drivers/usb/host/fhci-tds.c

   1 // SPDX-License-Identifier: GPL-2.0+
   2 /*
   3  * Freescale QUICC Engine USB Host Controller Driver
   4  *
   5  * Copyright (c) Freescale Semicondutor, Inc. 2006.
   6  *               Shlomi Gridish <gridish@freescale.com>
   7  *               Jerry Huang <Chang-Ming.Huang@freescale.com>
   8  * Copyright (c) Logic Product Development, Inc. 2007
   9  *               Peter Barada <peterb@logicpd.com>
  10  * Copyright (c) MontaVista Software, Inc. 2008.
  11  *               Anton Vorontsov <avorontsov@ru.mvista.com>
  12  */
  13
  14 #include <linux/kernel.h>
  15 #include <linux/types.h>
  16 #include <linux/errno.h>
  17 #include <linux/slab.h>
  18 #include <linux/list.h>
  19 #include <linux/io.h>
  20 #include <linux/usb.h>
  21 #include <linux/usb/hcd.h>
  22 #include "fhci.h"
  23
  24 #define DUMMY_BD_BUFFER  0xdeadbeef
  25 #define DUMMY2_BD_BUFFER 0xbaadf00d
  26
  27 /* Transaction Descriptors bits */
  28 #define TD_R            0x8000 /* ready bit */
  29 #define TD_W            0x2000 /* wrap bit */
  30 #define TD_I            0x1000 /* interrupt on completion */
  31 #define TD_L            0x0800 /* last */
  32 #define TD_TC           0x0400 /* transmit CRC */
  33 #define TD_CNF          0x0200 /* CNF - Must be always 1 */
  34 #define TD_LSP          0x0100 /* Low-speed transaction */
  35 #define TD_PID          0x00c0 /* packet id */
  36 #define TD_RXER         0x0020 /* Rx error or not */
  37
  38 #define TD_NAK          0x0010 /* No ack. */
  39 #define TD_STAL         0x0008 /* Stall received */
  40 #define TD_TO           0x0004 /* time out */
  41 #define TD_UN           0x0002 /* underrun */
  42 #define TD_NO           0x0010 /* Rx Non Octet Aligned Packet */
  43 #define TD_AB           0x0008 /* Frame Aborted */
  44 #define TD_CR           0x0004 /* CRC Error */
  45 #define TD_OV           0x0002 /* Overrun */
  46 #define TD_BOV          0x0001 /* Buffer Overrun */
  47
  48 #define TD_ERRORS       (TD_NAK | TD_STAL | TD_TO | TD_UN | \
  49                          TD_NO | TD_AB | TD_CR | TD_OV | TD_BOV)
  50
  51 #define TD_PID_DATA0    0x0080 /* Data 0 toggle */
  52 #define TD_PID_DATA1    0x00c0 /* Data 1 toggle */
  53 #define TD_PID_TOGGLE   0x00c0 /* Data 0/1 toggle mask */
  54
  55 #define TD_TOK_SETUP    0x0000
  56 #define TD_TOK_OUT      0x4000
  57 #define TD_TOK_IN       0x8000
  58 #define TD_ISO          0x1000
  59 #define TD_ENDP         0x0780
  60 #define TD_ADDR         0x007f
  61
  62 #define TD_ENDP_SHIFT 7
  63
  64 struct usb_td {
  65         __be16 status;
  66         __be16 length;
  67         __be32 buf_ptr;
  68         __be16 extra;
  69         __be16 reserved;
  70 };
  71
  72 static struct usb_td __iomem *next_bd(struct usb_td __iomem *base,
  73                                       struct usb_td __iomem *td,
  74                                       u16 status)
  75 {
  76         if (status & TD_W)
  77                 return base;
  78         else
  79                 return ++td;
  80 }
  81
  82 void fhci_push_dummy_bd(struct endpoint *ep)
  83 {
  84         if (!ep->already_pushed_dummy_bd) {
  85                 u16 td_status = in_be16(&ep->empty_td->status);
  86
  87                 out_be32(&ep->empty_td->buf_ptr, DUMMY_BD_BUFFER);
  88                 /* get the next TD in the ring */
  89                 ep->empty_td = next_bd(ep->td_base, ep->empty_td, td_status);
