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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/export.h> |
12 | #include <linux/jiffies.h> |
13 | #include <linux/mutex.h> |
14 | #include <linux/sched.h> |
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 | */ |
26 | int fw_iso_resources_init(struct fw_iso_resources *r, struct fw_unit *unit) |
27 | { |
28 | r->channels_mask = ~0uLL; |
29 | r->unit = fw_unit_get(unit); |
30 | mutex_init(&r->mutex); |
31 | r->allocated = false; |
32 | |
33 | return 0; |
34 | } |
35 | EXPORT_SYMBOL(fw_iso_resources_init); |
36 | |
37 | /** |
38 | * fw_iso_resources_destroy - destroy a resource manager |
39 | * @r: the resource manager that is no longer needed |
40 | */ |
41 | void fw_iso_resources_destroy(struct fw_iso_resources *r) |
42 | { |
43 | WARN_ON(r->allocated); |
44 | mutex_destroy(&r->mutex); |
45 | fw_unit_put(r->unit); |
46 | } |
47 | EXPORT_SYMBOL(fw_iso_resources_destroy); |
48 | |
49 | static unsigned int packet_bandwidth(unsigned int max_payload_bytes, int speed) |
50 | { |
51 | unsigned int bytes, s400_bytes; |
52 | |
53 | /* iso packets have three header quadlets and quadlet-aligned payload */ |
54 | bytes = 3 * 4 + ALIGN(max_payload_bytes, 4); |
55 | |
56 | /* convert to bandwidth units (quadlets at S1600 = bytes at S400) */ |
57 | if (speed <= SCODE_400) |
58 | s400_bytes = bytes * (1 << (SCODE_400 - speed)); |
59 | else |
60 | s400_bytes = DIV_ROUND_UP(bytes, 1 << (speed - SCODE_400)); |
61 | |
62 | return s400_bytes; |
63 | } |
64 | |
65 | static int current_bandwidth_overhead(struct fw_card *card) |
66 | { |
67 | /* |
68 | * Under the usual pessimistic assumption (cable length 4.5 m), the |
69 | * isochronous overhead for N cables is 1.797 µs + N * 0.494 µs, or |
70 | * 88.3 + N * 24.3 in bandwidth units. |
71 | * |
72 | * The calculation below tries to deduce N from the current gap count. |
73 | * If the gap count has been optimized by measuring the actual packet |
74 | * transmission time, this derived overhead should be near the actual |
75 | * overhead as well. |
76 | */ |
77 | return card->gap_count < 63 ? card->gap_count * 97 / 10 + 89 : 512; |
78 | } |
79 | |
80 | static int wait_isoch_resource_delay_after_bus_reset(struct fw_card *card) |
81 | { |
82 | for (;;) { |
83 | s64 delay = (card->reset_jiffies + HZ) - get_jiffies_64(); |
84 | if (delay <= 0) |
85 | return 0; |
86 | if (schedule_timeout_interruptible(delay) > 0) |
87 | return -ERESTARTSYS; |
88 | } |
89 | } |
90 | |
91 | /** |
92 | * fw_iso_resources_allocate - allocate isochronous channel and bandwidth |
93 | * @r: the resource manager |
94 | * @max_payload_bytes: the amount of data (including CIP headers) per packet |
95 | * @speed: the speed (e.g., SCODE_400) at which the packets will be sent |
96 | * |
97 | * This function allocates one isochronous channel and enough bandwidth for the |
98 | * specified packet size. |
99 | * |
100 | * Returns the channel number that the caller must use for streaming, or |
101 | * a negative error code. Due to potentionally long delays, this function is |
102 | * interruptible and can return -ERESTARTSYS. On success, the caller is |
103 | * responsible for calling fw_iso_resources_update() on bus resets, and |
104 | * fw_iso_resources_free() when the resources are not longer needed. |
105 | */ |
106 | int fw_iso_resources_allocate(struct fw_iso_resources *r, |
107 | unsigned int max_payload_bytes, int speed) |
108 | { |
109 | struct fw_card *card = fw_parent_device(r->unit)->card; |
110 | int bandwidth, channel, err; |
111 | |
112 | if (WARN_ON(r->allocated)) |
113 | return -EBADFD; |
114 | |
115 | r->bandwidth = packet_bandwidth(max_payload_bytes, speed); |
116 | |
117 | retry_after_bus_reset: |
118 | spin_lock_irq(&card->lock); |
