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| 1 | +// SPDX-License-Identifier: GPL-2.0 |
| 2 | +/* |
| 3 | + * Virtio Transport driver for Arm System Control and Management Interface |
| 4 | + * (SCMI). |
| 5 | + * |
| 6 | + * Copyright (C) 2020-2021 OpenSynergy. |
| 7 | + * Copyright (C) 2021 ARM Ltd. |
| 8 | + */ |
| 9 | + |
| 10 | +/** |
| 11 | + * DOC: Theory of Operation |
| 12 | + * |
| 13 | + * The scmi-virtio transport implements a driver for the virtio SCMI device. |
| 14 | + * |
| 15 | + * There is one Tx channel (virtio cmdq, A2P channel) and at most one Rx |
| 16 | + * channel (virtio eventq, P2A channel). Each channel is implemented through a |
| 17 | + * virtqueue. Access to each virtqueue is protected by spinlocks. |
| 18 | + */ |
| 19 | + |
| 20 | +#include <linux/errno.h> |
| 21 | +#include <linux/slab.h> |
| 22 | +#include <linux/virtio.h> |
| 23 | +#include <linux/virtio_config.h> |
| 24 | + |
| 25 | +#include <uapi/linux/virtio_ids.h> |
| 26 | +#include <uapi/linux/virtio_scmi.h> |
| 27 | + |
| 28 | +#include "common.h" |
| 29 | + |
| 30 | +#define VIRTIO_SCMI_MAX_MSG_SIZE 128 /* Value may be increased. */ |
| 31 | +#define VIRTIO_SCMI_MAX_PDU_SIZE \ |
| 32 | + (VIRTIO_SCMI_MAX_MSG_SIZE + SCMI_MSG_MAX_PROT_OVERHEAD) |
| 33 | +#define DESCRIPTORS_PER_TX_MSG 2 |
| 34 | + |
| 35 | +/** |
| 36 | + * struct scmi_vio_channel - Transport channel information |
| 37 | + * |
| 38 | + * @vqueue: Associated virtqueue |
| 39 | + * @cinfo: SCMI Tx or Rx channel |
| 40 | + * @free_list: List of unused scmi_vio_msg, maintained for Tx channels only |
| 41 | + * @is_rx: Whether channel is an Rx channel |
| 42 | + * @ready: Whether transport user is ready to hear about channel |
| 43 | + * @max_msg: Maximum number of pending messages for this channel. |
| 44 | + * @lock: Protects access to all members except ready. |
| 45 | + * @ready_lock: Protects access to ready. If required, it must be taken before |
| 46 | + * lock. |
| 47 | + */ |
| 48 | +struct scmi_vio_channel { |
| 49 | + struct virtqueue *vqueue; |
| 50 | + struct scmi_chan_info *cinfo; |
| 51 | + struct list_head free_list; |
| 52 | + bool is_rx; |
| 53 | + bool ready; |
| 54 | + unsigned int max_msg; |
| 55 | + /* lock to protect access to all members except ready. */ |
| 56 | + spinlock_t lock; |
| 57 | + /* lock to rotects access to ready flag. */ |
| 58 | + spinlock_t ready_lock; |
| 59 | +}; |
| 60 | + |
| 61 | +/** |
| 62 | + * struct scmi_vio_msg - Transport PDU information |
| 63 | + * |
| 64 | + * @request: SDU used for commands |
| 65 | + * @input: SDU used for (delayed) responses and notifications |
| 66 | + * @list: List which scmi_vio_msg may be part of |
| 67 | + * @rx_len: Input SDU size in bytes, once input has been received |
| 68 | + */ |
| 69 | +struct scmi_vio_msg { |
| 70 | + struct scmi_msg_payld *request; |
| 71 | + struct scmi_msg_payld *input; |
