Commit c5d6c770 authored by Alexander Shishkin's avatar Alexander Shishkin Committed by Russell King
Browse files

ARM: 5841/1: a driver for on-chip ETM and ETB 

This driver implements support for on-chip Embedded Tracing Macrocell and
Embedded Trace Buffer. It allows to trigger tracing of kernel execution flow
and exporting trace output to userspace via character device and a sysrq
combo.

Trace output can then be decoded by a fairly simple open source tool [1]
which is already sufficient to get the idea of what the kernel is doing.

[1]: http://github.com/virtuoso/etm2human



Signed-off-by: default avatarAlexander Shishkin <virtuoso@slind.org>
Signed-off-by: default avatarRussell King <rmk+kernel@arm.linux.org.uk>
parent 29e55363

arch/arm/Kconfig.debug

+8 −0
Original line number Diff line number Diff line
@@ -83,6 +83,14 @@ config DEBUG_ICEDCC 
	  It does include a timeout to ensure that the system does not

	  totally freeze when there is nothing connected to read.



config OC_ETM

	bool "On-chip ETM and ETB"

	select ARM_AMBA

	help

	  Enables the on-chip embedded trace macrocell and embedded trace

	  buffer driver that will allow you to collect traces of the

	  kernel code.



config DEBUG_DC21285_PORT

	bool "Kernel low-level debugging messages via footbridge serial port"

	depends on DEBUG_LL && FOOTBRIDGE

arch/arm/include/asm/hardware/coresight.h

0 → 100644
+165 −0
Original line number Diff line number Diff line 
/*

 * linux/arch/arm/include/asm/hardware/coresight.h

 *

 * CoreSight components' registers

 *

 * Copyright (C) 2009 Nokia Corporation.

 * Alexander Shishkin

 *

 * This program is free software; you can redistribute it and/or modify

 * it under the terms of the GNU General Public License version 2 as

 * published by the Free Software Foundation.

 */



#ifndef __ASM_HARDWARE_CORESIGHT_H

#define __ASM_HARDWARE_CORESIGHT_H



#define TRACER_ACCESSED_BIT	0

#define TRACER_RUNNING_BIT	1

#define TRACER_CYCLE_ACC_BIT	2

#define TRACER_ACCESSED		BIT(TRACER_ACCESSED_BIT)

#define TRACER_RUNNING		BIT(TRACER_RUNNING_BIT)

#define TRACER_CYCLE_ACC	BIT(TRACER_CYCLE_ACC_BIT)



struct tracectx {

	unsigned int	etb_bufsz;

	void __iomem	*etb_regs;

	void __iomem	*etm_regs;

	unsigned long	flags;

	int		ncmppairs;

	int		etm_portsz;

	struct device	*dev;

	struct clk	*emu_clk;

	struct mutex	mutex;

};



#define TRACER_TIMEOUT 10000



#define etm_writel(t, v, x) \

	(__raw_writel((v), (t)->etm_regs + (x)))

#define etm_readl(t, x) (__raw_readl((t)->etm_regs + (x)))



/* CoreSight Management Registers */

#define CSMR_LOCKACCESS 0xfb0

#define CSMR_LOCKSTATUS 0xfb4

#define CSMR_AUTHSTATUS 0xfb8

#define CSMR_DEVID	0xfc8

#define CSMR_DEVTYPE	0xfcc

/* CoreSight Component Registers */

#define CSCR_CLASS	0xff4



#define CSCR_PRSR	0x314



#define UNLOCK_MAGIC	0xc5acce55



/* ETM control register, "ETM Architecture", 3.3.1 */

#define ETMR_CTRL		0

#define ETMCTRL_POWERDOWN	1

#define ETMCTRL_PROGRAM		(1 << 10)

#define ETMCTRL_PORTSEL		(1 << 11)

#define ETMCTRL_DO_CONTEXTID	(3 << 14)

#define ETMCTRL_PORTMASK1	(7 << 4)

#define ETMCTRL_PORTMASK2	(1 << 21)

#define ETMCTRL_PORTMASK	(ETMCTRL_PORTMASK1 | ETMCTRL_PORTMASK2)

