aboutsummaryrefslogtreecommitdiff
path: root/sound/firewire/iso-resources.c
blob: 775dbd5f34452b76e53086d2f8b6225020cb6ce4 (plain)
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
138
139
140
141
142
143
144
145
146
147
148
149
150
151
152
153
154
155
156
157
158
159
160
161
162
163
164
165
166
167
168
169
170
171
172
173
174
175
176
177
178
179
180
181
182
183
184
185
186
187
188
189
190
191
192
193
194
195
196
197
198
199
200
201
202
203
204
205
206
207
208
209
210
211
212
213
214
215
216
217
218
219
220
221
222
223
224
225
226
227
228
229
230
231
232
/*
 * isochronous resources helper functions
 *
 * Copyright (c) Clemens Ladisch <clemens@ladisch.de>
 * Licensed under the terms of the GNU General Public License, version 2.
 */

#include <linux/device.h>
#include <linux/firewire.h>
#include <linux/firewire-constants.h>
#include <linux/jiffies.h>
#include <linux/mutex.h>
#include <linux/sched.h>
#include <linux/slab.h>
#include <linux/spinlock.h>
#include "iso-resources.h"

/**
 * fw_iso_resources_init - initializes a &struct fw_iso_resources
 * @r: the resource manager to initialize
 * @unit: the device unit for which the resources will be needed
 *
 * If the device does not support all channel numbers, change @r->channels_mask
 * after calling this function.
 */
int fw_iso_resources_init(struct fw_iso_resources *r, struct fw_unit *unit)
{
	r->buffer = kmalloc(2 * 4, GFP_KERNEL);
	if (!r->buffer)
		return -ENOMEM;

	r->channels_mask = ~0uLL;
	r->unit = fw_unit_get(unit);
	mutex_init(&r->mutex);
	r->allocated = false;

	return 0;
}

/**
 * fw_iso_resources_destroy - destroy a resource manager
 * @r: the resource manager that is no longer needed
 */
void fw_iso_resources_destroy(struct fw_iso_resources *r)
{
	WARN_ON(r->allocated);
	kfree(r->buffer);
	mutex_destroy(&r->mutex);
	fw_unit_put(r->unit);
}

static unsigned int packet_bandwidth(unsigned int max_payload_bytes, int speed)
{
	unsigned int bytes, s400_bytes;

	/* iso packets have three header quadlets and quadlet-aligned payload */
	bytes = 3 * 4 + ALIGN(max_payload_bytes, 4);

	/* convert to bandwidth units (quadlets at S1600 = bytes at S400) */
	if (speed <= SCODE_400)
		s400_bytes = bytes * (1 << (SCODE_400 - speed));
	else
		s400_bytes = DIV_ROUND_UP(bytes, 1 << (speed - SCODE_400));

	return s400_bytes;
}

static int current_bandwidth_overhead(struct fw_card *card)
{
	/*
	 * Under the usual pessimistic assumption (cable length 4.5 m), the
	 * isochronous overhead for N cables is 1.797 µs + N * 0.494 µs, or
	 * 88.3 + N * 24.3 in bandwidth units.
	 *
	 * The calculation below tries to deduce N from the current gap count.
	 * If the gap count has been optimized by measuring the actual packet
	 * transmission time, this derived overhead should be near the actual
	 * overhead as well.
	 */
	return card->gap_count < 63 ? card->gap_count * 97 / 10 + 89 : 512;
}

static int wait_isoch_resource_delay_after_bus_reset(struct fw_card *card)
{
	for (;;) {
		s64 delay = (card->reset_jiffies + HZ) - get_jiffies_64();
		if (delay <= 0)
			return 0;
		if (schedule_timeout_interruptible(delay) > 0)
			return -ERESTARTSYS;
	}
}