| 72 | + struct list_head list; |
| 73 | + unsigned int rx_len; |
| 74 | +}; |
| 75 | + |
| 76 | +/* Only one SCMI VirtIO device can possibly exist */ |
| 77 | +static struct virtio_device *scmi_vdev; |
| 78 | + |
| 79 | +static bool scmi_vio_have_vq_rx(struct virtio_device *vdev) |
| 80 | +{ |
| 81 | + return virtio_has_feature(vdev, VIRTIO_SCMI_F_P2A_CHANNELS); |
| 82 | +} |
| 83 | + |
| 84 | +static int scmi_vio_feed_vq_rx(struct scmi_vio_channel *vioch, |
| 85 | + struct scmi_vio_msg *msg) |
| 86 | +{ |
| 87 | + struct scatterlist sg_in; |
| 88 | + int rc; |
| 89 | + unsigned long flags; |
| 90 | + |
| 91 | + sg_init_one(&sg_in, msg->input, VIRTIO_SCMI_MAX_PDU_SIZE); |
| 92 | + |
| 93 | + spin_lock_irqsave(&vioch->lock, flags); |
| 94 | + |
| 95 | + rc = virtqueue_add_inbuf(vioch->vqueue, &sg_in, 1, msg, GFP_ATOMIC); |
| 96 | + if (rc) |
| 97 | + dev_err_once(vioch->cinfo->dev, |
| 98 | + "failed to add to virtqueue (%d)\n", rc); |
| 99 | + else |
| 100 | + virtqueue_kick(vioch->vqueue); |
| 101 | + |
| 102 | + spin_unlock_irqrestore(&vioch->lock, flags); |
| 103 | + |
| 104 | + return rc; |
| 105 | +} |
| 106 | + |
| 107 | +static void scmi_finalize_message(struct scmi_vio_channel *vioch, |
| 108 | + struct scmi_vio_msg *msg) |
| 109 | +{ |
| 110 | + if (vioch->is_rx) { |
| 111 | + scmi_vio_feed_vq_rx(vioch, msg); |
| 112 | + } else { |
| 113 | + unsigned long flags; |
| 114 | + |
| 115 | + spin_lock_irqsave(&vioch->lock, flags); |
| 116 | + list_add(&msg->list, &vioch->free_list); |
| 117 | + spin_unlock_irqrestore(&vioch->lock, flags); |
| 118 | + } |
| 119 | +} |
| 120 | + |
| 121 | +static void scmi_vio_complete_cb(struct virtqueue *vqueue) |
| 122 | +{ |
| 123 | + unsigned long ready_flags; |
| 124 | + unsigned long flags; |
| 125 | + unsigned int length; |
| 126 | + struct scmi_vio_channel *vioch; |
| 127 | + struct scmi_vio_msg *msg; |
| 128 | + bool cb_enabled = true; |
| 129 | + |
| 130 | + if (WARN_ON_ONCE(!vqueue->vdev->priv)) |
| 131 | + return; |
| 132 | + vioch = &((struct scmi_vio_channel *)vqueue->vdev->priv)[vqueue->index]; |
| 133 | + |
| 134 | + for (;;) { |
| 135 | + spin_lock_irqsave(&vioch->ready_lock, ready_flags); |
| 136 | + |
| 137 | + if (!vioch->ready) { |
| 138 | + if (!cb_enabled) |
| 139 | + (void)virtqueue_enable_cb(vqueue); |
| 140 | + goto unlock_ready_out; |
| 141 | + } |
| 142 | + |
| 143 | + spin_lock_irqsave(&vioch->lock, flags); |
| 144 | + if (cb_enabled) { |
| 145 | + virtqueue_disable_cb(vqueue); |
| 146 | + cb_enabled = false; |
| 147 | + } |
| 148 | + msg = virtqueue_get_buf(vqueue, &length); |
| 149 | + if (!msg) { |
| 150 | + if (virtqueue_enable_cb(vqueue)) |
| 151 | + goto unlock_out; |
| 152 | + cb_enabled = true; |
| 153 | + } |
| 154 | + spin_unlock_irqrestore(&vioch->lock, flags); |
| 155 | + |
| 156 | + if (msg) { |
| 157 | + msg->rx_len = length; |
