio.h
+++ b/arch/arm/mach-bcm2708/include/mach/vcio.h
@@ -27,17 +27,82 @@
 #define BCM_VCIO_DRIVER_NAME "bcm2708_vcio"
 
 /* Constants shared with the ARM identifying separate mailbox channels */
-#define MBOX_CHAN_POWER   0 /* for use by the power management interface */
-#define MBOX_CHAN_FB      1 /* for use by the frame buffer */
-#define MBOX_CHAN_VUART   2 /* for use by the virtual UART */
-#define MBOX_CHAN_VCHIQ   3 /* for use by the VCHIQ interface */
-#define MBOX_CHAN_LEDS    4 /* for use by the leds interface */
-#define MBOX_CHAN_BUTTONS 5 /* for use by the buttons interface */
-#define MBOX_CHAN_TOUCH   6 /* for use by the touchscreen interface */
+#define MBOX_CHAN_POWER    0 /* for use by the power management interface */
+#define MBOX_CHAN_FB       1 /* for use by the frame buffer */
+#define MBOX_CHAN_VCHIQ    3 /* for use by the VCHIQ interface */
 #define MBOX_CHAN_PROPERTY 8 /* for use by the property channel */
-#define MBOX_CHAN_COUNT   9
+#define MBOX_CHAN_COUNT    9
+
+/* Mailbox property tags */
+enum {
+	VCMSG_PROPERTY_END               = 0x00000000,
+	VCMSG_GET_FIRMWARE_REVISION      = 0x00000001,
+	VCMSG_GET_BOARD_MODEL            = 0x00010001,
+	VCMSG_GET_BOARD_REVISION	 = 0x00020002,
+	VCMSG_GET_BOARD_MAC_ADDRESS	 = 0x00020003,
+	VCMSG_GET_BOARD_SERIAL		 = 0x00020004,
+	VCMSG_GET_ARM_MEMORY		 = 0x00020005,
+	VCMSG_GET_VC_MEMORY		 = 0x00020006,
+	VCMSG_GET_CLOCKS		 = 0x00020007,
+	VCMSG_GET_COMMAND_LINE           = 0x00050001,
+	VCMSG_GET_DMA_CHANNELS           = 0x00060001,
+	VCMSG_GET_POWER_STATE            = 0x00020001,
+	VCMSG_GET_TIMING		 = 0x00020002,
+	VCMSG_SET_POWER_STATE            = 0x00028001,
+	VCMSG_GET_CLOCK_STATE            = 0x00030001,
+	VCMSG_SET_CLOCK_STATE            = 0x00038001,
+	VCMSG_GET_CLOCK_RATE             = 0x00030002,
+	VCMSG_SET_CLOCK_RATE             = 0x00038002,
+	VCMSG_GET_VOLTAGE                = 0x00030003,
+	VCMSG_SET_VOLTAGE                = 0x00038003,
+	VCMSG_GET_MAX_CLOCK              = 0x00030004,
+	VCMSG_GET_MAX_VOLTAGE            = 0x00030005,
+	VCMSG_GET_TEMPERATURE            = 0x00030006,
+	VCMSG_GET_MIN_CLOCK              = 0x00030007,
+	VCMSG_GET_MIN_VOLTAGE            = 0x00030008,
+	VCMSG_GET_TURBO                  = 0x00030009,
+	VCMSG_SET_TURBO                  = 0x00038009,
+	VCMSG_SET_ALLOCATE_BUFFER        = 0x00040001,
+	VCMSG_SET_RELEASE_BUFFER         = 0x00048001,
+	VCMSG_SET_BLANK_SCREEN           = 0x00040002,
+	VCMSG_TST_BLANK_SCREEN           = 0x00044002,
+	VCMSG_GET_PHYSICAL_WIDTH_HEIGHT  = 0x00040003,
+	VCMSG_TST_PHYSICAL_WIDTH_HEIGHT  = 0x00044003,
+	VCMSG_SET_PHYSICAL_WIDTH_HEIGHT  = 0x00048003,
+	VCMSG_GET_VIRTUAL_WIDTH_HEIGHT   = 0x00040004,
+	VCMSG_TST_VIRTUAL_WIDTH_HEIGHT   = 0x00044004,
+	VCMSG_SET_VIRTUAL_WIDTH_HEIGHT   = 0x00048004,
+	VCMSG_GET_DEPTH                  = 0x00040005,
+	VCMSG_TST_DEPTH                  = 0x00044005,
+	VCMSG_SET_DEPTH                  = 0x00048005,