#define ETMCTRL_PORTSIZE(x) ((((x) & 7) << 4) | (!!((x) & 8)) << 21)

#define ETMCTRL_DO_CPRT		(1 << 1)

#define ETMCTRL_DATAMASK	(3 << 2)

#define ETMCTRL_DATA_DO_DATA	(1 << 2)

#define ETMCTRL_DATA_DO_ADDR	(1 << 3)

#define ETMCTRL_DATA_DO_BOTH	(ETMCTRL_DATA_DO_DATA | ETMCTRL_DATA_DO_ADDR)

#define ETMCTRL_BRANCH_OUTPUT	(1 << 8)

#define ETMCTRL_CYCLEACCURATE	(1 << 12)



/* ETM configuration code register */

#define ETMR_CONFCODE		(0x04)



/* ETM trace start/stop resource control register */

#define ETMR_TRACESSCTRL	(0x18)



/* ETM trigger event register */

#define ETMR_TRIGEVT		(0x08)



/* address access type register bits, "ETM architecture",

 * table 3-27 */

/* - access type */

#define ETMAAT_IFETCH		0

#define ETMAAT_IEXEC		1

#define ETMAAT_IEXECPASS	2

#define ETMAAT_IEXECFAIL	3

#define ETMAAT_DLOADSTORE	4

#define ETMAAT_DLOAD		5

#define ETMAAT_DSTORE		6

/* - comparison access size */

#define ETMAAT_JAVA		(0 << 3)

#define ETMAAT_THUMB		(1 << 3)

#define ETMAAT_ARM		(3 << 3)

/* - data value comparison control */

#define ETMAAT_NOVALCMP		(0 << 5)

#define ETMAAT_VALMATCH		(1 << 5)

#define ETMAAT_VALNOMATCH	(3 << 5)

/* - exact match */

#define ETMAAT_EXACTMATCH	(1 << 7)

/* - context id comparator control */

#define ETMAAT_IGNCONTEXTID	(0 << 8)

#define ETMAAT_VALUE1		(1 << 8)

#define ETMAAT_VALUE2		(2 << 8)

#define ETMAAT_VALUE3		(3 << 8)

/* - security level control */

#define ETMAAT_IGNSECURITY	(0 << 10)

#define ETMAAT_NSONLY		(1 << 10)

#define ETMAAT_SONLY		(2 << 10)



#define ETMR_COMP_VAL(x)	(0x40 + (x) * 4)

#define ETMR_COMP_ACC_TYPE(x)	(0x80 + (x) * 4)



/* ETM status register, "ETM Architecture", 3.3.2 */

#define ETMR_STATUS		(0x10)

#define ETMST_OVERFLOW		(1 << 0)

#define ETMST_PROGBIT		(1 << 1)

#define ETMST_STARTSTOP		(1 << 2)

#define ETMST_TRIGGER		(1 << 3)



#define etm_progbit(t)		(etm_readl((t), ETMR_STATUS) & ETMST_PROGBIT)

#define etm_started(t)		(etm_readl((t), ETMR_STATUS) & ETMST_STARTSTOP)

#define etm_triggered(t)	(etm_readl((t), ETMR_STATUS) & ETMST_TRIGGER)



#define ETMR_TRACEENCTRL2	0x1c

#define ETMR_TRACEENCTRL	0x24

#define ETMTE_INCLEXCL		(1 << 24)

#define ETMR_TRACEENEVT		0x20

#define ETMCTRL_OPTS		(ETMCTRL_DO_CPRT | \

				ETMCTRL_DATA_DO_ADDR | \

				ETMCTRL_BRANCH_OUTPUT | \

				ETMCTRL_DO_CONTEXTID)



/* ETB registers, "CoreSight Components TRM", 9.3 */

#define ETBR_DEPTH		0x04

#define ETBR_STATUS		0x0c

#define ETBR_READMEM		0x10

#define ETBR_READADDR		0x14

#define ETBR_WRITEADDR		0x18

#define ETBR_TRIGGERCOUNT	0x1c

#define ETBR_CTRL		0x20

#define ETBR_FORMATTERCTRL	0x304

#define ETBFF_ENFTC		1

#define ETBFF_ENFCONT		(1 << 1)

