[linux-block.git] / arch / powerpc / platforms / pseries / dtl.c

// SPDX-License-Identifier: GPL-2.0-or-later
/*
 * Virtual Processor Dispatch Trace Log
 *
 * (C) Copyright IBM Corporation 2009
 *
 * Author: Jeremy Kerr <jk@ozlabs.org>
 */

#include <linux/slab.h>
#include <linux/spinlock.h>
#include <asm/smp.h>
#include <linux/uaccess.h>
#include <linux/debugfs.h>
#include <asm/firmware.h>
#include <asm/dtl.h>
#include <asm/lppaca.h>
#include <asm/plpar_wrappers.h>
#include <asm/machdep.h>

struct dtl {
	struct dtl_entry	*buf;
	int			cpu;
	int			buf_entries;
	u64			last_idx;
	spinlock_t		lock;
};
static DEFINE_PER_CPU(struct dtl, cpu_dtl);

static u8 dtl_event_mask = DTL_LOG_ALL;


/*
 * Size of per-cpu log buffers. Firmware requires that the buffer does
 * not cross a 4k boundary.
 */
static int dtl_buf_entries = N_DISPATCH_LOG;

#ifdef CONFIG_VIRT_CPU_ACCOUNTING_NATIVE

/*
 * When CONFIG_VIRT_CPU_ACCOUNTING_NATIVE = y, the cpu accounting code controls
 * reading from the dispatch trace log.  If other code wants to consume
 * DTL entries, it can set this pointer to a function that will get
 * called once for each DTL entry that gets processed.
 */
static void (*dtl_consumer)(struct dtl_entry *entry, u64 index);

struct dtl_ring {
	u64	write_index;
	struct dtl_entry *write_ptr;
	struct dtl_entry *buf;
	struct dtl_entry *buf_end;
};

static DEFINE_PER_CPU(struct dtl_ring, dtl_rings);

static atomic_t dtl_count;

/*
 * Scan the dispatch trace log and count up the stolen time.
 * Should be called with interrupts disabled.
 */
static notrace u64 scan_dispatch_log(u64 stop_tb)
{
	u64 i = local_paca->dtl_ridx;
	struct dtl_entry *dtl = local_paca->dtl_curr;
	struct dtl_entry *dtl_end = local_paca->dispatch_log_end;
	struct lppaca *vpa = local_paca->lppaca_ptr;
	u64 tb_delta;
	u64 stolen = 0;
	u64 dtb;

	if (!dtl)
		return 0;

	if (i == be64_to_cpu(vpa->dtl_idx))
		return 0;
	while (i < be64_to_cpu(vpa->dtl_idx)) {
		dtb = be64_to_cpu(dtl->timebase);
		tb_delta = be32_to_cpu(dtl->enqueue_to_dispatch_time) +
			be32_to_cpu(dtl->ready_to_enqueue_time);
		barrier();
		if (i + N_DISPATCH_LOG < be64_to_cpu(vpa->dtl_idx)) {
			/* buffer has overflowed */
			i = be64_to_cpu(vpa->dtl_idx) - N_DISPATCH_LOG;
			dtl = local_paca->dispatch_log + (i % N_DISPATCH_LOG);
			continue;
		}
		if (dtb > stop_tb)
			break;
		if (dtl_consumer)
			dtl_consumer(dtl, i);
		stolen += tb_delta;
		++i;
		++dtl;
		if (dtl == dtl_end)
			dtl = local_paca->dispatch_log;
	}
	local_paca->dtl_ridx = i;
	local_paca->dtl_curr = dtl;
	return stolen;
}

