[MIPS] Add bcm1480 ZBus trace support, fix wait related bugs

Make ZBus tracing generic - moving it to a common direcotry under
arch/mips/sibyte, add bcm1480 support and fix some wait related
bugs (thanks to Ralf for assistance on that).

Signed-off-by: Mark Mason <mason@broadcom.com>
Signed-off-by: Ralf Baechle <ralf@linux-mips.org>

2 files changed, 606 insertions, 0 deletions

diff --git a/arch/mips/sibyte/common/Makefile b/arch/mips/sibyte/common/Makefile
new file mode 100644
index 000000000000..8a06a4fb5212
--- /dev/null
+++ b/arch/mips/sibyte/common/Makefile
@@ -0,0 +1,5 @@
+obj-y :=
+
+obj-$(CONFIG_SIBYTE_TBPROF)		+= sb_tbprof.o
+
+EXTRA_AFLAGS := $(CFLAGS)
diff --git a/arch/mips/sibyte/common/sb_tbprof.c b/arch/mips/sibyte/common/sb_tbprof.c
new file mode 100644
index 000000000000..4fcdaa8ba514
--- /dev/null
+++ b/arch/mips/sibyte/common/sb_tbprof.c
@@ -0,0 +1,601 @@
+/*
+ * 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; either version 2
+ * of the License, or (at your option) any later version.
+ *
+ * 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., 59 Temple Place - Suite 330, Boston, MA  02111-1307, USA.
+ *
+ * Copyright (C) 2001, 2002, 2003 Broadcom Corporation
+ * Copyright (C) 2007 Ralf Baechle <ralf@linux-mips.org>
+ * Copyright (C) 2007 MIPS Technologies, Inc.
+ *    written by Ralf Baechle <ralf@linux-mips.org>
+ */
+
+#undef DEBUG
+
+#include <linux/device.h>
+#include <linux/module.h>
+#include <linux/kernel.h>
+#include <linux/types.h>
+#include <linux/init.h>
+#include <linux/interrupt.h>
+#include <linux/slab.h>
+#include <linux/vmalloc.h>
+#include <linux/fs.h>
+#include <linux/errno.h>
+#include <linux/wait.h>
+#include <asm/io.h>
+#include <asm/sibyte/sb1250.h>
+
+#if defined(CONFIG_SIBYTE_BCM1x55) || defined(CONFIG_SIBYTE_BCM1x80)
+#include <asm/sibyte/bcm1480_regs.h>
+#include <asm/sibyte/bcm1480_scd.h>
+#include <asm/sibyte/bcm1480_int.h>
+#elif defined(CONFIG_SIBYTE_SB1250) || defined(CONFIG_SIBYTE_BCM112X)
+#include <asm/sibyte/sb1250_regs.h>
+#include <asm/sibyte/sb1250_scd.h>
+#include <asm/sibyte/sb1250_int.h>
+#else
+#error invalid SiByte UART configuation
+#endif
+
+#if defined(CONFIG_SIBYTE_BCM1x55) || defined(CONFIG_SIBYTE_BCM1x80)
+#undef K_INT_TRACE_FREEZE
+#define K_INT_TRACE_FREEZE K_BCM1480_INT_TRACE_FREEZE
+#undef K_INT_PERF_CNT
+#define K_INT_PERF_CNT K_BCM1480_INT_PERF_CNT
+#endif
+
+#include <asm/system.h>
+#include <asm/uaccess.h>
+
+#define SBPROF_TB_MAJOR 240
+
+typedef u64 tb_sample_t[6*256];
+
+enum open_status {
+	SB_CLOSED,
+	SB_OPENING,
+	SB_OPEN
+};
+
+struct sbprof_tb {
+	wait_queue_head_t	tb_sync;
+	wait_queue_head_t	tb_read;
+	struct mutex		lock;
+	enum open_status	open;
+	tb_sample_t		*sbprof_tbbuf;
+	int			next_tb_sample;
+
+	volatile int		tb_enable;
+	volatile int		tb_armed;
+
+};
+
+static struct sbprof_tb sbp;
+
+#define MAX_SAMPLE_BYTES (24*1024*1024)
+#define MAX_TBSAMPLE_BYTES (12*1024*1024)
+
+#define MAX_SAMPLES (MAX_SAMPLE_BYTES/sizeof(u_int32_t))
+#define TB_SAMPLE_SIZE (sizeof(tb_sample_t))
+#define MAX_TB_SAMPLES (MAX_TBSAMPLE_BYTES/TB_SAMPLE_SIZE)
+
+/* ioctls */
+#define SBPROF_ZBSTART		_IOW('s', 0, int)
+#define SBPROF_ZBSTOP		_IOW('s', 1, int)
+#define SBPROF_ZBWAITFULL	_IOW('s', 2, int)
+
+/*
+ * Routines for using 40-bit SCD cycle counter
+ *
+ * Client responsible for either handling interrupts or making sure
+ * the cycles counter never saturates, e.g., by doing
+ * zclk_timer_init(0) at least every 2^40 - 1 ZCLKs.