  90                 ep->already_pushed_dummy_bd = true;
  91         }
  92 }
  93
  94 /* destroy an USB endpoint */
  95 void fhci_ep0_free(struct fhci_usb *usb)
  96 {
  97         struct endpoint *ep;
  98         int size;
  99
 100         ep = usb->ep0;
 101         if (ep) {
 102                 if (ep->td_base)
 103                         cpm_muram_free(cpm_muram_offset(ep->td_base));
 104
 105                 if (kfifo_initialized(&ep->conf_frame_Q)) {
 106                         size = cq_howmany(&ep->conf_frame_Q);
 107                         for (; size; size--) {
 108                                 struct packet *pkt = cq_get(&ep->conf_frame_Q);
 109
 110                                 kfree(pkt);
 111                         }
 112                         cq_delete(&ep->conf_frame_Q);
 113                 }
 114
 115                 if (kfifo_initialized(&ep->empty_frame_Q)) {
 116                         size = cq_howmany(&ep->empty_frame_Q);
 117                         for (; size; size--) {
 118                                 struct packet *pkt = cq_get(&ep->empty_frame_Q);
 119
 120                                 kfree(pkt);
 121                         }
 122                         cq_delete(&ep->empty_frame_Q);
 123                 }
 124
 125                 if (kfifo_initialized(&ep->dummy_packets_Q)) {
 126                         size = cq_howmany(&ep->dummy_packets_Q);
 127                         for (; size; size--) {
 128                                 u8 *buff = cq_get(&ep->dummy_packets_Q);
 129
 130                                 kfree(buff);
 131                         }
 132                         cq_delete(&ep->dummy_packets_Q);
 133                 }
 134
 135                 kfree(ep);
 136                 usb->ep0 = NULL;
 137         }
 138 }
 139
 140 /*
 141  * create the endpoint structure
 142  *
 143  * arguments:
 144  * usb          A pointer to the data structure of the USB
 145  * data_mem     The data memory partition(BUS)
 146  * ring_len     TD ring length
 147  */
 148 u32 fhci_create_ep(struct fhci_usb *usb, enum fhci_mem_alloc data_mem,
 149                            u32 ring_len)
 150 {
 151         struct endpoint *ep;
 152         struct usb_td __iomem *td;
 153         unsigned long ep_offset;
 154         char *err_for = "endpoint PRAM";
 155         int ep_mem_size;
 156         u32 i;
 157
 158         /* we need at least 3 TDs in the ring */
 159         if (!(ring_len > 2)) {
 160                 fhci_err(usb->fhci, "illegal TD ring length parameters\n");
 161                 return -EINVAL;
 162         }
 163
 164         ep = kzalloc(sizeof(*ep), GFP_KERNEL);
 165         if (!ep)
 166                 return -ENOMEM;
 167
 168         ep_mem_size = ring_len * sizeof(*td) + sizeof(struct fhci_ep_pram);
 169         ep_offset = cpm_muram_alloc(ep_mem_size, 32);
 170         if (IS_ERR_VALUE(ep_offset))
 171                 goto err;
 172         ep->td_base = cpm_muram_addr(ep_offset);
 173
 174         /* zero all queue pointers */
 175         if (cq_new(&ep->conf_frame_Q, ring_len + 2) ||
 176             cq_new(&ep->empty_frame_Q, ring_len + 2) ||
 177             cq_new(&ep->dummy_packets_Q, ring_len + 2)) {
 178                 err_for = "frame_queues";
 179                 goto err;
 180         }
 181
 182         for (i = 0; i < (ring_len + 1); i++) {
 183                 struct packet *pkt;
 184                 u8 *buff;
 185