| 158 | + scmi_rx_callback(vioch->cinfo, |
| 159 | + msg_read_header(msg->input), msg); |
| 160 | + |
| 161 | + scmi_finalize_message(vioch, msg); |
| 162 | + } |
| 163 | + |
| 164 | + spin_unlock_irqrestore(&vioch->ready_lock, ready_flags); |
| 165 | + } |
| 166 | + |
| 167 | +unlock_out: |
| 168 | + spin_unlock_irqrestore(&vioch->lock, flags); |
| 169 | +unlock_ready_out: |
| 170 | + spin_unlock_irqrestore(&vioch->ready_lock, ready_flags); |
| 171 | +} |
| 172 | + |
| 173 | +static const char *const scmi_vio_vqueue_names[] = { "tx", "rx" }; |
| 174 | + |
| 175 | +static vq_callback_t *scmi_vio_complete_callbacks[] = { |
| 176 | + scmi_vio_complete_cb, |
| 177 | + scmi_vio_complete_cb |
| 178 | +}; |
| 179 | + |
| 180 | +static unsigned int virtio_get_max_msg(struct scmi_chan_info *base_cinfo) |
| 181 | +{ |
| 182 | + struct scmi_vio_channel *vioch = base_cinfo->transport_info; |
| 183 | + |
| 184 | + return vioch->max_msg; |
| 185 | +} |
| 186 | + |
| 187 | +static int virtio_link_supplier(struct device *dev) |
| 188 | +{ |
| 189 | + if (!scmi_vdev) { |
| 190 | + dev_notice_once(dev, |
| 191 | + "Deferring probe after not finding a bound scmi-virtio device\n"); |
| 192 | + return -EPROBE_DEFER; |
| 193 | + } |
| 194 | + |
| 195 | + if (!device_link_add(dev, &scmi_vdev->dev, |
| 196 | + DL_FLAG_AUTOREMOVE_CONSUMER)) { |
| 197 | + dev_err(dev, "Adding link to supplier virtio device failed\n"); |
| 198 | + return -ECANCELED; |
| 199 | + } |
| 200 | + |
| 201 | + return 0; |
| 202 | +} |
| 203 | + |
| 204 | +static bool virtio_chan_available(struct device *dev, int idx) |
| 205 | +{ |
| 206 | + struct scmi_vio_channel *channels, *vioch = NULL; |
| 207 | + |
| 208 | + if (WARN_ON_ONCE(!scmi_vdev)) |
| 209 | + return false; |
| 210 | + |
| 211 | + channels = (struct scmi_vio_channel *)scmi_vdev->priv; |
| 212 | + |
| 213 | + switch (idx) { |
| 214 | + case VIRTIO_SCMI_VQ_TX: |
| 215 | + vioch = &channels[VIRTIO_SCMI_VQ_TX]; |
| 216 | + break; |
| 217 | + case VIRTIO_SCMI_VQ_RX: |
| 218 | + if (scmi_vio_have_vq_rx(scmi_vdev)) |
| 219 | + vioch = &channels[VIRTIO_SCMI_VQ_RX]; |
| 220 | + break; |
| 221 | + default: |
| 222 | + return false; |
| 223 | + } |
| 224 | + |
| 225 | + return vioch && !vioch->cinfo ? true : false; |
| 226 | +} |
| 227 | + |
| 228 | +static int virtio_chan_setup(struct scmi_chan_info *cinfo, struct device *dev, |
| 229 | + bool tx) |
| 230 | +{ |
| 231 | + unsigned long flags; |
| 232 | + struct scmi_vio_channel *vioch; |
| 233 | + int index = tx ? VIRTIO_SCMI_VQ_TX : VIRTIO_SCMI_VQ_RX; |
| 234 | + int i; |
| 235 | + |
| 236 | + if (!scmi_vdev) |
| 237 | + return -EPROBE_DEFER; |
| 238 | + |
| 239 | + vioch = &((struct scmi_vio_channel *)scmi_vdev->priv)[index]; |
| 240 | + |
| 241 | + for (i = 0; i < vioch->max_msg; i++) { |
| 242 | + struct scmi_vio_msg *msg; |
| 243 | + |
| 244 | + msg = devm_kzalloc(cinfo->dev, sizeof(*msg), GFP_KERNEL); |