+ */
+
+/*
+ * Configures SCD counter 0 to count ZCLKs starting from val;
+ * Configures SCD counters1,2,3 to count nothing.
+ * Must not be called while gathering ZBbus profiles.
+ */
+
+#define zclk_timer_init(val) \
+  __asm__ __volatile__ (".set push;" \
+			".set mips64;" \
+			"la   $8, 0xb00204c0;" /* SCD perf_cnt_cfg */ \
+			"sd   %0, 0x10($8);"   /* write val to counter0 */ \
+			"sd   %1, 0($8);"      /* config counter0 for zclks*/ \
+			".set pop" \
+			: /* no outputs */ \
+						     /* enable, counter0 */ \
+			: /* inputs */ "r"(val), "r" ((1ULL << 33) | 1ULL) \
+			: /* modifies */ "$8" )
+
+
+/* Reads SCD counter 0 and puts result in value
+   unsigned long long val; */
+#define zclk_get(val) \
+  __asm__ __volatile__ (".set push;" \
+			".set mips64;" \
+			"la   $8, 0xb00204c0;" /* SCD perf_cnt_cfg */ \
+			"ld   %0, 0x10($8);"   /* write val to counter0 */ \
+			".set pop" \
+			: /* outputs */ "=r"(val) \
+			: /* inputs */ \
+			: /* modifies */ "$8" )
+
+#define DEVNAME "sb_tbprof"
+
+#define TB_FULL (sbp.next_tb_sample == MAX_TB_SAMPLES)
+
+/*
+ * Support for ZBbus sampling using the trace buffer
+ *
+ * We use the SCD performance counter interrupt, caused by a Zclk counter
+ * overflow, to trigger the start of tracing.
+ *
+ * We set the trace buffer to sample everything and freeze on
+ * overflow.
+ *
+ * We map the interrupt for trace_buffer_freeze to handle it on CPU 0.
+ *
+ */
+
+static u64 tb_period;
+
+static void arm_tb(void)
+{
+        u64 scdperfcnt;
+	u64 next = (1ULL << 40) - tb_period;
+	u64 tb_options = M_SCD_TRACE_CFG_FREEZE_FULL;
+
+	/*
+	 * Generate an SCD_PERFCNT interrupt in TB_PERIOD Zclks to
+	 * trigger start of trace.  XXX vary sampling period
+	 */
+	__raw_writeq(0, IOADDR(A_SCD_PERF_CNT_1));
+	scdperfcnt = __raw_readq(IOADDR(A_SCD_PERF_CNT_CFG));
+
+	/*
+	 * Unfortunately, in Pass 2 we must clear all counters to knock down
+	 * a previous interrupt request.  This means that bus profiling
+	 * requires ALL of the SCD perf counters.
