USB: Driver for Freescale QUICC Engine USB Host Controller

This patch adds support for the FHCI USB controller, as found
in the Freescale MPC836x and MPC832x processors. It can support
Full or Low speed modes.

Quite a lot the hardware is doing by itself (SOF generation, CRC
generation and checking), though scheduling and retransmission is on
software's shoulders.

This controller does not integrate the root hub, so this driver also
fakes one-port hub. External hub is required to support more than
one device.

Signed-off-by: Anton Vorontsov <avorontsov@ru.mvista.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>

1 files changed, 626 insertions, 0 deletions

diff --git a/drivers/usb/host/fhci-tds.c b/drivers/usb/host/fhci-tds.c
new file mode 100644
index 000000000000..b40332290319
--- /dev/null
+++ b/drivers/usb/host/fhci-tds.c
@@ -0,0 +1,626 @@
+/*
+ * Freescale QUICC Engine USB Host Controller Driver
+ *
+ * Copyright (c) Freescale Semicondutor, Inc. 2006.
+ *               Shlomi Gridish <gridish@freescale.com>
+ *               Jerry Huang <Chang-Ming.Huang@freescale.com>
+ * Copyright (c) Logic Product Development, Inc. 2007
+ *               Peter Barada <peterb@logicpd.com>
+ * Copyright (c) MontaVista Software, Inc. 2008.
+ *               Anton Vorontsov <avorontsov@ru.mvista.com>
+ *
+ * This program is free software; you can redistribute  it and/or modify it
+ * under  the terms of  the GNU General  Public License as published by the
+ * Free Software Foundation;  either version 2 of the  License, or (at your
+ * option) any later version.
+ */
+
+#include <linux/kernel.h>
+#include <linux/types.h>
+#include <linux/errno.h>
+#include <linux/list.h>
+#include <linux/io.h>
+#include <linux/usb.h>
+#include "../core/hcd.h"
+#include "fhci.h"
+
+#define DUMMY_BD_BUFFER  0xdeadbeef
+#define DUMMY2_BD_BUFFER 0xbaadf00d
+
+/* Transaction Descriptors bits */
+#define TD_R            0x8000 /* ready bit */
+#define TD_W            0x2000 /* wrap bit */
+#define TD_I            0x1000 /* interrupt on completion */
+#define TD_L            0x0800 /* last */
+#define TD_TC           0x0400 /* transmit CRC */
+#define TD_CNF          0x0200 /* CNF - Must be always 1 */
+#define TD_LSP          0x0100 /* Low-speed transaction */
+#define TD_PID          0x00c0 /* packet id */
+#define TD_RXER         0x0020 /* Rx error or not */
+
+#define TD_NAK          0x0010 /* No ack. */
+#define TD_STAL         0x0008 /* Stall recieved */
+#define TD_TO           0x0004 /* time out */
+#define TD_UN           0x0002 /* underrun */
+#define TD_NO           0x0010 /* Rx Non Octet Aligned Packet */
+#define TD_AB           0x0008 /* Frame Aborted */
+#define TD_CR           0x0004 /* CRC Error */
+#define TD_OV           0x0002 /* Overrun */
+#define TD_BOV          0x0001 /* Buffer Overrun */
+
+#define TD_ERRORS       (TD_NAK | TD_STAL | TD_TO | TD_UN | \
+                         TD_NO | TD_AB | TD_CR | TD_OV | TD_BOV)
+
+#define TD_PID_DATA0    0x0080 /* Data 0 toggle */
+#define TD_PID_DATA1    0x00c0 /* Data 1 toggle */
+#define TD_PID_TOGGLE   0x00c0 /* Data 0/1 toggle mask */
+
+#define TD_TOK_SETUP    0x0000
+#define TD_TOK_OUT      0x4000
+#define TD_TOK_IN       0x8000
+#define TD_ISO          0x1000
+#define TD_ENDP         0x0780
+#define TD_ADDR         0x007f
+
+#define TD_ENDP_SHIFT 7
+
+struct usb_td {
+        __be16 status;
+        __be16 length;
+        __be32 buf_ptr;
+        __be16 extra;