+	VCMSG_GET_PIXEL_ORDER            = 0x00040006,
+	VCMSG_TST_PIXEL_ORDER            = 0x00044006,
+	VCMSG_SET_PIXEL_ORDER            = 0x00048006,
+	VCMSG_GET_ALPHA_MODE             = 0x00040007,
+	VCMSG_TST_ALPHA_MODE             = 0x00044007,
+	VCMSG_SET_ALPHA_MODE             = 0x00048007,
+	VCMSG_GET_PITCH                  = 0x00040008,
+	VCMSG_TST_PITCH                  = 0x00044008,
+	VCMSG_SET_PITCH                  = 0x00048008,
+	VCMSG_GET_VIRTUAL_OFFSET         = 0x00040009,
+	VCMSG_TST_VIRTUAL_OFFSET         = 0x00044009,
+	VCMSG_SET_VIRTUAL_OFFSET         = 0x00048009,
+	VCMSG_GET_OVERSCAN               = 0x0004000a,
+	VCMSG_TST_OVERSCAN               = 0x0004400a,
+	VCMSG_SET_OVERSCAN               = 0x0004800a,
+	VCMSG_GET_PALETTE                = 0x0004000b,
+	VCMSG_TST_PALETTE                = 0x0004400b,
+	VCMSG_SET_PALETTE                = 0x0004800b,
+	VCMSG_GET_LAYER                  = 0x0004000c,
+	VCMSG_TST_LAYER                  = 0x0004400c,
+	VCMSG_SET_LAYER                  = 0x0004800c,
+	VCMSG_GET_TRANSFORM              = 0x0004000d,
+	VCMSG_TST_TRANSFORM              = 0x0004400d,
+	VCMSG_SET_TRANSFORM              = 0x0004800d,
+};
 
 extern int /*rc*/ bcm_mailbox_read(unsigned chan, uint32_t *data28);
 extern int /*rc*/ bcm_mailbox_write(unsigned chan, uint32_t data28);
+extern int /*rc*/ bcm_mailbox_property(void *data, int size);
 
 #endif
diff --git a/arch/arm/mach-bcm2708/vc_mem.c b/arch/arm/mach-bcm2708/vc_mem.c
index 775c213..ae1810c 100644
--- a/arch/arm/mach-bcm2708/vc_mem.c
+++ b/arch/arm/mach-bcm2708/vc_mem.c
@@ -128,44 +128,33 @@ struct vc_set_msg {
 	uint32_t end_tag;			/* an end identifier, should be set to NULL */
 };
 
-#define VCMSG_GET_ARM_MEMORY 0x00010005
-#define VCMSG_GET_VC_MEMORY  0x00010006
-
 static void vc_mem_update(void)
 {
-	uint32_t success;
-	dma_addr_t vc_mem;						/* the memory address accessed from videocore */
-	struct vc_set_msg *get_mem;					/* the memory address accessed from driver */
-
-	/* allocate some memory for the messages to use throughout the lifetime of the driver, use the larger of the two message structures */
-	get_mem = (struct vc_set_msg *)dma_alloc_coherent(NULL, PAGE_ALIGN(sizeof(struct vc_set_msg)), &vc_mem, GFP_ATOMIC); 
-	/* clear any garbage */
-	memset(get_mem, 0, sizeof(struct vc_set_msg));
+	struct vc_set_msg msg;					/* the memory address accessed from driver */
+	uint32_t s;
+
+	memset(&msg, 0, sizeof msg);
 	/* create the message */
-	get_mem->msg_size = sizeof(struct vc_set_msg);
-	get_mem->tag[0].tag_id = VCMSG_GET_VC_MEMORY;
-	get_mem->tag[0].buffer_size = 8;
-	get_mem->tag[0].data_size   = 0;
-	get_mem->tag[1].tag_id = VCMSG_GET_ARM_MEMORY;
-	get_mem->tag[1].buffer_size = 8;
-	get_mem->tag[1].data_size   = 0;
+	msg.msg_size = sizeof msg;
+	msg.tag[0].tag_id = VCMSG_GET_VC_MEMORY;
+	msg.tag[0].buffer_size = 8;
+	msg.tag[0].data_size   = 0;