+	 */
+#if defined(CONFIG_SIBYTE_BCM1x55) || defined(CONFIG_SIBYTE_BCM1x80)
+	__raw_writeq((scdperfcnt & ~M_SPC_CFG_SRC1) |
+						/* keep counters 0,2,3,4,5,6,7 as is */
+		     V_SPC_CFG_SRC1(1),		/* counter 1 counts cycles */
+		     IOADDR(A_BCM1480_SCD_PERF_CNT_CFG0));
+	__raw_writeq(
+		     M_SPC_CFG_ENABLE |		/* enable counting */
+		     M_SPC_CFG_CLEAR |		/* clear all counters */
+		     V_SPC_CFG_SRC1(1),		/* counter 1 counts cycles */
+		     IOADDR(A_BCM1480_SCD_PERF_CNT_CFG1));
+#else
+	__raw_writeq((scdperfcnt & ~M_SPC_CFG_SRC1) |
+						/* keep counters 0,2,3 as is */
+		     M_SPC_CFG_ENABLE |		/* enable counting */
+		     M_SPC_CFG_CLEAR |		/* clear all counters */
+		     V_SPC_CFG_SRC1(1),		/* counter 1 counts cycles */
+		     IOADDR(A_SCD_PERF_CNT_CFG));
+#endif
+	__raw_writeq(next, IOADDR(A_SCD_PERF_CNT_1));
+	/* Reset the trace buffer */
+	__raw_writeq(M_SCD_TRACE_CFG_RESET, IOADDR(A_SCD_TRACE_CFG));
+#if 0 && defined(M_SCD_TRACE_CFG_FORCECNT)
+	/* XXXKW may want to expose control to the data-collector */
+	tb_options |= M_SCD_TRACE_CFG_FORCECNT;
+#endif
+	__raw_writeq(tb_options, IOADDR(A_SCD_TRACE_CFG));
+	sbp.tb_armed = 1;
+}
+
+static irqreturn_t sbprof_tb_intr(int irq, void *dev_id)
+{
+	int i;
+
+	pr_debug(DEVNAME ": tb_intr\n");
+
+	if (sbp.next_tb_sample < MAX_TB_SAMPLES) {
+		/* XXX should use XKPHYS to make writes bypass L2 */
+		u64 *p = sbp.sbprof_tbbuf[sbp.next_tb_sample++];
+		/* Read out trace */
+		__raw_writeq(M_SCD_TRACE_CFG_START_READ,
+			     IOADDR(A_SCD_TRACE_CFG));
+		__asm__ __volatile__ ("sync" : : : "memory");
+		/* Loop runs backwards because bundles are read out in reverse order */
+		for (i = 256 * 6; i > 0; i -= 6) {
+			/* Subscripts decrease to put bundle in the order */
+			/*   t0 lo, t0 hi, t1 lo, t1 hi, t2 lo, t2 hi */
+			p[i - 1] = __raw_readq(IOADDR(A_SCD_TRACE_READ));
+			/* read t2 hi */
+			p[i - 2] = __raw_readq(IOADDR(A_SCD_TRACE_READ));
+			/* read t2 lo */
+			p[i - 3] = __raw_readq(IOADDR(A_SCD_TRACE_READ));
+			/* read t1 hi */
+			p[i - 4] = __raw_readq(IOADDR(A_SCD_TRACE_READ));
+			/* read t1 lo */
+			p[i - 5] = __raw_readq(IOADDR(A_SCD_TRACE_READ));
+			/* read t0 hi */
+			p[i - 6] = __raw_readq(IOADDR(A_SCD_TRACE_READ));
+			/* read t0 lo */
+		}
+		if (!sbp.tb_enable) {
+			pr_debug(DEVNAME ": tb_intr shutdown\n");
+			__raw_writeq(M_SCD_TRACE_CFG_RESET,
+				     IOADDR(A_SCD_TRACE_CFG));
+			sbp.tb_armed = 0;
+			wake_up_interruptible(&sbp.tb_sync);
+		} else {
+			/* knock down current interrupt and get another one later */
+			arm_tb();
+		}
+	} else {
+		/* No more trace buffer samples */
+		pr_debug(DEVNAME ": tb_intr full\n");
+		__raw_writeq(M_SCD_TRACE_CFG_RESET, IOADDR(A_SCD_TRACE_CFG));
+		sbp.tb_armed = 0;
+		if (!sbp.tb_enable)
+			wake_up_interruptible(&sbp.tb_sync);
+		wake_up_interruptible(&sbp.tb_read);
+	}
+	return IRQ_HANDLED;
+}
+
+static irqreturn_t sbprof_pc_intr(int irq, void *dev_id)
+{
+	printk(DEVNAME ": unexpected pc_intr");
+	return IRQ_NONE;
+}
+
+/*
+ * Requires: Already called zclk_timer_init with a value that won't
+ *           saturate 40 bits.  No subsequent use of SCD performance counters
+ *           or trace buffer.