 186                 pkt = kmalloc(sizeof(*pkt), GFP_KERNEL);
 187                 if (!pkt) {
 188                         err_for = "frame";
 189                         goto err;
 190                 }
 191
 192                 buff = kmalloc_array(1028, sizeof(*buff), GFP_KERNEL);
 193                 if (!buff) {
 194                         kfree(pkt);
 195                         err_for = "buffer";
 196                         goto err;
 197                 }
 198                 cq_put(&ep->empty_frame_Q, pkt);
 199                 cq_put(&ep->dummy_packets_Q, buff);
 200         }
 201
 202         /* we put the endpoint parameter RAM right behind the TD ring */
 203         ep->ep_pram_ptr = (void __iomem *)ep->td_base + sizeof(*td) * ring_len;
 204
 205         ep->conf_td = ep->td_base;
 206         ep->empty_td = ep->td_base;
 207
 208         ep->already_pushed_dummy_bd = false;
 209
 210         /* initialize tds */
 211         td = ep->td_base;
 212         for (i = 0; i < ring_len; i++) {
 213                 out_be32(&td->buf_ptr, 0);
 214                 out_be16(&td->status, 0);
 215                 out_be16(&td->length, 0);
 216                 out_be16(&td->extra, 0);
 217                 td++;
 218         }
 219         td--;
 220         out_be16(&td->status, TD_W); /* for last TD set Wrap bit */
 221         out_be16(&td->length, 0);
 222
 223         /* endpoint structure has been created */
 224         usb->ep0 = ep;
 225
 226         return 0;
 227 err:
 228         fhci_ep0_free(usb);
 229         kfree(ep);
 230         fhci_err(usb->fhci, "no memory for the %s\n", err_for);
 231         return -ENOMEM;
 232 }
 233
 234 /*
 235  * initialize the endpoint register according to the given parameters
 236  *
 237  * artuments:
 238  * usb          A pointer to the data strucutre of the USB
 239  * ep           A pointer to the endpoint structre
 240  * data_mem     The data memory partition(BUS)
 241  */
 242 void fhci_init_ep_registers(struct fhci_usb *usb, struct endpoint *ep,
 243                             enum fhci_mem_alloc data_mem)
 244 {
 245         u8 rt;
 246
 247         /* set the endpoint registers according to the endpoint */
 248         out_be16(&usb->fhci->regs->usb_usep[0],
 249                  USB_TRANS_CTR | USB_EP_MF | USB_EP_RTE);
 250         out_be16(&usb->fhci->pram->ep_ptr[0],
 251                  cpm_muram_offset(ep->ep_pram_ptr));
 252
 253         rt = (BUS_MODE_BO_BE | BUS_MODE_GBL);
 254 #ifdef MULTI_DATA_BUS
 255         if (data_mem == MEM_SECONDARY)
 256                 rt |= BUS_MODE_DTB;
 257 #endif
 258         out_8(&ep->ep_pram_ptr->rx_func_code, rt);
 259         out_8(&ep->ep_pram_ptr->tx_func_code, rt);
 260         out_be16(&ep->ep_pram_ptr->rx_buff_len, 1028);
 261         out_be16(&ep->ep_pram_ptr->rx_base, 0);
 262         out_be16(&ep->ep_pram_ptr->tx_base, cpm_muram_offset(ep->td_base));
 263         out_be16(&ep->ep_pram_ptr->rx_bd_ptr, 0);
 264         out_be16(&ep->ep_pram_ptr->tx_bd_ptr, cpm_muram_offset(ep->td_base));
 265         out_be32(&ep->ep_pram_ptr->tx_state, 0);
 266 }
 267
 268 /*
 269  * Collect the submitted frames and inform the application about them
 270  * It is also preparing the TDs for new frames. If the Tx interrupts
 271  * are disabled, the application should call that routine to get
 272  * confirmation about the submitted frames. Otherwise, the routine is
 273  * called from the interrupt service routine during the Tx interrupt.