+	msg.tag[1].tag_id = VCMSG_GET_ARM_MEMORY;
+	msg.tag[1].buffer_size = 8;
+	msg.tag[1].data_size   = 0;
 
 	/* send the message */
-	wmb();
-	bcm_mailbox_write(MBOX_CHAN_PROPERTY,(uint32_t)vc_mem);
-	bcm_mailbox_read(MBOX_CHAN_PROPERTY, &success);
-	rmb();
+	s = bcm_mailbox_property(&msg, sizeof msg);
 
-	LOG_DBG("%s: resp %x, vcbase=%x vcsize=%x armbase=%x armsize=%x", __func__, get_mem->request_code, 
-		get_mem->tag[0].base, get_mem->tag[0].size, get_mem->tag[1].base, get_mem->tag[1].size);
+	LOG_DBG("%s: success=%d resp %x, vcbase=%x vcsize=%x armbase=%x armsize=%x", __func__, s, msg.request_code, 
+		msg.tag[0].base, msg.tag[0].size, msg.tag[1].base, msg.tag[1].size);
 
 	/* check we're all good */
-	if (get_mem->request_code & 0x80000000) {
-		mm_vc_mem_base = get_mem->tag[0].base;
-		mm_vc_mem_size = get_mem->tag[0].size+get_mem->tag[1].size;
-		mm_vc_mem_phys_addr = get_mem->tag[1].base;
+	if (s == 0 && msg.request_code & 0x80000000) {
+		mm_vc_mem_base = msg.tag[0].base;
+		mm_vc_mem_size = msg.tag[0].size+msg.tag[1].size;
+		mm_vc_mem_phys_addr = msg.tag[1].base;
 	}
-	dma_free_coherent(NULL, PAGE_ALIGN(sizeof(struct vc_set_msg)), (void *)get_mem, vc_mem);
 }
 
 
diff --git a/arch/arm/mach-bcm2708/vcio.c b/arch/arm/mach-bcm2708/vcio.c
index 3874051..468fdef 100644
--- a/arch/arm/mach-bcm2708/vcio.c
+++ b/arch/arm/mach-bcm2708/vcio.c
@@ -216,6 +216,40 @@ static void dev_mbox_register(const char *dev_name, struct device *dev)
 	mbox_dev = dev;
 }
 
+extern int bcm_mailbox_property(void *data, int size)
+{
+	uint32_t success;
+	dma_addr_t mem_bus;				/* the memory address accessed from videocore */
+	void *mem_kern;					/* the memory address accessed from driver */
+	int s = 0;
+
+	/* allocate some memory for the messages communicating with GPU */
+	mem_kern = dma_alloc_coherent(NULL, PAGE_ALIGN(size), &mem_bus, GFP_ATOMIC);
+	if (mem_kern) {
+		/* create the message */
+		memcpy(mem_kern, data, size);
+
+		/* send the message */
+		wmb();
+		s = bcm_mailbox_write(MBOX_CHAN_PROPERTY, (uint32_t)mem_bus);
+		if (s == 0) {
+			s = bcm_mailbox_read(MBOX_CHAN_PROPERTY, &success);
+		}
+		if (s == 0) {
+			/* copy the response */
+			rmb();
+			memcpy(data, mem_kern, size);
+		}
+		dma_free_coherent(NULL, PAGE_ALIGN(size), mem_kern, mem_bus);
+	} else {
+		s = -ENOMEM;
+	}
+	if (s != 0)
+		printk(KERN_ERR DRIVER_NAME ": %s failed (%d)\n", __func__, s);
+	return s;
+}
+EXPORT_SYMBOL_GPL(bcm_mailbox_property);
+
 /* ----------------------------------------------------------------------
  *	Platform Device for Mailbox
  * -------------------------------------------------------------------- */
diff --git a/drivers/cpufreq/Kconfig.arm b/drivers/cpufreq/Kconfig.arm
index 5961e64..6999dfd 100644
--- a/drivers/cpufreq/Kconfig.arm
+++ b/drivers/cpufreq/Kconfig.arm
@@ -76,3 +76,12 @@ config ARM_EXYNOS5250_CPUFREQ
 	help
 	  This adds the CPUFreq driver for Samsung EXYNOS5250
 	  SoC.