+ */
+
+static int sbprof_zbprof_start(struct file *filp)
+{
+	u64 scdperfcnt;
+	int err;
+
+	if (xchg(&sbp.tb_enable, 1))
+		return -EBUSY;
+
+	pr_debug(DEVNAME ": starting\n");
+
+	sbp.next_tb_sample = 0;
+	filp->f_pos = 0;
+
+	err = request_irq (K_INT_TRACE_FREEZE, sbprof_tb_intr, 0,
+			   DEVNAME " trace freeze", &sbp);
+	if (err)
+		return -EBUSY;
+
+	/* Make sure there isn't a perf-cnt interrupt waiting */
+	scdperfcnt = __raw_readq(IOADDR(A_SCD_PERF_CNT_CFG));
+	/* Disable and clear counters, override SRC_1 */
+	__raw_writeq((scdperfcnt & ~(M_SPC_CFG_SRC1 | M_SPC_CFG_ENABLE)) |
+		     M_SPC_CFG_ENABLE | M_SPC_CFG_CLEAR | V_SPC_CFG_SRC1(1),
+		     IOADDR(A_SCD_PERF_CNT_CFG));
+
+	/*
+	 * We grab this interrupt to prevent others from trying to use
+         * it, even though we don't want to service the interrupts
+         * (they only feed into the trace-on-interrupt mechanism)
+	 */
+	if (request_irq(K_INT_PERF_CNT, sbprof_pc_intr, 0, DEVNAME " scd perfcnt", &sbp)) {
+		free_irq(K_INT_TRACE_FREEZE, &sbp);
+		return -EBUSY;
+	}
+
+	/*
+	 * I need the core to mask these, but the interrupt mapper to
+	 *  pass them through.  I am exploiting my knowledge that
+	 *  cp0_status masks out IP[5]. krw
+	 */
+#if defined(CONFIG_SIBYTE_BCM1x55) || defined(CONFIG_SIBYTE_BCM1x80)
+	__raw_writeq(K_BCM1480_INT_MAP_I3,
+		     IOADDR(A_BCM1480_IMR_REGISTER(0, R_BCM1480_IMR_INTERRUPT_MAP_BASE_L) +
+			    ((K_BCM1480_INT_PERF_CNT & 0x3f) << 3)));
+#else
+	__raw_writeq(K_INT_MAP_I3,
+		     IOADDR(A_IMR_REGISTER(0, R_IMR_INTERRUPT_MAP_BASE) +
+			    (K_INT_PERF_CNT << 3)));
+#endif
+
+	/* Initialize address traps */
+	__raw_writeq(0, IOADDR(A_ADDR_TRAP_UP_0));
+	__raw_writeq(0, IOADDR(A_ADDR_TRAP_UP_1));
+	__raw_writeq(0, IOADDR(A_ADDR_TRAP_UP_2));
+	__raw_writeq(0, IOADDR(A_ADDR_TRAP_UP_3));
+
+	__raw_writeq(0, IOADDR(A_ADDR_TRAP_DOWN_0));
+	__raw_writeq(0, IOADDR(A_ADDR_TRAP_DOWN_1));
+	__raw_writeq(0, IOADDR(A_ADDR_TRAP_DOWN_2));
+	__raw_writeq(0, IOADDR(A_ADDR_TRAP_DOWN_3));
+
+	__raw_writeq(0, IOADDR(A_ADDR_TRAP_CFG_0));
+	__raw_writeq(0, IOADDR(A_ADDR_TRAP_CFG_1));
+	__raw_writeq(0, IOADDR(A_ADDR_TRAP_CFG_2));
+	__raw_writeq(0, IOADDR(A_ADDR_TRAP_CFG_3));
+
+	/* Initialize Trace Event 0-7 */
+	/*				when interrupt  */
+	__raw_writeq(M_SCD_TREVT_INTERRUPT, IOADDR(A_SCD_TRACE_EVENT_0));
+	__raw_writeq(0, IOADDR(A_SCD_TRACE_EVENT_1));
+	__raw_writeq(0, IOADDR(A_SCD_TRACE_EVENT_2));
+	__raw_writeq(0, IOADDR(A_SCD_TRACE_EVENT_3));
+	__raw_writeq(0, IOADDR(A_SCD_TRACE_EVENT_4));
+	__raw_writeq(0, IOADDR(A_SCD_TRACE_EVENT_5));
+	__raw_writeq(0, IOADDR(A_SCD_TRACE_EVENT_6));
+	__raw_writeq(0, IOADDR(A_SCD_TRACE_EVENT_7));
+
+	/* Initialize Trace Sequence 0-7 */
+	/*				     Start on event 0 (interrupt) */
+	__raw_writeq(V_SCD_TRSEQ_FUNC_START | 0x0fff,
+		     IOADDR(A_SCD_TRACE_SEQUENCE_0));
+	/*			  dsamp when d used | asamp when a used */