| 245 | + if (!msg) |
| 246 | + return -ENOMEM; |
| 247 | + |
| 248 | + if (tx) { |
| 249 | + msg->request = devm_kzalloc(cinfo->dev, |
| 250 | + VIRTIO_SCMI_MAX_PDU_SIZE, |
| 251 | + GFP_KERNEL); |
| 252 | + if (!msg->request) |
| 253 | + return -ENOMEM; |
| 254 | + } |
| 255 | + |
| 256 | + msg->input = devm_kzalloc(cinfo->dev, VIRTIO_SCMI_MAX_PDU_SIZE, |
| 257 | + GFP_KERNEL); |
| 258 | + if (!msg->input) |
| 259 | + return -ENOMEM; |
| 260 | + |
| 261 | + if (tx) { |
| 262 | + spin_lock_irqsave(&vioch->lock, flags); |
| 263 | + list_add_tail(&msg->list, &vioch->free_list); |
| 264 | + spin_unlock_irqrestore(&vioch->lock, flags); |
| 265 | + } else { |
| 266 | + scmi_vio_feed_vq_rx(vioch, msg); |
| 267 | + } |
| 268 | + } |
| 269 | + |
| 270 | + spin_lock_irqsave(&vioch->lock, flags); |
| 271 | + cinfo->transport_info = vioch; |
| 272 | + /* Indirectly setting channel not available any more */ |
| 273 | + vioch->cinfo = cinfo; |
| 274 | + spin_unlock_irqrestore(&vioch->lock, flags); |
| 275 | + |
| 276 | + spin_lock_irqsave(&vioch->ready_lock, flags); |
| 277 | + vioch->ready = true; |
| 278 | + spin_unlock_irqrestore(&vioch->ready_lock, flags); |
| 279 | + |
| 280 | + return 0; |
| 281 | +} |
| 282 | + |
| 283 | +static int virtio_chan_free(int id, void *p, void *data) |
| 284 | +{ |
| 285 | + unsigned long flags; |
| 286 | + struct scmi_chan_info *cinfo = p; |
| 287 | + struct scmi_vio_channel *vioch = cinfo->transport_info; |
| 288 | + |
| 289 | + spin_lock_irqsave(&vioch->ready_lock, flags); |
| 290 | + vioch->ready = false; |
| 291 | + spin_unlock_irqrestore(&vioch->ready_lock, flags); |
| 292 | + |
| 293 | + scmi_free_channel(cinfo, data, id); |
| 294 | + |
| 295 | + spin_lock_irqsave(&vioch->lock, flags); |
| 296 | + vioch->cinfo = NULL; |
| 297 | + spin_unlock_irqrestore(&vioch->lock, flags); |
| 298 | + |
| 299 | + return 0; |
| 300 | +} |
| 301 | + |
| 302 | +static int virtio_send_message(struct scmi_chan_info *cinfo, |
| 303 | + struct scmi_xfer *xfer) |
| 304 | +{ |
| 305 | + struct scmi_vio_channel *vioch = cinfo->transport_info; |
| 306 | + struct scatterlist sg_out; |
| 307 | + struct scatterlist sg_in; |
| 308 | + struct scatterlist *sgs[DESCRIPTORS_PER_TX_MSG] = { &sg_out, &sg_in }; |
| 309 | + unsigned long flags; |
| 310 | + int rc; |
| 311 | + struct scmi_vio_msg *msg; |
| 312 | + |
| 313 | + spin_lock_irqsave(&vioch->lock, flags); |
| 314 | + |
| 315 | + if (list_empty(&vioch->free_list)) { |
| 316 | + spin_unlock_irqrestore(&vioch->lock, flags); |
| 317 | + return -EBUSY; |
| 318 | + } |
| 319 | + |
| 320 | + msg = list_first_entry(&vioch->free_list, typeof(*msg), list); |
| 321 | + list_del(&msg->list); |
| 322 | + |
| 323 | + msg_tx_prepare(msg->request, xfer); |
| 324 | + |
| 325 | + sg_init_one(&sg_out, msg->request, msg_command_size(xfer)); |