+
+config ARM_BCM2835_CPUFREQ
+	bool "BCM2835 Driver"
+	default y
+	help
+	  This adds the CPUFreq driver for BCM2835
+
+	  If in doubt, say N.
+
diff --git a/drivers/cpufreq/Makefile b/drivers/cpufreq/Makefile
index 9531fc2..860ab83 100644
--- a/drivers/cpufreq/Makefile
+++ b/drivers/cpufreq/Makefile
@@ -48,6 +48,7 @@ obj-$(CONFIG_ARM_EXYNOS4210_CPUFREQ)	+= exynos4210-cpufreq.o
 obj-$(CONFIG_ARM_EXYNOS4X12_CPUFREQ)	+= exynos4x12-cpufreq.o
 obj-$(CONFIG_ARM_EXYNOS5250_CPUFREQ)	+= exynos5250-cpufreq.o
 obj-$(CONFIG_ARM_OMAP2PLUS_CPUFREQ)     += omap-cpufreq.o
+obj-$(CONFIG_ARM_BCM2835_CPUFREQ)	+= bcm2835-cpufreq.o
 
 ##################################################################################
 # PowerPC platform drivers
diff --git a/drivers/cpufreq/bcm2835-cpufreq.c b/drivers/cpufreq/bcm2835-cpufreq.c
new file mode 100755
index 0000000..aa6fc66
--- /dev/null
+++ b/drivers/cpufreq/bcm2835-cpufreq.c
@@ -0,0 +1,239 @@
+/*****************************************************************************
+* Copyright 2011 Broadcom Corporation.  All rights reserved.
+*
+* Unless you and Broadcom execute a separate written software license
+* agreement governing use of this software, this software is licensed to you
+* under the terms of the GNU General Public License version 2, available at
+* http://www.broadcom.com/licenses/GPLv2.php (the "GPL").
+*	
+* Notwithstanding the above, under no circumstances may you combine this
+* software in any way with any other Broadcom software provided under a
+* license other than the GPL, without Broadcom's express prior written
+* consent.
+*****************************************************************************/
+
+/*****************************************************************************
+* FILENAME: bcm2835-cpufreq.h
+* DESCRIPTION: This driver dynamically manages the CPU Frequency of the ARM
+* processor. Messages are sent to Videocore either setting or requesting the
+* frequency of the ARM in order to match an appropiate frequency to the current
+* usage of the processor. The policy which selects the frequency to use is
+* defined in the kernel .config file, but can be changed during runtime.
+*****************************************************************************/
+
+/* ---------- INCLUDES ---------- */
+#include <linux/kernel.h>
+#include <linux/init.h>
+#include <linux/module.h>
+#include <linux/cpufreq.h>
+#include <mach/vcio.h>
+
+/* ---------- DEFINES ---------- */
+/*#define CPUFREQ_DEBUG_ENABLE*/		/* enable debugging */
+#define MODULE_NAME "bcm2835-cpufreq"
+
+#define VCMSG_ID_ARM_CLOCK 0x000000003		/* Clock/Voltage ID's */
+
+/* debug printk macros */
+#ifdef CPUFREQ_DEBUG_ENABLE
+#define print_debug(fmt,...) pr_debug("%s:%s:%d: "fmt, MODULE_NAME, __func__, __LINE__, ##__VA_ARGS__)
+#else
+#define print_debug(fmt,...)
