[MIPS] Sibyte: Fix ZBbus profiler

 o Fix build error.
 o Handle error returns.
 o Deal with signals received while sleeping.
 o Don't allow to be selected when we're not building the directory with
   the driver anyway.
 o Coding style cleanups.

Signed-off-by: Ralf Baechle <ralf@linux-mips.org>

3 files changed, 283 insertions, 108 deletions

diff --git a/arch/mips/sibyte/Kconfig b/arch/mips/sibyte/Kconfig
index 10cc40304347..bdf24a7b5494 100644
--- a/arch/mips/sibyte/Kconfig
+++ b/arch/mips/sibyte/Kconfig
@@ -8,12 +8,14 @@ config SIBYTE_SB1250
 config SIBYTE_BCM1120
 	bool
 	select SIBYTE_BCM112X
+	select SIBYTE_HAS_ZBUS_PROFILING
 	select SIBYTE_SB1xxx_SOC
 
 config SIBYTE_BCM1125
 	bool
 	select HW_HAS_PCI
 	select SIBYTE_BCM112X
+	select SIBYTE_HAS_ZBUS_PROFILING
 	select SIBYTE_SB1xxx_SOC
 
 config SIBYTE_BCM1125H
@@ -21,11 +23,13 @@ config SIBYTE_BCM1125H
 	select HW_HAS_PCI
 	select SIBYTE_BCM112X
 	select SIBYTE_ENABLE_LDT_IF_PCI
+	select SIBYTE_HAS_ZBUS_PROFILING
 	select SIBYTE_SB1xxx_SOC
 
 config SIBYTE_BCM112X
 	bool
 	select SIBYTE_SB1xxx_SOC
+	select SIBYTE_HAS_ZBUS_PROFILING
 
 config SIBYTE_BCM1x80
 	bool
@@ -37,6 +41,7 @@ config SIBYTE_BCM1x55
 	bool
 	select HW_HAS_PCI
 	select SIBYTE_SB1xxx_SOC
+	select SIBYTE_HAS_ZBUS_PROFILING
 	select SYS_SUPPORTS_SMP
 
 config SIBYTE_SB1xxx_SOC
@@ -164,5 +169,8 @@ config SIBYTE_SB1250_PROF
 	depends on SIBYTE_SB1xxx_SOC
 
 config SIBYTE_TBPROF
-	bool "Support for ZBbus profiling"
-	depends on SIBYTE_SB1xxx_SOC
+	tristate "Support for ZBbus profiling"
+	depends on SIBYTE_HAS_ZBUS_PROFILING
+
+config SIBYTE_HAS_ZBUS_PROFILING
+	bool
diff --git a/arch/mips/sibyte/sb1250/bcm1250_tbprof.c b/arch/mips/sibyte/sb1250/bcm1250_tbprof.c
index 212547c57310..ea0ca131a3cf 100644
--- a/arch/mips/sibyte/sb1250/bcm1250_tbprof.c
+++ b/arch/mips/sibyte/sb1250/bcm1250_tbprof.c
@@ -1,6 +1,4 @@
 /*
- * Copyright (C) 2001, 2002, 2003 Broadcom Corporation
- *
  * 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
@@ -14,10 +12,16 @@
  * 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>
  */
 
-#define SBPROF_TB_DEBUG 0
+#undef DEBUG
 
+#include <linux/device.h>
 #include <linux/module.h>
 #include <linux/kernel.h>
 #include <linux/types.h>
@@ -27,24 +31,98 @@
 #include <linux/vmalloc.h>
 #include <linux/fs.h>
 #include <linux/errno.h>
-#include <linux/reboot.h>
-#include <linux/smp_lock.h>
+#include <linux/types.h>
 #include <linux/wait.h>
-#include <asm/uaccess.h>
+
 #include <asm/io.h>
 #include <asm/sibyte/sb1250.h>
 #include <asm/sibyte/sb1250_regs.h>
 #include <asm/sibyte/sb1250_scd.h>
 #include <asm/sibyte/sb1250_int.h>
-#include <asm/sibyte/trace_prof.h>
+#include <asm/system.h>
+#include <asm/uaccess.h>
 
-#define DEVNAME "bcm1250_tbprof"
+#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 "bcm1250_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
@@ -54,30 +132,36 @@ static struct sbprof_tb sbp;
  * overflow.
  *
  * We map the interrupt for trace_buffer_freeze to handle it on CPU 0.
- *
- ************************************************************************/
+ */
 