#define ETBFF_FONFLIN		(1 << 4)

#define ETBFF_MANUAL_FLUSH	(1 << 6)

#define ETBFF_TRIGIN		(1 << 8)

#define ETBFF_TRIGEVT		(1 << 9)

#define ETBFF_TRIGFL		(1 << 10)



#define etb_writel(t, v, x) \

	(__raw_writel((v), (t)->etb_regs + (x)))

#define etb_readl(t, x) (__raw_readl((t)->etb_regs + (x)))



#define etm_lock(t) do { etm_writel((t), 0, CSMR_LOCKACCESS); } while (0)

#define etm_unlock(t) \

	do { etm_writel((t), UNLOCK_MAGIC, CSMR_LOCKACCESS); } while (0)



#define etb_lock(t) do { etb_writel((t), 0, CSMR_LOCKACCESS); } while (0)

#define etb_unlock(t) \

	do { etb_writel((t), UNLOCK_MAGIC, CSMR_LOCKACCESS); } while (0)



#endif /* __ASM_HARDWARE_CORESIGHT_H */

arch/arm/kernel/Makefile

+2 −0
Original line number Diff line number Diff line
@@ -17,6 +17,8 @@ obj-y := compat.o elf.o entry-armv.o entry-common.o irq.o \ 
		   process.o ptrace.o return_address.o setup.o signal.o \

		   sys_arm.o stacktrace.o time.o traps.o



obj-$(CONFIG_OC_ETM)		+= etm.o



obj-$(CONFIG_ISA_DMA_API)	+= dma.o

obj-$(CONFIG_ARCH_ACORN)	+= ecard.o 

obj-$(CONFIG_FIQ)		+= fiq.o

arch/arm/kernel/etm.c

0 → 100644
+641 −0
Original line number Diff line number Diff line 
/*

 * linux/arch/arm/kernel/etm.c

 *

 * Driver for ARM's Embedded Trace Macrocell and Embedded Trace Buffer.

 *

 * Copyright (C) 2009 Nokia Corporation.

 * Alexander Shishkin

 *

 * This program is free software; you can redistribute it and/or modify

 * it under the terms of the GNU General Public License version 2 as

 * published by the Free Software Foundation.

 */



#include <linux/kernel.h>

#include <linux/init.h>

#include <linux/types.h>

#include <linux/io.h>

#include <linux/sysrq.h>

#include <linux/device.h>

#include <linux/clk.h>

#include <linux/amba/bus.h>

#include <linux/fs.h>

#include <linux/uaccess.h>

#include <linux/miscdevice.h>

#include <linux/vmalloc.h>

#include <linux/mutex.h>

#include <asm/hardware/coresight.h>

#include <asm/sections.h>



MODULE_LICENSE("GPL");

MODULE_AUTHOR("Alexander Shishkin");



static struct tracectx tracer;



static inline bool trace_isrunning(struct tracectx *t)

{

	return !!(t->flags & TRACER_RUNNING);

}



static int etm_setup_address_range(struct tracectx *t, int n,

		unsigned long start, unsigned long end, int exclude, int data)

{

	u32 flags = ETMAAT_ARM | ETMAAT_IGNCONTEXTID | ETMAAT_NSONLY | \

		    ETMAAT_NOVALCMP;



	if (n < 1 || n > t->ncmppairs)

		return -EINVAL;



	/* comparators and ranges are numbered starting with 1 as opposed

	 * to bits in a word */

	n--;



	if (data)

		flags |= ETMAAT_DLOADSTORE;

	else

		flags |= ETMAAT_IEXEC;



	/* first comparator for the range */

	etm_writel(t, flags, ETMR_COMP_ACC_TYPE(n * 2));

	etm_writel(t, start, ETMR_COMP_VAL(n * 2));



	/* second comparator is right next to it */

	etm_writel(t, flags, ETMR_COMP_ACC_TYPE(n * 2 + 1));

	etm_writel(t, end, ETMR_COMP_VAL(n * 2 + 1));



	flags = exclude ? ETMTE_INCLEXCL : 0;

	etm_writel(t, flags | (1 << n), ETMR_TRACEENCTRL);



	return 0;

