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31ef9134 CL |
1 | /* |
2 | * isochronous resources helper functions | |
3 | * | |
4 | * Copyright (c) Clemens Ladisch <clemens@ladisch.de> | |
5 | * Licensed under the terms of the GNU General Public License, version 2. | |
6 | */ | |
7 | ||
8 | #include <linux/device.h> | |
9 | #include <linux/firewire.h> | |
10 | #include <linux/firewire-constants.h> | |
11 | #include <linux/jiffies.h> | |
12 | #include <linux/mutex.h> | |
13 | #include <linux/sched.h> | |
5b2599a0 | 14 | #include <linux/slab.h> |
31ef9134 CL |
15 | #include <linux/spinlock.h> |
16 | #include "iso-resources.h" | |
17 | ||
18 | /** | |
19 | * fw_iso_resources_init - initializes a &struct fw_iso_resources | |
20 | * @r: the resource manager to initialize | |
21 | * @unit: the device unit for which the resources will be needed | |
22 | * | |
23 | * If the device does not support all channel numbers, change @r->channels_mask | |
24 | * after calling this function. | |
25 | */ | |
5b2599a0 | 26 | int fw_iso_resources_init(struct fw_iso_resources *r, struct fw_unit *unit) |
31ef9134 | 27 | { |
5b2599a0 CL |
28 | r->buffer = kmalloc(2 * 4, GFP_KERNEL); |
29 | if (!r->buffer) | |
30 | return -ENOMEM; | |
31 | ||
31ef9134 CL |
32 | r->channels_mask = ~0uLL; |
33 | r->unit = fw_unit_get(unit); | |
34 | mutex_init(&r->mutex); | |
35 | r->allocated = false; | |
5b2599a0 CL |
36 | |
37 | return 0; | |
31ef9134 CL |
38 | } |
39 | ||
40 | /** | |
41 | * fw_iso_resources_destroy - destroy a resource manager | |
42 | * @r: the resource manager that is no longer needed | |
43 | */ | |
44 | void fw_iso_resources_destroy(struct fw_iso_resources *r) | |
45 | { | |
46 | WARN_ON(r->allocated); | |
5b2599a0 | 47 | kfree(r->buffer); |
31ef9134 CL |
48 | mutex_destroy(&r->mutex); |
49 | fw_unit_put(r->unit); | |
50 | } | |
51 | ||
52 | static unsigned int packet_bandwidth(unsigned int max_payload_bytes, int speed) | |
53 | { | |
54 | unsigned int bytes, s400_bytes; | |
55 | ||
56 | /* iso packets have three header quadlets and quadlet-aligned payload */ | |
57 | bytes = 3 * 4 + ALIGN(max_payload_bytes, 4); | |
58 | ||
59 | /* convert to bandwidth units (quadlets at S1600 = bytes at S400) */ | |
60 | if (speed <= SCODE_400) | |
61 | s400_bytes = bytes * (1 << (SCODE_400 - speed)); | |
62 | else | |
63 | s400_bytes = DIV_ROUND_UP(bytes, 1 << (speed - SCODE_400)); | |
64 | ||
65 | return s400_bytes; | |
66 | } | |
67 | ||
68 | static int current_bandwidth_overhead(struct fw_card *card) | |
69 | { | |
70 | /* | |
71 | * Under the usual pessimistic assumption (cable length 4.5 m), the | |
72 | * isochronous overhead for N cables is 1.797 µs + N * 0.494 µs, or | |
73 | * 88.3 + N * 24.3 in bandwidth units. | |
74 | * | |
75 | * The calculation below tries to deduce N from the current gap count. | |
76 | * If the gap count has been optimized by measuring the actual packet | |
77 | * transmission time, this derived overhead should be near the actual | |
78 | * overhead as well. | |
79 | */ | |
80 | return card->gap_count < 63 ? card->gap_count * 97 / 10 + 89 : 512; | |
81 | } | |
82 | ||
83 | static int wait_isoch_resource_delay_after_bus_reset(struct fw_card *card) | |
84 | { | |
85 | for (;;) { | |
86 | s64 delay = (card->reset_jiffies + HZ) - get_jiffies_64(); | |
87 | if (delay <= 0) | |
88 | return 0; | |
89 | if (schedule_timeout_interruptible(delay) > 0) | |
90 | return -ERESTARTSYS; | |
91 | } | |
92 | } | |
93 | ||
94 | /** | |
95 | * fw_iso_resources_allocate - allocate isochronous channel and bandwidth | |
96 | * @r: the resource manager | |
97 | * @max_payload_bytes: the amount of data (including CIP headers) per packet | |
98 | * @speed: the speed (e.g., SCODE_400) at which the packets will be sent | |
99 | * | |
100 | * This function allocates one isochronous channel and enough bandwidth for the | |
101 | * specified packet size. | |
102 | * | |
103 | * Returns the channel number that the caller must use for streaming, or | |
104 | * a negative error code. Due to potentionally long delays, this function is | |
105 | * interruptible and can return -ERESTARTSYS. On success, the caller is | |
106 | * responsible for calling fw_iso_resources_update() on bus resets, and | |
107 | * fw_iso_resources_free() when the resources are not longer needed. | |