/*
 * Accumulate stolen time by scanning the dispatch trace log.
 * Called on entry from user mode.
 */
void notrace pseries_accumulate_stolen_time(void)
{
	u64 sst, ust;
	struct cpu_accounting_data *acct = &local_paca->accounting;

	sst = scan_dispatch_log(acct->starttime_user);
	ust = scan_dispatch_log(acct->starttime);
	acct->stime -= sst;
	acct->utime -= ust;
	acct->steal_time += ust + sst;
}

u64 pseries_calculate_stolen_time(u64 stop_tb)
{
	if (!firmware_has_feature(FW_FEATURE_SPLPAR))
		return 0;

	if (get_paca()->dtl_ridx != be64_to_cpu(get_lppaca()->dtl_idx))
		return scan_dispatch_log(stop_tb);

	return 0;
}

/*
 * The cpu accounting code controls the DTL ring buffer, and we get
 * given entries as they are processed.
 */
static void consume_dtle(struct dtl_entry *dtle, u64 index)
{
	struct dtl_ring *dtlr = this_cpu_ptr(&dtl_rings);
	struct dtl_entry *wp = dtlr->write_ptr;
	struct lppaca *vpa = local_paca->lppaca_ptr;

	if (!wp)
		return;

	*wp = *dtle;
	barrier();

	/* check for hypervisor ring buffer overflow, ignore this entry if so */
	if (index + N_DISPATCH_LOG < be64_to_cpu(vpa->dtl_idx))
		return;

	++wp;
	if (wp == dtlr->buf_end)
		wp = dtlr->buf;
	dtlr->write_ptr = wp;

	/* incrementing write_index makes the new entry visible */
	smp_wmb();
	++dtlr->write_index;
}

static int dtl_start(struct dtl *dtl)
{
	struct dtl_ring *dtlr = &per_cpu(dtl_rings, dtl->cpu);

	dtlr->buf = dtl->buf;
	dtlr->buf_end = dtl->buf + dtl->buf_entries;
	dtlr->write_index = 0;

	/* setting write_ptr enables logging into our buffer */
	smp_wmb();
	dtlr->write_ptr = dtl->buf;

	/* enable event logging */
	lppaca_of(dtl->cpu).dtl_enable_mask |= dtl_event_mask;

	dtl_consumer = consume_dtle;
	atomic_inc(&dtl_count);
	return 0;
}

static void dtl_stop(struct dtl *dtl)
{
	struct dtl_ring *dtlr = &per_cpu(dtl_rings, dtl->cpu);

	dtlr->write_ptr = NULL;
	smp_wmb();

	dtlr->buf = NULL;

	/* restore dtl_enable_mask */
	lppaca_of(dtl->cpu).dtl_enable_mask = DTL_LOG_PREEMPT;

	if (atomic_dec_and_test(&dtl_count))
		dtl_consumer = NULL;
}

static u64 dtl_current_index(struct dtl *dtl)
{
	return per_cpu(dtl_rings, dtl->cpu).write_index;
}

#else /* CONFIG_VIRT_CPU_ACCOUNTING_NATIVE */

static int dtl_start(struct dtl *dtl)
{
	unsigned long addr;
	int ret, hwcpu;

	/* Register our dtl buffer with the hypervisor. The HV expects the
	 * buffer size to be passed in the second word of the buffer */
	((u32 *)dtl->buf)[1] = cpu_to_be32(DISPATCH_LOG_BYTES);

	hwcpu = get_hard_smp_processor_id(dtl->cpu);
	addr = __pa(dtl->buf);
	ret = register_dtl(hwcpu, addr);
	if (ret) {
		printk(KERN_WARNING "%s: DTL registration for cpu %d (hw %d) "
		       "failed with %d\n", __func__, dtl->cpu, hwcpu, ret);
		return -EIO;
	}

	/* set our initial buffer indices */
	lppaca_of(dtl->cpu).dtl_idx = 0;

	/* ensure that our updates to the lppaca fields have occurred before
	 * we actually enable the logging */
	smp_wmb();