}



static int trace_start(struct tracectx *t)

{

	u32 v;

	unsigned long timeout = TRACER_TIMEOUT;



	etb_unlock(t);



	etb_writel(t, 0, ETBR_FORMATTERCTRL);

	etb_writel(t, 1, ETBR_CTRL);



	etb_lock(t);



	/* configure etm */

	v = ETMCTRL_OPTS | ETMCTRL_PROGRAM | ETMCTRL_PORTSIZE(t->etm_portsz);



	if (t->flags & TRACER_CYCLE_ACC)

		v |= ETMCTRL_CYCLEACCURATE;



	etm_unlock(t);



	etm_writel(t, v, ETMR_CTRL);



	while (!(etm_readl(t, ETMR_CTRL) & ETMCTRL_PROGRAM) && --timeout)

		;

	if (!timeout) {

		dev_dbg(t->dev, "Waiting for progbit to assert timed out\n");

		etm_lock(t);

		return -EFAULT;

	}



	etm_setup_address_range(t, 1, (unsigned long)_stext,

			(unsigned long)_etext, 0, 0);

	etm_writel(t, 0, ETMR_TRACEENCTRL2);

	etm_writel(t, 0, ETMR_TRACESSCTRL);

	etm_writel(t, 0x6f, ETMR_TRACEENEVT);



	v &= ~ETMCTRL_PROGRAM;

	v |= ETMCTRL_PORTSEL;



	etm_writel(t, v, ETMR_CTRL);



	timeout = TRACER_TIMEOUT;

	while (etm_readl(t, ETMR_CTRL) & ETMCTRL_PROGRAM && --timeout)

		;

	if (!timeout) {

		dev_dbg(t->dev, "Waiting for progbit to deassert timed out\n");

		etm_lock(t);

		return -EFAULT;

	}



	etm_lock(t);



	t->flags |= TRACER_RUNNING;



	return 0;

}



static int trace_stop(struct tracectx *t)

{

	unsigned long timeout = TRACER_TIMEOUT;



	etm_unlock(t);



	etm_writel(t, 0x440, ETMR_CTRL);

	while (!(etm_readl(t, ETMR_CTRL) & ETMCTRL_PROGRAM) && --timeout)

		;

	if (!timeout) {

		dev_dbg(t->dev, "Waiting for progbit to assert timed out\n");

		etm_lock(t);

		return -EFAULT;

	}



	etm_lock(t);



	etb_unlock(t);

	etb_writel(t, ETBFF_MANUAL_FLUSH, ETBR_FORMATTERCTRL);



	timeout = TRACER_TIMEOUT;

	while (etb_readl(t, ETBR_FORMATTERCTRL) &

			ETBFF_MANUAL_FLUSH && --timeout)

		;

	if (!timeout) {

		dev_dbg(t->dev, "Waiting for formatter flush to commence "

				"timed out\n");

		etb_lock(t);

		return -EFAULT;

	}



	etb_writel(t, 0, ETBR_CTRL);



	etb_lock(t);



	t->flags &= ~TRACER_RUNNING;



	return 0;

}



static int etb_getdatalen(struct tracectx *t)

{

	u32 v;

	int rp, wp;



	v = etb_readl(t, ETBR_STATUS);



	if (v & 1)

		return t->etb_bufsz;



	rp = etb_readl(t, ETBR_READADDR);

	wp = etb_readl(t, ETBR_WRITEADDR);



	if (rp > wp) {

		etb_writel(t, 0, ETBR_READADDR);

		etb_writel(t, 0, ETBR_WRITEADDR);



		return 0;

	}



	return wp - rp;

}



/* sysrq+v will always stop the running trace and leave it at that */

static void etm_dump(void)

{

	struct tracectx *t = &tracer;

	u32 first = 0;

	int length;



	if (!t->etb_regs) {

		printk(KERN_INFO "No tracing hardware found\n");

		return;