119 | r->generation = card->generation; |
120 | r->bandwidth_overhead = current_bandwidth_overhead(card); |
121 | spin_unlock_irq(&card->lock); |
122 | |
123 | err = wait_isoch_resource_delay_after_bus_reset(card); |
124 | if (err < 0) |
125 | return err; |
126 | |
127 | mutex_lock(&r->mutex); |
128 | |
129 | bandwidth = r->bandwidth + r->bandwidth_overhead; |
130 | fw_iso_resource_manage(card, r->generation, r->channels_mask, |
131 | &channel, &bandwidth, true); |
132 | if (channel == -EAGAIN) { |
133 | mutex_unlock(&r->mutex); |
134 | goto retry_after_bus_reset; |
135 | } |
136 | if (channel >= 0) { |
137 | r->channel = channel; |
138 | r->allocated = true; |
139 | } else { |
140 | if (channel == -EBUSY) |
141 | dev_err(&r->unit->device, |
142 | "isochronous resources exhausted\n"); |
143 | else |
144 | dev_err(&r->unit->device, |
145 | "isochronous resource allocation failed\n"); |
146 | } |
147 | |
148 | mutex_unlock(&r->mutex); |
149 | |
150 | return channel; |
151 | } |
152 | EXPORT_SYMBOL(fw_iso_resources_allocate); |
153 | |
154 | /** |
155 | * fw_iso_resources_update - update resource allocations after a bus reset |
156 | * @r: the resource manager |
157 | * |
158 | * This function must be called from the driver's .update handler to reallocate |
159 | * any resources that were allocated before the bus reset. It is safe to call |
160 | * this function if no resources are currently allocated. |
161 | * |
162 | * Returns a negative error code on failure. If this happens, the caller must |
163 | * stop streaming. |
164 | */ |
165 | int fw_iso_resources_update(struct fw_iso_resources *r) |
166 | { |
167 | struct fw_card *card = fw_parent_device(r->unit)->card; |
168 | int bandwidth, channel; |
169 | |
170 | mutex_lock(&r->mutex); |
171 | |
172 | if (!r->allocated) { |
173 | mutex_unlock(&r->mutex); |
174 | return 0; |
175 | } |
176 | |
177 | spin_lock_irq(&card->lock); |
178 | r->generation = card->generation; |
179 | r->bandwidth_overhead = current_bandwidth_overhead(card); |
180 | spin_unlock_irq(&card->lock); |
181 | |
182 | bandwidth = r->bandwidth + r->bandwidth_overhead; |
183 | |
184 | fw_iso_resource_manage(card, r->generation, 1uLL << r->channel, |
185 | &channel, &bandwidth, true); |
186 | /* |
187 | * When another bus reset happens, pretend that the allocation |
188 | * succeeded; we will try again for the new generation later. |
189 | */ |
190 | if (channel < 0 && channel != -EAGAIN) { |
191 | r->allocated = false; |
192 | if (channel == -EBUSY) |
193 | dev_err(&r->unit->device, |
194 | "isochronous resources exhausted\n"); |
195 | else |
196 | dev_err(&r->unit->device, |
197 | "isochronous resource allocation failed\n"); |
198 | } |
199 | |
200 | mutex_unlock(&r->mutex); |
201 | |
202 | return channel; |
203 | } |
204 | EXPORT_SYMBOL(fw_iso_resources_update); |
205 | |
206 | /** |
207 | * fw_iso_resources_free - frees allocated resources |
208 | * @r: the resource manager |
209 | * |
210 | * This function deallocates the channel and bandwidth, if allocated. |
211 | */ |
212 | void fw_iso_resources_free(struct fw_iso_resources *r) |
213 | { |
214 | struct fw_card *card = fw_parent_device(r->unit)->card; |
215 | int bandwidth, channel; |
216 | |
217 | mutex_lock(&r->mutex); |
218 | |
219 | if (r->allocated) { |
220 | bandwidth = r->bandwidth + r->bandwidth_overhead; |
221 | fw_iso_resource_manage(card, r->generation, 1uLL << r->channel, |
222 | &channel, &bandwidth, false); |
223 | if (channel < 0) |
224 | dev_err(&r->unit->device, |
225 | "isochronous resource deallocation failed\n"); |
226 | |
227 | r->allocated = false; |
228 | } |
229 | |
230 | mutex_unlock(&r->mutex); |
231 | } |
232 | EXPORT_SYMBOL(fw_iso_resources_free); |
233 |
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