	/* enable event logging */
	lppaca_of(dtl->cpu).dtl_enable_mask = dtl_event_mask;

	return 0;
}

static void dtl_stop(struct dtl *dtl)
{
	int hwcpu = get_hard_smp_processor_id(dtl->cpu);

	lppaca_of(dtl->cpu).dtl_enable_mask = 0x0;

	unregister_dtl(hwcpu);
}

static u64 dtl_current_index(struct dtl *dtl)
{
	return be64_to_cpu(lppaca_of(dtl->cpu).dtl_idx);
}
#endif /* CONFIG_VIRT_CPU_ACCOUNTING_NATIVE */

static int dtl_enable(struct dtl *dtl)
{
	long int n_entries;
	long int rc;
	struct dtl_entry *buf = NULL;

	if (!dtl_cache)
		return -ENOMEM;

	/* only allow one reader */
	if (dtl->buf)
		return -EBUSY;

	/* ensure there are no other conflicting dtl users */
	if (!read_trylock(&dtl_access_lock))
		return -EBUSY;

	n_entries = dtl_buf_entries;
	buf = kmem_cache_alloc_node(dtl_cache, GFP_KERNEL, cpu_to_node(dtl->cpu));
	if (!buf) {
		printk(KERN_WARNING "%s: buffer alloc failed for cpu %d\n",
				__func__, dtl->cpu);
		read_unlock(&dtl_access_lock);
		return -ENOMEM;
	}

	spin_lock(&dtl->lock);
	rc = -EBUSY;
	if (!dtl->buf) {
		/* store the original allocation size for use during read */
		dtl->buf_entries = n_entries;
		dtl->buf = buf;
		dtl->last_idx = 0;
		rc = dtl_start(dtl);
		if (rc)
			dtl->buf = NULL;
	}
	spin_unlock(&dtl->lock);

	if (rc) {
		read_unlock(&dtl_access_lock);
		kmem_cache_free(dtl_cache, buf);
	}

	return rc;
}

static void dtl_disable(struct dtl *dtl)
{
	spin_lock(&dtl->lock);
	dtl_stop(dtl);
	kmem_cache_free(dtl_cache, dtl->buf);
	dtl->buf = NULL;
	dtl->buf_entries = 0;
	spin_unlock(&dtl->lock);
	read_unlock(&dtl_access_lock);
}

/* file interface */

static int dtl_file_open(struct inode *inode, struct file *filp)
{
	struct dtl *dtl = inode->i_private;
	int rc;

	rc = dtl_enable(dtl);
	if (rc)
		return rc;

	filp->private_data = dtl;
	return 0;
}

static int dtl_file_release(struct inode *inode, struct file *filp)
{
	struct dtl *dtl = inode->i_private;
	dtl_disable(dtl);
	return 0;
}

static ssize_t dtl_file_read(struct file *filp, char __user *buf, size_t len,
		loff_t *pos)
{
	long int rc, n_read, n_req, read_size;
	struct dtl *dtl;
	u64 cur_idx, last_idx, i;

	if ((len % sizeof(struct dtl_entry)) != 0)
		return -EINVAL;

	dtl = filp->private_data;

	/* requested number of entries to read */
	n_req = len / sizeof(struct dtl_entry);

	/* actual number of entries read */
	n_read = 0;

	spin_lock(&dtl->lock);

	cur_idx = dtl_current_index(dtl);
	last_idx = dtl->last_idx;

	if (last_idx + dtl->buf_entries <= cur_idx)
		last_idx = cur_idx - dtl->buf_entries + 1;

	if (last_idx + n_req > cur_idx)
		n_req = cur_idx - last_idx;

	if (n_req > 0)
		dtl->last_idx = last_idx + n_req;

	spin_unlock(&dtl->lock);

	if (n_req <= 0)
		return 0;

	i = last_idx % dtl->buf_entries;

	/* read the tail of the buffer if we've wrapped */
	if (i + n_req > dtl->buf_entries) {
		read_size = dtl->buf_entries - i;

		rc = copy_to_user(buf, &dtl->buf[i],
				read_size * sizeof(struct dtl_entry));
		if (rc)
			return -EFAULT;

		i = 0;
		n_req -= read_size;
		n_read += read_size;
		buf += read_size * sizeof(struct dtl_entry);
	}