	}



	if (trace_isrunning(t))

		trace_stop(t);



	etb_unlock(t);



	length = etb_getdatalen(t);



	if (length == t->etb_bufsz)

		first = etb_readl(t, ETBR_WRITEADDR);



	etb_writel(t, first, ETBR_READADDR);



	printk(KERN_INFO "Trace buffer contents length: %d\n", length);

	printk(KERN_INFO "--- ETB buffer begin ---\n");

	for (; length; length--)

		printk("%08x", cpu_to_be32(etb_readl(t, ETBR_READMEM)));

	printk(KERN_INFO "\n--- ETB buffer end ---\n");



	/* deassert the overflow bit */

	etb_writel(t, 1, ETBR_CTRL);

	etb_writel(t, 0, ETBR_CTRL);



	etb_writel(t, 0, ETBR_TRIGGERCOUNT);

	etb_writel(t, 0, ETBR_READADDR);

	etb_writel(t, 0, ETBR_WRITEADDR);



	etb_lock(t);

}



static void sysrq_etm_dump(int key, struct tty_struct *tty)

{

	dev_dbg(tracer.dev, "Dumping ETB buffer\n");

	etm_dump();

}



static struct sysrq_key_op sysrq_etm_op = {

	.handler = sysrq_etm_dump,

	.help_msg = "ETM buffer dump",

	.action_msg = "etm",

};



static int etb_open(struct inode *inode, struct file *file)

{

	if (!tracer.etb_regs)

		return -ENODEV;



	file->private_data = &tracer;



	return nonseekable_open(inode, file);

}



static ssize_t etb_read(struct file *file, char __user *data,

		size_t len, loff_t *ppos)

{

	int total, i;

	long length;

	struct tracectx *t = file->private_data;

	u32 first = 0;

	u32 *buf;



	mutex_lock(&t->mutex);



	if (trace_isrunning(t)) {

		length = 0;

		goto out;

	}



	etb_unlock(t);



	total = etb_getdatalen(t);

	if (total == t->etb_bufsz)

		first = etb_readl(t, ETBR_WRITEADDR);



	etb_writel(t, first, ETBR_READADDR);



	length = min(total * 4, (int)len);

	buf = vmalloc(length);



	dev_dbg(t->dev, "ETB buffer length: %d\n", total);

	dev_dbg(t->dev, "ETB status reg: %x\n", etb_readl(t, ETBR_STATUS));

	for (i = 0; i < length / 4; i++)

		buf[i] = etb_readl(t, ETBR_READMEM);



	/* the only way to deassert overflow bit in ETB status is this */

	etb_writel(t, 1, ETBR_CTRL);

	etb_writel(t, 0, ETBR_CTRL);



	etb_writel(t, 0, ETBR_WRITEADDR);

	etb_writel(t, 0, ETBR_READADDR);

	etb_writel(t, 0, ETBR_TRIGGERCOUNT);



	etb_lock(t);



	length -= copy_to_user(data, buf, length);

	vfree(buf);



out:

	mutex_unlock(&t->mutex);



	return length;

}



static int etb_release(struct inode *inode, struct file *file)

{

	/* there's nothing to do here, actually */

	return 0;

}



static const struct file_operations etb_fops = {

	.owner = THIS_MODULE,

	.read = etb_read,

	.open = etb_open,

	.release = etb_release,

};



static struct miscdevice etb_miscdev = {

	.name = "tracebuf",

	.minor = 0,

	.fops = &etb_fops,

};



static int __init etb_probe(struct amba_device *dev, struct amba_id *id)

{

	struct tracectx *t = &tracer;

	int ret = 0;



	ret = amba_request_regions(dev, NULL);

	if (ret)

		goto out;



	t->etb_regs = ioremap_nocache(dev->res.start, resource_size(&dev->res));

	if (!t->etb_regs) {

		ret = -ENOMEM;

		goto out_release;

	}



	amba_set_drvdata(dev, t);



	etb_miscdev.parent = &dev->dev;



	ret = misc_register(&etb_miscdev);

	if (ret)

		goto out_unmap;



	t->emu_clk = clk_get(&dev->dev, "emu_src_ck");

	if (IS_ERR(t->emu_clk)) {

		dev_dbg(&dev->dev, "Failed to obtain emu_src_ck.\n");

		return -EFAULT;