 274  * In that case the application is informed by calling the application
 275  * specific 'fhci_transaction_confirm' routine
 276  */
 277 static void fhci_td_transaction_confirm(struct fhci_usb *usb)
 278 {
 279         struct endpoint *ep = usb->ep0;
 280         struct packet *pkt;
 281         struct usb_td __iomem *td;
 282         u16 extra_data;
 283         u16 td_status;
 284         u16 td_length;
 285         u32 buf;
 286
 287         /*
 288          * collect transmitted BDs from the chip. The routine clears all BDs
 289          * with R bit = 0 and the pointer to data buffer is not NULL, that is
 290          * BDs which point to the transmitted data buffer
 291          */
 292         while (1) {
 293                 td = ep->conf_td;
 294                 td_status = in_be16(&td->status);
 295                 td_length = in_be16(&td->length);
 296                 buf = in_be32(&td->buf_ptr);
 297                 extra_data = in_be16(&td->extra);
 298
 299                 /* check if the TD is empty */
 300                 if (!(!(td_status & TD_R) && ((td_status & ~TD_W) || buf)))
 301                         break;
 302                 /* check if it is a dummy buffer */
 303                 else if ((buf == DUMMY_BD_BUFFER) && !(td_status & ~TD_W))
 304                         break;
 305
 306                 /* mark TD as empty */
 307                 clrbits16(&td->status, ~TD_W);
 308                 out_be16(&td->length, 0);
 309                 out_be32(&td->buf_ptr, 0);
 310                 out_be16(&td->extra, 0);
 311                 /* advance the TD pointer */
 312                 ep->conf_td = next_bd(ep->td_base, ep->conf_td, td_status);
 313
 314                 /* check if it is a dummy buffer(type2) */
 315                 if ((buf == DUMMY2_BD_BUFFER) && !(td_status & ~TD_W))
 316                         continue;
 317
 318                 pkt = cq_get(&ep->conf_frame_Q);
 319                 if (!pkt)
 320                         fhci_err(usb->fhci, "no frame to confirm\n");
 321
 322                 if (td_status & TD_ERRORS) {
 323                         if (td_status & TD_RXER) {
 324                                 if (td_status & TD_CR)
 325                                         pkt->status = USB_TD_RX_ER_CRC;
 326                                 else if (td_status & TD_AB)
 327                                         pkt->status = USB_TD_RX_ER_BITSTUFF;
 328                                 else if (td_status & TD_OV)
 329                                         pkt->status = USB_TD_RX_ER_OVERUN;
 330                                 else if (td_status & TD_BOV)
 331                                         pkt->status = USB_TD_RX_DATA_OVERUN;
 332                                 else if (td_status & TD_NO)
 333                                         pkt->status = USB_TD_RX_ER_NONOCT;
 334                                 else
 335                                         fhci_err(usb->fhci, "illegal error "
 336                                                  "occurred\n");
 337                         } else if (td_status & TD_NAK)
 338                                 pkt->status = USB_TD_TX_ER_NAK;
 339                         else if (td_status & TD_TO)
 340                                 pkt->status = USB_TD_TX_ER_TIMEOUT;
 341                         else if (td_status & TD_UN)
 342                                 pkt->status = USB_TD_TX_ER_UNDERUN;