+        __be16 reserved;
+};
+
+static struct usb_td __iomem *next_bd(struct usb_td __iomem *base,
+                                      struct usb_td __iomem *td,
+                                      u16 status)
+{
+        if (status & TD_W)
+                return base;
+        else
+                return ++td;
+}
+
+void fhci_push_dummy_bd(struct endpoint *ep)
+{
+        if (ep->already_pushed_dummy_bd == false) {
+                u16 td_status = in_be16(&ep->empty_td->status);
+
+                out_be32(&ep->empty_td->buf_ptr, DUMMY_BD_BUFFER);
+                /* get the next TD in the ring */
+                ep->empty_td = next_bd(ep->td_base, ep->empty_td, td_status);
+                ep->already_pushed_dummy_bd = true;
+        }
+}
+
+/* destroy an USB endpoint */
+void fhci_ep0_free(struct fhci_usb *usb)
+{
+        struct endpoint *ep;
+        int size;
+
+        ep = usb->ep0;
+        if (ep) {
+                if (ep->td_base)
+                        cpm_muram_free(cpm_muram_offset(ep->td_base));
+
+                if (ep->conf_frame_Q) {
+                        size = cq_howmany(ep->conf_frame_Q);
+                        for (; size; size--) {
+                                struct packet *pkt = cq_get(ep->conf_frame_Q);
+
+                                kfree(pkt);
+                        }
+                        cq_delete(ep->conf_frame_Q);
+                }
+
+                if (ep->empty_frame_Q) {
+                        size = cq_howmany(ep->empty_frame_Q);
+                        for (; size; size--) {
+                                struct packet *pkt = cq_get(ep->empty_frame_Q);
+
+                                kfree(pkt);
+                        }
+                        cq_delete(ep->empty_frame_Q);
+                }
+
+                if (ep->dummy_packets_Q) {
+                        size = cq_howmany(ep->dummy_packets_Q);
+                        for (; size; size--) {
+                                u8 *buff = cq_get(ep->dummy_packets_Q);
+
+                                kfree(buff);
+                        }
+                        cq_delete(ep->dummy_packets_Q);
+                }
+
+                kfree(ep);
+                usb->ep0 = NULL;
+        }
+}
+
+/*
+ * create the endpoint structure
+ *
+ * arguments:
+ * usb          A pointer to the data structure of the USB
+ * data_mem     The data memory partition(BUS)
+ * ring_len     TD ring length
+ */
+u32 fhci_create_ep(struct fhci_usb *usb, enum fhci_mem_alloc data_mem,
+                           u32 ring_len)
+{
+        struct endpoint *ep;
+        struct usb_td __iomem *td;
+        unsigned long ep_offset;
+        char *err_for = "enpoint PRAM";
+        int ep_mem_size;
+        u32 i;
+
+        /* we need at least 3 TDs in the ring */
+        if (!(ring_len > 2)) {
+                fhci_err(usb->fhci, "illegal TD ring length parameters\n");
+                return -EINVAL;
+        }
+
+        ep = kzalloc(sizeof(*ep), GFP_KERNEL);
+        if (!ep)
+                return -ENOMEM;
+
+        ep_mem_size = ring_len * sizeof(*td) + sizeof(struct fhci_ep_pram);
+        ep_offset = cpm_muram_alloc(ep_mem_size, 32);
+        if (IS_ERR_VALUE(ep_offset))
+                goto err;
+        ep->td_base = cpm_muram_addr(ep_offset);
+
+        /* zero all queue pointers */
+        ep->conf_frame_Q = cq_new(ring_len + 2);
+        ep->empty_frame_Q = cq_new(ring_len + 2);