	}



	clk_enable(t->emu_clk);



	etb_unlock(t);

	t->etb_bufsz = etb_readl(t, ETBR_DEPTH);

	dev_dbg(&dev->dev, "Size: %x\n", t->etb_bufsz);



	/* make sure trace capture is disabled */

	etb_writel(t, 0, ETBR_CTRL);

	etb_writel(t, 0x1000, ETBR_FORMATTERCTRL);

	etb_lock(t);



	dev_dbg(&dev->dev, "ETB AMBA driver initialized.\n");



out:

	return ret;



out_unmap:

	amba_set_drvdata(dev, NULL);

	iounmap(t->etb_regs);



out_release:

	amba_release_regions(dev);



	return ret;

}



static int etb_remove(struct amba_device *dev)

{

	struct tracectx *t = amba_get_drvdata(dev);



	amba_set_drvdata(dev, NULL);



	iounmap(t->etb_regs);

	t->etb_regs = NULL;



	clk_disable(t->emu_clk);

	clk_put(t->emu_clk);



	amba_release_regions(dev);



	return 0;

}



static struct amba_id etb_ids[] = {

	{

		.id	= 0x0003b907,

		.mask	= 0x0007ffff,

	},

	{ 0, 0 },

};



static struct amba_driver etb_driver = {

	.drv		= {

		.name	= "etb",

		.owner	= THIS_MODULE,

	},

	.probe		= etb_probe,

	.remove		= etb_remove,

	.id_table	= etb_ids,

};



/* use a sysfs file "trace_running" to start/stop tracing */

static ssize_t trace_running_show(struct kobject *kobj,

				  struct kobj_attribute *attr,

				  char *buf)

{

	return sprintf(buf, "%x\n", trace_isrunning(&tracer));

}



static ssize_t trace_running_store(struct kobject *kobj,

				   struct kobj_attribute *attr,

				   const char *buf, size_t n)

{

	unsigned int value;

	int ret;



	if (sscanf(buf, "%u", &value) != 1)

		return -EINVAL;



	mutex_lock(&tracer.mutex);

	ret = value ? trace_start(&tracer) : trace_stop(&tracer);

	mutex_unlock(&tracer.mutex);



	return ret ? : n;

}



static struct kobj_attribute trace_running_attr =

	__ATTR(trace_running, 0644, trace_running_show, trace_running_store);



static ssize_t trace_info_show(struct kobject *kobj,

				  struct kobj_attribute *attr,

				  char *buf)

{

	u32 etb_wa, etb_ra, etb_st, etb_fc, etm_ctrl, etm_st;

	int datalen;



	etb_unlock(&tracer);

	datalen = etb_getdatalen(&tracer);

	etb_wa = etb_readl(&tracer, ETBR_WRITEADDR);

	etb_ra = etb_readl(&tracer, ETBR_READADDR);

	etb_st = etb_readl(&tracer, ETBR_STATUS);

	etb_fc = etb_readl(&tracer, ETBR_FORMATTERCTRL);

	etb_lock(&tracer);



	etm_unlock(&tracer);

	etm_ctrl = etm_readl(&tracer, ETMR_CTRL);

	etm_st = etm_readl(&tracer, ETMR_STATUS);

	etm_lock(&tracer);



	return sprintf(buf, "Trace buffer len: %d\nComparator pairs: %d\n"

			"ETBR_WRITEADDR:\t%08x\n"

			"ETBR_READADDR:\t%08x\n"

			"ETBR_STATUS:\t%08x\n"

			"ETBR_FORMATTERCTRL:\t%08x\n"

			"ETMR_CTRL:\t%08x\n"

			"ETMR_STATUS:\t%08x\n",

			datalen,

			tracer.ncmppairs,

			etb_wa,

			etb_ra,

			etb_st,

			etb_fc,

			etm_ctrl,

			etm_st

			);

}



static struct kobj_attribute trace_info_attr =

	__ATTR(trace_info, 0444, trace_info_show, NULL);



static ssize_t trace_mode_show(struct kobject *kobj,

				  struct kobj_attribute *attr,

				  char *buf)

{

	return sprintf(buf, "%d %d\n",

			!!(tracer.flags & TRACER_CYCLE_ACC),

			tracer.etm_portsz);