	/* .. and now the head */
	rc = copy_to_user(buf, &dtl->buf[i], n_req * sizeof(struct dtl_entry));
	if (rc)
		return -EFAULT;

	n_read += n_req;

	return n_read * sizeof(struct dtl_entry);
}

static const struct file_operations dtl_fops = {
	.open		= dtl_file_open,
	.release	= dtl_file_release,
	.read		= dtl_file_read,
	.llseek		= no_llseek,
};

static struct dentry *dtl_dir;

static void dtl_setup_file(struct dtl *dtl)
{
	char name[10];

	sprintf(name, "cpu-%d", dtl->cpu);

	debugfs_create_file(name, 0400, dtl_dir, dtl, &dtl_fops);
}

static int dtl_init(void)
{
	int i;

	if (!firmware_has_feature(FW_FEATURE_SPLPAR))
		return -ENODEV;

	/* set up common debugfs structure */

	dtl_dir = debugfs_create_dir("dtl", arch_debugfs_dir);

	debugfs_create_x8("dtl_event_mask", 0600, dtl_dir, &dtl_event_mask);
	debugfs_create_u32("dtl_buf_entries", 0400, dtl_dir, &dtl_buf_entries);

	/* set up the per-cpu log structures */
	for_each_possible_cpu(i) {
		struct dtl *dtl = &per_cpu(cpu_dtl, i);
		spin_lock_init(&dtl->lock);
		dtl->cpu = i;