+        ep->dummy_packets_Q = cq_new(ring_len + 2);
+        if (!ep->conf_frame_Q || !ep->empty_frame_Q || !ep->dummy_packets_Q) {
+                err_for = "frame_queues";
+                goto err;
+        }
+
+        for (i = 0; i < (ring_len + 1); i++) {
+                struct packet *pkt;
+                u8 *buff;
+
+                pkt = kmalloc(sizeof(*pkt), GFP_KERNEL);
+                if (!pkt) {
+                        err_for = "frame";
+                        goto err;
+                }
+
+                buff = kmalloc(1028 * sizeof(*buff), GFP_KERNEL);
+                if (!buff) {
+                        kfree(pkt);
+                        err_for = "buffer";
+                        goto err;
+                }
+                cq_put(ep->empty_frame_Q, pkt);
+                cq_put(ep->dummy_packets_Q, buff);
+        }
+
+        /* we put the endpoint parameter RAM right behind the TD ring */
+        ep->ep_pram_ptr = (void __iomem *)ep->td_base + sizeof(*td) * ring_len;
+
+        ep->conf_td = ep->td_base;
+        ep->empty_td = ep->td_base;
+
+        ep->already_pushed_dummy_bd = false;
+
+        /* initialize tds */
+        td = ep->td_base;
+        for (i = 0; i < ring_len; i++) {
+                out_be32(&td->buf_ptr, 0);
+                out_be16(&td->status, 0);
+                out_be16(&td->length, 0);
+                out_be16(&td->extra, 0);
+                td++;
+        }
+        td--;
+        out_be16(&td->status, TD_W); /* for last TD set Wrap bit */
+        out_be16(&td->length, 0);
+
+        /* endpoint structure has been created */
+        usb->ep0 = ep;
+
+        return 0;
+err:
+        fhci_ep0_free(usb);
+        kfree(ep);
+        fhci_err(usb->fhci, "no memory for the %s\n", err_for);
+        return -ENOMEM;
+}
+
+/*
+ * initialize the endpoint register according to the given parameters
+ *
+ * artuments:
+ * usb          A pointer to the data strucutre of the USB
+ * ep           A pointer to the endpoint structre
+ * data_mem     The data memory partition(BUS)
+ */
+void fhci_init_ep_registers(struct fhci_usb *usb, struct endpoint *ep,
+                            enum fhci_mem_alloc data_mem)
+{
+        u8 rt;
+
+        /* set the endpoint registers according to the endpoint */
+        out_be16(&usb->fhci->regs->usb_ep[0],
+                 USB_TRANS_CTR | USB_EP_MF | USB_EP_RTE);
+        out_be16(&usb->fhci->pram->ep_ptr[0],
+                 cpm_muram_offset(ep->ep_pram_ptr));
+
+        rt = (BUS_MODE_BO_BE | BUS_MODE_GBL);
+#ifdef MULTI_DATA_BUS
+        if (data_mem == MEM_SECONDARY)
+                rt |= BUS_MODE_DTB;
+#endif
+        out_8(&ep->ep_pram_ptr->rx_func_code, rt);
+        out_8(&ep->ep_pram_ptr->tx_func_code, rt);
+        out_be16(&ep->ep_pram_ptr->rx_buff_len, 1028);
+        out_be16(&ep->ep_pram_ptr->rx_base, 0);
+        out_be16(&ep->ep_pram_ptr->tx_base, cpm_muram_offset(ep->td_base));
+        out_be16(&ep->ep_pram_ptr->rx_bd_ptr, 0);
+        out_be16(&ep->ep_pram_ptr->tx_bd_ptr, cpm_muram_offset(ep->td_base));
+        out_be32(&ep->ep_pram_ptr->tx_state, 0);
+}
+
+/*
+ * Collect the submitted frames and inform the application about them
+ * It is also prepearing the TDs for new frames. If the Tx interrupts
+ * are diabled, the application should call that routine to get
+ * confirmation about the submitted frames. Otherwise, the routine is
+ * called frome the interrupt service routine during the Tx interrupt.