| 326 | + sg_init_one(&sg_in, msg->input, msg_response_size(xfer)); |
| 327 | + |
| 328 | + rc = virtqueue_add_sgs(vioch->vqueue, sgs, 1, 1, msg, GFP_ATOMIC); |
| 329 | + if (rc) { |
| 330 | + list_add(&msg->list, &vioch->free_list); |
| 331 | + dev_err_once(vioch->cinfo->dev, |
| 332 | + "%s() failed to add to virtqueue (%d)\n", __func__, |
| 333 | + rc); |
| 334 | + } else { |
| 335 | + virtqueue_kick(vioch->vqueue); |
| 336 | + } |
| 337 | + |
| 338 | + spin_unlock_irqrestore(&vioch->lock, flags); |
| 339 | + |
| 340 | + return rc; |
| 341 | +} |
| 342 | + |
| 343 | +static void virtio_fetch_response(struct scmi_chan_info *cinfo, |
| 344 | + struct scmi_xfer *xfer) |
| 345 | +{ |
| 346 | + struct scmi_vio_msg *msg = xfer->priv; |
| 347 | + |
| 348 | + if (msg) { |
| 349 | + msg_fetch_response(msg->input, msg->rx_len, xfer); |
| 350 | + xfer->priv = NULL; |
| 351 | + } |
| 352 | +} |
| 353 | + |
| 354 | +static void virtio_fetch_notification(struct scmi_chan_info *cinfo, |
| 355 | + size_t max_len, struct scmi_xfer *xfer) |
| 356 | +{ |
| 357 | + struct scmi_vio_msg *msg = xfer->priv; |
| 358 | + |
| 359 | + if (msg) { |
| 360 | + msg_fetch_notification(msg->input, msg->rx_len, max_len, xfer); |
| 361 | + xfer->priv = NULL; |
| 362 | + } |
| 363 | +} |
| 364 | + |
| 365 | +static const struct scmi_transport_ops scmi_virtio_ops = { |
| 366 | + .link_supplier = virtio_link_supplier, |
| 367 | + .chan_available = virtio_chan_available, |
| 368 | + .chan_setup = virtio_chan_setup, |
| 369 | + .chan_free = virtio_chan_free, |
| 370 | + .get_max_msg = virtio_get_max_msg, |
| 371 | + .send_message = virtio_send_message, |
| 372 | + .fetch_response = virtio_fetch_response, |
| 373 | + .fetch_notification = virtio_fetch_notification, |
| 374 | +}; |
| 375 | + |
| 376 | +static int scmi_vio_probe(struct virtio_device *vdev) |
| 377 | +{ |
| 378 | + struct device *dev = &vdev->dev; |
| 379 | + struct scmi_vio_channel *channels; |
| 380 | + bool have_vq_rx; |
| 381 | + int vq_cnt; |
| 382 | + int i; |
| 383 | + int ret; |
| 384 | + struct virtqueue *vqs[VIRTIO_SCMI_VQ_MAX_CNT]; |
| 385 | + |
| 386 | + /* Only one SCMI VirtiO device allowed */ |
| 387 | + if (scmi_vdev) |
| 388 | + return -EINVAL; |
| 389 | + |
| 390 | + have_vq_rx = scmi_vio_have_vq_rx(vdev); |
| 391 | + vq_cnt = have_vq_rx ? VIRTIO_SCMI_VQ_MAX_CNT : 1; |
| 392 | + |
| 393 | + channels = devm_kcalloc(dev, vq_cnt, sizeof(*channels), GFP_KERNEL); |
| 394 | + if (!channels) |
| 395 | + return -ENOMEM; |
| 396 | + |
| 397 | + if (have_vq_rx) |
| 398 | + channels[VIRTIO_SCMI_VQ_RX].is_rx = true; |
| 399 | + |
| 400 | + ret = virtio_find_vqs(vdev, vq_cnt, vqs, scmi_vio_complete_callbacks, |
| 401 | + scmi_vio_vqueue_names, NULL); |
| 402 | + if (ret) { |
| 403 | + dev_err(dev, "Failed to get %d virtqueue(s)\n", vq_cnt); |
| 404 | + return ret; |
| 405 | + } |
| 406 | + |
| 407 | + for (i = 0; i < vq_cnt; i++) { |
