1 | // SPDX-License-Identifier: GPL-2.0-only |
2 | /* |
3 | * isochronous resources helper functions |
4 | * |
5 | * Copyright (c) Clemens Ladisch <clemens@ladisch.de> |
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 = 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(lock: &r->mutex); |
45 | } |
46 | EXPORT_SYMBOL(fw_iso_resources_destroy); |
47 | |
48 | static unsigned int packet_bandwidth(unsigned int max_payload_bytes, int speed) |
49 | { |
50 | unsigned int bytes, s400_bytes; |
51 | |
52 | /* iso packets have three header quadlets and quadlet-aligned payload */ |
53 | bytes = 3 * 4 + ALIGN(max_payload_bytes, 4); |
54 | |
55 | /* convert to bandwidth units (quadlets at S1600 = bytes at S400) */ |
56 | if (speed <= SCODE_400) |
57 | s400_bytes = bytes * (1 << (SCODE_400 - speed)); |
58 | else |
59 | s400_bytes = DIV_ROUND_UP(bytes, 1 << (speed - SCODE_400)); |
60 | |
61 | return s400_bytes; |
62 | } |
63 | |
64 | static int current_bandwidth_overhead(struct fw_card *card) |
65 | { |
66 | /* |
67 | * Under the usual pessimistic assumption (cable length 4.5 m), the |
68 | * isochronous overhead for N cables is 1.797 µs + N * 0.494 µs, or |
69 | * 88.3 + N * 24.3 in bandwidth units. |
70 | * |
71 | * The calculation below tries to deduce N from the current gap count. |
72 | * If the gap count has been optimized by measuring the actual packet |
73 | * transmission time, this derived overhead should be near the actual |
74 | * overhead as well. |
75 | */ |
76 | return card->gap_count < 63 ? card->gap_count * 97 / 10 + 89 : 512; |
77 | } |
78 | |
79 | static int wait_isoch_resource_delay_after_bus_reset(struct fw_card *card) |
80 | { |
81 | for (;;) { |
82 | s64 delay = (card->reset_jiffies + HZ) - get_jiffies_64(); |
83 | if (delay <= 0) |
84 | return 0; |
85 | if (schedule_timeout_interruptible(timeout: delay) > 0) |
86 | return -ERESTARTSYS; |
87 | } |
88 | } |
89 | |
90 | /** |
91 | * fw_iso_resources_allocate - allocate isochronous channel and bandwidth |
92 | * @r: the resource manager |
93 | * @max_payload_bytes: the amount of data (including CIP headers) per packet |
94 | * @speed: the speed (e.g., SCODE_400) at which the packets will be sent |
95 | * |
96 | * This function allocates one isochronous channel and enough bandwidth for the |
97 | * specified packet size. |
98 | * |
99 | * Returns the channel number that the caller must use for streaming, or |
100 | * a negative error code. Due to potentionally long delays, this function is |
101 | * interruptible and can return -ERESTARTSYS. On success, the caller is |
102 | * responsible for calling fw_iso_resources_update() on bus resets, and |
103 | * fw_iso_resources_free() when the resources are not longer needed. |
104 | */ |
105 | int fw_iso_resources_allocate(struct fw_iso_resources *r, |
106 | unsigned int max_payload_bytes, int speed) |
107 | { |
108 | struct fw_card *card = fw_parent_device(r->unit)->card; |
109 | int bandwidth, channel, err; |
110 | |
111 | if (WARN_ON(r->allocated)) |
112 | return -EBADFD; |
113 | |
114 | r->bandwidth = packet_bandwidth(max_payload_bytes, speed); |
115 | |
116 | retry_after_bus_reset: |
117 | spin_lock_irq(lock: &card->lock); |
118 | r->generation = card->generation; |
119 | r->bandwidth_overhead = current_bandwidth_overhead(card); |
120 | spin_unlock_irq(lock: &card->lock); |
121 | |
122 | err = wait_isoch_resource_delay_after_bus_reset(card); |
123 | if (err < 0) |
124 | return err; |
125 | |
126 | mutex_lock(&r->mutex); |
127 | |
128 | bandwidth = r->bandwidth + r->bandwidth_overhead; |
129 | fw_iso_resource_manage(card, generation: r->generation, channels_mask: r->channels_mask, |