+ * In that case the application is informed by calling the application
+ * specific 'fhci_transaction_confirm' routine
+ */
+static void fhci_td_transaction_confirm(struct fhci_usb *usb)
+{
+        struct endpoint *ep = usb->ep0;
+        struct packet *pkt;
+        struct usb_td __iomem *td;
+        u16 extra_data;
+        u16 td_status;
+        u16 td_length;
+        u32 buf;
+
+        /*
+         * collect transmitted BDs from the chip. The routine clears all BDs
+         * with R bit = 0 and the pointer to data buffer is not NULL, that is
+         * BDs which point to the transmitted data buffer
+         */
+        while (1) {
+                td = ep->conf_td;
+                td_status = in_be16(&td->status);
+                td_length = in_be16(&td->length);
+                buf = in_be32(&td->buf_ptr);
+                extra_data = in_be16(&td->extra);
+
+                /* check if the TD is empty */
+                if (!(!(td_status & TD_R) && ((td_status & ~TD_W) || buf)))
+                        break;
+                /* check if it is a dummy buffer */
+                else if ((buf == DUMMY_BD_BUFFER) && !(td_status & ~TD_W))
+                        break;
+
+                /* mark TD as empty */
+                clrbits16(&td->status, ~TD_W);
+                out_be16(&td->length, 0);
+                out_be32(&td->buf_ptr, 0);
+                out_be16(&td->extra, 0);
+                /* advance the TD pointer */
+                ep->conf_td = next_bd(ep->td_base, ep->conf_td, td_status);
+
+                /* check if it is a dummy buffer(type2) */
+                if ((buf == DUMMY2_BD_BUFFER) && !(td_status & ~TD_W))
+                        continue;
+
+                pkt = cq_get(ep->conf_frame_Q);
+                if (!pkt)
+                        fhci_err(usb->fhci, "no frame to confirm\n");
+
+                if (td_status & TD_ERRORS) {
+                        if (td_status & TD_RXER) {
+                                if (td_status & TD_CR)
+                                        pkt->status = USB_TD_RX_ER_CRC;
+                                else if (td_status & TD_AB)
+                                        pkt->status = USB_TD_RX_ER_BITSTUFF;
+                                else if (td_status & TD_OV)
+                                        pkt->status = USB_TD_RX_ER_OVERUN;
+                                else if (td_status & TD_BOV)
+                                        pkt->status = USB_TD_RX_DATA_OVERUN;
+                                else if (td_status & TD_NO)
+                                        pkt->status = USB_TD_RX_ER_NONOCT;
+                                else
+                                        fhci_err(usb->fhci, "illegal error "
+                                                 "occured\n");
+                        } else if (td_status & TD_NAK)
+                                pkt->status = USB_TD_TX_ER_NAK;
+                        else if (td_status & TD_TO)
+                                pkt->status = USB_TD_TX_ER_TIMEOUT;
+                        else if (td_status & TD_UN)
+                                pkt->status = USB_TD_TX_ER_UNDERUN;
+                        else if (td_status & TD_STAL)
+                                pkt->status = USB_TD_TX_ER_STALL;
+                        else
+                                fhci_err(usb->fhci, "illegal error occured\n");
+                } else if ((extra_data & TD_TOK_IN) &&
+                                pkt->len > td_length - CRC_SIZE) {
+                        pkt->status = USB_TD_RX_DATA_UNDERUN;
+                }
+
+                if (extra_data & TD_TOK_IN)
+                        pkt->len = td_length - CRC_SIZE;
+                else if (pkt->info & PKT_ZLP)
+                        pkt->len = 0;
+                else
+                        pkt->len = td_length;
+
+                fhci_transaction_confirm(usb, pkt);
+        }
+}
+
+/*
+ * Submitting a data frame to a specified endpoint of a USB device
+ * The frame is put in the driver's transmit queue for this endpoint
+ *
+ * Arguments:
+ * usb          A pointer to the USB structure
+ * pkt          A pointer to the user frame structure
+ * trans_type   Transaction tyep - IN,OUT or SETUP
+ * dest_addr    Device address - 0~127
+ * dest_ep      Endpoint number of the device - 0~16
+ * trans_mode   Pipe type - ISO,Interrupt,bulk or control
+ * dest_speed   USB speed - Low speed or FULL speed
+ * data_toggle  Data sequence toggle - 0 or 1
+ */
+u32 fhci_host_transaction(struct fhci_usb *usb,
+                          struct packet *pkt,
+                          enum fhci_ta_type trans_type,
+                          u8 dest_addr,