		dtl_setup_file(dtl);
	}

	return 0;
}
machine_arch_initcall(pseries, dtl_init);
Commit	Line	Data
de6cc651	1	// SPDX-License-Identifier: GPL-2.0-or-later
fc59a3fc JK	2	/*
	3	* Virtual Processor Dispatch Trace Log
	4	*
	5	* (C) Copyright IBM Corporation 2009
	6	*
	7	* Author: Jeremy Kerr <jk@ozlabs.org>
fc59a3fc JK	8	*/
fc59a3fc JK	9
5a0e3ad6	10	#include <linux/slab.h>
872e439a	11	#include <linux/spinlock.h>
fc59a3fc	12	#include <asm/smp.h>
7c0f6ba6	13	#include <linux/uaccess.h>
dbf77fed	14	#include <linux/debugfs.h>
b71a0c29	15	#include <asm/firmware.h>
d6bdceb6	16	#include <asm/dtl.h>
cf9efce0	17	#include <asm/lppaca.h>
212bebb4	18	#include <asm/plpar_wrappers.h>
8e83e905	19	#include <asm/machdep.h>
fc59a3fc	20
fc59a3fc JK	21	struct dtl {
fc59a3fc JK	22	struct dtl_entry *buf;
fc59a3fc JK	23	int cpu;
	24	int buf_entries;
	25	u64 last_idx;
872e439a	26	spinlock_t lock;
fc59a3fc	27	};
6b7487fc	28	static DEFINE_PER_CPU(struct dtl, cpu_dtl);
fc59a3fc	29
515bbc8a	30	static u8 dtl_event_mask = DTL_LOG_ALL;
fc59a3fc JK	31
	32
	33	/*
af442a1b NA	34	* Size of per-cpu log buffers. Firmware requires that the buffer does
af442a1b NA	35	* not cross a 4k boundary.
fc59a3fc	36	*/
af442a1b	37	static int dtl_buf_entries = N_DISPATCH_LOG;
fc59a3fc	38
abf917cd	39	#ifdef CONFIG_VIRT_CPU_ACCOUNTING_NATIVE
6ba5aa54 NP	40
	41	/*
	42	* When CONFIG_VIRT_CPU_ACCOUNTING_NATIVE = y, the cpu accounting code controls
	43	* reading from the dispatch trace log. If other code wants to consume
	44	* DTL entries, it can set this pointer to a function that will get
	45	* called once for each DTL entry that gets processed.
	46	*/
	47	static void (dtl_consumer)(struct dtl_entry entry, u64 index);
	48
872e439a PM	49	struct dtl_ring {
	50	u64 write_index;
	51	struct dtl_entry *write_ptr;
	52	struct dtl_entry *buf;
	53	struct dtl_entry *buf_end;
872e439a PM	54	};
	55
	56	static DEFINE_PER_CPU(struct dtl_ring, dtl_rings);
	57
	58	static atomic_t dtl_count;
	59
6ba5aa54 NP	60	/*
	61	* Scan the dispatch trace log and count up the stolen time.
	62	* Should be called with interrupts disabled.
	63	*/
	64	static notrace u64 scan_dispatch_log(u64 stop_tb)
	65	{
	66	u64 i = local_paca->dtl_ridx;
	67	struct dtl_entry *dtl = local_paca->dtl_curr;
	68	struct dtl_entry *dtl_end = local_paca->dispatch_log_end;
	69	struct lppaca *vpa = local_paca->lppaca_ptr;
	70	u64 tb_delta;
	71	u64 stolen = 0;
	72	u64 dtb;
	73
	74	if (!dtl)
	75	return 0;
	76
	77	if (i == be64_to_cpu(vpa->dtl_idx))
	78	return 0;
	79	while (i < be64_to_cpu(vpa->dtl_idx)) {
	80	dtb = be64_to_cpu(dtl->timebase);
	81	tb_delta = be32_to_cpu(dtl->enqueue_to_dispatch_time) +
	82	be32_to_cpu(dtl->ready_to_enqueue_time);
	83	barrier();
	84	if (i + N_DISPATCH_LOG < be64_to_cpu(vpa->dtl_idx)) {
	85	/* buffer has overflowed */
	86	i = be64_to_cpu(vpa->dtl_idx) - N_DISPATCH_LOG;
	87	dtl = local_paca->dispatch_log + (i % N_DISPATCH_LOG);
	88	continue;
	89	}
	90	if (dtb > stop_tb)
	91	break;
	92	if (dtl_consumer)
	93	dtl_consumer(dtl, i);
	94	stolen += tb_delta;
	95	++i;
	96	++dtl;
	97	if (dtl == dtl_end)
	98	dtl = local_paca->dispatch_log;
	99	}
	100	local_paca->dtl_ridx = i;
	101	local_paca->dtl_curr = dtl;