-static u_int64_t tb_period;
+static u64 tb_period;
 
 static void arm_tb(void)
 {
-        u_int64_t scdperfcnt;
-	u_int64_t next = (1ULL << 40) - tb_period;
-	u_int64_t 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 */
+        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. */
+
+	/*
+	 * 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.
+	 */
 	__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
+						/* 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));
 	__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)
@@ -91,43 +175,45 @@ static void arm_tb(void)
 static irqreturn_t sbprof_tb_intr(int irq, void *dev_id)
 {
 	int i;
-	DBG(printk(DEVNAME ": tb_intr\n"));
+
+	pr_debug(DEVNAME ": tb_intr\n");
+
 	if (sbp.next_tb_sample < MAX_TB_SAMPLES) {
 		/* XXX should use XKPHYS to make writes bypass L2 */
-		u_int64_t *p = sbp.sbprof_tbbuf[sbp.next_tb_sample++];
+		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
+			/* 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
+								/* read t2 hi */
 			p[i - 2] = __raw_readq(IOADDR(A_SCD_TRACE_READ));
-								// read t2 lo
+								/* read t2 lo */
 			p[i - 3] = __raw_readq(IOADDR(A_SCD_TRACE_READ));
-								// read t1 hi
+								/* read t1 hi */
 			p[i - 4] = __raw_readq(IOADDR(A_SCD_TRACE_READ));
-								// read t1 lo
+								/* read t1 lo */
 			p[i - 5] = __raw_readq(IOADDR(A_SCD_TRACE_READ));
-								// read t0 hi
+								/* read t0 hi */
 			p[i - 6] = __raw_readq(IOADDR(A_SCD_TRACE_READ));
-								// read t0 lo
+								/* read t0 lo */
 		}
 		if (!sbp.tb_enable) {
-			DBG(printk(DEVNAME ": tb_intr shutdown\n"));
+			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(&sbp.tb_sync);
 		} else {
-			arm_tb();	// knock down current interrupt and get another one later
+			arm_tb();	/* knock down current interrupt and get another one later */
 		}
 	} else {
 		/* No more trace buffer samples */
-		DBG(printk(DEVNAME ": tb_intr full\n"));
+		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) {
@@ -135,6 +221,7 @@ static irqreturn_t sbprof_tb_intr(int irq, void *dev_id)
 		}
 		wake_up(&sbp.tb_read);
 	}
+
 	return IRQ_HANDLED;
 }
 
@@ -144,23 +231,30 @@ static irqreturn_t sbprof_pc_intr(int irq, void *dev_id)
 	return IRQ_NONE;
 }
 
-int sbprof_zbprof_start(struct file *filp)
+/*
+ * 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)
 {
-	u_int64_t scdperfcnt;
+	u64 scdperfcnt;
+	int err;
 
-	if (sbp.tb_enable)
+	if (xchg(&sbp.tb_enable, 1))
 		return -EBUSY;
 
-	DBG(printk(DEVNAME ": starting\n"));
+	pr_debug(DEVNAME ": starting\n");
 
-	sbp.tb_enable = 1;
 	sbp.next_tb_sample = 0;
 	filp->f_pos = 0;
 
-	if (request_irq
-	    (K_INT_TRACE_FREEZE, sbprof_tb_intr, 0, DEVNAME " trace freeze", &sbp)) {
+	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 */
@@ -168,18 +262,21 @@ int sbprof_zbprof_start(struct file *filp)
 		     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 */
+	/*
+	 * 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)
+	 */
+	err = request_irq(K_INT_PERF_CNT, sbprof_pc_intr, 0,
+	                DEVNAME " scd perfcnt", &sbp);
+	if (err)
+		goto out_free_irq;
+
+	/*
+	 * 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
+	 */
 	__raw_writeq(K_INT_MAP_I3,
 		     IOADDR(A_IMR_REGISTER(0, R_IMR_INTERRUPT_MAP_BASE) +
 			    (K_INT_PERF_CNT << 3)));
@@ -201,7 +298,7 @@ int sbprof_zbprof_start(struct file *filp)
 	__raw_writeq(0, IOADDR(A_ADDR_TRAP_CFG_3));
 
 	/* Initialize Trace Event 0-7 */
-	//				when interrupt
+	/*				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));
@@ -212,10 +309,10 @@ int sbprof_zbprof_start(struct file *filp)
 	__raw_writeq(0, IOADDR(A_SCD_TRACE_EVENT_7));
 
 	/* Initialize Trace Sequence 0-7 */
-	//				     Start on event 0 (interrupt)
+	/*				     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
+	/*			  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));
@@ -232,33 +329,41 @@ int sbprof_zbprof_start(struct file *filp)
 
 	arm_tb();
 
-	DBG(printk(DEVNAME ": done starting\n"));
+	pr_debug(DEVNAME ": done starting\n");
 
 	return 0;
+
+out_free_irq:
+	free_irq(K_INT_TRACE_FREEZE, &sbp);
+
+	return err;
 }
 