/**
 * fw_iso_resources_allocate - allocate isochronous channel and bandwidth
 * @r: the resource manager
 * @max_payload_bytes: the amount of data (including CIP headers) per packet
 * @speed: the speed (e.g., SCODE_400) at which the packets will be sent
 *
 * This function allocates one isochronous channel and enough bandwidth for the
 * specified packet size.
 *
 * Returns the channel number that the caller must use for streaming, or
 * a negative error code.  Due to potentionally long delays, this function is
 * interruptible and can return -ERESTARTSYS.  On success, the caller is
 * responsible for calling fw_iso_resources_update() on bus resets, and
 * fw_iso_resources_free() when the resources are not longer needed.
 */
int fw_iso_resources_allocate(struct fw_iso_resources *r,
			      unsigned int max_payload_bytes, int speed)
{
	struct fw_card *card = fw_parent_device(r->unit)->card;
	int bandwidth, channel, err;

	if (WARN_ON(r->allocated))
		return -EBADFD;

	r->bandwidth = packet_bandwidth(max_payload_bytes, speed);

retry_after_bus_reset:
	spin_lock_irq(&card->lock);
	r->generation = card->generation;
	r->bandwidth_overhead = current_bandwidth_overhead(card);
	spin_unlock_irq(&card->lock);

	err = wait_isoch_resource_delay_after_bus_reset(card);
	if (err < 0)
		return err;

	mutex_lock(&r->mutex);

	bandwidth = r->bandwidth + r->bandwidth_overhead;
	fw_iso_resource_manage(card, r->generation, r->channels_mask,
			       &channel, &bandwidth, true, r->buffer);
	if (channel == -EAGAIN) {
		mutex_unlock(&r->mutex);
		goto retry_after_bus_reset;
	}
	if (channel >= 0) {
		r->channel = channel;
		r->allocated = true;
	} else {
		if (channel == -EBUSY)
			dev_err(&r->unit->device,
				"isochronous resources exhausted\n");
		else
			dev_err(&r->unit->device,
				"isochronous resource allocation failed\n");
	}

	mutex_unlock(&r->mutex);

	return channel;
}

/**
 * fw_iso_resources_update - update resource allocations after a bus reset
 * @r: the resource manager
 *
 * This function must be called from the driver's .update handler to reallocate
 * any resources that were allocated before the bus reset.  It is safe to call
 * this function if no resources are currently allocated.
 *
 * Returns a negative error code on failure.  If this happens, the caller must
 * stop streaming.
 */
int fw_iso_resources_update(struct fw_iso_resources *r)
{
	struct fw_card *card = fw_parent_device(r->unit)->card;
	int bandwidth, channel;

	mutex_lock(&r->mutex);

	if (!r->allocated) {
		mutex_unlock(&r->mutex);
		return 0;
	}

	spin_lock_irq(&card->lock);
	r->generation = card->generation;
	r->bandwidth_overhead = current_bandwidth_overhead(card);
	spin_unlock_irq(&card->lock);

	bandwidth = r->bandwidth + r->bandwidth_overhead;

	fw_iso_resource_manage(card, r->generation, 1uLL << r->channel,
			       &channel, &bandwidth, true, r->buffer);
	/*
	 * When another bus reset happens, pretend that the allocation
	 * succeeded; we will try again for the new generation later.
	 */
	if (channel < 0 && channel != -EAGAIN) {
		r->allocated = false;
		if (channel == -EBUSY)
			dev_err(&r->unit->device,
				"isochronous resources exhausted\n");
		else
			dev_err(&r->unit->device,
				"isochronous resource allocation failed\n");
	}

	mutex_unlock(&r->mutex);

	return channel;
}

/**
 * fw_iso_resources_free - frees allocated resources
 * @r: the resource manager
 *
 * This function deallocates the channel and bandwidth, if allocated.
 */
void fw_iso_resources_free(struct fw_iso_resources *r)
{
	struct fw_card *card = fw_parent_device(r->unit)->card;
	int bandwidth, channel;

	mutex_lock(&r->mutex);

	if (r->allocated) {
		bandwidth = r->bandwidth + r->bandwidth_overhead;
		fw_iso_resource_manage(card, r->generation, 1uLL << r->channel,
				       &channel, &bandwidth, false, r->buffer);
		if (channel < 0)
			dev_err(&r->unit->device,
				"isochronous resource deallocation failed\n");

		r->allocated = false;
	}

	mutex_unlock(&r->mutex);
}