+	__raw_writeq(M_SCD_TRSEQ_ASAMPLE | M_SCD_TRSEQ_DSAMPLE |
+		     K_SCD_TRSEQ_TRIGGER_ALL,
+		     IOADDR(A_SCD_TRACE_SEQUENCE_1));
+	__raw_writeq(0, IOADDR(A_SCD_TRACE_SEQUENCE_2));
+	__raw_writeq(0, IOADDR(A_SCD_TRACE_SEQUENCE_3));
+	__raw_writeq(0, IOADDR(A_SCD_TRACE_SEQUENCE_4));
+	__raw_writeq(0, IOADDR(A_SCD_TRACE_SEQUENCE_5));
+	__raw_writeq(0, IOADDR(A_SCD_TRACE_SEQUENCE_6));
+	__raw_writeq(0, IOADDR(A_SCD_TRACE_SEQUENCE_7));
+
+	/* Now indicate the PERF_CNT interrupt as a trace-relevant interrupt */
+#if defined(CONFIG_SIBYTE_BCM1x55) || defined(CONFIG_SIBYTE_BCM1x80)
+	__raw_writeq(1ULL << (K_BCM1480_INT_PERF_CNT & 0x3f),
+		     IOADDR(A_BCM1480_IMR_REGISTER(0, R_BCM1480_IMR_INTERRUPT_TRACE_L)));
+#else
+	__raw_writeq(1ULL << K_INT_PERF_CNT,
+		     IOADDR(A_IMR_REGISTER(0, R_IMR_INTERRUPT_TRACE)));
+#endif
+	arm_tb();
+
+	pr_debug(DEVNAME ": done starting\n");
+
+	return 0;
+}
+
+static int sbprof_zbprof_stop(void)
+{
+	int err = 0;
+
+	pr_debug(DEVNAME ": stopping\n");
+
+	if (sbp.tb_enable) {
+		/*
+		 * XXXKW there is a window here where the intr handler may run,
+		 * see the disable, and do the wake_up before this sleep
+		 * happens.
+		 */
+		pr_debug(DEVNAME ": wait for disarm\n");
+		err = wait_event_interruptible(sbp.tb_sync, !sbp.tb_armed);
+		pr_debug(DEVNAME ": disarm complete, stat %d\n", err);
+
+		if (err)
+			return err;
+
+		sbp.tb_enable = 0;
+		free_irq(K_INT_TRACE_FREEZE, &sbp);
+		free_irq(K_INT_PERF_CNT, &sbp);
+	}
+
+	pr_debug(DEVNAME ": done stopping\n");
+
+	return err;
+}
+
+static int sbprof_tb_open(struct inode *inode, struct file *filp)
+{
+	int minor;
+
+	minor = iminor(inode);
+	if (minor != 0)
+		return -ENODEV;
+
+	if (xchg(&sbp.open, SB_OPENING) != SB_CLOSED)
+		return -EBUSY;
+
+	memset(&sbp, 0, sizeof(struct sbprof_tb));
+	sbp.sbprof_tbbuf = vmalloc(MAX_TBSAMPLE_BYTES);
+	if (!sbp.sbprof_tbbuf)
+		return -ENOMEM;
+	memset(sbp.sbprof_tbbuf, 0, MAX_TBSAMPLE_BYTES);
+	init_waitqueue_head(&sbp.tb_sync);
+	init_waitqueue_head(&sbp.tb_read);
+	mutex_init(&sbp.lock);
+
+	sbp.open = SB_OPEN;
+
+	return 0;
+}
+
+static int sbprof_tb_release(struct inode *inode, struct file *filp)
+{
+	int minor;
+
+	minor = iminor(inode);
+	if (minor != 0 || !sbp.open)
+		return -ENODEV;
+
+	mutex_lock(&sbp.lock);
+
+	if (sbp.tb_armed || sbp.tb_enable)
+		sbprof_zbprof_stop();
+
+	vfree(sbp.sbprof_tbbuf);
+	sbp.open = 0;
+
+	mutex_unlock(&sbp.lock);
+
+	return 0;
+}
+
+static ssize_t sbprof_tb_read(struct file *filp, char *buf,
+			      size_t size, loff_t *offp)
+{
+	int cur_sample, sample_off, cur_count, sample_left;
+	char *src;
+	int   count   =	 0;
+	char *dest    =	 buf;
+	long  cur_off = *offp;
+
+	if (!access_ok(VERIFY_WRITE, buf, size))
+		return -EFAULT;
+
+	mutex_lock(&sbp.lock);
+
+	count = 0;
+	cur_sample = cur_off / TB_SAMPLE_SIZE;
+	sample_off = cur_off % TB_SAMPLE_SIZE;
+	sample_left = TB_SAMPLE_SIZE - sample_off;
+