 343                         else if (td_status & TD_STAL)
 344                                 pkt->status = USB_TD_TX_ER_STALL;
 345                         else
 346                                 fhci_err(usb->fhci, "illegal error occurred\n");
 347                 } else if ((extra_data & TD_TOK_IN) &&
 348                                 pkt->len > td_length - CRC_SIZE) {
 349                         pkt->status = USB_TD_RX_DATA_UNDERUN;
 350                 }
 351
 352                 if (extra_data & TD_TOK_IN)
 353                         pkt->len = td_length - CRC_SIZE;
 354                 else if (pkt->info & PKT_ZLP)
 355                         pkt->len = 0;
 356                 else
 357                         pkt->len = td_length;
 358
 359                 fhci_transaction_confirm(usb, pkt);
 360         }
 361 }
 362
 363 /*
 364  * Submitting a data frame to a specified endpoint of a USB device
 365  * The frame is put in the driver's transmit queue for this endpoint
 366  *
 367  * Arguments:
 368  * usb          A pointer to the USB structure
 369  * pkt          A pointer to the user frame structure
 370  * trans_type   Transaction tyep - IN,OUT or SETUP
 371  * dest_addr    Device address - 0~127
 372  * dest_ep      Endpoint number of the device - 0~16
 373  * trans_mode   Pipe type - ISO,Interrupt,bulk or control
 374  * dest_speed   USB speed - Low speed or FULL speed
 375  * data_toggle  Data sequence toggle - 0 or 1
 376  */
 377 u32 fhci_host_transaction(struct fhci_usb *usb,
 378                           struct packet *pkt,
 379                           enum fhci_ta_type trans_type,
 380                           u8 dest_addr,
 381                           u8 dest_ep,
 382                           enum fhci_tf_mode trans_mode,
 383                           enum fhci_speed dest_speed, u8 data_toggle)
 384 {
 385         struct endpoint *ep = usb->ep0;
 386         struct usb_td __iomem *td;
 387         u16 extra_data;
 388         u16 td_status;
 389
 390         fhci_usb_disable_interrupt(usb);
 391         /* start from the next BD that should be filled */
 392         td = ep->empty_td;
 393         td_status = in_be16(&td->status);
 394
 395         if (td_status & TD_R && in_be16(&td->length)) {
 396                 /* if the TD is not free */
 397                 fhci_usb_enable_interrupt(usb);
 398                 return -1;
 399         }
 400
 401         /* get the next TD in the ring */
 402         ep->empty_td = next_bd(ep->td_base, ep->empty_td, td_status);
 403         fhci_usb_enable_interrupt(usb);
 404         pkt->priv_data = td;
 405         out_be32(&td->buf_ptr, virt_to_phys(pkt->data));
 406         /* sets up transaction parameters - addr,endp,dir,and type */
 407         extra_data = (dest_ep << TD_ENDP_SHIFT) | dest_addr;
 408         switch (trans_type) {
 409         case FHCI_TA_IN:
 410                 extra_data |= TD_TOK_IN;
 411                 break;
 412         case FHCI_TA_OUT:
 413                 extra_data |= TD_TOK_OUT;
 414                 break;
 415         case FHCI_TA_SETUP:
 416                 extra_data |= TD_TOK_SETUP;
 417                 break;
 418         }
 419         if (trans_mode == FHCI_TF_ISO)
 420                 extra_data |= TD_ISO;
 421         out_be16(&td->extra, extra_data);
 422
 423         /* sets up the buffer descriptor */
 424         td_status = ((td_status & TD_W) | TD_R | TD_L | TD_I | TD_CNF);