108 | */ | |
109 | int fw_iso_resources_allocate(struct fw_iso_resources *r, | |
110 | unsigned int max_payload_bytes, int speed) | |
111 | { | |
112 | struct fw_card *card = fw_parent_device(r->unit)->card; | |
113 | int bandwidth, channel, err; | |
114 | ||
115 | if (WARN_ON(r->allocated)) | |
116 | return -EBADFD; | |
117 | ||
118 | r->bandwidth = packet_bandwidth(max_payload_bytes, speed); | |
119 | ||
120 | retry_after_bus_reset: | |
121 | spin_lock_irq(&card->lock); | |
122 | r->generation = card->generation; | |
123 | r->bandwidth_overhead = current_bandwidth_overhead(card); | |
124 | spin_unlock_irq(&card->lock); | |
125 | ||
126 | err = wait_isoch_resource_delay_after_bus_reset(card); | |
127 | if (err < 0) | |
128 | return err; | |
129 | ||
130 | mutex_lock(&r->mutex); | |
131 | ||
132 | bandwidth = r->bandwidth + r->bandwidth_overhead; | |
133 | fw_iso_resource_manage(card, r->generation, r->channels_mask, | |
134 | &channel, &bandwidth, true, r->buffer); | |
135 | if (channel == -EAGAIN) { | |
136 | mutex_unlock(&r->mutex); | |
137 | goto retry_after_bus_reset; | |
138 | } | |
139 | if (channel >= 0) { | |
140 | r->channel = channel; | |
141 | r->allocated = true; | |
142 | } else { | |
143 | if (channel == -EBUSY) | |
144 | dev_err(&r->unit->device, | |
145 | "isochronous resources exhausted\n"); | |
146 | else | |
147 | dev_err(&r->unit->device, | |
148 | "isochronous resource allocation failed\n"); | |
149 | } | |
150 | ||
151 | mutex_unlock(&r->mutex); | |
152 | ||
153 | return channel; | |
154 | } | |
155 | ||
156 | /** | |
157 | * fw_iso_resources_update - update resource allocations after a bus reset | |
158 | * @r: the resource manager | |
159 | * | |
160 | * This function must be called from the driver's .update handler to reallocate | |
161 | * any resources that were allocated before the bus reset. It is safe to call | |
162 | * this function if no resources are currently allocated. | |
163 | * | |
164 | * Returns a negative error code on failure. If this happens, the caller must | |
165 | * stop streaming. | |
166 | */ | |
167 | int fw_iso_resources_update(struct fw_iso_resources *r) | |
168 | { | |
169 | struct fw_card *card = fw_parent_device(r->unit)->card; | |
170 | int bandwidth, channel; | |
171 | ||
172 | mutex_lock(&r->mutex); | |
173 | ||
174 | if (!r->allocated) { | |
175 | mutex_unlock(&r->mutex); | |
176 | return 0; | |
177 | } | |
178 | ||
179 | spin_lock_irq(&card->lock); | |
180 | r->generation = card->generation; | |
181 | r->bandwidth_overhead = current_bandwidth_overhead(card); | |
182 | spin_unlock_irq(&card->lock); | |
183 | ||
184 | bandwidth = r->bandwidth + r->bandwidth_overhead; | |
185 | ||
186 | fw_iso_resource_manage(card, r->generation, 1uLL << r->channel, | |
187 | &channel, &bandwidth, true, r->buffer); | |
188 | /* | |
189 | * When another bus reset happens, pretend that the allocation | |
190 | * succeeded; we will try again for the new generation later. | |
191 | */ | |
192 | if (channel < 0 && channel != -EAGAIN) { | |
193 | r->allocated = false; | |
194 | if (channel == -EBUSY) | |
195 | dev_err(&r->unit->device, | |
196 | "isochronous resources exhausted\n"); | |
197 | else | |
198 | dev_err(&r->unit->device, | |
199 | "isochronous resource allocation failed\n"); | |
200 | } | |
201 | ||
202 | mutex_unlock(&r->mutex); | |
203 | ||
204 | return channel; | |
205 | } | |
206 | ||
207 | /** | |
208 | * fw_iso_resources_free - frees allocated resources | |
209 | * @r: the resource manager | |
210 | * | |
211 | * This function deallocates the channel and bandwidth, if allocated. | |
212 | */ | |
213 | void fw_iso_resources_free(struct fw_iso_resources *r) | |
214 | { | |
215 | struct fw_card *card = fw_parent_device(r->unit)->card; | |
216 | int bandwidth, channel; | |
217 | ||
218 | mutex_lock(&r->mutex); | |
219 | ||
220 | if (r->allocated) { | |
221 | bandwidth = r->bandwidth + r->bandwidth_overhead; | |
222 | fw_iso_resource_manage(card, r->generation, 1uLL << r->channel, | |
223 | &channel, &bandwidth, false, r->buffer); | |
224 | if (channel < 0) | |
225 | dev_err(&r->unit->device, | |
226 | "isochronous resource deallocation failed\n"); | |
227 | ||
228 | r->allocated = false; | |
229 | } | |
230 | ||
231 | mutex_unlock(&r->mutex); | |
232 | } |