	102	return stolen;
	103	}
	104
	105	/*
	106	* Accumulate stolen time by scanning the dispatch trace log.
	107	* Called on entry from user mode.
	108	*/
	109	void notrace pseries_accumulate_stolen_time(void)
	110	{
	111	u64 sst, ust;
	112	struct cpu_accounting_data *acct = &local_paca->accounting;
	113
	114	sst = scan_dispatch_log(acct->starttime_user);
	115	ust = scan_dispatch_log(acct->starttime);
	116	acct->stime -= sst;
	117	acct->utime -= ust;
	118	acct->steal_time += ust + sst;
	119	}
	120
	121	u64 pseries_calculate_stolen_time(u64 stop_tb)
	122	{
	123	if (!firmware_has_feature(FW_FEATURE_SPLPAR))
124	return 0;
125
126	if (get_paca()->dtl_ridx != be64_to_cpu(get_lppaca()->dtl_idx))
127	return scan_dispatch_log(stop_tb);
128
129	return 0;
130	}
131
872e439a PM	132	/*
	133	* The cpu accounting code controls the DTL ring buffer, and we get
	134	* given entries as they are processed.
	135	*/
	136	static void consume_dtle(struct dtl_entry *dtle, u64 index)
fc59a3fc	137	{
69111bac	138	struct dtl_ring *dtlr = this_cpu_ptr(&dtl_rings);
872e439a PM	139	struct dtl_entry *wp = dtlr->write_ptr;
872e439a PM	140	struct lppaca *vpa = local_paca->lppaca_ptr;
fc59a3fc	141
872e439a PM	142	if (!wp)
872e439a PM	143	return;
fc59a3fc	144
872e439a PM	145	wp = dtle;
872e439a PM	146	barrier();
fc59a3fc	147
872e439a	148	/* check for hypervisor ring buffer overflow, ignore this entry if so */
7ffcf8ec	149	if (index + N_DISPATCH_LOG < be64_to_cpu(vpa->dtl_idx))
872e439a PM	150	return;
	151
	152	++wp;
	153	if (wp == dtlr->buf_end)
	154	wp = dtlr->buf;
	155	dtlr->write_ptr = wp;
	156
	157	/* incrementing write_index makes the new entry visible */
	158	smp_wmb();
	159	++dtlr->write_index;
	160	}
	161
	162	static int dtl_start(struct dtl *dtl)
	163	{
	164	struct dtl_ring *dtlr = &per_cpu(dtl_rings, dtl->cpu);
	165
	166	dtlr->buf = dtl->buf;
	167	dtlr->buf_end = dtl->buf + dtl->buf_entries;
	168	dtlr->write_index = 0;
	169
	170	/* setting write_ptr enables logging into our buffer */
	171	smp_wmb();
	172	dtlr->write_ptr = dtl->buf;
	173
	174	/* enable event logging */
872e439a PM	175	lppaca_of(dtl->cpu).dtl_enable_mask \|= dtl_event_mask;
	176
	177	dtl_consumer = consume_dtle;
	178	atomic_inc(&dtl_count);
	179	return 0;
	180	}
	181
	182	static void dtl_stop(struct dtl *dtl)
	183	{
	184	struct dtl_ring *dtlr = &per_cpu(dtl_rings, dtl->cpu);
	185
	186	dtlr->write_ptr = NULL;
	187	smp_wmb();
	188
	189	dtlr->buf = NULL;
	190
	191	/* restore dtl_enable_mask */
5b3306f0	192	lppaca_of(dtl->cpu).dtl_enable_mask = DTL_LOG_PREEMPT;
872e439a PM	193
	194	if (atomic_dec_and_test(&dtl_count))
	195	dtl_consumer = NULL;
	196	}
	197
	198	static u64 dtl_current_index(struct dtl *dtl)
	199	{
	200	return per_cpu(dtl_rings, dtl->cpu).write_index;
	201	}
	202
abf917cd	203	#else /* CONFIG_VIRT_CPU_ACCOUNTING_NATIVE */
872e439a PM	204
	205	static int dtl_start(struct dtl *dtl)
	206	{
	207	unsigned long addr;
	208	int ret, hwcpu;
fc59a3fc JK	209
	210	/* Register our dtl buffer with the hypervisor. The HV expects the
	211	* buffer size to be passed in the second word of the buffer */
db787af1	212	((u32 *)dtl->buf)[1] = cpu_to_be32(DISPATCH_LOG_BYTES);
fc59a3fc JK	213
