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 = 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 } 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(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(&card->lock); 118 r->generation = card->generation; 119 r->bandwidth_overhead = current_bandwidth_overhead(card); 120 spin_unlock_irq(&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, r->generation, r->channels_mask, 130 &channel, &bandwidth, true); 131 if (channel == -EAGAIN) { 132 mutex_unlock(&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(&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(&r->mutex); 173 return 0; 174 } 175 176 spin_lock_irq(&card->lock); 177 r->generation = card->generation; 178 r->bandwidth_overhead = current_bandwidth_overhead(card); 179 spin_unlock_irq(&card->lock); 180 181 bandwidth = r->bandwidth + r->bandwidth_overhead; 182 183 fw_iso_resource_manage(card, r->generation, 1uLL << r->channel, 184 &channel, &bandwidth, 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(&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, r->generation, 1uLL << r->channel, 226 &channel, &bandwidth, 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(&r->mutex); 235 } 236 EXPORT_SYMBOL(fw_iso_resources_free); 237