}



static ssize_t trace_mode_store(struct kobject *kobj,

				   struct kobj_attribute *attr,

				   const char *buf, size_t n)

{

	unsigned int cycacc, portsz;



	if (sscanf(buf, "%u %u", &cycacc, &portsz) != 2)

		return -EINVAL;



	mutex_lock(&tracer.mutex);

	if (cycacc)

		tracer.flags |= TRACER_CYCLE_ACC;

	else

		tracer.flags &= ~TRACER_CYCLE_ACC;



	tracer.etm_portsz = portsz & 0x0f;

	mutex_unlock(&tracer.mutex);



	return n;

}



static struct kobj_attribute trace_mode_attr =

	__ATTR(trace_mode, 0644, trace_mode_show, trace_mode_store);



static int __init etm_probe(struct amba_device *dev, struct amba_id *id)

{

	struct tracectx *t = &tracer;

	int ret = 0;



	if (t->etm_regs) {

		dev_dbg(&dev->dev, "ETM already initialized\n");

		ret = -EBUSY;

		goto out;

	}



	ret = amba_request_regions(dev, NULL);

	if (ret)

		goto out;



	t->etm_regs = ioremap_nocache(dev->res.start, resource_size(&dev->res));

	if (!t->etm_regs) {

		ret = -ENOMEM;

		goto out_release;

	}



	amba_set_drvdata(dev, t);



	mutex_init(&t->mutex);

	t->dev = &dev->dev;

	t->flags = TRACER_CYCLE_ACC;

	t->etm_portsz = 1;



	etm_unlock(t);

	ret = etm_readl(t, CSCR_PRSR);



	t->ncmppairs = etm_readl(t, ETMR_CONFCODE) & 0xf;

	etm_writel(t, 0x440, ETMR_CTRL);

	etm_lock(t);



	ret = sysfs_create_file(&dev->dev.kobj,

			&trace_running_attr.attr);

	if (ret)

		goto out_unmap;



	/* failing to create any of these two is not fatal */

	ret = sysfs_create_file(&dev->dev.kobj, &trace_info_attr.attr);

	if (ret)

		dev_dbg(&dev->dev, "Failed to create trace_info in sysfs\n");



	ret = sysfs_create_file(&dev->dev.kobj, &trace_mode_attr.attr);

	if (ret)

		dev_dbg(&dev->dev, "Failed to create trace_mode in sysfs\n");



	dev_dbg(t->dev, "ETM AMBA driver initialized.\n");



out:

	return ret;



out_unmap:

	amba_set_drvdata(dev, NULL);

	iounmap(t->etm_regs);



out_release:

	amba_release_regions(dev);



	return ret;

}



static int etm_remove(struct amba_device *dev)

{

	struct tracectx *t = amba_get_drvdata(dev);



	amba_set_drvdata(dev, NULL);



	iounmap(t->etm_regs);

	t->etm_regs = NULL;



	amba_release_regions(dev);



	sysfs_remove_file(&dev->dev.kobj, &trace_running_attr.attr);

	sysfs_remove_file(&dev->dev.kobj, &trace_info_attr.attr);

	sysfs_remove_file(&dev->dev.kobj, &trace_mode_attr.attr);



	return 0;

}



static struct amba_id etm_ids[] = {

	{

		.id	= 0x0003b921,

		.mask	= 0x0007ffff,

	},

	{ 0, 0 },

};



static struct amba_driver etm_driver = {

	.drv		= {

		.name   = "etm",

		.owner  = THIS_MODULE,

	},

	.probe		= etm_probe,

	.remove		= etm_remove,

	.id_table	= etm_ids,

};



static int __init etm_init(void)

{

	int retval;



	retval = amba_driver_register(&etb_driver);

	if (retval) {

		printk(KERN_ERR "Failed to register etb\n");

		return retval;

	}



	retval = amba_driver_register(&etm_driver);

	if (retval) {

		amba_driver_unregister(&etb_driver);

		printk(KERN_ERR "Failed to probe etm\n");

		return retval;

	}



	/* not being able to install this handler is not fatal */

	(void)register_sysrq_key('v', &sysrq_etm_op);



	return 0;

}



device_initcall(etm_init);

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