 425         if (!(pkt->info & PKT_NO_CRC))
 426                 td_status |= TD_TC;
 427
 428         switch (trans_type) {
 429         case FHCI_TA_IN:
 430                 if (data_toggle)
 431                         pkt->info |= PKT_PID_DATA1;
 432                 else
 433                         pkt->info |= PKT_PID_DATA0;
 434                 break;
 435         default:
 436                 if (data_toggle) {
 437                         td_status |= TD_PID_DATA1;
 438                         pkt->info |= PKT_PID_DATA1;
 439                 } else {
 440                         td_status |= TD_PID_DATA0;
 441                         pkt->info |= PKT_PID_DATA0;
 442                 }
 443                 break;
 444         }
 445
 446         if ((dest_speed == FHCI_LOW_SPEED) &&
 447             (usb->port_status == FHCI_PORT_FULL))
 448                 td_status |= TD_LSP;
 449
 450         out_be16(&td->status, td_status);
 451
 452         /* set up buffer length */
 453         if (trans_type == FHCI_TA_IN)
 454                 out_be16(&td->length, pkt->len + CRC_SIZE);
 455         else
 456                 out_be16(&td->length, pkt->len);
 457
 458         /* put the frame to the confirmation queue */
 459         cq_put(&ep->conf_frame_Q, pkt);
 460
 461         if (cq_howmany(&ep->conf_frame_Q) == 1)
 462                 out_8(&usb->fhci->regs->usb_uscom, USB_CMD_STR_FIFO);
 463
 464         return 0;
 465 }
 466
 467 /* Reset the Tx BD ring */
 468 void fhci_flush_bds(struct fhci_usb *usb)
 469 {
 470         u16 td_status;
 471         struct usb_td __iomem *td;
 472         struct endpoint *ep = usb->ep0;
 473
 474         td = ep->td_base;
 475         while (1) {
 476                 td_status = in_be16(&td->status);
 477                 in_be32(&td->buf_ptr);
 478                 in_be16(&td->extra);
 479
 480                 /* if the TD is not empty - we'll confirm it as Timeout */
 481                 if (td_status & TD_R)
 482                         out_be16(&td->status, (td_status & ~TD_R) | TD_TO);
 483                 /* if this TD is dummy - let's skip this TD */
 484                 else if (in_be32(&td->buf_ptr) == DUMMY_BD_BUFFER)
 485                         out_be32(&td->buf_ptr, DUMMY2_BD_BUFFER);
 486                 /* if this is the last TD - break */
 487                 if (td_status & TD_W)
 488                         break;
 489
 490                 td++;
 491         }
 492
 493         fhci_td_transaction_confirm(usb);
 494
 495         td = ep->td_base;
 496         do {
 497                 out_be16(&td->status, 0);
 498                 out_be16(&td->length, 0);
 499                 out_be32(&td->buf_ptr, 0);
 500                 out_be16(&td->extra, 0);
 501                 td++;
 502         } while (!(in_be16(&td->status) & TD_W));
 503         out_be16(&td->status, TD_W); /* for last TD set Wrap bit */
 504         out_be16(&td->length, 0);
 505         out_be32(&td->buf_ptr, 0);
 506         out_be16(&td->extra, 0);
 507
 508         out_be16(&ep->ep_pram_ptr->tx_bd_ptr,
 509                  in_be16(&ep->ep_pram_ptr->tx_base));
 510         out_be32(&ep->ep_pram_ptr->tx_state, 0);
 511         out_be16(&ep->ep_pram_ptr->tx_cnt, 0);
 512         ep->empty_td = ep->td_base;
 513         ep->conf_td = ep->td_base;
 514 }
 515
 516 /*
 517  * Flush all transmitted packets from TDs in the actual frame.