+#endif
+#define print_err(fmt,...) pr_err("%s:%s:%d: "fmt, MODULE_NAME, __func__,__LINE__, ##__VA_ARGS__)
+#define print_info(fmt,...) pr_info("%s: "fmt, MODULE_NAME, ##__VA_ARGS__)
+
+/* tag part of the message */
+struct vc_msg_tag {
+	uint32_t tag_id;		/* the message id */
+	uint32_t buffer_size;		/* size of the buffer (which in this case is always 8 bytes) */
+	uint32_t data_size;		/* amount of data being sent or received */
+	uint32_t dev_id;		/* the ID of the clock/voltage to get or set */
+	uint32_t val;			/* the value (e.g. rate (in Hz)) to set */
+};
+
+/* message structure to be sent to videocore */
+struct vc_msg {
+	uint32_t msg_size;		/* simply, sizeof(struct vc_msg) */
+	uint32_t request_code;		/* holds various information like the success and number of bytes returned (refer to mailboxes wiki) */
+	struct vc_msg_tag tag;		/* the tag structure above to make */
+	uint32_t end_tag;		/* an end identifier, should be set to NULL */
+};
+
+/* ---------- GLOBALS ---------- */
+static struct cpufreq_driver bcm2835_cpufreq_driver;	/* the cpufreq driver global */
+
+/*
+ ===============================================
+  clk_rate either gets or sets the clock rates.
+ ===============================================
+*/
+static uint32_t bcm2835_cpufreq_set_clock(int cur_rate, int arm_rate)
+{
+	int s, actual_rate=0;
+	struct vc_msg msg;
+	
+	/* wipe all previous message data */
+	memset(&msg, 0, sizeof msg);
+	
+	msg.msg_size = sizeof msg;
+			
+	msg.tag.tag_id = VCMSG_SET_CLOCK_RATE;
+	msg.tag.buffer_size = 8;
+	msg.tag.data_size = 8;   /* we're sending the clock ID and the new rates which is a total of 2 words */
+	msg.tag.dev_id = VCMSG_ID_ARM_CLOCK;
+	msg.tag.val = arm_rate * 1000;
+			
+	/* send the message */
+	s = bcm_mailbox_property(&msg, sizeof msg);
+	
+	/* check if it was all ok and return the rate in KHz */
+	if (s == 0 && (msg.request_code & 0x80000000))
+		actual_rate = msg.tag.val/1000;
+
+	print_debug("Setting new frequency = %d -> %d (actual %d)", cur_rate, arm_rate, actual_rate);	
+	return actual_rate;
+}
+
+static uint32_t bcm2835_cpufreq_get_clock(int tag)
+{
+	int s;
+	int arm_rate = 0;
+	struct vc_msg msg;
+	
+	/* wipe all previous message data */
+	memset(&msg, 0, sizeof msg);
+	
+	msg.msg_size = sizeof msg;
+	msg.tag.tag_id = tag;
+	msg.tag.buffer_size = 8;
+	msg.tag.data_size = 4; /* we're just sending the clock ID which is one word long */
+	msg.tag.dev_id = VCMSG_ID_ARM_CLOCK;
+	
+	/* send the message */
+	s = bcm_mailbox_property(&msg, sizeof msg);
+
+	/* check if it was all ok and return the rate in KHz */
+	if (s == 0 && (msg.request_code & 0x80000000))
+		arm_rate = msg.tag.val/1000;
+
+	print_debug("%s frequency = %d",
+		tag == VCMSG_GET_CLOCK_RATE ? "Current":
+		tag == VCMSG_GET_MIN_CLOCK ? "Min":
+		tag == VCMSG_GET_MAX_CLOCK ? "Max":
+		"Unexpected", arm_rate);
+	
+	return arm_rate;
+}
+
+/*
+ ====================================================
+  Module Initialisation registers the cpufreq driver
+ ====================================================
+*/
+static int __init bcm2835_cpufreq_module_init(void)
+{	
+	print_debug("IN");
+	return cpufreq_register_driver(&bcm2835_cpufreq_driver);
+}
+
+/*
+ =============
+  Module exit
+ =============
+*/
+static void __exit bcm2835_cpufreq_module_exit(void)
+{
+	print_debug("IN");