130 | channel: &channel, bandwidth: &bandwidth, allocate: true); |
131 | if (channel == -EAGAIN) { |
132 | mutex_unlock(lock: &r->mutex); |
133 | goto retry_after_bus_reset; |
134 | } |
135 | if (channel >= 0) { |
136 | r->channel = channel; |
137 | r->allocated = true; |
138 | } else { |
139 | if (channel == -EBUSY) |
140 | dev_err(&r->unit->device, |
141 | "isochronous resources exhausted\n" ); |
142 | else |
143 | dev_err(&r->unit->device, |
144 | "isochronous resource allocation failed\n" ); |
145 | } |
146 | |
147 | mutex_unlock(lock: &r->mutex); |
148 | |
149 | return channel; |
150 | } |
151 | EXPORT_SYMBOL(fw_iso_resources_allocate); |
152 | |
153 | /** |
154 | * fw_iso_resources_update - update resource allocations after a bus reset |
155 | * @r: the resource manager |
156 | * |
157 | * This function must be called from the driver's .update handler to reallocate |
158 | * any resources that were allocated before the bus reset. It is safe to call |
159 | * this function if no resources are currently allocated. |
160 | * |
161 | * Returns a negative error code on failure. If this happens, the caller must |
162 | * stop streaming. |
163 | */ |
164 | int fw_iso_resources_update(struct fw_iso_resources *r) |
165 | { |
166 | struct fw_card *card = fw_parent_device(r->unit)->card; |
167 | int bandwidth, channel; |
168 | |
169 | mutex_lock(&r->mutex); |
170 | |
171 | if (!r->allocated) { |
172 | mutex_unlock(lock: &r->mutex); |
173 | return 0; |
174 | } |
175 | |
176 | spin_lock_irq(lock: &card->lock); |
177 | r->generation = card->generation; |
178 | r->bandwidth_overhead = current_bandwidth_overhead(card); |
179 | spin_unlock_irq(lock: &card->lock); |
180 | |
181 | bandwidth = r->bandwidth + r->bandwidth_overhead; |
182 | |
183 | fw_iso_resource_manage(card, generation: r->generation, channels_mask: 1uLL << r->channel, |
184 | channel: &channel, bandwidth: &bandwidth, allocate: true); |
185 | /* |
186 | * When another bus reset happens, pretend that the allocation |
187 | * succeeded; we will try again for the new generation later. |
188 | */ |
189 | if (channel < 0 && channel != -EAGAIN) { |
190 | r->allocated = false; |
191 | if (channel == -EBUSY) |
192 | dev_err(&r->unit->device, |
193 | "isochronous resources exhausted\n" ); |
194 | else |
195 | dev_err(&r->unit->device, |
196 | "isochronous resource allocation failed\n" ); |
197 | } |
198 | |
199 | mutex_unlock(lock: &r->mutex); |
200 | |
201 | return channel; |
202 | } |
203 | EXPORT_SYMBOL(fw_iso_resources_update); |
204 | |
205 | /** |
206 | * fw_iso_resources_free - frees allocated resources |
207 | * @r: the resource manager |
208 | * |
209 | * This function deallocates the channel and bandwidth, if allocated. |
210 | */ |
211 | void fw_iso_resources_free(struct fw_iso_resources *r) |
212 | { |
213 | struct fw_card *card; |
214 | int bandwidth, channel; |
215 | |
216 | /* Not initialized. */ |
217 | if (r->unit == NULL) |
218 | return; |
219 | card = fw_parent_device(r->unit)->card; |
220 | |
221 | mutex_lock(&r->mutex); |
222 | |
223 | if (r->allocated) { |
224 | bandwidth = r->bandwidth + r->bandwidth_overhead; |
225 | fw_iso_resource_manage(card, generation: r->generation, channels_mask: 1uLL << r->channel, |
226 | channel: &channel, bandwidth: &bandwidth, allocate: false); |
227 | if (channel < 0) |
228 | dev_err(&r->unit->device, |
229 | "isochronous resource deallocation failed\n" ); |
230 | |
231 | r->allocated = false; |
232 | } |
233 | |
234 | mutex_unlock(lock: &r->mutex); |
235 | } |
236 | EXPORT_SYMBOL(fw_iso_resources_free); |
237 | |