 518  * This routine is called when something wrong with the controller and
 519  * we want to get rid of the actual frame and start again next frame
 520  */
 521 void fhci_flush_actual_frame(struct fhci_usb *usb)
 522 {
 523         u8 mode;
 524         u16 tb_ptr;
 525         u16 td_status;
 526         u32 buf_ptr;
 527         struct usb_td __iomem *td;
 528         struct endpoint *ep = usb->ep0;
 529
 530         /* disable the USB controller */
 531         mode = in_8(&usb->fhci->regs->usb_usmod);
 532         out_8(&usb->fhci->regs->usb_usmod, mode & ~USB_MODE_EN);
 533
 534         tb_ptr = in_be16(&ep->ep_pram_ptr->tx_bd_ptr);
 535         td = cpm_muram_addr(tb_ptr);
 536         td_status = in_be16(&td->status);
 537         buf_ptr = in_be32(&td->buf_ptr);
 538         in_be16(&td->extra);
 539         do {
 540                 if (td_status & TD_R) {
 541                         out_be16(&td->status, (td_status & ~TD_R) | TD_TO);
 542                 } else {
 543                         out_be32(&td->buf_ptr, 0);
 544                         ep->already_pushed_dummy_bd = false;
 545                         break;
 546                 }
 547
 548                 /* advance the TD pointer */
 549                 td = next_bd(ep->td_base, td, td_status);
 550                 td_status = in_be16(&td->status);
 551                 buf_ptr = in_be32(&td->buf_ptr);
 552                 in_be16(&td->extra);
 553         } while ((td_status & TD_R) || buf_ptr);
 554
 555         fhci_td_transaction_confirm(usb);
 556
 557         out_be16(&ep->ep_pram_ptr->tx_bd_ptr,
 558                  in_be16(&ep->ep_pram_ptr->tx_base));
 559         out_be32(&ep->ep_pram_ptr->tx_state, 0);
 560         out_be16(&ep->ep_pram_ptr->tx_cnt, 0);
 561         ep->empty_td = ep->td_base;
 562         ep->conf_td = ep->td_base;
 563
 564         usb->actual_frame->frame_status = FRAME_TIMER_END_TRANSMISSION;
 565
 566         /* reset the event register */
 567         out_be16(&usb->fhci->regs->usb_usber, 0xffff);
 568         /* enable the USB controller */
 569         out_8(&usb->fhci->regs->usb_usmod, mode | USB_MODE_EN);
 570 }
 571
 572 /* handles Tx confirm and Tx error interrupt */
 573 void fhci_tx_conf_interrupt(struct fhci_usb *usb)
 574 {
 575         fhci_td_transaction_confirm(usb);
 576
 577         /*
 578          * Schedule another transaction to this frame only if we have
 579          * already confirmed all transaction in the frame.
 580          */
 581         if (((fhci_get_sof_timer_count(usb) < usb->max_frame_usage) ||
 582              (usb->actual_frame->frame_status & FRAME_END_TRANSMISSION)) &&
 583             (list_empty(&usb->actual_frame->tds_list)))
 584                 fhci_schedule_transactions(usb);
 585 }
 586
 587 void fhci_host_transmit_actual_frame(struct fhci_usb *usb)
 588 {
 589         u16 tb_ptr;
 590         u16 td_status;
 591         struct usb_td __iomem *td;
 592         struct endpoint *ep = usb->ep0;
 593
 594         tb_ptr = in_be16(&ep->ep_pram_ptr->tx_bd_ptr);
 595         td = cpm_muram_addr(tb_ptr);
 596
 597         if (in_be32(&td->buf_ptr) == DUMMY_BD_BUFFER) {
 598                 struct usb_td __iomem *old_td = td;
 599
 600                 ep->already_pushed_dummy_bd = false;
 601                 td_status = in_be16(&td->status);
 602                 /* gets the next TD in the ring */
 603                 td = next_bd(ep->td_base, td, td_status);
 604                 tb_ptr = cpm_muram_offset(td);
 605                 out_be16(&ep->ep_pram_ptr->tx_bd_ptr, tb_ptr);
 606
 607                 /* start transmit only if we have something in the TDs */
 608                 if (in_be16(&td->status) & TD_R)
 609                         out_8(&usb->fhci->regs->usb_uscom, USB_CMD_STR_FIFO);
 610
 611                 if (in_be32(&ep->conf_td->buf_ptr) == DUMMY_BD_BUFFER) {
 612                         out_be32(&old_td->buf_ptr, 0);
 613                         ep->conf_td = next_bd(ep->td_base, ep->conf_td,
 614                                               td_status);
 615                 } else {
 616                         out_be32(&old_td->buf_ptr, DUMMY2_BD_BUFFER);
 617                 }
 618         }
 619 }