+	cpufreq_unregister_driver(&bcm2835_cpufreq_driver);
+	return;
+}
+
+/*
+ ==============================================================
+  Initialisation function sets up the CPU policy for first use
+ ==============================================================
+*/
+static int bcm2835_cpufreq_driver_init(struct cpufreq_policy *policy)
+{
+	/* measured value of how long it takes to change frequency */	
+	policy->cpuinfo.transition_latency = 355000; /* ns */
+
+	/* now find out what the maximum and minimum frequencies are */
+	policy->min = policy->cpuinfo.min_freq = bcm2835_cpufreq_get_clock(VCMSG_GET_MIN_CLOCK);
+	policy->max = policy->cpuinfo.max_freq = bcm2835_cpufreq_get_clock(VCMSG_GET_MAX_CLOCK);
+	policy->cur = bcm2835_cpufreq_get_clock(VCMSG_GET_CLOCK_RATE);
+	
+	print_info("min=%d max=%d cur=%d", policy->min, policy->max, policy->cur);
+	return 0;
+}
+
+/*
+ =================================================================================
+  Target function chooses the most appropriate frequency from the table to enable
+ =================================================================================
+*/
+
+static int bcm2835_cpufreq_driver_target(struct cpufreq_policy *policy, unsigned int target_freq, unsigned int relation)
+{
+	unsigned int target = target_freq;
+	unsigned int cur = policy->cur;
+	print_debug("%s: min=%d max=%d cur=%d target=%d",policy->governor->name,policy->min,policy->max,policy->cur,target_freq);
+	
+	/* if we are above min and using ondemand, then just use max */
+	if (strcmp("ondemand", policy->governor->name)==0 && target > policy->min)
+		target = policy->max;
+	/* if the frequency is the same, just quit */
+	if (target == policy->cur)
+		return 0;
+
+	/* otherwise were good to set the clock frequency */
+	policy->cur = bcm2835_cpufreq_set_clock(policy->cur, target);
+	
+	if (!policy->cur)
+	{
+		print_err("Error occurred setting a new frequency (%d)!", target);
+		policy->cur = bcm2835_cpufreq_get_clock(VCMSG_GET_CLOCK_RATE);
+		return -EINVAL;
+	}
+	print_info("Freq %d->%d (min=%d max=%d target=%d request=%d)", cur, policy->cur, policy->min, policy->max, target_freq, target);
+	return 0;
+}
+
+static unsigned int bcm2835_cpufreq_driver_get(unsigned int cpu)
+{
+	unsigned int actual_rate = bcm2835_cpufreq_get_clock(VCMSG_GET_CLOCK_RATE);
+	print_debug("%d", actual_rate);
+	return actual_rate;
+}
+
+/*
+ =================================================================================
+  Verify ensures that when a policy is changed, it is suitable for the CPU to use
+ =================================================================================
+*/
+
+static int bcm2835_cpufreq_driver_verify(struct cpufreq_policy *policy)
+{
+	print_info("switching to governor %s", policy->governor->name);
+	return 0;
+}
+
+
+/* the CPUFreq driver */
+static struct cpufreq_driver bcm2835_cpufreq_driver = {
+		.name   = "BCM2835 CPUFreq",
+		.owner  = THIS_MODULE,
+		.init   = bcm2835_cpufreq_driver_init,
+		.verify = bcm2835_cpufreq_driver_verify,
+		.target = bcm2835_cpufreq_driver_target,
+		.get    = bcm2835_cpufreq_driver_get
+};
+
+MODULE_AUTHOR("Dorian Peake and Dom Cobley");
+MODULE_DESCRIPTION("CPU frequency driver for BCM2835 chip");
+MODULE_LICENSE("GPL");
+
+module_init(bcm2835_cpufreq_module_init);
+module_exit(bcm2835_cpufreq_module_exit);
+