	214	hwcpu = get_hard_smp_processor_id(dtl->cpu);
	215	addr = __pa(dtl->buf);
	216	ret = register_dtl(hwcpu, addr);
	217	if (ret) {
	218	printk(KERN_WARNING "%s: DTL registration for cpu %d (hw %d) "
	219	"failed with %d\n", __func__, dtl->cpu, hwcpu, ret);
fc59a3fc JK	220	return -EIO;
	221	}
	222
	223	/* set our initial buffer indices */
872e439a	224	lppaca_of(dtl->cpu).dtl_idx = 0;
fc59a3fc	225
82631f5d JK	226	/* ensure that our updates to the lppaca fields have occurred before
	227	* we actually enable the logging */
	228	smp_wmb();
	229
fc59a3fc	230	/* enable event logging */
8154c5d2	231	lppaca_of(dtl->cpu).dtl_enable_mask = dtl_event_mask;
fc59a3fc JK	232
	233	return 0;
	234	}
	235
872e439a	236	static void dtl_stop(struct dtl *dtl)
fc59a3fc JK	237	{
	238	int hwcpu = get_hard_smp_processor_id(dtl->cpu);
	239
8154c5d2	240	lppaca_of(dtl->cpu).dtl_enable_mask = 0x0;
fc59a3fc	241
b1301797	242	unregister_dtl(hwcpu);
872e439a PM	243	}
	244
	245	static u64 dtl_current_index(struct dtl *dtl)
	246	{
9258227e	247	return be64_to_cpu(lppaca_of(dtl->cpu).dtl_idx);
872e439a	248	}
abf917cd	249	#endif /* CONFIG_VIRT_CPU_ACCOUNTING_NATIVE */
fc59a3fc	250
872e439a PM	251	static int dtl_enable(struct dtl *dtl)
	252	{
	253	long int n_entries;
	254	long int rc;
	255	struct dtl_entry *buf = NULL;
	256
af442a1b NA	257	if (!dtl_cache)
	258	return -ENOMEM;
	259
872e439a PM	260	/* only allow one reader */
	261	if (dtl->buf)
	262	return -EBUSY;
	263
06220d78 NR	264	/* ensure there are no other conflicting dtl users */
	265	if (!read_trylock(&dtl_access_lock))
	266	return -EBUSY;
	267
872e439a	268	n_entries = dtl_buf_entries;
af442a1b	269	buf = kmem_cache_alloc_node(dtl_cache, GFP_KERNEL, cpu_to_node(dtl->cpu));
872e439a PM	270	if (!buf) {
	271	printk(KERN_WARNING "%s: buffer alloc failed for cpu %d\n",
	272	__func__, dtl->cpu);
06220d78	273	read_unlock(&dtl_access_lock);
872e439a PM	274	return -ENOMEM;
	275	}
	276
	277	spin_lock(&dtl->lock);
	278	rc = -EBUSY;
	279	if (!dtl->buf) {
	280	/* store the original allocation size for use during read */
	281	dtl->buf_entries = n_entries;
	282	dtl->buf = buf;
	283	dtl->last_idx = 0;
	284	rc = dtl_start(dtl);
	285	if (rc)
	286	dtl->buf = NULL;
	287	}
	288	spin_unlock(&dtl->lock);
	289
06220d78 NR	290	if (rc) {
06220d78 NR	291	read_unlock(&dtl_access_lock);
af442a1b	292	kmem_cache_free(dtl_cache, buf);
06220d78 NR	293	}
06220d78 NR	294
872e439a PM	295	return rc;
	296	}
	297
	298	static void dtl_disable(struct dtl *dtl)
	299	{
	300	spin_lock(&dtl->lock);
	301	dtl_stop(dtl);
af442a1b	302	kmem_cache_free(dtl_cache, dtl->buf);
fc59a3fc JK	303	dtl->buf = NULL;
fc59a3fc JK	304	dtl->buf_entries = 0;
872e439a	305	spin_unlock(&dtl->lock);
06220d78	306	read_unlock(&dtl_access_lock);
fc59a3fc JK	307	}
	308
	309	/* file interface */
	310
	311	static int dtl_file_open(struct inode inode, struct file filp)
	312	{
	313	struct dtl *dtl = inode->i_private;
	314	int rc;
	315
	316	rc = dtl_enable(dtl);
	317	if (rc)
	318	return rc;
	319
	320	filp->private_data = dtl;
	321	return 0;
	322	}
	323
	324	static int dtl_file_release(struct inode inode, struct file filp)
	325	{
	326	struct dtl *dtl = inode->i_private;