+	while (size && (cur_sample < sbp.next_tb_sample)) {
+		int err;
+
+		cur_count = size < sample_left ? size : sample_left;
+		src = (char *)(((long)sbp.sbprof_tbbuf[cur_sample])+sample_off);
+		err = __copy_to_user(dest, src, cur_count);
+		if (err) {
+			*offp = cur_off + cur_count - err;
+			mutex_unlock(&sbp.lock);
+			return err;
+		}
+		pr_debug(DEVNAME ": read from sample %d, %d bytes\n",
+		         cur_sample, cur_count);
+		size -= cur_count;
+		sample_left -= cur_count;
+		if (!sample_left) {
+			cur_sample++;
+			sample_off = 0;
+			sample_left = TB_SAMPLE_SIZE;
+		} else {
+			sample_off += cur_count;
+		}
+		cur_off += cur_count;
+		dest += cur_count;
+		count += cur_count;
+	}
+	*offp = cur_off;
+	mutex_unlock(&sbp.lock);
+
+	return count;
+}
+
+static long sbprof_tb_ioctl(struct file *filp,
+			    unsigned int command,
+			    unsigned long arg)
+{
+	int err = 0;
+
+	switch (command) {
+	case SBPROF_ZBSTART:
+		mutex_lock(&sbp.lock);
+		err = sbprof_zbprof_start(filp);
+		mutex_unlock(&sbp.lock);
+		break;
+
+	case SBPROF_ZBSTOP:
+		mutex_lock(&sbp.lock);
+		err = sbprof_zbprof_stop();
+		mutex_unlock(&sbp.lock);
+		break;
+
+	case SBPROF_ZBWAITFULL: {
+		err = wait_event_interruptible(sbp.tb_read, TB_FULL);
+		if (err)
+			break;
+
+		err = put_user(TB_FULL, (int *) arg);
+		break;
+	}
+
+	default:
+		err = -EINVAL;
+		break;
+	}
+
+	return err;
+}
+
+static const struct file_operations sbprof_tb_fops = {
+	.owner		= THIS_MODULE,
+	.open		= sbprof_tb_open,
+	.release	= sbprof_tb_release,
+	.read		= sbprof_tb_read,
+	.unlocked_ioctl	= sbprof_tb_ioctl,
+	.compat_ioctl	= sbprof_tb_ioctl,
+	.mmap		= NULL,
+};
+
+static struct class *tb_class;
+static struct device *tb_dev;
+
+static int __init sbprof_tb_init(void)
+{
+	struct device *dev;
+	struct class *tbc;
+	int err;
+
+	if (register_chrdev(SBPROF_TB_MAJOR, DEVNAME, &sbprof_tb_fops)) {
+		printk(KERN_WARNING DEVNAME ": initialization failed (dev %d)\n",
+		       SBPROF_TB_MAJOR);
+		return -EIO;
+	}
+
+	tbc = class_create(THIS_MODULE, "sb_tracebuffer");
+	if (IS_ERR(tbc)) {
+		err = PTR_ERR(tbc);
+		goto out_chrdev;
+	}
+
+	tb_class = tbc;
+
+	dev = device_create(tbc, NULL, MKDEV(SBPROF_TB_MAJOR, 0), "tb");
+	if (IS_ERR(dev)) {
+		err = PTR_ERR(dev);
+		goto out_class;
+	}
+	tb_dev = dev;
+
+	sbp.open = 0;
+	tb_period = zbbus_mhz * 10000LL;
+	pr_info(DEVNAME ": initialized - tb_period = %lld\n",
+		(long long) tb_period);
+	return 0;
+
+out_class:
+	class_destroy(tb_class);
+out_chrdev:
+	unregister_chrdev(SBPROF_TB_MAJOR, DEVNAME);
+
+	return err;
+}
+
+static void __exit sbprof_tb_cleanup(void)
+{
+	device_destroy(tb_class, MKDEV(SBPROF_TB_MAJOR, 0));
+	unregister_chrdev(SBPROF_TB_MAJOR, DEVNAME);
+	class_destroy(tb_class);
+}
+
+module_init(sbprof_tb_init);
+module_exit(sbprof_tb_cleanup);
+
+MODULE_ALIAS_CHARDEV_MAJOR(SBPROF_TB_MAJOR);
+MODULE_AUTHOR("Ralf Baechle <ralf@linux-mips.org>");
+MODULE_LICENSE("GPL");