-int sbprof_zbprof_stop(void)
+static int sbprof_zbprof_stop(void)
 {
-	DEFINE_WAIT(wait);
-	DBG(printk(DEVNAME ": stopping\n"));
+	int err;
+
+	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;
-		/* XXXKW there is a window here where the intr handler
-		   may run, see the disable, and do the wake_up before
-		   this sleep happens. */
-		if (sbp.tb_armed) {
-			DBG(printk(DEVNAME ": wait for disarm\n"));
-			prepare_to_wait(&sbp.tb_sync, &wait, TASK_INTERRUPTIBLE);
-			schedule();
-			finish_wait(&sbp.tb_sync, &wait);
-			DBG(printk(DEVNAME ": disarm complete\n"));
-		}
 		free_irq(K_INT_TRACE_FREEZE, &sbp);
 		free_irq(K_INT_PERF_CNT, &sbp);
 	}
 
-	DBG(printk(DEVNAME ": done stopping\n"));
+	pr_debug(DEVNAME ": done stopping\n");
 
 	return 0;
 }
@@ -268,42 +373,45 @@ static int sbprof_tb_open(struct inode *inode, struct file *filp)
 	int minor;
 
 	minor = iminor(inode);
-	if (minor != 0) {
+	if (minor != 0)
 		return -ENODEV;
-	}
-	if (sbp.open) {
+
+	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) {
+	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);
-	sbp.open = 1;
+	mutex_init(&sbp.lock);
+
+	sbp.open = SB_OPEN;
 
 	return 0;
 }
 
 static int sbprof_tb_release(struct inode *inode, struct file *filp)
 {
-	int minor;
+	int minor = iminor(inode);
 
-	minor = iminor(inode);
-	if (minor != 0 || !sbp.open) {
+	if (minor != 0 || !sbp.open)
 		return -ENODEV;
-	}
 
-	if (sbp.tb_armed || sbp.tb_enable) {
+	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;
 }
 
@@ -311,21 +419,35 @@ 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;
+	char *dest    =	 buf;
+	int   count   =	 0;
+	char *src;
+
+	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);
-		copy_to_user(dest, src, cur_count);
-		DBG(printk(DEVNAME ": read from sample %d, %d bytes\n",
-			   cur_sample, cur_count));
+		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) {
@@ -339,37 +461,43 @@ static ssize_t sbprof_tb_read(struct file *filp, char *buf,
 		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)
+static long sbprof_tb_ioctl(struct file *filp, unsigned int command,
+	unsigned long arg)
 {
 	int error = 0;
 
-	lock_kernel();
 	switch (command) {
 	case SBPROF_ZBSTART:
+		mutex_lock(&sbp.lock);
 		error = sbprof_zbprof_start(filp);
+		mutex_unlock(&sbp.lock);
 		break;
+
 	case SBPROF_ZBSTOP:
+		mutex_lock(&sbp.lock);
 		error = sbprof_zbprof_stop();
+		mutex_unlock(&sbp.lock);
 		break;
+
 	case SBPROF_ZBWAITFULL:
-		DEFINE_WAIT(wait);
-		prepare_to_wait(&sbp.tb_read, &wait, TASK_INTERRUPTIBLE);
-		schedule();
-		finish_wait(&sbp.tb_read, &wait);
-		/* XXXKW check if interrupted? */
-		return put_user(TB_FULL, (int *) arg);
+		error = wait_event_interruptible(sbp.tb_read, TB_FULL);
+		if (error)
+			break;
+
+		error = put_user(TB_FULL, (int *) arg);
+		break;
+
 	default:
 		error = -EINVAL;
 		break;
 	}
-	unlock_kernel();
 
 	return error;
 }
@@ -384,23 +512,60 @@ static const struct file_operations sbprof_tb_fops = {
 	.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;
-	printk(KERN_INFO DEVNAME ": initialized - tb_period = %lld\n", tb_period);
+	pr_info(DEVNAME ": initialized - tb_period = %lld\n", 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");
diff --git a/arch/mips/sibyte/sb1250/setup.c b/arch/mips/sibyte/sb1250/setup.c
index 1cb042eab720..87188f0f6fbe 100644
--- a/arch/mips/sibyte/sb1250/setup.c
+++ b/arch/mips/sibyte/sb1250/setup.c
@@ -16,6 +16,7 @@
  * Foundation, Inc., 59 Temple Place - Suite 330, Boston, MA  02111-1307, USA.
  */
 #include <linux/init.h>
+#include <linux/module.h>
 #include <linux/kernel.h>
 #include <linux/reboot.h>
 #include <linux/string.h>
@@ -32,6 +33,7 @@ unsigned int soc_pass;
 unsigned int soc_type;
 unsigned int periph_rev;
 unsigned int zbbus_mhz;
+EXPORT_SYMBOL(zbbus_mhz);
 
 static char *soc_str;
 static char *pass_str;