	327	dtl_disable(dtl);
	328	return 0;
	329	}
	330
	331	static ssize_t dtl_file_read(struct file filp, char __user buf, size_t len,
	332	loff_t *pos)
	333	{
872e439a	334	long int rc, n_read, n_req, read_size;
fc59a3fc	335	struct dtl *dtl;
872e439a	336	u64 cur_idx, last_idx, i;
fc59a3fc JK	337
	338	if ((len % sizeof(struct dtl_entry)) != 0)
	339	return -EINVAL;
	340
	341	dtl = filp->private_data;
	342
	343	/* requested number of entries to read */
	344	n_req = len / sizeof(struct dtl_entry);
	345
	346	/* actual number of entries read */
	347	n_read = 0;
	348
872e439a PM	349	spin_lock(&dtl->lock);
	350
	351	cur_idx = dtl_current_index(dtl);
fc59a3fc JK	352	last_idx = dtl->last_idx;
fc59a3fc JK	353
872e439a PM	354	if (last_idx + dtl->buf_entries <= cur_idx)
	355	last_idx = cur_idx - dtl->buf_entries + 1;
	356
	357	if (last_idx + n_req > cur_idx)
	358	n_req = cur_idx - last_idx;
fc59a3fc	359
872e439a PM	360	if (n_req > 0)
	361	dtl->last_idx = last_idx + n_req;
	362
	363	spin_unlock(&dtl->lock);
	364
	365	if (n_req <= 0)
	366	return 0;
	367
	368	i = last_idx % dtl->buf_entries;
fc59a3fc JK	369
fc59a3fc JK	370	/* read the tail of the buffer if we've wrapped */
872e439a PM	371	if (i + n_req > dtl->buf_entries) {
872e439a PM	372	read_size = dtl->buf_entries - i;
fc59a3fc	373
872e439a	374	rc = copy_to_user(buf, &dtl->buf[i],
fc59a3fc JK	375	read_size * sizeof(struct dtl_entry));
	376	if (rc)
	377	return -EFAULT;
	378
872e439a	379	i = 0;
fc59a3fc JK	380	n_req -= read_size;
	381	n_read += read_size;
	382	buf += read_size * sizeof(struct dtl_entry);
	383	}
	384
	385	/* .. and now the head */
872e439a	386	rc = copy_to_user(buf, &dtl->buf[i], n_req * sizeof(struct dtl_entry));
fc59a3fc JK	387	if (rc)
	388	return -EFAULT;
	389
872e439a	390	n_read += n_req;
fc59a3fc JK	391
	392	return n_read * sizeof(struct dtl_entry);
	393	}
	394
828c0950	395	static const struct file_operations dtl_fops = {
fc59a3fc JK	396	.open = dtl_file_open,
	397	.release = dtl_file_release,
	398	.read = dtl_file_read,
	399	.llseek = no_llseek,
	400	};
	401
	402	static struct dentry *dtl_dir;
	403
ff229319	404	static void dtl_setup_file(struct dtl *dtl)
fc59a3fc JK	405	{
	406	char name[10];
	407
	408	sprintf(name, "cpu-%d", dtl->cpu);
	409
ff229319	410	debugfs_create_file(name, 0400, dtl_dir, dtl, &dtl_fops);
fc59a3fc JK	411	}
	412
	413	static int dtl_init(void)
	414	{
ff229319	415	int i;
fc59a3fc JK	416
	417	if (!firmware_has_feature(FW_FEATURE_SPLPAR))
	418	return -ENODEV;
	419
	420	/* set up common debugfs structure */
	421
dbf77fed	422	dtl_dir = debugfs_create_dir("dtl", arch_debugfs_dir);
fc59a3fc	423
ff229319 GKH	424	debugfs_create_x8("dtl_event_mask", 0600, dtl_dir, &dtl_event_mask);
ff229319 GKH	425	debugfs_create_u32("dtl_buf_entries", 0400, dtl_dir, &dtl_buf_entries);
fc59a3fc JK	426
	427	/* set up the per-cpu log structures */
	428	for_each_possible_cpu(i) {
6b7487fc	429	struct dtl *dtl = &per_cpu(cpu_dtl, i);
872e439a	430	spin_lock_init(&dtl->lock);
fc59a3fc JK	431	dtl->cpu = i;
fc59a3fc JK	432
ff229319	433	dtl_setup_file(dtl);
fc59a3fc JK	434	}
	435
	436	return 0;
fc59a3fc	437	}
8e83e905	438	machine_arch_initcall(pseries, dtl_init);