+                          u8 dest_ep,
+                          enum fhci_tf_mode trans_mode,
+                          enum fhci_speed dest_speed, u8 data_toggle)
+{
+        struct endpoint *ep = usb->ep0;
+        struct usb_td __iomem *td;
+        u16 extra_data;
+        u16 td_status;
+
+        fhci_usb_disable_interrupt(usb);
+        /* start from the next BD that should be filled */
+        td = ep->empty_td;
+        td_status = in_be16(&td->status);
+
+        if (td_status & TD_R && in_be16(&td->length)) {
+                /* if the TD is not free */
+                fhci_usb_enable_interrupt(usb);
+                return -1;
+        }
+
+        /* get the next TD in the ring */
+        ep->empty_td = next_bd(ep->td_base, ep->empty_td, td_status);
+        fhci_usb_enable_interrupt(usb);
+        pkt->priv_data = td;
+        out_be32(&td->buf_ptr, virt_to_phys(pkt->data));
+        /* sets up transaction parameters - addr,endp,dir,and type */
+        extra_data = (dest_ep << TD_ENDP_SHIFT) | dest_addr;
+        switch (trans_type) {
+        case FHCI_TA_IN:
+                extra_data |= TD_TOK_IN;
+                break;
+        case FHCI_TA_OUT:
+                extra_data |= TD_TOK_OUT;
+                break;
+        case FHCI_TA_SETUP:
+                extra_data |= TD_TOK_SETUP;
+                break;
+        }
+        if (trans_mode == FHCI_TF_ISO)
+                extra_data |= TD_ISO;
+        out_be16(&td->extra, extra_data);
+
+        /* sets up the buffer descriptor */
+        td_status = ((td_status & TD_W) | TD_R | TD_L | TD_I | TD_CNF);
+        if (!(pkt->info & PKT_NO_CRC))
+                td_status |= TD_TC;
+
+        switch (trans_type) {
+        case FHCI_TA_IN:
+                if (data_toggle)
+                        pkt->info |= PKT_PID_DATA1;
+                else
+                        pkt->info |= PKT_PID_DATA0;
+                break;
+        default:
+                if (data_toggle) {
+                        td_status |= TD_PID_DATA1;
+                        pkt->info |= PKT_PID_DATA1;
+                } else {
+                        td_status |= TD_PID_DATA0;
+                        pkt->info |= PKT_PID_DATA0;
+                }
+                break;
+        }
+
+        if ((dest_speed == FHCI_LOW_SPEED) &&
+            (usb->port_status == FHCI_PORT_FULL))
+                td_status |= TD_LSP;
+
+        out_be16(&td->status, td_status);
+
+        /* set up buffer length */
+        if (trans_type == FHCI_TA_IN)
+                out_be16(&td->length, pkt->len + CRC_SIZE);
+        else
+                out_be16(&td->length, pkt->len);
+
+        /* put the frame to the confirmation queue */
+        cq_put(ep->conf_frame_Q, pkt);
+
+        if (cq_howmany(ep->conf_frame_Q) == 1)
+                out_8(&usb->fhci->regs->usb_comm, USB_CMD_STR_FIFO);
+
+        return 0;
+}
+
+/* Reset the Tx BD ring */
+void fhci_flush_bds(struct fhci_usb *usb)
+{
+        u16 extra_data;
+        u16 td_status;
+        u32 buf;
+        struct usb_td __iomem *td;
+        struct endpoint *ep = usb->ep0;
+
+        td = ep->td_base;
+        while (1) {
+                td_status = in_be16(&td->status);
+                buf = in_be32(&td->buf_ptr);
+                extra_data = in_be16(&td->extra);
+
+                /* if the TD is not empty - we'll confirm it as Timeout */
+                if (td_status & TD_R)
+                        out_be16(&td->status, (td_status & ~TD_R) | TD_TO);
+                /* if this TD is dummy - let's skip this TD */
+                else if (in_be32(&td->buf_ptr) == DUMMY_BD_BUFFER)
+                        out_be32(&td->buf_ptr, DUMMY2_BD_BUFFER);
+                /* if this is the last TD - break */
+                if (td_status & TD_W)
+                        break;
+
+                td++;
+        }
+
+        fhci_td_transaction_confirm(usb);
+
+        td = ep->td_base;
+        do {
+                out_be16(&td->status, 0);
+                out_be16(&td->length, 0);
+                out_be32(&td->buf_ptr, 0);
+                out_be16(&td->extra, 0);
+                td++;
+        } while (!(in_be16(&td->status) & TD_W));
+        out_be16(&td->status, TD_W); /* for last TD set Wrap bit */
+        out_be16(&td->length, 0);
+        out_be32(&td->buf_ptr, 0);
+        out_be16(&td->extra, 0);
+
+        out_be16(&ep->ep_pram_ptr->tx_bd_ptr,
+                 in_be16(&ep->ep_pram_ptr->tx_base));
+        out_be32(&ep->ep_pram_ptr->tx_state, 0);
+        out_be16(&ep->ep_pram_ptr->tx_cnt, 0);
+        ep->empty_td = ep->td_base;
+        ep->conf_td = ep->td_base;
+}
+
+/*
+ * Flush all transmitted packets from TDs in the actual frame.