| 408 | + unsigned int sz; |
| 409 | + |
| 410 | + spin_lock_init(&channels[i].lock); |
| 411 | + spin_lock_init(&channels[i].ready_lock); |
| 412 | + INIT_LIST_HEAD(&channels[i].free_list); |
| 413 | + channels[i].vqueue = vqs[i]; |
| 414 | + |
| 415 | + sz = virtqueue_get_vring_size(channels[i].vqueue); |
| 416 | + /* Tx messages need multiple descriptors. */ |
| 417 | + if (!channels[i].is_rx) |
| 418 | + sz /= DESCRIPTORS_PER_TX_MSG; |
| 419 | + |
| 420 | + if (sz > MSG_TOKEN_MAX) { |
| 421 | + dev_info_once(dev, |
| 422 | + "%s virtqueue could hold %d messages. Only %ld allowed to be pending.\n", |
| 423 | + channels[i].is_rx ? "rx" : "tx", |
| 424 | + sz, MSG_TOKEN_MAX); |
| 425 | + sz = MSG_TOKEN_MAX; |
| 426 | + } |
| 427 | + channels[i].max_msg = sz; |
| 428 | + } |
| 429 | + |
| 430 | + vdev->priv = channels; |
| 431 | + scmi_vdev = vdev; |
| 432 | + |
| 433 | + return 0; |
| 434 | +} |
| 435 | + |
| 436 | +static void scmi_vio_remove(struct virtio_device *vdev) |
| 437 | +{ |
| 438 | + vdev->config->reset(vdev); |
| 439 | + vdev->config->del_vqs(vdev); |
| 440 | + scmi_vdev = NULL; |
| 441 | +} |
| 442 | + |
| 443 | +static int scmi_vio_validate(struct virtio_device *vdev) |
| 444 | +{ |
| 445 | + if (!virtio_has_feature(vdev, VIRTIO_F_VERSION_1)) { |
| 446 | + dev_err(&vdev->dev, |
| 447 | + "device does not comply with spec version 1.x\n"); |
| 448 | + return -EINVAL; |
| 449 | + } |
| 450 | + |
| 451 | + return 0; |
| 452 | +} |
| 453 | + |
| 454 | +static unsigned int features[] = { |
| 455 | + VIRTIO_SCMI_F_P2A_CHANNELS, |
| 456 | +}; |
| 457 | + |
| 458 | +static const struct virtio_device_id id_table[] = { |
| 459 | + { VIRTIO_ID_SCMI, VIRTIO_DEV_ANY_ID }, |
| 460 | + { 0 } |
| 461 | +}; |
| 462 | + |
| 463 | +static struct virtio_driver virtio_scmi_driver = { |
| 464 | + .driver.name = "scmi-virtio", |
| 465 | + .driver.owner = THIS_MODULE, |
| 466 | + .feature_table = features, |
| 467 | + .feature_table_size = ARRAY_SIZE(features), |
| 468 | + .id_table = id_table, |
| 469 | + .probe = scmi_vio_probe, |
| 470 | + .remove = scmi_vio_remove, |
| 471 | + .validate = scmi_vio_validate, |
| 472 | +}; |
| 473 | + |
| 474 | +static int __init virtio_scmi_init(void) |
| 475 | +{ |
| 476 | + return register_virtio_driver(&virtio_scmi_driver); |
| 477 | +} |
| 478 | + |
| 479 | +static void __exit virtio_scmi_exit(void) |
| 480 | +{ |
| 481 | + unregister_virtio_driver(&virtio_scmi_driver); |
| 482 | +} |
| 483 | + |
| 484 | +const struct scmi_desc scmi_virtio_desc = { |
| 485 | + .transport_init = virtio_scmi_init, |
| 486 | + .transport_exit = virtio_scmi_exit, |
| 487 | + .ops = &scmi_virtio_ops, |
| 488 | + .max_rx_timeout_ms = 60000, /* for non-realtime virtio devices */ |
| 489 | + .max_msg = 0, /* overridden by virtio_get_max_msg() */ |
| 490 | + .max_msg_size = VIRTIO_SCMI_MAX_MSG_SIZE, |
| 491 | +}; |