+ * This routine is called when something wrong with the controller and
+ * we want to get rid of the actual frame and start again next frame
+ */
+void fhci_flush_actual_frame(struct fhci_usb *usb)
+{
+        u8 mode;
+        u16 tb_ptr;
+        u16 extra_data;
+        u16 td_status;
+        u32 buf_ptr;
+        struct usb_td __iomem *td;
+        struct endpoint *ep = usb->ep0;
+
+        /* disable the USB controller */
+        mode = in_8(&usb->fhci->regs->usb_mod);
+        out_8(&usb->fhci->regs->usb_mod, mode & ~USB_MODE_EN);
+
+        tb_ptr = in_be16(&ep->ep_pram_ptr->tx_bd_ptr);
+        td = cpm_muram_addr(tb_ptr);
+        td_status = in_be16(&td->status);
+        buf_ptr = in_be32(&td->buf_ptr);
+        extra_data = in_be16(&td->extra);
+        do {
+                if (td_status & TD_R) {
+                        out_be16(&td->status, (td_status & ~TD_R) | TD_TO);
+                } else {
+                        out_be32(&td->buf_ptr, 0);
+                        ep->already_pushed_dummy_bd = false;
+                        break;
+                }
+
+                /* advance the TD pointer */
+                td = next_bd(ep->td_base, td, td_status);
+                td_status = in_be16(&td->status);
+                buf_ptr = in_be32(&td->buf_ptr);
+                extra_data = in_be16(&td->extra);
+        } while ((td_status & TD_R) || buf_ptr);
+
+        fhci_td_transaction_confirm(usb);
+
+        out_be16(&ep->ep_pram_ptr->tx_bd_ptr,
+                 in_be16(&ep->ep_pram_ptr->tx_base));
+        out_be32(&ep->ep_pram_ptr->tx_state, 0);
+        out_be16(&ep->ep_pram_ptr->tx_cnt, 0);
+        ep->empty_td = ep->td_base;
+        ep->conf_td = ep->td_base;
+
+        usb->actual_frame->frame_status = FRAME_TIMER_END_TRANSMISSION;
+
+        /* reset the event register */
+        out_be16(&usb->fhci->regs->usb_event, 0xffff);
+        /* enable the USB controller */
+        out_8(&usb->fhci->regs->usb_mod, mode | USB_MODE_EN);
+}
+
+/* handles Tx confirm and Tx error interrupt */
+void fhci_tx_conf_interrupt(struct fhci_usb *usb)
+{
+        fhci_td_transaction_confirm(usb);
+
+        /*
+         * Schedule another transaction to this frame only if we have
+         * already confirmed all transaction in the frame.
+         */
+        if (((fhci_get_sof_timer_count(usb) < usb->max_frame_usage) ||
+             (usb->actual_frame->frame_status & FRAME_END_TRANSMISSION)) &&
+            (list_empty(&usb->actual_frame->tds_list)))
+                fhci_schedule_transactions(usb);
+}
+
+void fhci_host_transmit_actual_frame(struct fhci_usb *usb)
+{
+        u16 tb_ptr;
+        u16 td_status;
+        struct usb_td __iomem *td;
+        struct endpoint *ep = usb->ep0;
+
+        tb_ptr = in_be16(&ep->ep_pram_ptr->tx_bd_ptr);
+        td = cpm_muram_addr(tb_ptr);
+
+        if (in_be32(&td->buf_ptr) == DUMMY_BD_BUFFER) {
+                struct usb_td __iomem *old_td = td;
+
+                ep->already_pushed_dummy_bd = false;
+                td_status = in_be16(&td->status);
+                /* gets the next TD in the ring */
+                td = next_bd(ep->td_base, td, td_status);
+                tb_ptr = cpm_muram_offset(td);
+                out_be16(&ep->ep_pram_ptr->tx_bd_ptr, tb_ptr);
+
+                /* start transmit only if we have something in the TDs */
+                if (in_be16(&td->status) & TD_R)
+                        out_8(&usb->fhci->regs->usb_comm, USB_CMD_STR_FIFO);
+
+                if (in_be32(&ep->conf_td->buf_ptr) == DUMMY_BD_BUFFER) {
+                        out_be32(&old_td->buf_ptr, 0);
+                        ep->conf_td = next_bd(ep->td_base, ep->conf_td,
+                                              td_status);
+                } else {
+                        out_be32(&old_td->buf_ptr, DUMMY2_BD_BUFFER);
+                }
+        }
+}